Incorporation of oxygen into abscisic Acid and phaseic Acid from molecular oxygen.

PubMed

Creelman, R A; Zeevaart, J A

1984-05-01

Abscisic acid accumulates in detached, wilted leaves of Xanthium strumarium. When these leaves are subsequently rehydrated, phaseic acid, a catabolite of abscisic acid, accumulates. Analysis by gas chromatography-mass spectrometry of phaseic acid isolated from stressed and subsequently rehydrated leaves placed in an atmosphere containing 20% (18)O(2) and 80% N(2) indicates that one atom of (18)O is incorporated in the 6'-hydroxymethyl group of phaseic acid. This suggests that the enzyme that converts abscisic acid to phaseic acid is an oxygenase.Analysis by gas chromatography-mass spectrometry of abscisic acid isolated from stressed leaves kept in an atmosphere containing (18)O(2) indicates that one atom of (18)O is present in the carboxyl group of abscisic acid. Thus, when abscisic acid accumulates in water-stressed leaves, only one of the four oxygens present in the abscisic acid molecule is derived from molecular oxygen. This suggests that either (a) the oxygen present in the 1'-, 4'-, and one of the two oxygens at the 1-position of abscisic acid arise from water, or (b) there exists a stored precursor with oxygen atoms already present in the 1'- and 4'-positions of abscisic acid which is converted to abscisic acid under conditions of water stress.

A SHATTERPROOF-like gene controls ripening in non-climacteric strawberries, and auxin and abscisic acid antagonistically affect its expression.

PubMed

Daminato, Margherita; Guzzo, Flavia; Casadoro, Giorgio

2013-09-01

Strawberries (Fragaria×ananassa) are false fruits the ripening of which follows the non-climacteric pathway. The role played by a C-type MADS-box gene [SHATTERPROOF-like (FaSHP)] in the ripening of strawberries has been studied by transiently modifying gene expression through either over-expression or RNA-interference-mediated down-regulation. The altered expression of the FaSHP gene caused a change in the time taken by the over-expressing and the down- regulated fruits to attain the pink stage, which was slightly shorter and much longer, respectively, compared to controls. In parallel with the modified ripening times, the metabolome components and the expression of ripening-related genes also appeared different in the transiently modified fruits. Differences in the response time of the analysed genes suggest that FaSHP can control the expression of ripening genes either directly or indirectly through other transcription factor-encoding genes. Because fleshy strawberries are false fruits these results indicate that C-type MADS-box genes like SHATTERPROOF may act as modulators of ripening in fleshy fruit-like structures independently of their anatomical origin. Treatment of strawberries with either auxin or abscisic acid had antagonistic impacts on both the expression of FaSHP and the expression of ripening-related genes and metabolome components.

Abscisic Acid Stimulates Elongation of Excised Pea Root Tips

PubMed Central

Gaither, Douglas H.; Lutz, Donald H.; Forrence, Leonard E.

1975-01-01

Excised Pisum sativum L. root tips were incubated in a pH 5.2 sucrose medium containing abscisic acid. Elongation growth was inhibited by 100 μm abscisic acid. However, decreasing the abscisic acid concentration caused stimulation of elongation, the maximum response (25% to 30%) occurring at 1 μm abscisic acid. Prior to two hours, stimulation of elongation by 1 μm abscisic acid was not detectable. Increased elongation did not occur in abscisic acid-treated root tips of Lens culinaris L., Phaseolus vulgaris L., or Zea mays L. PMID:16659198

Multiparameter imaging of calcium and abscisic acid and high-resolution quantitative calcium measurements using R-GECO1-mTurquoise in Arabidopsis.

PubMed

Waadt, Rainer; Krebs, Melanie; Kudla, Jörg; Schumacher, Karin

2017-10-01

Calcium signals occur in specific spatio-temporal patterns in response to various stimuli and are coordinated with, for example, hormonal signals, for physiological and developmental adaptations. Quantification of calcium together with other signalling molecules is required for correlative analyses and to decipher downstream calcium-decoding mechanisms. Simultaneous in vivo imaging of calcium and abscisic acid has been performed here to investigate the interdependence of the respective signalling processes in Arabidopsis thaliana roots. Advanced ratiometric genetically encoded calcium indicators have been generated and in vivo calcium calibration protocols were established to determine absolute calcium concentration changes in response to auxin and ATP. In roots, abscisic acid induced long-term basal calcium concentration increases, while auxin triggered rapid signals in the elongation zone. The advanced ratiometric calcium indicator R-GECO1-mTurquoise exhibited an increased calcium signal resolution compared to commonly used Förster resonance energy transfer-based indicators. Quantitative calcium measurements in Arabidopsis root tips using R-GECO1-mTurquoise revealed detailed maps of absolute calcium concentration changes in response to auxin and ATP. Calcium calibration protocols using R-GECO1-mTurquoise enabled high-resolution quantitative imaging of resting cytosolic calcium concentrations and their dynamic changes that revealed distinct hormonal and ATP responses in roots. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Incorporation of Oxygen into Abscisic Acid and Phaseic Acid from Molecular Oxygen 1

PubMed Central

Creelman, Robert A.; Zeevaart, Jan A. D.

1984-01-01

Abscisic acid accumulates in detached, wilted leaves of Xanthium strumarium. When these leaves are subsequently rehydrated, phaseic acid, a catabolite of abscisic acid, accumulates. Analysis by gas chromatography-mass spectrometry of phaseic acid isolated from stressed and subsequently rehydrated leaves placed in an atmosphere containing 20% 18O2 and 80% N2 indicates that one atom of 18O is incorporated in the 6′-hydroxymethyl group of phaseic acid. This suggests that the enzyme that converts abscisic acid to phaseic acid is an oxygenase. Analysis by gas chromatography-mass spectrometry of abscisic acid isolated from stressed leaves kept in an atmosphere containing 18O2 indicates that one atom of 18O is present in the carboxyl group of abscisic acid. Thus, when abscisic acid accumulates in water-stressed leaves, only one of the four oxygens present in the abscisic acid molecule is derived from molecular oxygen. This suggests that either (a) the oxygen present in the 1′-, 4′-, and one of the two oxygens at the 1-position of abscisic acid arise from water, or (b) there exists a stored precursor with oxygen atoms already present in the 1′- and 4′-positions of abscisic acid which is converted to abscisic acid under conditions of water stress. PMID:16663564

The roles of auxin in seed dormancy and germination.

PubMed

Shuai, Hai-wei; Meng, Yong-jie; Luo, Xiao-feng; Chen, Feng; Qi, Ying; Yang, Wen-yu; Shu, Kai

2016-04-01

Seed dormancy and germination are attractive topics in the fields of plant molecular biology as they are key stages during plant growth and development. Seed dormancy is intricately regulated by complex networks of phytohormones and numerous key genes, combined with diverse environmental cues. The transition from dormancy to germination is a very important biological process, and extensive studies have demonstrated that phytohormones abscisic acid (ABA) and gibberellin acid (GA) are major determinants. Consequently, the precise balance between ABA and GA can ensure that the seeds remain dormant under stress conditions and germinate at optimal times. Here we review the role of auxin in seed dormancy and germination. Auxin is one of the classic phytohormones effective during tropism growth and tissue differentiation. Recent studies, however, show that auxin possesses positive effects on seed dormancy, which suggests that auxin is the second phytohormone that induces seed dormancy, besides ABA. We will focus on the synthetic effects in detail between auxin and ABA pathways on seed dormancy and propose future research directions.

Solanum lycopersicum IAA15 functions in the 2,4-dichlorophenoxyacetic acid herbicide mechanism of action by mediating abscisic acid signalling.

PubMed

Xu, Tao; Wang, Yanling; Liu, Xin; Gao, Song; Qi, Mingfang; Li, Tianlai

2015-07-01

2,4-Dichlorophenoxyacetic acid (2,4-D), an important plant growth regulator, is the herbicide most commonly used worldwide to control weeds. However, broad-leaf fruits and vegetables are extremely sensitive to herbicides, which can cause damage and result in lost crops when applied in a manner inconsistent with the directions. Despite detailed knowledge of the mechanism of 2,4-D, the regulation of auxin signalling is still unclear. For example, although the major mediators of auxin signalling, including auxin/indole acetic acid (AUX/IAA) proteins and auxin response factors (ARFs), are known to mediate auxinic herbicides, the underlying mechanisms are still unclear. In this study, the effects of 2,4-D on AUX/IAA gene expression in tomato were investigated, and the two most notably up-regulated genes, SlIAA15 and SlIAA29, were selected for further study. Western blotting revealed the substantial accumulation of both SlIAA15 and SlIAA29, and the expression levels of the corresponding genes were increased following abscisic acid (ABA) and ethylene treatment. Overexpressing SlIAA15, but not SlIAA29, induced a 2,4-D herbicide damage phenotype. The 35S::SlIAA15 line exhibited a strong reduction in leaf stomatal density and altered expression of some R2R3 MYB genes that are putatively involved in the regulation of stomatal differentiation. Further study revealed that root elongation in 35S::SlIAA15 was sensitive to ABA treatment, and was most probably due to the altered expression of an ABA signal transduction gene. In addition, the altered auxin sensitivities of SlIAA15 transformants were also explored. These results suggested that SlIAA15 plays an important role in determining the effects of the herbicide 2,4-D. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Strongly Acidic Auxin Indole-3-Methanesulfonic Acid

PubMed Central

Cohen, Jerry D.; Baldi, Bruce G.; Bialek, Krystyna

1985-01-01

A radiochemical synthesis is described for [14C]indole-3-methanesulfonic acid (IMS), a strongly acidic auxin analog. Techniques were developed for fractionation and purification of IMS using normal and reverse phase chromatography. In addition, the utility of both Fourier transform infrared spectrometry and fast atom bombardment mass spectrometry for analysis of IMS has been demonstrated. IMS was shown to be an active auxin, stimulating soybean hypocotyl elongation, bean first internode curvature, and ethylene production. IMS uptake by thin sections of soybean hypocotyl was essentially independent of solution pH and, when applied at a 100 micromolar concentration, IMS exhibited a basipetal polarity in its transport in both corn coleoptile and soybean hypocotyl sections. [14C]IMS should, therefore, be a useful compound to study fundamental processes related to the movement of auxins in plant tissues and organelles. PMID:16664007

Sequestration of auxin by the indole-3-acetic acid-amido synthetase GH3-1 in grape berry (Vitis vinifera L.) and the proposed role of auxin conjugation during ripening.

PubMed

Böttcher, Christine; Keyzers, Robert A; Boss, Paul K; Davies, Christopher

2010-08-01

In fleshy fruit, levels of indole-3-acetic acid (IAA), the most abundant auxin, decline towards the onset of ripening. The application of auxins to immature fruit can delay the ripening processes. However, the mechanisms by which the decrease in endogenous IAA concentrations and the maintenance of low auxin levels in maturing fruit are achieved remain elusive. The transcript of a GH3 gene (GH3-1), encoding for an IAA-amido synthetase which conjugates IAA to amino acids, was detected in grape berries (Vitis vinifera L.). GH3-1 expression increased at the onset of ripening (veraison), suggesting that it might be involved in the establishment and maintenance of low IAA concentrations in ripening berries. Furthermore, this grapevine GH3 gene, responded positively to the combined application of abscisic acid and sucrose and to ethylene, linking it to the control of ripening processes. Levels of IAA-aspartic acid (IAA-Asp), an in vitro product of recombinant GH3-1, rose after veraison and remained high during the following weeks of the ripening phase when levels of free IAA were low. A similar pattern of changes in free IAA and IAA-Asp levels was detected in developing tomatoes (Solanum lycopersicum Mill.), where low concentrations of IAA and an increase in IAA-Asp concentrations coincided with the onset of ripening in this climacteric fruit. Since IAA-Asp might be involved in IAA degradation, the GH3 catalysed formation of this conjugate at, and after, the onset of ripening could represent a common IAA inactivation mechanism in climacteric and non-climacteric fruit which enables ripening.

Presence of abscisic acid, a phytohormone, in the mammalian brain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Page-Degivry, M.T.; Bidard, J.N.; Rouvier, E.

1986-02-01

This paper reports the presence of abscisic acid, one of the most important phytohormones, in the central nervous system of pigs and rats. The identification of this hormone in brain was made after extensive purification by using a radioimmunoassay that is very specific for (+)-cis-abscisic acid. The final product of purification from mammalian brain has the same properties as authentic abscisic acid: it crossreacts in the radioimmunoassay for the phytohormone and it has the same retention properties and the same gas chromatography/mass spectrometry characteristics. Moreover, like (+)-cis-abscisic acid itself, the brain factor inhibits stomatal apertures of abaxial epidermis strips ofmore » Setcreasea purpurea Boom (Commelinaceae). The presence of abscisic acid conjugates that are present in plants has also been identified in brain.« less

Fruit load induces changes in global gene expression and in abscisic acid (ABA) and indole acetic acid (IAA) homeostasis in citrus buds

PubMed Central

Shalom, Liron; Samuels, Sivan; Zur, Naftali; Shlizerman, Lyudmila; Doron-Faigenboim, Adi; Blumwald, Eduardo; Sadka, Avi

2014-01-01

Many fruit trees undergo cycles of heavy fruit load (ON-Crop) in one year, followed by low fruit load (OFF-Crop) the following year, a phenomenon known as alternate bearing (AB). The mechanism by which fruit load affects flowering induction during the following year (return bloom) is still unclear. Although not proven, it is commonly accepted that the fruit or an organ which senses fruit presence generates an inhibitory signal that moves into the bud and inhibits apical meristem transition. Indeed, fruit removal from ON-Crop trees (de-fruiting) induces return bloom. Identification of regulatory or metabolic processes modified in the bud in association with altered fruit load might shed light on the nature of the AB signalling process. The bud transcriptome of de-fruited citrus trees was compared with those of ON- and OFF-Crop trees. Fruit removal resulted in relatively rapid changes in global gene expression, including induction of photosynthetic genes and proteins. Altered regulatory mechanisms included abscisic acid (ABA) metabolism and auxin polar transport. Genes of ABA biosynthesis were induced; however, hormone analyses showed that the ABA level was reduced in OFF-Crop buds and in buds shortly following fruit removal. Additionally, genes associated with Ca2+-dependent auxin polar transport were remarkably induced in buds of OFF-Crop and de-fruited trees. Hormone analyses showed that auxin levels were reduced in these buds as compared with ON-Crop buds. In view of the auxin transport autoinhibition theory, the possibility that auxin distribution plays a role in determining bud fate is discussed. PMID:24706719

Structure-Activity Correlations with Compounds Related to Abscisic Acid 1

PubMed Central

Sondheimer, Ernest; Walton, Daniel C.

1970-01-01

Inhibition of cell expansion of excised embryonic axes of Phaseolus vulgaris was used to evaluate the growth-inhibiting activity of abscisic acid and related compounds. None of the 13 compounds tested was as active as abscisic acid. 4-Hydroxyisophorone, a substance representative of the abscisic acid ring system was essentially inactive; cis, trans-3-methylsorbic acid, a compound resembling the side chain of abscisic acid, had low activity; and cis, trans-β-ionylideneacetic acid was one-sixth as active. Loss of the ring double bond results in a drastic decrease in biological activity. Comparison of our results with those reported previously leads to the suggestion that the double bond of the cyclohexyl moiety may have an important function in determining the degree of activity of cis, trans-ionylideneacetic acids. Two modes of action are discussed. It seems possible that the ring double bond is involved in covalent bonding in binding of the abscisic acid analogue to macromolecules. This may require formation of an intermediate epoxide. It can also be argued that stereochemical differences between cyclohexane derivatives are important factors in determining the degree of biological activity. PMID:5423465

Enhancing tolerance of rice (Oryza sativa) to simulated acid rain by exogenous abscisic acid.

PubMed

Wu, Xi; Liang, Chanjuan

2017-02-01

Abscisic acid (ABA) regulates much important plant physiological and biochemical processes and induces tolerance to different stresses. Here, we studied the regulation of exogenous ABA on adaptation of rice seedlings to simulated acid rain (SAR) stress by measuring biomass dry weight, stomatal conductance, net photosynthesis rate, nutrient elements, and endogenous hormones. The application of 10 μM ABA alleviated the SAR-induced inhibition on growth, stomatal conductance, net photosynthesis rate, and decreases in contents of nutrient (K, Mg, N, and P) and hormone (auxin, gibberellins, and zeatin). Moreover, 10 μM ABA could stimulate the Ca content as signaling molecules under SAR stress. Contrarily, the application of 100 μM ABA aggravated the SAR-induced inhibition on growth, stomatal conductance, net photosynthesis rate, and contents of nutrient and hormone. The results got after a 5-day recovery (without SAR) show that exogenous 10 μM ABA can promote self-restoration process in rice whereas 100 μM ABA hindered the restoration by increasing deficiency of nutrients and disturbing the balance of hormones. These results confirmed that exogenous ABA at proper concentration could enhance the tolerance of rice to SAR stress.

Fruit load induces changes in global gene expression and in abscisic acid (ABA) and indole acetic acid (IAA) homeostasis in citrus buds.

PubMed

Shalom, Liron; Samuels, Sivan; Zur, Naftali; Shlizerman, Lyudmila; Doron-Faigenboim, Adi; Blumwald, Eduardo; Sadka, Avi

2014-07-01

Many fruit trees undergo cycles of heavy fruit load (ON-Crop) in one year, followed by low fruit load (OFF-Crop) the following year, a phenomenon known as alternate bearing (AB). The mechanism by which fruit load affects flowering induction during the following year (return bloom) is still unclear. Although not proven, it is commonly accepted that the fruit or an organ which senses fruit presence generates an inhibitory signal that moves into the bud and inhibits apical meristem transition. Indeed, fruit removal from ON-Crop trees (de-fruiting) induces return bloom. Identification of regulatory or metabolic processes modified in the bud in association with altered fruit load might shed light on the nature of the AB signalling process. The bud transcriptome of de-fruited citrus trees was compared with those of ON- and OFF-Crop trees. Fruit removal resulted in relatively rapid changes in global gene expression, including induction of photosynthetic genes and proteins. Altered regulatory mechanisms included abscisic acid (ABA) metabolism and auxin polar transport. Genes of ABA biosynthesis were induced; however, hormone analyses showed that the ABA level was reduced in OFF-Crop buds and in buds shortly following fruit removal. Additionally, genes associated with Ca(2+)-dependent auxin polar transport were remarkably induced in buds of OFF-Crop and de-fruited trees. Hormone analyses showed that auxin levels were reduced in these buds as compared with ON-Crop buds. In view of the auxin transport autoinhibition theory, the possibility that auxin distribution plays a role in determining bud fate is discussed. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Do rice suspension-cultured cells treated with abscisic acid mimic developing seeds?

PubMed

Matsuno, Koya; Fujimura, Tatsuhito

2015-08-01

Starch synthesis is activated in the endosperm during seed development and also in rice suspension cells cultured with abscisic acid. In the anticipation that the mechanisms of starch synthesis are similar between the endosperm and the suspension cells cultured with abscisic acid, expression of genes involved in starch synthesis was evaluated in the suspension cells after abscisic acid treatment. However, it was found that the regulatory mechanism of starch synthesis in the suspension cells cultured with abscisic acid was different from that in developing seeds. Expression analyses of genes involved in oil bodies, which accumulate in the embryo and aleurone layer, and seed storage proteins, which accumulate mainly in the endosperm, showed that the former were activated in the suspension cells cultured with abscisic acid, but the latter were not. Master regulators for embryogenesis, OsVP1 (homologue of AtABI3) and OsLFL1 (homologue of AtFUS3 or AtLFL2), were expressed in the suspension cells at levels comparable to those in the embryo. From these results, it is suggested that interactions between regulators and abscisic acid control the synthesis of phytic acid and oil bodies in the cultured cells and embryo. We suggest that the system of suspension cells cultured with abscisic acid helps to reveal the mechanisms of phytic acid and oil body synthesis in embryo.

Comprehensive Analysis of the Soybean (Glycine max) GmLAX Auxin Transporter Gene Family

PubMed Central

Chai, Chenglin; Wang, Yongqin; Valliyodan, Babu; Nguyen, Henry T.

2016-01-01

The phytohormone auxin plays a critical role in regulation of plant growth and development as well as plant responses to abiotic stresses. This is mainly achieved through its uneven distribution in plant via a polar auxin transport process. Auxin transporters are major players in polar auxin transport. The AUXIN RESISTENT 1/LIKE AUX1 (AUX/LAX) auxin influx carriers belong to the amino acid permease family of proton-driven transporters and function in the uptake of indole-3-acetic acid (IAA). In this study, genome-wide comprehensive analysis of the soybean AUX/LAX (GmLAX) gene family, including phylogenic relationships, chromosome localization, and gene structure, was carried out. A total of 15 GmLAX genes, including seven duplicated gene pairs, were identified in the soybean genome. They were distributed on 10 chromosomes. Despite their higher percentage identities at the protein level, GmLAXs exhibited versatile tissue-specific expression patterns, indicating coordinated functioning during plant growth and development. Most GmLAXs were responsive to drought and dehydration stresses and auxin and abscisic acid (ABA) stimuli, in a tissue- and/or time point- sensitive mode. Several GmLAX members were involved in responding to salt stress. Sequence analysis revealed that promoters of GmLAXs contained different combinations of stress-related cis-regulatory elements. These studies suggest that the soybean GmLAXs were under control of a very complex regulatory network, responding to various internal and external signals. This study helps to identity candidate GmLAXs for further analysis of their roles in soybean development and adaption to adverse environments. PMID:27014306

Shoot-derived abscisic acid promotes root growth.

PubMed

McAdam, Scott A M; Brodribb, Timothy J; Ross, John J

2016-03-01

The phytohormone abscisic acid (ABA) plays a major role in regulating root growth. Most work to date has investigated the influence of root-sourced ABA on root growth during water stress. Here, we tested whether foliage-derived ABA could be transported to the roots, and whether this foliage-derived ABA had an influence on root growth under well-watered conditions. Using both application studies of deuterium-labelled ABA and reciprocal grafting between wild-type and ABA-biosynthetic mutant plants, we show that both ABA levels in the roots and root growth in representative angiosperms are controlled by ABA synthesized in the leaves rather than sourced from the roots. Foliage-derived ABA was found to promote root growth relative to shoot growth but to inhibit the development of lateral roots. Increased root auxin (IAA) levels in plants with ABA-deficient scions suggest that foliage-derived ABA inhibits root growth through the root growth-inhibitor IAA. These results highlight the physiological and morphological importance, beyond the control of stomata, of foliage-derived ABA. The use of foliar ABA as a signal for root growth has important implications for regulating root to shoot growth under normal conditions and suggests that leaf rather than root hydration is the main signal for regulating plant responses to moisture. © 2015 John Wiley & Sons Ltd.

Abscisic Acid and the Photoperiodic Induction of Dormancy in Salix viminalis L.

PubMed

Alvim, R; Saunders, P F; Barros, R S

1979-04-01

A series of growth room experiments was carried out aiming to establish the role of abscisic acid on dormancy of Salix viminalis L. The inhibitor content and abscisic acid levels of extracts from roots, sap, leaves, and apical tissues of willow were measured using biological assay and gas-liquid chromatography.No evidence was obtained that photoperiodically mediated dormancy is associated with changes in abscisic acid levels or beta-inhibitor activity.

WRKY Transcription Factors: Key Components in Abscisic Acid Signaling

DTIC Science & Technology

2011-01-01

Review article WRKY transcription factors : key components in abscisic acid signalling Deena L. Rushton1, Prateek Tripathi1, Roel C. Rabara1, Jun Lin1...May 2011. *Correspondence (Tel +605 688 5749; fax +605 688 5624; email paul.rushton@sdstate.edu) Keywords: abscisic acid, WRKY transcription factor ...seed germination, drought, abiotic stress. Summary WRKY transcription factors (TFs) are key regulators of many plant processes, including the responses

Genome-wide identification, expression analysis of auxin-responsive GH3 family genes in maize (Zea mays L.) under abiotic stresses.

PubMed

Feng, Shangguo; Yue, Runqing; Tao, Sun; Yang, Yanjun; Zhang, Lei; Xu, Mingfeng; Wang, Huizhong; Shen, Chenjia

2015-09-01

Auxin is involved in different aspects of plant growth and development by regulating the expression of auxin-responsive family genes. As one of the three major auxin-responsive families, GH3 (Gretchen Hagen3) genes participate in auxin homeostasis by catalyzing auxin conjugation and bounding free indole-3-acetic acid (IAA) to amino acids. However, how GH3 genes function in responses to abiotic stresses and various hormones in maize is largely unknown. Here, the latest updated maize (Zea mays L.) reference genome sequence was used to characterize and analyze the ZmGH3 family genes from maize. The results showed that 13 ZmGH3 genes were mapped on five maize chromosomes (total 10 chromosomes). Highly diversified gene structures and tissue-specific expression patterns suggested the possibility of function diversification for these genes in response to environmental stresses and hormone stimuli. The expression patterns of ZmGH3 genes are responsive to several abiotic stresses (salt, drought and cadmium) and major stress-related hormones (abscisic acid, salicylic acid and jasmonic acid). Various environmental factors suppress auxin free IAA contents in maize roots suggesting that these abiotic stresses and hormones might alter GH3-mediated auxin levels. The responsiveness of ZmGH3 genes to a wide range of abiotic stresses and stress-related hormones suggested that ZmGH3s are involved in maize tolerance to environmental stresses. © 2014 Institute of Botany, Chinese Academy of Sciences.

Effects of Abscisic Acid and Ethylene on the Gibberellic Acid-Induced Synthesis of α-Amylase by Isolated Wheat Aleurone Layers 1

PubMed Central

Varty, Keith; Arreguín, Barbarín L.; Gómez, Miguel T.; López, Pablo Jaime T.; Gómez, Miguel Angel L.

1983-01-01

Gibberellic acid-induced α-amylase synthesis in wheat aleurone layers (Triticum aestivum L. var Potam S-70) escaped from transcriptional control 30 h after addition of the hormone, as evidenced by the tissue's loss of susceptibility to cordycepin. Abscisic acid inhibited the accumulation of α-amylase activity when added to the tissue during this cordycepin-insensitive phase of enzyme induction. α-Amylase synthesis was not restored by the addition of cordycepin, indicating that the response to abscisic acid was not dependent upon the continuous synthesis of a short lived RNA. When ethylene was added simultaneously or some time after abscisic acid, the accumulation of α-amylase activity was sustained or quickly restored. The loss of susceptibility to cordycepin was completely prevented when aleurone layers were incubated with a combination of gibberellic and abscisic acids from the start of the induction period. This effect of abscisic acid was not reversed by ethylene. On the basis of these observations, it is suggested that abscisic acid inhibits both the transcription and translation of α-amylase mRNA, and that only the latter site of action is susceptible to reversal by ethylene. The rate of incorporation of [methyl-14C]choline into phospholipids was also inhibited by abscisic acid. Ethylene reversed this effect. The effects of abscisic acid and ethylene on phospholipid synthesis were not dependent upon the presence of gibberellic acid. No direct relationship was found between the control of α-amylase synthesis and membrane formation by abscisic acid and ethylene. PMID:16663284

Abscisic Acid and the Photoperiodic Induction of Dormancy in Salix viminalis L 1

PubMed Central

Alvim, Ronald; Saunders, Peter F.; Barros, Raimundo S.

1979-01-01

A series of growth room experiments was carried out aiming to establish the role of abscisic acid on dormancy of Salix viminalis L. The inhibitor content and abscisic acid levels of extracts from roots, sap, leaves, and apical tissues of willow were measured using biological assay and gas-liquid chromatography. No evidence was obtained that photoperiodically mediated dormancy is associated with changes in abscisic acid levels or β-inhibitor activity. PMID:16660810

Integration of Auxin and Salt Signals by the NAC Transcription Factor NTM2 during Seed Germination in Arabidopsis1[W

PubMed Central

Park, Jungmin; Kim, Youn-Sung; Kim, Sang-Gyu; Jung, Jae-Hoon; Woo, Je-Chang; Park, Chung-Mo

2011-01-01

Seed germination is regulated through elaborately interacting signaling networks that integrate diverse environmental cues into hormonal signaling pathways. Roles of gibberellic acid and abscisic acid in germination have been studied extensively using Arabidopsis (Arabidopsis thaliana) mutants having alterations in seed germination. Auxin has also been implicated in seed germination. However, how auxin influences germination is largely unknown. Here, we demonstrate that auxin is linked via the IAA30 gene with a salt signaling cascade mediated by the NAM-ATAF1/2-CUC2 transcription factor NTM2/Arabidopsis NAC domain-containing protein 69 (for NAC with Transmembrane Motif1) during seed germination. Germination of the NTM2-deficient ntm2-1 mutant seeds exhibited enhanced resistance to high salinity. However, the salt resistance disappeared in the ntm2-1 mutant overexpressing the IAA30 gene, which was induced by salt in a NTM2-dependent manner. Auxin exhibited no discernible effects on germination under normal growth conditions. Under high salinity, however, whereas exogenous application of auxin further suppressed the germination of control seeds, the auxin effects were reduced in the ntm2-1 mutant. Consistent with the inhibitory effects of auxin on germination, germination of YUCCA 3-overexpressing plants containing elevated levels of active auxin was more severely influenced by salt. These observations indicate that auxin delays seed germination under high salinity through cross talk with the NTM2-mediated salt signaling in Arabidopsis. PMID:21450938

Isolation of Abscisic Acid from Korean Acacia Honey with Anti-Helicobacter pylori Activity

PubMed Central

Kim, SeGun; Hong, InPyo; Woo, SoonOk; Jang, HyeRi; Pak, SokCheon; Han, SangMi

2017-01-01

Background: Helicobacter pylori (H. pylori) is linked to the development of the majority of peptic ulcers and some types of gastric cancers, and its antibiotic resistance is currently found worldwide. Objective: This study is aimed at evaluating the anti-H. pylori activity of Korean acacia honey and isolating the related active components using organic solvents. Material and Methods: The crude acacia honey was extracted with n-hexane, dichloromethane, ethyl acetate (EtOAc), and n-butanol. The EtOAc extract was subjected to octadecyl-silica chromatography. The extracts and fractions were then examined for anti-H. pylori activity using the agar well diffusion method. The antimicrobial activity of abscisic acid against H. pylori was investigated by determining the minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), and by performing a time-kill assay. Results: Abscisic acid related to the botanical origins of acacia honey from Korea has been analyzed using ultra-performance liquid chromatography. The MICs and MBCs of abscisic acid were 2.7 ± 1.3 and 6.9 ± 1.9 μg/mL, respectively. The bactericidal activity of abscisic acid (at 10.8 μg/mL corresponding to 4 × MIC) killed the organism within 36–72 h. These results suggest that abscisic acid isolated from Korean acacia honey has antibacterial activity against H. pylori. Conclusion: Abscisic acid isolated from Korean acacia honey can be therapeutic and may be further exploited as a potential lead candidate for the development of treatments for H. pylori-induced infections. SUMMARY The crude acacia honey was extracted with n-hexane, dichloromethane, EtOAc, and n-butanolThe EtOAc extract yielded eight fractions and four subfractions were subsequently obtained chromatographicallyAbscisic acid was isolated from one subfractionAll the solvent extracts and fractions showed antibacterial activity against H. pyloriAbscisic acid exhibited antibacterial activity against H. pylori

Isolation of Abscisic Acid from Korean Acacia Honey with Anti-Helicobacter pylori Activity.

PubMed

Kim, SeGun; Hong, InPyo; Woo, SoonOk; Jang, HyeRi; Pak, SokCheon; Han, SangMi

2017-07-01

Helicobacter pylori ( H. pylori ) is linked to the development of the majority of peptic ulcers and some types of gastric cancers, and its antibiotic resistance is currently found worldwide. This study is aimed at evaluating the anti- H. pylori activity of Korean acacia honey and isolating the related active components using organic solvents. The crude acacia honey was extracted with n -hexane, dichloromethane, ethyl acetate (EtOAc), and n -butanol. The EtOAc extract was subjected to octadecyl-silica chromatography. The extracts and fractions were then examined for anti- H. pylori activity using the agar well diffusion method. The antimicrobial activity of abscisic acid against H. pylori was investigated by determining the minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), and by performing a time-kill assay. Abscisic acid related to the botanical origins of acacia honey from Korea has been analyzed using ultra-performance liquid chromatography. The MICs and MBCs of abscisic acid were 2.7 ± 1.3 and 6.9 ± 1.9 μg/mL, respectively. The bactericidal activity of abscisic acid (at 10.8 μg/mL corresponding to 4 × MIC) killed the organism within 36-72 h. These results suggest that abscisic acid isolated from Korean acacia honey has antibacterial activity against H. pylori . Abscisic acid isolated from Korean acacia honey can be therapeutic and may be further exploited as a potential lead candidate for the development of treatments for H. pylori -induced infections. The crude acacia honey was extracted with n -hexane, dichloromethane, EtOAc, and n -butanolThe EtOAc extract yielded eight fractions and four subfractions were subsequently obtained chromatographicallyAbscisic acid was isolated from one subfractionAll the solvent extracts and fractions showed antibacterial activity against H. pylori Abscisic acid exhibited antibacterial activity against H. pylori . Abbreviations used: MeOH: Methanol; EtOAc: Ethyl acetate; TSB: Trypticase

Rational Discovery of (+) (S) Abscisic Acid as a Potential Antifungal Agent: a Repurposing Approach.

PubMed

Khedr, Mohammed A; Massarotti, Alberto; Mohamed, Maged E

2018-06-04

Fungal infections are spreading widely worldwide, and the types of treatment are limited due to the lack of diverse therapeutic agents and their associated side effects and toxicity. The discovery of new antifungal classes is vital and critical. We discovered the antifungal activity of abscisic acid through a rational drug design methodology that included the building of homology models for fungal chorismate mutases and a pharmacophore model derived from a transition state inhibitor. Ligand-based virtual screening resulted in some hits that were filtered using molecular docking and molecular dynamic simulations studies. Both in silico methods and in vitro antifungal assays were used as tools to select and validate the abscisic acid repurposing. Abscisic acid inhibition assays confirmed the inhibitory effect of abscisic acid on chorismate mutase through the inhibition of phenylpyruvate production. The repositioning of abscisic acid, the well-known and naturally occurring plant growth regulator, as a potential antifungal agent because of its suggested action as an inhibitor to several fungal chorismate mutases was the main result of this work.

A Highly Sensitive Method for Quantitative Determination of Abscisic Acid 1

PubMed Central

Michler, Charles H.; Lineberger, R. Daniel; Chism, Grady W.

1986-01-01

An abscisic acid derivative was formed by reaction with pentafluorobenzyl bromide which allowed highly sensitive detection by gas-liquid chromatography with electron capture detection. In comparison to the methyl ester derivative, the pentafluorobenzyl derivative of abscisic acid was four times more sensitive to electron capture detection and was stable at room temperature in the presence of ultraviolet light. Derivatization was rapid and the molecular weight of the new compound was confirmed by gas-liquid chromatography-mass spectrometry. PMID:16665076

Species differences in ligand specificity of auxin-controlled elongation and auxin transport: comparing Zea and Vigna

NASA Technical Reports Server (NTRS)

Zhao, Hu; Hertel, Rainer; Ishikawa, Hideo; Evans, Michael L.

2002-01-01

The plant hormone auxin affects cell elongation in both roots and shoots. In roots, the predominant action of auxin is to inhibit cell elongation while in shoots auxin, at normal physiological levels, stimulates elongation. The question of whether the primary receptor for auxin is the same in roots and shoots has not been resolved. In addition to its action on cell elongation in roots and shoots, auxin is transported in a polar fashion in both organs. Although auxin transport is well characterized in both roots and shoots, there is relatively little information on the connection, if any, between auxin transport and its action on elongation. In particular, it is not clear whether the protein mediating polar auxin movement is separate from the protein mediating auxin action on cell elongation or whether these two processes might be mediated by one and the same receptor. We examined the identity of the auxin growth receptor in roots and shoots by comparing the response of roots and shoots of the grass Zea mays L. and the legume Vigna mungo L. to indole-3-acetic acid, 2-naphthoxyacetic acid, 4,6-dichloroindoleacetic acid, and 4,7-dichloroindoleacetic acid. We also studied whether or not a single protein might mediate both auxin transport and auxin action by comparing the polar transport of indole-3-acetic acid and 2-naphthoxyacetic acid through segments from Vigna hypocotyls and maize coleoptiles. For all of the assays performed (root elongation, shoot elongation, and polar transport) the action and transport of the auxin derivatives was much greater in the dicots than in the grass species. The preservation of ligand specificity between roots and shoots and the parallels in ligand specificity between auxin transport and auxin action on growth are consistent with the hypothesis that the auxin receptor is the same in roots and shoots and that this protein may mediate auxin efflux as well as auxin action in both organ types.

Crystal structure of an indole-3-acetic acid amido synthetase from grapevine involved in auxin homeostasis.

PubMed

Peat, Thomas S; Böttcher, Christine; Newman, Janet; Lucent, Del; Cowieson, Nathan; Davies, Christopher

2012-11-01

Auxins are important for plant growth and development, including the control of fruit ripening. Conjugation to amino acids by indole-3-acetic acid (IAA)-amido synthetases is an important part of auxin homeostasis. The structure of the auxin-conjugating Gretchen Hagen3-1 (GH3-1) enzyme from grapevine (Vitis vinifera), in complex with an inhibitor (adenosine-5'-[2-(1H-indol-3-yl)ethyl]phosphate), is presented. Comparison with a previously published benzoate-conjugating enzyme from Arabidopsis thaliana indicates that grapevine GH3-1 has a highly similar domain structure and also undergoes a large conformational change during catalysis. Mutational analyses and structural comparisons with other proteins have identified residues likely to be involved in acyl group, amino acid, and ATP substrate binding. Vv GH3-1 is a monomer in solution and requires magnesium ions solely for the adenlyation reaction. Modeling of IAA and two synthetic auxins, benzothiazole-2-oxyacetic acid (BTOA) and 1-naphthaleneacetic acid (NAA), into the active site indicates that NAA and BTOA are likely to be poor substrates for this enzyme, confirming previous enzyme kinetic studies. This suggests a reason for the increased effectiveness of NAA and BTOA as auxins in planta and provides a tool for designing new and effective auxins.

Abscisic acid accumulation modulates auxin transport in the root tip to enhance proton secretion for maintaining root growth under moderate water stress.

PubMed

Xu, Weifeng; Jia, Liguo; Shi, Weiming; Liang, Jiansheng; Zhou, Feng; Li, Qianfeng; Zhang, Jianhua

2013-01-01

Maintenance of root growth is essential for plant adaptation to soil drying. Here, we tested the hypothesis that auxin transport is involved in mediating ABA's modulation by activating proton secretion in the root tip to maintain root growth under moderate water stress. Rice and Arabidopsis plants were raised under a hydroponic system and subjected to moderate water stress (-0.47 MPa) with polyethylene glycol (PEG). ABA accumulation, auxin transport and plasma membrane H(+)-ATPase activity at the root tip were monitored in addition to the primary root elongation and root hair density. We found that moderate water stress increases ABA accumulation and auxin transport in the root apex. Additionally, ABA modulation is involved in the regulation of auxin transport in the root tip. The transported auxin activates the plasma membrane H(+)-ATPase to release more protons along the root tip in its adaption to moderate water stress. The proton secretion in the root tip is essential in maintaining or promoting primary root elongation and root hair development under moderate water stress. These results suggest that ABA accumulation modulates auxin transport in the root tip, which enhances proton secretion for maintaining root growth under moderate water stress. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

[Cloning and bioinformatics analysis of abscisic acid 8'-hydroxylase from Pseudostellariae Radix].

PubMed

Li, Jun; Long, Deng-Kai; Zhou, Tao; Ding, Ling; Zheng, Wei; Jiang, Wei-Ke

2016-07-01

Abscisic acid 8'-hydroxylase was one of key enzymes genes in the metabolism of abscisic acid (ABA). Seven menbers of abscisic acid 8'-hydroxylase were identified from Pseudostellaria heterophylla transcriptome sequencing results by using sequence homology. The expression profiles of these genes were analyzed by transcriptome data. The coding sequence of ABA8ox1 was cloned and analyzed by informational technology. The full-length cDNA of ABA8ox1 was 1 401 bp,with 480 encoded amino acids. The predicated isoelectric point (pI) and relative molecular mass (MW) were 8.55 and 53 kDa,respectively. Transmembrane structure analysis showed that there were 21 amino acids in-side and 445 amino acids out-side. High level of transcripts can detect in bark of root and fibrous root. Multi-alignment and phylogenetic analysis both show that ABA8ox1 had a high similarity with the CYP707As from other plants,especially with AtCYP707A1 and AtCYP707A3 in Arabidopsis thaliana. These results lay a foundation for molecular mechanism of tuberous root expanding and response to adversity stress. Copyright© by the Chinese Pharmaceutical Association.

Involvement of abscisic acid in correlative control of flower abscission in soybean

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yarrow, G.L.

1985-01-01

Studies were carried out in three parts: (1) analysis of endogenous abscisic acid (ABA) in abscising and non-abscising flowers, (2) partitioning of radio-labelled ABA and photoassimilates within the soybean raceme, and (3) shading experiments, wherein endogenous levels, metabolism and partitioning of ABA were determined. Endogenous concentrations of ABA failed to show any consistent relationship to abscission of soybean flowers. Partitioning of radiolabelled ABA and photoassimilates displayed consistently higher sink strengths (% DPM) for both /sup 3/H-ABA and /sup 14/C-photoassimilates for non-abscising flowers than for abscising flowers within control racemes. Shading flowers with aluminum foil, 48 hrs prior to sampling, resultedmore » in lowered endogenous ABA concentrations at 12, 17 and 22 days after anthesis (DAA), but not at 0 or 4 DAA. No differences were found in the catabolism of /sup 3/H-ABA between shaded (abscising) and non-shaded (non-abscising) flowers. Reduced partitioning of ABA and photoassimilates to shaded flowers resulted when shades were applied at 0, 4, 12, and 17 DAA, but not at 22 DAA.« less

Suppression of asymmetric acid efflux and gravitropism in maize roots treated with auxin transport inhibitors of sodium orthovanadate

NASA Technical Reports Server (NTRS)

Mulkey, T. J.; Evans, M. L.

1982-01-01

In gravitropically stimulated roots of maize (Zea mays L., hybrid WF9 x 38MS), there is more acid efflux on the rapidly growing upper side than on the slowly growing lower side. In light of the Cholodny/Went hypothesis of gravitropism which states that gravitropic curvature results from lateral redistribution of auxin, the effects of auxin transport inhibitors on the development of acid efflux asymmetry and curvature in gravistimulated roots were examined. All the transport inhibitors tested prevented both gravitropism and the development of asymmetric acid efflux in gravistimulated roots. The results indicate that auxin redistribution may cause the asymmetry of acid efflux, a finding consistent with the Cholodny/Went hypothesis of gravitropism. As further evidence that auxin-induced acid efflux asymmetry may mediate gravitropic curvature, sodium orthovanadate, an inhibitor of auxin-induced H+ efflux was found to prevent both gravitropism and the development of asymmetric acid efflux in gravistimulated roots.

Dynamic regulation of auxin oxidase and conjugating enzymes AtDAO1 and GH3 modulates auxin homeostasis

PubMed Central

Mellor, Nathan; Band, Leah R.; Pěnčík, Aleš; Rashed, Afaf; Holman, Tara; Wilson, Michael H.; Voß, Ute; Bishopp, Anthony; King, John R.

2016-01-01

The hormone auxin is a key regulator of plant growth and development, and great progress has been made understanding auxin transport and signaling. Here, we show that auxin metabolism and homeostasis are also regulated in a complex manner. The principal auxin degradation pathways in Arabidopsis include oxidation by Arabidopsis thaliana gene DIOXYGENASE FOR AUXIN OXIDATION 1/2 (AtDAO1/2) and conjugation by Gretchen Hagen3s (GH3s). Metabolic profiling of dao1-1 root tissues revealed a 50% decrease in the oxidation product 2-oxoindole-3-acetic acid (oxIAA) and increases in the conjugated forms indole-3-acetic acid aspartic acid (IAA-Asp) and indole-3-acetic acid glutamic acid (IAA-Glu) of 438- and 240-fold, respectively, whereas auxin remains close to the WT. By fitting parameter values to a mathematical model of these metabolic pathways, we show that, in addition to reduced oxidation, both auxin biosynthesis and conjugation are increased in dao1-1. Transcripts of AtDAO1 and GH3 genes increase in response to auxin over different timescales and concentration ranges. Including this regulation of AtDAO1 and GH3 in an extended model reveals that auxin oxidation is more important for auxin homoeostasis at lower hormone concentrations, whereas auxin conjugation is most significant at high auxin levels. Finally, embedding our homeostasis model in a multicellular simulation to assess the spatial effect of the dao1-1 mutant shows that auxin increases in outer root tissues in agreement with the dao1-1 mutant root hair phenotype. We conclude that auxin homeostasis is dependent on AtDAO1, acting in concert with GH3, to maintain auxin at optimal levels for plant growth and development. PMID:27651495

Dynamic regulation of auxin oxidase and conjugating enzymes AtDAO1 and GH3 modulates auxin homeostasis.

PubMed

Mellor, Nathan; Band, Leah R; Pěnčík, Aleš; Novák, Ondřej; Rashed, Afaf; Holman, Tara; Wilson, Michael H; Voß, Ute; Bishopp, Anthony; King, John R; Ljung, Karin; Bennett, Malcolm J; Owen, Markus R

2016-09-27

The hormone auxin is a key regulator of plant growth and development, and great progress has been made understanding auxin transport and signaling. Here, we show that auxin metabolism and homeostasis are also regulated in a complex manner. The principal auxin degradation pathways in Arabidopsis include oxidation by Arabidopsis thaliana gene DIOXYGENASE FOR AUXIN OXIDATION 1/2 (AtDAO1/2) and conjugation by Gretchen Hagen3s (GH3s). Metabolic profiling of dao1-1 root tissues revealed a 50% decrease in the oxidation product 2-oxoindole-3-acetic acid (oxIAA) and increases in the conjugated forms indole-3-acetic acid aspartic acid (IAA-Asp) and indole-3-acetic acid glutamic acid (IAA-Glu) of 438- and 240-fold, respectively, whereas auxin remains close to the WT. By fitting parameter values to a mathematical model of these metabolic pathways, we show that, in addition to reduced oxidation, both auxin biosynthesis and conjugation are increased in dao1-1 Transcripts of AtDAO1 and GH3 genes increase in response to auxin over different timescales and concentration ranges. Including this regulation of AtDAO1 and GH3 in an extended model reveals that auxin oxidation is more important for auxin homoeostasis at lower hormone concentrations, whereas auxin conjugation is most significant at high auxin levels. Finally, embedding our homeostasis model in a multicellular simulation to assess the spatial effect of the dao1-1 mutant shows that auxin increases in outer root tissues in agreement with the dao1-1 mutant root hair phenotype. We conclude that auxin homeostasis is dependent on AtDAO1, acting in concert with GH3, to maintain auxin at optimal levels for plant growth and development.

Glucose and auxin signaling interaction in controlling Arabidopsis thaliana seedlings root growth and development.

PubMed

Mishra, Bhuwaneshwar S; Singh, Manjul; Aggrawal, Priyanka; Laxmi, Ashverya

2009-01-01

Plant root growth and development is highly plastic and can adapt to many environmental conditions. Sugar signaling has been shown to affect root growth and development by interacting with phytohormones such as gibberellins, cytokinin and abscisic acid. Auxin signaling and transport has been earlier shown to be controlling plant root length, number of lateral roots, root hair and root growth direction. Increasing concentration of glucose not only controls root length, root hair and number of lateral roots but can also modulate root growth direction. Since root growth and development is also controlled by auxin, whole genome transcript profiling was done to find out the extent of interaction between glucose and auxin response pathways. Glucose alone could transcriptionally regulate 376 (62%) genes out of 604 genes affected by IAA. Presence of glucose could also modulate the extent of regulation 2 fold or more of almost 63% genes induced or repressed by IAA. Interestingly, glucose could affect induction or repression of IAA affected genes (35%) even if glucose alone had no significant effect on the transcription of these genes itself. Glucose could affect auxin biosynthetic YUCCA genes family members, auxin transporter PIN proteins, receptor TIR1 and members of a number of gene families including AUX/IAA, GH3 and SAUR involved in auxin signaling. Arabidopsis auxin receptor tir1 and response mutants, axr2, axr3 and slr1 not only display a defect in glucose induced change in root length, root hair elongation and lateral root production but also accentuate glucose induced increase in root growth randomization from vertical suggesting glucose effects on plant root growth and development are mediated by auxin signaling components. Our findings implicate an important role of the glucose interacting with auxin signaling and transport machinery to control seedling root growth and development in changing nutrient conditions.

Circadian changes in endogenous concentrations of indole-3-acetic acid, melatonin, serotonin, abscisic acid and jasmonic acid in Characeae (Chara australis Brown).

PubMed

Beilby, Mary J; Turi, Christina E; Baker, Teesha C; Tymm, Fiona Jm; Murch, Susan J

2015-01-01

Giant-celled Characeae (Chara australis Brown), grown for 4 months on 12/12 hr day/night cycle and summer/autumn temperatures, exhibited distinct concentration maxima in auxin (indole-3-acetic acid; IAA), melatonin and serotonin about 4 hr after subjective daybreak. These concentration peaks persisted after 3 day pretreatment in continuous darkness: confirming a circadian rhythm, rather than a response to "light on." The plants pretreated for 3 d in continuous light exhibited several large IAA concentration maxima throughout the 24 hr. The melatonin and serotonin concentrations decreased and were less synchronized with IAA. Chara plants grown on 9/15 hr day/night cycle for 4 months and winter/spring temperatures contained much smaller concentrations of IAA, melatonin and serotonin. The IAA concentration maxima were observed in subjective dark phase. Serotonin concentration peaks were weakly correlated with those of IAA. Melatonin concentration was low and mostly independent of circadian cycle. The "dark" IAA concentration peaks persisted in plants treated for 3 d in the dark. The plants pretreated for 3 d in the light again developed more IAA concentration peaks. In this case the concentration maxima in melatonin and serotonin became more synchronous with those in IAA. The abscisic acid (ABA) and jasmonic acid (JA) concentrations were also measured in plants on winter regime. The ABA concentration did not exhibit circadian pattern, while JA concentration peaks were out of phase with those of IAA. The data are discussed in terms of crosstalk between metabolic pathways.

Phytohormone abscisic acid elicits antinociceptive effects in rats through the activation of opioid and peroxisome proliferator-activated receptors β/δ.

PubMed

Mollashahi, Mahtab; Abbasnejad, Mehdi; Esmaeili-Mahani, Saeed

2018-08-05

The phytohormone abscisic acid exists in animal tissues particularly in the brain. However, its neurophysiological effects have not yet been fully clarified. This study was designed to evaluate the possible antinociceptive effects of abscisic acid on animal models of pain and determine its possible signaling mechanism. Tail-flick, hot-plate and formalin tests were used to assess the nociceptive threshold. All experiments were carried out on male Wistar rats. To determine the role of Peroxisome proliferator-activated receptor β/δ (PPARβ/δ) and opioid receptors on the induction of abscisic acid antinociception, specific antagonists were injected 15 min before abscisic acid. The data showed that abscisic acid (5, 10 and 15 µg/rat, i.c.v.) significantly decreased pain responses in formalin test. In addition, it could also produce dose-dependent antinociceptive effect in tail-flick and hot-plate tests. Administration of PPARβ/δ antagonist (GSK0660, 80 nM, i.c.v.) significantly attenuated the antinociceptive effect of abscisic acid in all tests. The antinociceptive effects of abscisic acid were completely inhibited by naloxone (6 µg, i.c.v.) during the time course of tail-flick and hot-plate tests. The results indicated that the central injection of abscisic acid has potent pain-relieving property which is mediated partly via the PPAR β/δ and opioid signaling. Copyright © 2018 Elsevier B.V. All rights reserved.

Transport of the two natural auxins, indole-3-butyric acid and indole-3-acetic acid, in Arabidopsis

NASA Technical Reports Server (NTRS)

Rashotte, Aaron M.; Poupart, Julie; Waddell, Candace S.; Muday, Gloria K.; Brown, C. S. (Principal Investigator)

2003-01-01

Polar transport of the natural auxin indole-3-acetic acid (IAA) is important in a number of plant developmental processes. However, few studies have investigated the polar transport of other endogenous auxins, such as indole-3-butyric acid (IBA), in Arabidopsis. This study details the similarities and differences between IBA and IAA transport in several tissues of Arabidopsis. In the inflorescence axis, no significant IBA movement was detected, whereas IAA is transported in a basipetal direction from the meristem tip. In young seedlings, both IBA and IAA were transported only in a basipetal direction in the hypocotyl. In roots, both auxins moved in two distinct polarities and in specific tissues. The kinetics of IBA and IAA transport appear similar, with transport rates of 8 to 10 mm per hour. In addition, IBA transport, like IAA transport, is saturable at high concentrations of auxin, suggesting that IBA transport is protein mediated. Interestingly, IAA efflux inhibitors and mutations in genes encoding putative IAA transport proteins reduce IAA transport but do not alter IBA movement, suggesting that different auxin transport protein complexes are likely to mediate IBA and IAA transport. Finally, the physiological effects of IBA and IAA on hypocotyl elongation under several light conditions were examined and analyzed in the context of the differences in IBA and IAA transport. Together, these results present a detailed picture of IBA transport and provide the basis for a better understanding of the transport of these two endogenous auxins.

Sinapic acid or its derivatives interfere with abscisic acid homeostasis during Arabidopsis thaliana seed germination.

PubMed

Bi, Baodi; Tang, Jingliang; Han, Shuang; Guo, Jinggong; Miao, Yuchen

2017-06-06

Sinapic acid and its esters have broad functions in different stages of seed germination and plant development and are thought to play a role in protecting against ultraviolet irradiation. To better understand the interactions between sinapic acid esters and seed germination processes in response to various stresses, we analyzed the role of the plant hormone abscisic acid (ABA) in the regulation of sinapic acid esters involved in seed germination and early seedling growth. We found that exogenous sinapic acid promotes seed germination in a dose-dependent manner in Arabidopsis thaliana. High-performance liquid chromatography mass spectrometry analysis showed that exogenous sinapic acid increased the sinapoylcholine content of imbibed seeds. Furthermore, sinapic acid affected ABA catabolism, resulting in reduced ABA levels and increased levels of the ABA-glucose ester. Using mutants deficient in the synthesis of sinapate esters, we showed that the germination of mutant sinapoylglucose accumulator 2 (sng2) and bright trichomes 1 (brt1) seeds was more sensitive to ABA than the wild-type. Moreover, Arabidopsis mutants deficient in either abscisic acid deficient 2 (ABA2) or abscisic acid insensitive 3 (ABI3) displayed increased expression of the sinapoylglucose:choline sinapoyltransferase (SCT) and sinapoylcholine esterase (SCE) genes with sinapic acid treatment. This treatment also affected the accumulation of sinapoylcholine and free choline during seed germination. We demonstrated that sinapoylcholine, which constitutes the major phenolic component in seeds among various minor sinapate esters, affected ABA homeostasis during seed germination and early seedling growth in Arabidopsis. Our findings provide insights into the role of sinapic acid and its esters in regulating ABA-mediated inhibition of Arabidopsis seed germination in response to drought stress.

Cross-talk between abscisic acid-dependent and abscisic acid-independent pathways during abiotic stress.

PubMed

Roychoudhury, Aryadeep; Paul, Saikat; Basu, Supratim

2013-07-01

Salinity, drought and low temperature are the common forms of abiotic stress encountered by land plants. To cope with these adverse environmental factors, plants execute several physiological and metabolic responses. Both osmotic stress (elicited by water deficit or high salt) and cold stress increase the endogenous level of the phytohormone abscisic acid (ABA). ABA-dependent stomatal closure to reduce water loss is associated with small signaling molecules like nitric oxide, reactive oxygen species and cytosolic free calcium, and mediated by rapidly altering ion fluxes in guard cells. ABA also triggers the expression of osmotic stress-responsive (OR) genes, which usually contain single/multiple copies of cis-acting sequence called abscisic acid-responsive element (ABRE) in their upstream regions, mostly recognized by the basic leucine zipper-transcription factors (TFs), namely, ABA-responsive element-binding protein/ABA-binding factor. Another conserved sequence called the dehydration-responsive element (DRE)/C-repeat, responding to cold or osmotic stress, but not to ABA, occurs in some OR promoters, to which the DRE-binding protein/C-repeat-binding factor binds. In contrast, there are genes or TFs containing both DRE/CRT and ABRE, which can integrate input stimuli from salinity, drought, cold and ABA signaling pathways, thereby enabling cross-tolerance to multiple stresses. A strong candidate that mediates such cross-talk is calcium, which serves as a common second messenger for abiotic stress conditions and ABA. The present review highlights the involvement of both ABA-dependent and ABA-independent signaling components and their interaction or convergence in activating the stress genes. We restrict our discussion to salinity, drought and cold stress.

P-chlorophenoxyisobutyric acid impairs auxin response for gravity-regulated peg formation in cucumber (Cucumis sativus) seedlings.

PubMed

Shimizu, Minobu; Miyazawa, Yutaka; Fujii, Nobuharu; Takahashi, Hideyuki

2008-01-01

Cucumber (Cucumis sativus L.) seedlings form a specialized protuberance, the peg, on the transition zone between the hypocotyl and the root. When cucumber seeds germinate in a horizontal position, the seedlings develop a peg on the lower side of the transition zone. To verify the role of auxin action in peg formation, we examined the effect of the anti-auxin, p-chlorophenoxyisobutyric acid (PCIB), on peg formation and mRNA accumulation of auxin-regulated genes. Application of PCIB to cucumber seedlings inhibited peg formation. The application of indole-3-acetic acid (IAA) competed with PCIB and induced peg formation. Furthermore, application of PCIB decreased auxin-inducible CsIAA1 mRNA and increased auxin-repressible CsGRP1 mRNA in the lower side of the transition zone. The differential accumulation of CsIAA1 and CsGRP1 mRNAs in the transition zone of cucumber seedlings grown in a horizontal position was smaller in the PCIB-treated seedlings. These results demonstrate that endogenous auxin redistributes and induces the differential expression of auxin-regulated genes, and ultimately results in the suppression or induction of peg formation in the gravistimulated transition zone of cucumber seedlings.

Arabidopsis thaliana GH3.5 acyl acid amido synthetase mediates metabolic crosstalk in auxin and salicylic acid homeostasis

PubMed Central

Westfall, Corey S.; Sherp, Ashley M.; Zubieta, Chloe; Alvarez, Sophie; Schraft, Evelyn; Marcellin, Romain; Ramirez, Loren; Jez, Joseph M.

2016-01-01

In Arabidopsis thaliana, the acyl acid amido synthetase Gretchen Hagen 3.5 (AtGH3.5) conjugates both indole-3-acetic acid (IAA) and salicylic acid (SA) to modulate auxin and pathogen response pathways. To understand the molecular basis for the activity of AtGH3.5, we determined the X-ray crystal structure of the enzyme in complex with IAA and AMP. Biochemical analysis demonstrates that the substrate preference of AtGH3.5 is wider than originally described and includes the natural auxin phenylacetic acid (PAA) and the potential SA precursor benzoic acid (BA). Residues that determine IAA versus BA substrate preference were identified. The dual functionality of AtGH3.5 is unique to this enzyme although multiple IAA-conjugating GH3 proteins share nearly identical acyl acid binding sites. In planta analysis of IAA, PAA, SA, and BA and their respective aspartyl conjugates were determined in wild-type and overexpressing lines of A. thaliana. This study suggests that AtGH3.5 conjugates auxins (i.e., IAA and PAA) and benzoates (i.e., SA and BA) to mediate crosstalk between different metabolic pathways, broadening the potential roles for GH3 acyl acid amido synthetases in plants. PMID:27849615

Biosynthesis of the Halogenated Auxin, 4-Chloroindole-3-Acetic Acid1[W][OA

PubMed Central

Tivendale, Nathan D.; Davidson, Sandra E.; Davies, Noel W.; Smith, Jason A.; Dalmais, Marion; Bendahmane, Abdelhafid I.; Quittenden, Laura J.; Sutton, Lily; Bala, Raj K.; Le Signor, Christine; Thompson, Richard; Horne, James; Reid, James B.; Ross, John J.

2012-01-01

Seeds of several agriculturally important legumes are rich sources of the only halogenated plant hormone, 4-chloroindole-3-acetic acid. However, the biosynthesis of this auxin is poorly understood. Here, we show that in pea (Pisum sativum) seeds, 4-chloroindole-3-acetic acid is synthesized via the novel intermediate 4-chloroindole-3-pyruvic acid, which is produced from 4-chlorotryptophan by two aminotransferases, TRYPTOPHAN AMINOTRANSFERASE RELATED1 and TRYPTOPHAN AMINOTRANSFERASE RELATED2. We characterize a tar2 mutant, obtained by Targeting Induced Local Lesions in Genomes, the seeds of which contain dramatically reduced 4-chloroindole-3-acetic acid levels as they mature. We also show that the widespread auxin, indole-3-acetic acid, is synthesized by a parallel pathway in pea. PMID:22573801

Auxin-Dependent Cell Division and Cell Elongation. 1-Naphthaleneacetic Acid and 2,4-Dichlorophenoxyacetic Acid Activate Different Pathways1

PubMed Central

Campanoni, Prisca; Nick, Peter

2005-01-01

During exponential phase, the tobacco (Nicotiana tabacum) cell line cv Virginia Bright Italia-0 divides axially to produce linear cell files of distinct polarity. This axial division is controlled by exogenous auxin. We used exponential tobacco cv Virginia Bright Italia-0 cells to dissect early auxin signaling, with cell division and cell elongation as physiological markers. Experiments with 1-naphthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D) demonstrated that these 2 auxin species affect cell division and cell elongation differentially; NAA stimulates cell elongation at concentrations that are much lower than those required to stimulate cell division. In contrast, 2,4-D promotes cell division but not cell elongation. Pertussis toxin, a blocker of heterotrimeric G-proteins, inhibits the stimulation of cell division by 2,4-D but does not affect cell elongation. Aluminum tetrafluoride, an activator of the G-proteins, can induce cell division at NAA concentrations that are not permissive for division and even in the absence of any exogenous auxin. The data are discussed in a model where the two different auxins activate two different pathways for the control of cell division and cell elongation. PMID:15734918

Circadian changes in endogenous concentrations of indole-3-acetic acid, melatonin, serotonin, abscisic acid and jasmonic acid in Characeae (Chara australis Brown)

PubMed Central

Beilby, Mary J; Turi, Christina E; Baker, Teesha C; Tymm, Fiona JM; Murch, Susan J

2015-01-01

Giant-celled Characeae (Chara australis Brown), grown for 4 months on 12/12 hr day/night cycle and summer/autumn temperatures, exhibited distinct concentration maxima in auxin (indole-3-acetic acid; IAA), melatonin and serotonin about 4 hr after subjective daybreak. These concentration peaks persisted after 3 day pretreatment in continuous darkness: confirming a circadian rhythm, rather than a response to “light on.” The plants pretreated for 3 d in continuous light exhibited several large IAA concentration maxima throughout the 24 hr. The melatonin and serotonin concentrations decreased and were less synchronized with IAA. Chara plants grown on 9/15 hr day/night cycle for 4 months and winter/spring temperatures contained much smaller concentrations of IAA, melatonin and serotonin. The IAA concentration maxima were observed in subjective dark phase. Serotonin concentration peaks were weakly correlated with those of IAA. Melatonin concentration was low and mostly independent of circadian cycle. The “dark” IAA concentration peaks persisted in plants treated for 3 d in the dark. The plants pretreated for 3 d in the light again developed more IAA concentration peaks. In this case the concentration maxima in melatonin and serotonin became more synchronous with those in IAA. The abscisic acid (ABA) and jasmonic acid (JA) concentrations were also measured in plants on winter regime. The ABA concentration did not exhibit circadian pattern, while JA concentration peaks were out of phase with those of IAA. The data are discussed in terms of crosstalk between metabolic pathways. PMID:26382914

The Acid Growth Theory of auxin-induced cell elongation is alive and well

NASA Technical Reports Server (NTRS)

Rayle, D. L.; Cleland, R. E.

1992-01-01

Plant cells elongate irreversibly only when load-bearing bonds in the walls are cleaved. Auxin causes the elongation of stem and coleoptile cells by promoting wall loosening via cleavage of these bonds. This process may be coupled with the intercalation of new cell wall polymers. Because the primary site of auxin action appears to be the plasma membrane or some intracellular site, and wall loosening is extracellular, there must be communication between the protoplast and the wall. Some "wall-loosening factor" must be exported from auxin-impacted cells, which sets into motion the wall loosening events. About 20 years ago, it was suggested that the wall-loosening factor is hydrogen ions. This idea and subsequent supporting data gave rise to the Acid Growth Theory, which states that when exposed to auxin, susceptible cells excrete protons into the wall (apoplast) at an enhanced rate, resulting in a decrease in apoplastic pH. The lowered wall pH then activates wall-loosening processes, the precise nature of which is unknown. Because exogenous acid causes a transient (1-4 h) increase in growth rate, auxin must also mediate events in addition to wall acidification for growth to continue for an extended period of time. These events may include osmoregulation, cell wall synthesis, and maintenance of the capacity of walls to undergo acid-induced wall loosening. At present, we do not know if these phenomena are tightly coupled to wall acidification or if they are the products of multiple independent signal transduction pathways.

Abscisic acid regulation of DC8, a carrot embryonic gene. [Daucus carota

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hatzopoulos, P.; Fong, F.; Sung, Z.R.

1990-10-01

DC8 encodes a hydrophylic 66 kilodalton protein located in the cytoplasm and cell walls of carrot (Daucus carota) embryo and endosperm. During somatic embryogenesis, the levels of DC8 mRNA and protein begin to increase 5 days after removal of auxin. To study the role of abscisic acid (ABA) in the regulation of DC8 gene, fluridone, 1-methyl-3-phenyl,-5(3-trifluoro-methyl-phenyl)-4(1H)-pyridinone, was used to inhibit the endogenous ABA content of the embryos. Fluridone, 50 micrograms per milliliter, effectively inhibits the accumulation of ABA in globular-tage embryos. Western and Northern analysis show that when fluridone is added to the culture medium DC8 protein and mRNA decreasemore » to very low levels. ABA added to fluridone supplemented culture media restores the DC8 protein and mRNA to control levels. Globular-stage embryos contain 0.9 to 1.4 {times} 10{sup {minus}7} molar ABA while 10{sup {minus}6} molar exogenously supplied ABA is the optimal concentration for restoration of DC8 protein accumulation in fluridone-treated embryos. The mRNA level is increased after 15 minutes of ABA addition and reaches maximal levels by 60 minutes. Evidence is presented that, unlike other ABA-regulated genes, DC8 is not induced in nonembryonic tissues via desiccation nor addition of ABA.« less

Abscisic Acid Content and Stomatal Sensitivity to CO(2) in Leaves of Xanthium strumarium L. after Pretreatments in Warm and Cold Growth Chambers.

PubMed

Raschke, K; Pierce, M; Popiela, C C

1976-01-01

The degree of stomatal sensitivity to CO(2) was positively correlated with the content of abscisic acid of leaves of Xanthium strumarium grown in a greenhouse and then transferred for 24 hours or more to a cold (5/10 C, night/day) or a warm growth chamber (20/23 C). This correlation did not exist in plants kept in the greehouse continuously (high abscisic acid, no CO(2) sensitivity), nor in plants transferred from the cold to the warm chamber (low abscisic acid, high CO(2) sensitivity). The abscisic acid content of leaves was correlated with water content only within narrow limits, if at all. At equal water contents, prechilled leaves contained more abscisic acid than leaves of plants pretreated in the warm chamber. There appear to be at least two compartments for abscisic acid in the leaf.

Profiling Abscisic Acid-Induced Changes in Fatty Acid Composition in Mosses.

PubMed

Shinde, Suhas; Devaiah, Shivakumar; Kilaru, Aruna

2017-01-01

In plants, change in lipid composition is a common response to various abiotic stresses. Lipid constituents of bryophytes are of particular interest as they differ from that of flowering plants. Unlike higher plants, mosses have high content of very long-chain polyunsaturated fatty acids. Such lipids are considered to be important for survival of nonvascular plants. Here, using abscisic acid (ABA )-induced changes in lipid composition in Physcomitrella patens as an example, a protocol for total lipid extraction and quantification by gas chromatography (GC) coupled with flame ionization detector (FID) is described.

Auxin synthesis gene tms1 driven by tuber-specific promoter alters hormonal status of transgenic potato plants and their responses to exogenous phytohormones.

PubMed

Kolachevskaya, Oksana O; Sergeeva, Lidiya I; Floková, Kristyna; Getman, Irina A; Lomin, Sergey N; Alekseeva, Valeriya V; Rukavtsova, Elena B; Buryanov, Yaroslav I; Romanov, Georgy A

2017-03-01

Ectopic auxin overproduction in transgenic potato leads to enhanced productivity accompanied with concerted and occasional changes in hormonal status, and causing altered response of transformants to exogenous auxin or cytokinin. Previously, we generated potato transformants expressing Agrobacterium-derived auxin synthesis gene tms1 driven by tuber-specific patatin gene promoter (B33-promoter). Here, we studied the endogenous hormonal status and the response to exogenous phytohormones in tms1 transformants cultured in vitro. Adding indole-3-acetic acid (IAA) or kinetin to culture medium affected differently tuberization of tms1-transformed and control plants, depending also on sucrose content in the medium. Exogenous phytohormones ceased to stimulate the tuber initiation in transformants at high (5-8%) sucrose concentration, while in control plants the stimulation was observed in all experimental settings. Furthermore, exogenous auxin partly inhibited the tuber initiation, and exogenous cytokinin reduced the average tuber weight in most transformants at high sucrose content. The elevated auxin level in tubers of the transformants was accompanied with a decrease in content of cytokinin bases and their ribosides in tubers and most shoots. No concerted changes in contents of abscisic, jasmonic, salicylic acids and gibberellins in tubers were detected. The data on hormonal status indicated that the enhanced productivity of tms1 transformants was due to auxin and not mediated by other phytohormones. In addition, exogenous cytokinin was shown to upregulate the expression of genes encoding orthologs of auxin receptors. Overall, the results showed that tms1 expression and local increase in IAA level in transformants affect both the balance of endogenous cytokinins and the dynamics of tuberization in response to exogenous hormones (auxin, cytokinin), the latter reaction depending also on the carbohydrate supply. We introduce a basic model for the hormonal network

Enhanced growth and fatty acid accumulation of microalgae Scenedesmus sp. LX1 by two types of auxin.

PubMed

Dao, Guo-Hua; Wu, Guang-Xue; Wang, Xiao-Xiong; Zhuang, Lin-Lan; Zhang, Tian-Yuan; Hu, Hong-Ying

2018-01-01

Microalgae are potential candidates for the production of valuable products, such as renewable biodiesel, health products and pigments. However, low biomass productivity has restricted their large-scale applications. In this study, the effects of two auxins (one natural type of indole-3-acetic acid (IAA) and the other synthetic type of 2,4-dichlorophenoxyacetic acid (2,4-D)) on the growth and fatty acid methyl esters (FAMEs) production of a freshwater microalgae Scenedesmus sp. LX1 were investigated. Both auxins showed a "low dosage-promotion and high dosage-inhibition" effect on the growth and FAMEs accumulation. The optimum dosage of IAA and 2,4-D were 1mgL -1 and 0.1mgL -1 , respectively. Moreover, the IAA could increase the monounsaturated fatty acid content. The auxins may promote the growth by enhancing the photosynthetic activity through increasing chlorophyll contents. Therefore, auxin significantly enhanced microalgal growth and FAMEs accumulation, and has a potential for application in developing efficient microalgal cultivation. Copyright © 2017. Published by Elsevier Ltd.

Abscisic Acid Metabolism in Salt-Stressed Cells of Dunaliella salina

PubMed Central

Cowan, A. Keith; Rose, Peter D.

1991-01-01

The interrelationship between abscisic acid (ABA) production and β-carotene accumulation was investigated in salt-stressed cells of the halotolerant green alga Dunaliella salina var bardawil. Cells were supplied with either R-[2-14C]mevalonolactone or [14C] sodium bicarbonate for 20 hours and then exposed to increased salinity (1.5 to 3.0 molar NaCl) for various lengths of time. Incorporation of label into abscisic acid and phaseic acid and the distribution of [14C]ABA between the cells and incubation media were monitored. [14C]ABA and [14C]phaseic acid were identified as products of both R-[2-14C]mevalonolactone and [14C]sodium bicarbonate metabolism. ABA metabolism was enhanced by hypersalinity stress. Actinomycin D, chloramphenicol, and cycloheximide abolished the stress-induced production of ABA, suggesting a role for gene activation in the process. Kinetic analysis of both ABA and β-carotene production demonstrated two stages of accelerated β-carotene production. In addition, ABA levels increased rapidly, and this increase occurred coincident with the early period of accelerated β-carotene production. A possible role for ABA as a regulator of carotenogenesis in cells of D. salina is therefore discussed. PMID:16668469

Synthesis, photostability and bioactivity of 2,3-cyclopropanated abscisic acid.

PubMed

Wenjian, Liu; Xiaoqiang, Han; Yumei, Xiao; Jinlong, Fan; Yuanzhi, Zhang; Huizhe, Lu; Mingan, Wang; Zhaohai, Qin

2013-12-01

The plant hormone abscisic acid (ABA) plays a central role in the regulation of plant development and adaptation to environmental stress. The isomerization of ABA to the biologically inactive 2E-isomer by light considerably limits its applications in agricultural fields. To overcome this shortcoming, an ABA analogue, cis-2,3-cyclopropanated ABA, was synthesized, and its photostability and biological activities were investigated. This compound showed high photostability under UV light exposure, which was 4-fold higher than that of (±)-ABA. cis-2,3-cyclopropanated ABA exhibited high ABA-like activity, including the ability to effectively inhibit seed germination, seedling growth and stomatal movements of Arabidopsis. In some cases, its bioactivity approaches that of (±)-ABA. trans-2,3-cyclopropanated abscisic acid was also prepared, an isomer that was more photostable but which showed weak ABA-like activity. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

Abscisic Acid Content and Stomatal Sensitivity to CO2 in Leaves of Xanthium strumarium L. after Pretreatments in Warm and Cold Growth Chambers 1

PubMed Central

Raschke, Klaus; Pierce, Margaret; Popiela, Chu Chen

1976-01-01

The degree of stomatal sensitivity to CO2 was positively correlated with the content of abscisic acid of leaves of Xanthium strumarium grown in a greenhouse and then transferred for 24 hours or more to a cold (5/10 C, night/day) or a warm growth chamber (20/23 C). This correlation did not exist in plants kept in the greehouse continuously (high abscisic acid, no CO2 sensitivity), nor in plants transferred from the cold to the warm chamber (low abscisic acid, high CO2 sensitivity). The abscisic acid content of leaves was correlated with water content only within narrow limits, if at all. At equal water contents, prechilled leaves contained more abscisic acid than leaves of plants pretreated in the warm chamber. There appear to be at least two compartments for abscisic acid in the leaf. PMID:16659416

Investigation into the Physiological Significance of the Phytohormone Abscisic Acid in Perkinsus marinus, an Oyster Parasite Harboring a Nonphotosynthetic Plastid.

PubMed

Sakamoto, Hirokazu; Suzuki, Shigeo; Nagamune, Kisaburo; Kita, Kiyoshi; Matsuzaki, Motomichi

2017-07-01

Some organisms have retained plastids even after they have lost the ability to photosynthesize. Several studies of nonphotosynthetic plastids in apicomplexan parasites have shown that the isopentenyl pyrophosphate biosynthesis pathway in the organelle is essential for their survival. A phytohormone, abscisic acid, one of several compounds biosynthesized from isopentenyl pyrophosphate, regulates the parasite cell cycle. Thus, it is possible that the phytohormone is universally crucial, even in nonphotosynthetic plastids. Here, we examined this possibility using the oyster parasite Perkinsus marinus, which is a plastid-harboring cousin of apicomplexan parasites and has independently lost photosynthetic ability. Fluridone, an inhibitor of abscisic acid biosynthesis, blocked parasite growth and induced cell clustering. Nevertheless, abscisic acid and its intermediate carotenoids did not affect parasite growth or rescue the parasite from inhibition. Moreover, abscisic acid was not detected from the parasite using liquid chromatography mass spectrometry. Our findings show that abscisic acid does not play any significant roles in P. marinus. © 2016 The Authors. Journal of Eukaryotic Microbiology published by Wiley Periodicals, Inc. on behalf of International Society of Protistologists.

Grape berry ripening delay induced by a pre-véraison NAA treatment is paralleled by a shift in the expression pattern of auxin- and ethylene-related genes.

PubMed

Ziliotto, Fiorenza; Corso, Massimiliano; Rizzini, Fabio Massimo; Rasori, Angela; Botton, Alessandro; Bonghi, Claudio

2012-10-09

Auxins act as repressors of ripening inception in grape (véraison), while ethylene and abscisic acid (ABA) play a positive role as inducers of the syndrome. Despite the increasing amount of information made available on this topic, the complex network of interactions among these hormones remains elusive. In order to shed light on these aspects, a holistic approach was adopted to evaluate, at the transcriptomic level, the crosstalk between hormones in grape berries, whose ripening progression was delayed by applying naphtalenacetic acid (NAA) one week before véraison. The NAA treatment caused significant changes in the transcription rate of about 1,500 genes, indicating that auxin delayed grape berry ripening also at the transcriptional level, along with the recovery of a steady state of its intracellular concentration. Hormone indices analysis carried out with the HORMONOMETER tool suggests that biologically active concentrations of auxins were achieved throughout a homeostatic recovery. This occurred within 7 days after the treatment, during which the physiological response was mainly unspecific and due to a likely pharmacological effect of NAA. This hypothesis is strongly supported by the up-regulation of genes involved in auxin conjugation (GH3-like) and action (IAA4- and IAA31-like). A strong antagonistic effect between auxin and ethylene was also observed, along with a substantial 'synergism' between auxins and ABA, although to a lesser extent. This study suggests that, in presence of altered levels of auxins, the crosstalk between hormones involves diverse mechanisms, acting at both the hormone response and biosynthesis levels, creating a complex response network.

Molecular dynamics simulations of the auxin-binding protein 1 in complex with indole-3-acetic acid and naphthalen-1-acetic acid.

PubMed

Grandits, Melanie; Oostenbrink, Chris

2014-10-01

Auxin-binding protein 1 (ABP1) is suggested to be an auxin receptor which plays an important role in several processes in green plants. Maize ABP1 was simulated with the natural auxin indole-3-acetic acid (IAA) and the synthetic analog naphthalen-1-acetic acid (NAA), to elucidate the role of the KDEL sequence and the helix at the C-terminus. The KDEL sequence weakens the intermolecular interactions between the monomers but stabilizes the C-terminal helix. Conformational changes at the C-terminus occur within the KDEL sequence and are influenced by the binding of the simulated ligands. This observation helps to explain experimental findings on ABP1 interactions with antibodies that are modulated by the presence of auxin, and supports the hypothesis that ABP1 acts as an auxin receptor. Stable hydrogen bonds between the monomers are formed between Glu40 and Glu62, Arg10 and Thr97, Lys39, and Glu62 in all simulations. The amino acids Ile22, Leu25, Trp44, Pro55, Ile130, and Phe149 are located in the binding pocket and are involved in hydrophobic interactions with the ring system of the ligand. Trp151 is stably involved in a face to end interaction with the ligand. The calculated free energy of binding using the linear interaction energy approach showed a higher binding affinity for NAA as compared to IAA. Our simulations confirm the asymmetric behavior of the two monomers, the stronger interaction of NAA than IAA and offers insight into the possible mechanism of ABP1 as an auxin receptor. © 2014 Wiley Periodicals, Inc.

cis-Cinnamic Acid Is a Novel, Natural Auxin Efflux Inhibitor That Promotes Lateral Root Formation1[OPEN

PubMed Central

Steenackers, Ward; Corneillie, Sander; Araújo, Pedro; Viaene, Tom; Nowack, Moritz K.; Blakeslee, Joshua J.; Novák, Ondřej; Zažímalová, Eva

2017-01-01

Auxin steers numerous physiological processes in plants, making the tight control of its endogenous levels and spatiotemporal distribution a necessity. This regulation is achieved by different mechanisms, including auxin biosynthesis, metabolic conversions, degradation, and transport. Here, we introduce cis-cinnamic acid (c-CA) as a novel and unique addition to a small group of endogenous molecules affecting in planta auxin concentrations. c-CA is the photo-isomerization product of the phenylpropanoid pathway intermediate trans-CA (t-CA). When grown on c-CA-containing medium, an evolutionary diverse set of plant species were shown to exhibit phenotypes characteristic for high auxin levels, including inhibition of primary root growth, induction of root hairs, and promotion of adventitious and lateral rooting. By molecular docking and receptor binding assays, we showed that c-CA itself is neither an auxin nor an anti-auxin, and auxin profiling data revealed that c-CA does not significantly interfere with auxin biosynthesis. Single cell-based auxin accumulation assays showed that c-CA, and not t-CA, is a potent inhibitor of auxin efflux. Auxin signaling reporters detected changes in spatiotemporal distribution of the auxin response along the root of c-CA-treated plants, and long-distance auxin transport assays showed no inhibition of rootward auxin transport. Overall, these results suggest that the phenotypes of c-CA-treated plants are the consequence of a local change in auxin accumulation, induced by the inhibition of auxin efflux. This work reveals a novel mechanism how plants may regulate auxin levels and adds a novel, naturally occurring molecule to the chemical toolbox for the studies of auxin homeostasis. PMID:27837086

Exogenous abscisic acid alleviates zinc uptake and accumulation in Populus × canescens exposed to excess zinc.

PubMed

Shi, Wen-Guang; Li, Hong; Liu, Tong-Xian; Polle, Andrea; Peng, Chang-Hui; Luo, Zhi-Bin

2015-01-01

A greenhouse experiment was conducted to study whether exogenous abscisic acid (ABA) mediates the responses of poplars to excess zinc (Zn). Populus × canescens seedlings were treated with either basal or excess Zn levels and either 0 or 10 μm ABA. Excess Zn led to reduced photosynthetic rates, increased Zn accumulation, induced foliar ABA and salicylic acid (SA), decreased foliar gibberellin (GA3 ) and auxin (IAA), elevated root H2 O2 levels, and increased root ratios of glutathione (GSH) to GSSG and foliar ratios of ascorbate (ASC) to dehydroascorbate (DHA) in poplars. While exogenous ABA decreased foliar Zn concentrations with 7 d treatments, it increased levels of endogenous ABA, GA3 and SA in roots, and resulted in highly increased foliar ASC accumulation and ratios of ASC to DHA. The transcript levels of several genes involved in Zn uptake and detoxification, such as yellow stripe-like family protein 2 (YSL2) and plant cadmium resistance protein 2 (PCR2), were enhanced in poplar roots by excess Zn but repressed by exogenous ABA application. These results suggest that exogenous ABA can decrease Zn concentrations in P. × canescens under excess Zn for 7 d, likely by modulating the transcript levels of key genes involved in Zn uptake and detoxification. © 2014 John Wiley & Sons Ltd.

Effects of norflurazon, an inhibitor of carotenogenesis, on abscisic acid and xanthoxin in the caps of gravistimulated maize roots

NASA Technical Reports Server (NTRS)

Feldman, L. J.; Sun, P. S.

1986-01-01

Maize seeds were germinated in the dark in the presence of the carotenoid synthesis inhibitor norflurazon and the levels of abscisic acid, xanthoxin and total carotenoids were measured in the root cap and in the adjacent 1.5 mm segment. In norflurazon-treated roots abscisic acid levels were markedly reduced, but an increase occurred in the levels of xanthoxin, a compound structurally and physiologically similar to abscisic acid. In the cultivar of maize (Zea mays L. cv. Merit) used for this work, brief illumination of the root is required for gravitropic curving. Following illumination both control and norflurazon-treated roots showed normal gravitropic curvature; however, the rate of curvature was delayed in norflurazon-treated roots. Our data from norflurazon-treated roots are consistent with a role for xanthoxin in maize root gravitropism. The increase in xanthoxin in the presence of an inhibitor of carotenoid synthesis suggests that xanthoxin and abscisic acid originate, at least in part, via different metabolic pathways.

The Barley Magnesium Chelatase 150-kD Subunit Is Not an Abscisic Acid Receptor1[OA

PubMed Central

Müller, André H.; Hansson, Mats

2009-01-01

Magnesium chelatase is the first unique enzyme of the chlorophyll biosynthetic pathway. It is composed of three gene products of which the largest is 150 kD. This protein was recently identified as an abscisic acid receptor in Arabidopsis (Arabidopsis thaliana). We have evaluated whether the barley (Hordeum vulgare) magnesium chelatase large subunit, XanF, could be a receptor for the phytohormone. The study involved analysis of recombinant magnesium chelatase protein as well as several induced chlorophyll-deficient magnesium chelatase mutants with defects identified at the gene and protein levels. Abscisic acid had no effect on magnesium chelatase activity and binding to the barley 150-kD protein could not be shown. Magnesium chelatase mutants showed a wild-type response in respect to postgermination growth and stomatal aperture. Our results question the function of the large magnesium chelatase subunit as an abscisic acid receptor. PMID:19176716

Abscisic acid-regulated protein degradation causes osmotic stress-induced accumulation of branched-chain amino acids in Arabidopsis thaliana.

PubMed

Huang, Tengfang; Jander, Georg

2017-10-01

Whereas proline accumulates through de novo biosynthesis in plants subjected to osmotic stress, leucine, isoleucine, and valine accumulation in drought-stressed Arabidopsis thaliana is caused by abscisic acid-regulated protein degradation. In response to several kinds of abiotic stress, plants greatly increase their accumulation of free amino acids. Although stress-induced proline increases have been studied the most extensively, the fold-increase of other amino acids, in particular branched-chain amino acids (BCAAs; leucine, isoleucine, and valine), is often higher than that of proline. In Arabidopsis thaliana (Arabidopsis), BCAAs accumulate in response to drought, salt, mannitol, polyethylene glycol, herbicide treatment, and nitrogen starvation. Plants that are deficient in abscisic acid signaling accumulate lower amounts of BCAAs, but not proline and most other amino acids. Previous bioinformatic studies had suggested that amino acid synthesis, rather than protein degradation, is responsible for the observed BCAA increase in osmotically stressed Arabidopsis. However, whereas treatment with the protease inhibitor MG132 decreased drought-induced BCAA accumulation, inhibition of BCAA biosynthesis with the acetolactate synthase inhibitors chlorsulfuron and imazapyr did not. Additionally, overexpression of BRANCHED-CHAIN AMINO ACID TRANSFERASE2 (BCAT2), which is upregulated in response to osmotic stress and functions in BCAA degradation, decreased drought-induced BCAA accumulation. Together, these results demonstrate that BCAA accumulation in osmotically stressed Arabidopsis is primarily the result of protein degradation. After relief of the osmotic stress, BCAA homeostasis is restored over time by amino acid degradation involving BCAT2. Thus, drought-induced BCAA accumulation is different from that of proline, which is accumulated due to de novo synthesis in an abscisic acid-independent manner and remains elevated for a more prolonged period of time after removal of

Regulation of Auxin Homeostasis and Gradients in Arabidopsis Roots through the Formation of the Indole-3-Acetic Acid Catabolite 2-Oxindole-3-Acetic Acid[C][W][OPEN

PubMed Central

Pěnčík, Aleš; Simonovik, Biljana; Petersson, Sara V.; Henyková, Eva; Simon, Sibu; Greenham, Kathleen; Zhang, Yi; Kowalczyk, Mariusz; Estelle, Mark; Zažímalová, Eva; Novák, Ondřej; Sandberg, Göran; Ljung, Karin

2013-01-01

The native auxin, indole-3-acetic acid (IAA), is a major regulator of plant growth and development. Its nonuniform distribution between cells and tissues underlies the spatiotemporal coordination of many developmental events and responses to environmental stimuli. The regulation of auxin gradients and the formation of auxin maxima/minima most likely involve the regulation of both metabolic and transport processes. In this article, we have demonstrated that 2-oxindole-3-acetic acid (oxIAA) is a major primary IAA catabolite formed in Arabidopsis thaliana root tissues. OxIAA had little biological activity and was formed rapidly and irreversibly in response to increases in auxin levels. We further showed that there is cell type–specific regulation of oxIAA levels in the Arabidopsis root apex. We propose that oxIAA is an important element in the regulation of output from auxin gradients and, therefore, in the regulation of auxin homeostasis and response mechanisms. PMID:24163311

Development of an ultrahigh-performance liquid chromatography-electrospray ionization-tandem mass spectrometry method for the simultaneous determination of salicylic acid, jasmonic acid, and abscisic acid in rose leaves.

PubMed

Bosco, Renato; Daeseleire, Els; Van Pamel, Els; Scariot, Valentina; Leus, Leen

2014-07-09

This paper describes a method to detect and quantitate the endogenous plant hormones (±)-2-cis-4-trans-abscisic acid, (-)-jasmonic acid, and salicylic acid by means of ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) in hybrid rose leaf matrices. Deuterium-labeled [(2)H6] (+)-2-cis-4-trans-abscisic acid, [(2)H6] (±)-jasmonic acid, and [(2)H4]-salicylic acid were used as internal standards. Rose samples (10 mg) were extracted with methanol/water/acetic acid (10:89:1) and subsequently purified on an Oasis MCX 1 cm(3) Vac SPE cartridge. Performance characteristics were validated according to Commission Decision 2002/657/EC. Recovery, repeatability, and within-laboratory reproducibility were acceptable for all phytohormones tested at three different concentrations. The decision limit and detection capability for (±)-2-cis-4-trans-abscisic acid, (-)-jasmonic acid, and salicylic acid were 0.0075 and 0.015 μg/g, 0.00015 and 0.00030 μg/g, and 0.0089 and 0.018 μg/g, respectively. Matrix effects (signal suppression or enhancement) appeared to be high for all substances considered, implying the need for quantitation based on matrix-matched calibration curves.

Vesicular secretion of auxin

PubMed Central

Schlicht, Markus; Volkmann, Dieter; Mancuso, Stefano

2008-01-01

The plant hormone auxin is secreted in root apices via phospholipase Dζ2 (PLDζ2) activity which produces specific population of phosphatidic acid that stimulates secretion of vesicles enriched with auxin. These vesicles were reported to be localized at plant synapses which are active in auxin secretion, especially at the transition zone of the root apex. There are several implications of this vesicular secretion of auxin. In root apices, auxin emerges as plant neurotransmitter-like signal molecule which coordinates activities of adjacent cells via electric and chemical signaling. Putative quantal release of auxin after electrical stimulation, if confirmed, would be part of neuronal communication between plant cells. As auxin transport across plant synapses is tightly linked with integrated sensory perception of environment, especially of omnipresent gravity and light, this process is proposed to mediate the plant perception of environment. These neuronal features allow sessile plants to integrate multitude of sensory signals into the adaptive behavior of whole plants and the animal-like exploratory behavior of growing roots. PMID:19704646

Abscisic Acid Metabolism by a Cell-free Preparation from Echinocystis lobata Liquid Endoserum 1

PubMed Central

Gillard, Douglas F.; Walton, Daniel C.

1976-01-01

A cell-free enzyme system capable of metabolizing abscisic acid has been obtained from Eastern Wild Cucumber (Echinocystis lobata Michx.) liquid endosperm. The reaction products were determined to be phaseic acid (PA) and dihydrophaseic acid (DPA) by co-chromatography on thin layer chromatograms as the free acids, methyl esters, and their respective oxidation or reduction products. The crude enzyme preparation was separated by centrifugation into a particulate abscisic acid (ABA)-hydroxylating activity and a soluble PA-reducing activity. The particulate ABA-hydroxylating enzyme showed a requirement for O2 and NADPH, inhibition by CO, and high substrate specificity for (+)-ABA. Acetylation of short term incubation mixtures gave evidence for the presence of 6′-hydroxymethyl-ABA as an intermediate in PA formation. Determinations of endogenous ABA and DPA concentrations suggest that the ABA-hydroxylating and PA-reducing enzymes are extensively metabolizing ABA in the intact E. lobata seed. PMID:16659768

Influence of exogenously applied abscisic acid on carotenoid content and water uptake in flowers of the tea plant (Camellia sinensis).

PubMed

Baldermann, Susanne; Yang, Ziyin; Sakai, Miwa; Fleischmann, Peter; Morita, Akio; Todoroki, Yasushi; Watanabe, Naoharu

2013-05-01

Carotenoids are a major class of plant pigments and fulfill many functions in different organisms that either produce or consume them. Although the color of the stamina of tea (Camellia sinensis) flowers is clearly due to the presence of carotenoids, the carotenoid profile and content remain to be discovered. We investigated the carotenoid profile of tea flowers and determined changes in concentrations over the floral development. The flowers contained oxygenated xanthophylls such as neoxanthin, lutein and zeaxanthin, as well as the hydrocarbons β-carotene and α-carotene. Flowers of the tea plant contain to vegetables comparable amounts of carotenoids. The content of 9'-cis-epoxycarotenoids, which serve as abscisic acid precursors, as well as changes in concentration of abscisic acid were studied. The concentrations of carotenoids decreased whereas the abscisic acid content increased over the floral development. Exogenously applied S-abscisic acid affected water uptake, flower opening and carotenoid accumulation. In summary, this paper reports, for the first time, the carotenoid profile and content of tea flowers. The study revealed that carotenoids in tea flowers are an interesting target in respect of possible applications of tea flower extracts as well as biological functions of abscisic acid during floral development. © 2012 Society of Chemical Industry.

Synthesis and biological activity of amino acid conjugates of abscisic acid.

PubMed

Todoroki, Yasushi; Narita, Kenta; Muramatsu, Taku; Shimomura, Hajime; Ohnishi, Toshiyuki; Mizutani, Masaharu; Ueno, Kotomi; Hirai, Nobuhiro

2011-03-01

We prepared 19 amino acid conjugates of the plant hormone abscisic acid (ABA) and investigated their biological activity, enzymatic hydrolysis by a recombinant Arabidopsis amidohydrolases GST-ILR1 and GST-IAR3, and metabolic fate in rice seedlings. Different sets of ABA-amino acids induced ABA-like responses in different plants. Some ABA-amino acids, including some that were active in bioassays, were hydrolyzed by recombinant Arabidopsis GST-IAR3, although GST-ILR1 did not show hydrolysis activity for any of the ABA-amino acids. ABA-L-Ala, which was active in all the bioassays, an Arabidopsis seed germination, spinach seed germination, and rice seedling elongation assays, except in a lettuce seed germination assay and was hydrolyzed by GST-IAR3, was hydrolyzed to free ABA in rice seedlings. These findings suggest that some plant amidohydrolases hydrolyze some ABA-amino acid conjugates. Because our study indicates the possibility that different plants have hydrolyzing activity toward different ABA-amino acids, an ABA-amino acid may function as a species-selective pro-hormone of ABA. Copyright © 2011 Elsevier Ltd. All rights reserved.

Abscisic Acid Synthesis and Response

PubMed Central

Finkelstein, Ruth

2013-01-01

Abscisic acid (ABA) is one of the “classical” plant hormones, i.e. discovered at least 50 years ago, that regulates many aspects of plant growth and development. This chapter reviews our current understanding of ABA synthesis, metabolism, transport, and signal transduction, emphasizing knowledge gained from studies of Arabidopsis. A combination of genetic, molecular and biochemical studies has identified nearly all of the enzymes involved in ABA metabolism, almost 200 loci regulating ABA response, and thousands of genes regulated by ABA in various contexts. Some of these regulators are implicated in cross-talk with other developmental, environmental or hormonal signals. Specific details of the ABA signaling mechanisms vary among tissues or developmental stages; these are discussed in the context of ABA effects on seed maturation, germination, seedling growth, vegetative stress responses, stomatal regulation, pathogen response, flowering, and senescence. PMID:24273463

Light Moderates the Induction of Phosphoenolpyruvate Carboxylase by NaCl and Abscisic Acid in Mesembryanthemum crystallinum 1

PubMed Central

McElwain, Elizabeth F.; Bohnert, Hans J.; Thomas, John C.

1992-01-01

In Mesembryanthemum crystallinum, phosphoenolpyruvate carboxylase is synthesized de novo in response to osmotic stress, as part of the switch from C3-photosynthesis to Crassulacean acid metabolism. To better understand the environmental signals involved in this pathway, we have investigated the effects of light on the induced expression of phosphoenolpyruvate carboxylase mRNA and protein in response to stress by 400 millimolar NaCl or 10 micromolar abscisic acid in hydroponically grown plants. When plants were grown in high-intensity fluorescent or incandescent light (850 microeinsteins per square meter per second), NaCl and abscisic acid induced approximately an eightfold accumulation of phosphoenolpyruvate carboxylase mRNA when compared to untreated controls. Levels of phosphoenolpyruvate carboxylase protein were high in these abscisic acid- and NaCl-treated plants, and detectable in the unstressed control. Growth in high-intensity incandescent (red) light resulted in approximately twofold higher levels of phosphoenolpyruvate carboxylase mRNA in the untreated plants when compared to control plants grown in high-intensity fluorescent light. In low light (300 microeinsteins per square meter per second fluorescent), only NaCl induced mRNA levels significantly above the untreated controls. Low light grown abscisic acid- and NaCl-treated plants contained a small amount of phosphoenolpyruvate carboxylase protein, whereas the (untreated) control plants did not contain detectable amounts of phosphoenolpyruvate carboxylase. Environmental stimuli, such as light and osmotic stress, exert a combined effect on gene expression in this facultative halophyte. ImagesFigure 1Figure 2 PMID:16668999

Abscisic acid (ABA) receptors: light at the end of the tunnel

USDA-ARS?s Scientific Manuscript database

The plant hormone abscisic acid (ABA) plays a role in several aspects of plant growth and development. Understanding how this hormonal stimulus is sensed and transduced turned out to be one of the major tasks in the field of plant signaling. A series of recent papers proposed several different prote...

Auxin Controls Arabidopsis Adventitious Root Initiation by Regulating Jasmonic Acid Homeostasis[W

PubMed Central

Gutierrez, Laurent; Mongelard, Gaëlle; Floková, Kristýna; Păcurar, Daniel I.; Novák, Ondřej; Staswick, Paul; Kowalczyk, Mariusz; Păcurar, Monica; Demailly, Hervé; Geiss, Gaia; Bellini, Catherine

2012-01-01

Vegetative shoot-based propagation of plants, including mass propagation of elite genotypes, is dependent on the development of shoot-borne roots, which are also called adventitious roots. Multiple endogenous and environmental factors control the complex process of adventitious rooting. In the past few years, we have shown that the auxin response factors ARF6 and ARF8, targets of the microRNA miR167, are positive regulators of adventitious rooting, whereas ARF17, a target of miR160, is a negative regulator. We showed that these genes have overlapping expression profiles during adventitious rooting and that they regulate each other’s expression at the transcriptional and posttranscriptional levels by modulating the homeostasis of miR160 and miR167. We demonstrate here that this complex network of transcription factors regulates the expression of three auxin-inducible Gretchen Hagen3 (GH3) genes, GH3.3, GH3.5, and GH3.6, encoding acyl-acid-amido synthetases. We show that these three GH3 genes are required for fine-tuning adventitious root initiation in the Arabidopsis thaliana hypocotyl, and we demonstrate that they act by modulating jasmonic acid homeostasis. We propose a model in which adventitious rooting is an adaptive developmental response involving crosstalk between the auxin and jasmonate regulatory pathways. PMID:22730403

Auxin Produced by the Indole-3-Pyruvic Acid Pathway Regulates Development and Gemmae Dormancy in the Liverwort Marchantia polymorpha[OPEN

PubMed Central

Eklund, D. Magnus; Ishizaki, Kimitsune; Flores-Sandoval, Eduardo; Kikuchi, Saya; Takebayashi, Yumiko; Tsukamoto, Shigeyuki; Hirakawa, Yuki; Nonomura, Maiko; Kato, Hirotaka; Kouno, Masaru; Bhalerao, Rishikesh P.; Lagercrantz, Ulf; Kasahara, Hiroyuki; Kohchi, Takayuki; Bowman, John L.

2015-01-01

The plant hormone auxin (indole-3-acetic acid [IAA]) has previously been suggested to regulate diverse forms of dormancy in both seed plants and liverworts. Here, we use loss- and gain-of-function alleles for auxin synthesis- and signaling-related genes, as well as pharmacological approaches, to study how auxin regulates development and dormancy in the gametophyte generation of the liverwort Marchantia polymorpha. We found that M. polymorpha possess the smallest known toolkit for the indole-3-pyruvic acid (IPyA) pathway in any land plant and that this auxin synthesis pathway mainly is active in meristematic regions of the thallus. Previously a Trp-independent auxin synthesis pathway has been suggested to produce a majority of IAA in bryophytes. Our results indicate that the Trp-dependent IPyA pathway produces IAA that is essential for proper development of the gametophyte thallus of M. polymorpha. Furthermore, we show that dormancy of gemmae is positively regulated by auxin synthesized by the IPyA pathway in the apex of the thallus. Our results indicate that auxin synthesis, transport, and signaling, in addition to its role in growth and development, have a critical role in regulation of gemmae dormancy in M. polymorpha. PMID:26036256

Role of auxin and protons in plant shoot gravitropism

NASA Technical Reports Server (NTRS)

Rayle, D. L.; Migliaccio, F.; Watson, E.

1982-01-01

Experiments designed to probe the relationship between asymmetric acid efflux and auxin redistribution during gravitropism are reported. Gravistimulation of sunflower hypocotyls results in the retardation of growth on the upper surface and the acceleration of growth on the lower surface relative to a vertically oriented control. Auxin and H(+) both elicit growth over a similarly broad region of the hypocotyl. The correspondence between auxin, H(+), and gravisensitive tissues is consistent with the notion that auxin redistribution may initiate asymmetric acid efflux during gravistimulation. Data are presented showing a redistribution of C-14-IAA and H-3-IAA occurs within 20-30 minutes of gravistimulation. Data on the effects of selected inhibitors of shoot gravitropism are also presented. Taken together, the data suggest that lateral transport of auxin initiates asymmetric acid efflux in gravitropically stimulated shoots.

Absence of a Causal Relationship between Auxin-Induced Growth and Changes in the Content of Ascorbic and Dehydroascorbic Acids in Excised Plant Tissues 12

PubMed Central

Lin, C. Y.; Key, Joe L.

1967-01-01

The data reported indicate that the oxidation-reduction balance of the ascorbic acid system is not causally related to the auxin-regulation of cell elongation. There was no shift in the ascorbic acid (AA) to dehydroascorbic acid (DHA) ratio with growth-promoting concentration of auxin in several plant tissues. The AA to DHA ratio was experimentally increased without altering the growth rate. Inhibition of growth by supra-optimal auxin was associated with a decrease in the AA to DHA ratio. Since the AA to DHA ratio was lowered by EDTA treatment without altering growth, it seems unlikely that the decrease in the AA to DHA ratio related to the inhibition of growth by high levels of auxin. PMID:16656564

Auxin Uptake and the Rapid Auxin-Induced Growth in Isolated Sections of Helianthus annuus

PubMed Central

Firn, Richard D.

1982-01-01

When a sunflower (Helianthus annuus L.) hypocotyl section is placed in a solution of 10 micromolar 1-naphthylacetic acid, the majority of the auxin enters via the cut surfaces. However, it is the minority entering radially which causes the typical growth response. Auxin supplied only to the apical cut surface gives a weak, slower response. PMID:16662719

Abscisic Acid Levels and Seed Dormancy

PubMed Central

Sondheimer, E.; Tzou, D. S.; Galson, Eva C.

1968-01-01

Dormant seeds from Fraxinus species require cold-temperature after-ripening prior to germination. Earlier, we found that abscisic acid (ABA) will inhibit germination of excised nondormant embryos and that this can be reversed with a combination of gibberellic acid and kinetin. Using Milborrow's quantitative “racemate dilution” method the ABA concentration in 3 types of Fraxinus seed and pericarp were determined. While ABA was present in all tissues, the highest concentration was found in the seed and pericarp of dormant F. americana. During the chilling treatment of F. americana the ABA levels decreased 37% in the pericarp and 68% in the seed. The ABA concentration of the seed of the nondormant species, F. ornus, is as low as that found in F. americana seeds after cold treatment. Experiments with exogenously added ABA solutions indicate that it is unlikely that the ABA in the pericarp functions in the regulation of seed dormancy. However, the ABA in the seed does seem to have a regulatory role in germination. Images PMID:16656935

Auxin physiology of the tomato mutant diageotropica

NASA Technical Reports Server (NTRS)

Daniel, S. G.; Rayle, D. L.; Cleland, R. E.

1989-01-01

The tomato (Lycopersicon esculentum, Mill.) mutant diageotropica (dgt) exhibits biochemical, physiological, and morphological abnormalities that suggest the mutation may have affected a primary site of auxin perception or action. We have compared two aspects of the auxin physiology of dgt and wild-type (VFN8) seedlings: auxin transport and cellular growth parameters. The rates of basipetal indole-3-acetic acid (IAA) polar transport are identical in hypocotyl sections of the two genotypes, but dgt sections have a slightly greater capacity for IAA transport. 2,3,5-Triiodobenzoic acid and ethylene reduce transport in both mutant and wild-type sections. The kinetics of auxin uptake into VFN8 and dgt sections are nearly identical. These results make it unlikely that an altered IAA efflux carrier or IAA uptake symport are responsible for the pleiotropic effects resulting from the dgt mutation. The lack of auxin-induced cell elongation in dgt plants is not due to insufficient turgor, as the osmotic potential of dgt cell sap is less (more negative) than that of VFN8. An auxin-induced increase in wall extensibility, as measured by the Instron technique, only occurs in the VFN8 plants. These data suggest dgt hypocotyls suffer a defect in the sequence of events culminating in auxin-induced cell wall loosening.

Abscisic acid related compounds and lignans in prunes (Prunus domestica L.) and their oxygen radical absorbance capacity (ORAC).

PubMed

Kikuzaki, Hiroe; Kayano, Shin-ichi; Fukutsuka, Naoko; Aoki, Asuka; Kasamatsu, Kumi; Yamasaki, Yuka; Mitani, Takahiko; Nakatani, Nobuji

2004-01-28

Four new abscisic acid related compounds (1-4), together with (+)-abscisic acid (5), (+)-beta-D-glucopyranosyl abscisate (6), (6S,9R)-roseoside (7), and two lignan glucosides ((+)-pinoresinol mono-beta-D-glucopyranoside (8) and 3-(beta-D-glucopyranosyloxymethyl)-2- (4-hydroxy-3-methoxyphenyl)-5-(3-hydroxypropyl)-7-methoxy-(2R,3S)-dihydrobenzofuran (9)) were isolated from the antioxidative ethanol extract of prunes (Prunus domestica L.). The structures of 1-4 were elucidated on the basis of NMR and MS spectrometric data to be rel-5-(3S,8S-dihydroxy-1R,5S-dimethyl-7-oxa-6-oxobicyclo[3,2,1]oct-8-yl)-3-methyl-2Z,4E-pentadienoic acid (1), rel-5-(3S,8S-dihydroxy-1R,5S-dimethyl-7-oxa-6-oxobicyclo[3,2,1]oct-8-yl)-3-methyl-2Z,4E-pentadienoic acid 3'-O-beta-d-glucopyranoside (2), rel-5-(1R,5S-dimethyl-3R,4R,8S-trihydroxy-7-oxa-6-oxobicyclo[3,2,1]oct-8-yl)-3-methyl-2Z,4E-pentadienoic acid (3), and rel-5-(1R,5S-dimethyl-3R,4R,8S-trihydroxy-7-oxabicyclo[3,2,1]- oct-8-yl)-3-methyl-2Z,4E-pentadienoic acid (4). The antioxidant activities of these isolated compounds were evaluated on the basis of oxygen radical absorbance capacity (ORAC). The ORAC values of abscisic acid related compounds (1-7) were very low. Two lignans (8 and 9) were more effective antioxidants whose ORAC values were 1.09 and 2.33 micromol of Trolox equiv/micromol, respectively.

Effects of natural and synthetic auxins on the gravitropic growth habit of roots in two auxin-resistant mutants of Arabidopsis, axr1 and axr4: evidence for defects in the auxin influx mechanism of axr4

NASA Technical Reports Server (NTRS)

Yamamoto, M.; Yamamoto, K. T.

1999-01-01

The partially agravitropic growth habit of roots of an auxin-resistant mutant of Arabidopsis thaliana, axr4, was restored by the addition of 30-300 nM 1-naphthaleneacetic acid (NAA) to the growth medium. Neither indole 3-acetic acid (IAA) nor 2,4-dichlorophenoxyacetic acid (2,4-D) showed such an effect. Growth of axr4 roots was resistant to IAA and 2,4-D, but not at all to NAA. The differential effects of the three auxins suggest that the defects of axr4 result from a lower auxin influx into its cells. The partially agravitropic growth habit of axr1 roots, which was less severe than that of axr4 roots, was only slightly affected by the three auxins in the growth medium at concentrations up to 300 nM; growth of axr1 roots was resistant to all three of the auxins. These results suggest that the lesion of axrl mutants is different from that of axr4.

Investigating organic molecules responsible of auxin-like activity of humic acid fraction extracted from vermicompost.

PubMed

Scaglia, Barbara; Nunes, Ramom Rachide; Rezende, Maria Olímpia Oliveira; Tambone, Fulvia; Adani, Fabrizio

2016-08-15

This work studied the auxin-like activity of humic acids (HA) obtained from vermicomposts produced using leather wastes plus cattle dung at different maturation stages (fresh, stable and mature). Bioassays were performed by testing HA concentrations in the range of 100-6000mgcarbonL(-1). (13)C CPMAS-NMR and GC-MS instrumental methods were used to assess the effect of biological processes and starting organic mixtures on HA composition. Not all HAs showed IAA-like activity and in general, IAA-like activity increased with the length of the vermicomposting process. The presence of leather wastes was not necessary to produce the auxin-like activity of HA, since HA extracted from a mix of cattle manure and sawdust, where no leather waste was added, showed IAA-like activity as well. CPMAS (13)CNMR revealed that HAs were similar independently of the mix used and that the humification process involved the increasing concentration of pre-existing alkali soluble fractions in the biomass. GC/MS allowed the identification of the molecules involved in IAA-like effects: carboxylic acids and amino acids. The concentration of active molecules, rather than their simple presence in HA, determined the bio-stimulating effect, and a good linear regression between auxin-like activity and active stimulating molecules concentration was found (R(2)=-0.85; p<0.01, n=6). Copyright © 2016 Elsevier B.V. All rights reserved.

40 CFR 180.1281 - S-Abscisic Acid, (S)-5-(1-hydroxy-2,6,6-trimethyl-4-oxo-1-cyclohex-2-enyl)-3-methyl-penta-(2Z,4E...

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 23 2010-07-01 2010-07-01 false S-Abscisic Acid, (S)-5-(1-hydroxy-2,6... Exemptions From Tolerances § 180.1281 S-Abscisic Acid, (S)-5-(1-hydroxy-2,6,6-trimethyl-4-oxo-1-cyclohex-2... from the requirement of a tolerance is established for residues of S-Abscisic Acid in or on all food...

Abscisic acid-type sesquiterpenes and ansamycins from Amycolatopsis alba DSM 44262.

PubMed

Li, Xiao-Mei; Li, Xiao-Man; Lu, Chun-Hua

2017-10-01

Two new abscisic acid-type sesquiterpenes (1, 2), and one new ansamycin (3), together with four known ansamycins, namely ansacarbamitocins 4-7, were isolated from the fermentation extract of Amycolatopsis alba DSM 44262. The structures of the new compounds were elucidated to be (E)-3-methyl-5-(2,6,6-trimethyl-3-oxocyclohex-1-enyl)pent-2-enoic acid (1) and (E)-3-methyl-5-(2,6,6-trimethyl-4-oxocyclohex-2-enyl)pent-2-enoic acid (2), and 9-O-methylansacarbamitocin A1 (3), on the basis of comprehensive analysis of spectroscopic data, respectively. The antimicrobial activities were also evaluated for all seven compounds.

Characterization of major ripening events during softening in grape: turgor, sugar accumulation, abscisic acid metabolism, colour development, and their relationship with growth

PubMed Central

Castellarin, Simone D.; Gambetta, Gregory A.; Wada, Hiroshi; Krasnow, Mark N.; Cramer, Grant R.; Peterlunger, Enrico; Shackel, Kenneth A.; Matthews, Mark A.

2016-01-01

Along with sugar accumulation and colour development, softening is an important physiological change during the onset of ripening in fruits. In this work, we investigated the relationships among major events during softening in grape (Vitis vinifera L.) by quantifying elasticity in individual berries. In addition, we delayed softening and inhibited sugar accumulation using a mechanical growth-preventing treatment in order to identify processes that are sugar and/or growth dependent. Ripening processes commenced on various days after anthesis, but always at similarly low elasticity and turgor. Much of the softening occurred in the absence of other changes in berry physiology investigated here. Several genes encoding key cell wall-modifying enzymes were not up-regulated until softening was largely completed, suggesting softening may result primarily from decreases in turgor. Similarly, there was no decrease in solute potential, increase in sugar concentration, or colour development until elasticity and turgor were near minimum values, and these processes were inhibited when berry growth was prevented. Increases in abscisic acid occurred early during softening and in the absence of significant expression of the V. vinifera 9-cis-epoxycarotenoid dioxygenases. However, these increases were coincident with decreases in the abscisic acid catabolite diphasic acid, indicating that initial increases in abscisic acid may result from decreases in catabolism and/or exogenous import. These data suggest that softening, decreases in turgor, and increases in abscisic acid represent some of the earliest events during the onset of ripening. Later, physical growth, further increases in abscisic acid, and the accumulation of sugar are integral for colour development. PMID:26590311

Differential Behavior within a Grapevine Cluster: Decreased Ethylene-Related Gene Expression Dependent on Auxin Transport Is Correlated with Low Abscission of First Developed Berries

PubMed Central

Godoy, Francisca; Delrot, Serge; Arce-Johnson, Patricio

2014-01-01

In grapevine, fruit abscission is known to occur within the first two to three weeks after flowering, but the reason why some berries in a cluster persist and others abscise is not yet understood. Ethylene sensitivity modulates abscission in several fruit species, based on a mechanism where continuous polar auxin transport across the pedicel results in a decrease in ethylene perception, which prevents abscission. In grapevine, flowering takes about four to seven days in a single cluster, thus while some flowers are developing into berries, others are just starting to open. So, in this work it was assessed whether uneven flowering accounted for differences in berry abscission dependent on polar auxin transport and ethylene-related gene expression. For this, flowers that opened in a cluster were tagged daily, which allowed to separately analyze berries, regarding their ability to persist. It was found that berries derived from flowers that opened the day that flowering started – named as “first berries” – had lower abscission rate than berries derived from flowers that opened during the following days – named as “late berries”. Use of radiolabeled auxin showed that “first berries” had higher polar auxin transport, correlated with lower ethylene content and lower ethylene-related transcript abundance than “late berries”. When “first berries” were treated with a polar auxin transport inhibitor they showed higher ethylene-related transcript abundance and were more prone to abscise than control berries. This study provides new insights on fruit abscission control. Our results indicate that polar auxin transport sustains the ability of “first berries” to persist in the cluster during grapevine abscission and also suggest that this could be associated with changes in ethylene-related gene expression. PMID:25365421

Immunolocalization of endogenous indole-3-acetic acid and abscisic acid in the shoot internodes of Fargesia yunnanensis bamboo during development

Treesearch

Shuguang Wang; Yongpeng Ma; Chengbin Wan; Chungyun Hse; Todd F. Shupe; Yujun Wang; Changming Wang

2016-01-01

The Bambusoideae subfamily includes the fastest-growing plants worldwide, as a consequence of fast internode elongation. However, few studies have evaluated the temporal and spatial distribution of endogenous hormones during internode elongation. In this paper, endogenous indole-3-acetic acid (IAA) and abscisic acid (ABA) were detected in different developmental...

Uprooting an abscisic acid paradigm: Shoots are the primary source.

PubMed

McAdam, Scott A M; Manzi, Matías; Ross, John J; Brodribb, Timothy J; Gómez-Cadenas, Aurelio

2016-06-02

In the past, a conventional wisdom has been that abscisic acid (ABA) is a xylem-transported hormone that is synthesized in the roots, while acting in the shoot to close stomata in response to a decrease in plant water status. Now, however, evidence from two studies, which we have conducted independently, challenges this root-sourced ABA paradigm. We show that foliage-derived ABA has a major influence over root development and that leaves are the predominant location for ABA biosynthesis during drought stress.

Characterization of major ripening events during softening in grape: turgor, sugar accumulation, abscisic acid metabolism, colour development, and their relationship with growth.

PubMed

Castellarin, Simone D; Gambetta, Gregory A; Wada, Hiroshi; Krasnow, Mark N; Cramer, Grant R; Peterlunger, Enrico; Shackel, Kenneth A; Matthews, Mark A

2016-02-01

Along with sugar accumulation and colour development, softening is an important physiological change during the onset of ripening in fruits. In this work, we investigated the relationships among major events during softening in grape (Vitis vinifera L.) by quantifying elasticity in individual berries. In addition, we delayed softening and inhibited sugar accumulation using a mechanical growth-preventing treatment in order to identify processes that are sugar and/or growth dependent. Ripening processes commenced on various days after anthesis, but always at similarly low elasticity and turgor. Much of the softening occurred in the absence of other changes in berry physiology investigated here. Several genes encoding key cell wall-modifying enzymes were not up-regulated until softening was largely completed, suggesting softening may result primarily from decreases in turgor. Similarly, there was no decrease in solute potential, increase in sugar concentration, or colour development until elasticity and turgor were near minimum values, and these processes were inhibited when berry growth was prevented. Increases in abscisic acid occurred early during softening and in the absence of significant expression of the V. vinifera 9-cis-epoxycarotenoid dioxygenases. However, these increases were coincident with decreases in the abscisic acid catabolite diphasic acid, indicating that initial increases in abscisic acid may result from decreases in catabolism and/or exogenous import. These data suggest that softening, decreases in turgor, and increases in abscisic acid represent some of the earliest events during the onset of ripening. Later, physical growth, further increases in abscisic acid, and the accumulation of sugar are integral for colour development. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Auxin Chemical and Molecular Biology

USDA-ARS?s Scientific Manuscript database

Auxins function as key regulators at the intersection between developmental and environmental events and the response pathways that they trigger. Naturally occurring members of this hormone group include indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), and 4-chloro-indole-3-acetic acid (4-Cl...

Auxin flow-mediated competition between axillary buds to restore apical dominance

PubMed Central

Balla, Jozef; Medveďová, Zuzana; Kalousek, Petr; Matiješčuková, Natálie; Friml, Jiří; Reinöhl, Vilém; Procházka, Stanislav

2016-01-01

Apical dominance is one of the fundamental developmental phenomena in plant biology, which determines the overall architecture of aerial plant parts. Here we show apex decapitation activated competition for dominance in adjacent upper and lower axillary buds. A two-nodal-bud pea (Pisum sativum L.) was used as a model system to monitor and assess auxin flow, auxin transport channels, and dormancy and initiation status of axillary buds. Auxin flow was manipulated by lateral stem wounds or chemically by auxin efflux inhibitors 2,3,5-triiodobenzoic acid (TIBA), 1-N-naphtylphtalamic acid (NPA), or protein synthesis inhibitor cycloheximide (CHX) treatments, which served to interfere with axillary bud competition. Redirecting auxin flow to different points influenced which bud formed the outgrowing and dominant shoot. The obtained results proved that competition between upper and lower axillary buds as secondary auxin sources is based on the same auxin canalization principle that operates between the shoot apex and axillary bud. PMID:27824063

Long-Term Inhibition by Auxin of Leaf Blade Expansion in Bean and Arabidopsis1

PubMed Central

Keller, Christopher P.; Stahlberg, Rainer; Barkawi, Lana S.; Cohen, Jerry D.

2004-01-01

The role of auxin in controlling leaf expansion remains unclear. Experimental increases to normal auxin levels in expanding leaves have shown conflicting results, with both increases and decreases in leaf growth having been measured. Therefore, the effects of both auxin application and adjustment of endogenous leaf auxin levels on midrib elongation and final leaf size (fresh weight and area) were examined in attached primary monofoliate leaves of the common bean (Phaseolus vulgaris) and in early Arabidopsis rosette leaves. Aqueous auxin application inhibited long-term leaf blade elongation. Bean leaves, initially 40 to 50 mm in length, treated once with α-naphthalene acetic acid (1.0 mm), were, after 6 d, approximately 80% the length and weight of controls. When applied at 1.0 and 0.1 mm, α-naphthalene acetic acid significantly inhibited long-term leaf growth. The weak auxin, β-naphthalene acetic acid, was effective at 1.0 mm; and a weak acid control, benzoic acid, was ineffective. Indole-3-acetic acid (1 μm, 10 μm, 0.1 mm, and 1 mm) required daily application to be effective at any concentration. Application of the auxin transport inhibitor, 1-N-naphthylphthalamic acid (1% [w/w] in lanolin), to petioles also inhibited long-term leaf growth. This treatment also was found to lead to a sustained elevation of leaf free indole-3-acetic acid content relative to untreated control leaves. Auxin-induced inhibition of leaf growth appeared not to be mediated by auxin-induced ethylene synthesis because growth inhibition was not rescued by inhibition of ethylene synthesis. Also, petiole treatment of Arabidopsis with 1-N-naphthylphthalamic acid similarly inhibited leaf growth of both wild-type plants and ethylene-insensitive ein4 mutants. PMID:14988474

Seasonal Variation in the Hormone Content of Willow: II. Effect of Photoperiod on Growth and Abscisic Acid Content of Trees under Field Conditions.

PubMed

Alvim, R

1978-11-01

Levels of abscisic acid were followed in the xylem sap, mature leaves, and apices of field-grown willow (Salix viminalis L.) during the summer months, under natural and artificially extended photoperiods. Although the long day treatment prevented the general onset of dormancy, the plants grown under natural daylengths showed lower concentration of abscisic acid than those kept under long days.

Fruitlet abscission: A cDNA-AFLP approach to study genes differentially expressed during shedding of immature fruits reveals the involvement of a putative auxin hydrogen symporter in apple (Malus domestica L. Borkh).

PubMed

Dal Cin, Valeriano; Barbaro, Enrico; Danesin, Marcello; Murayama, Hideki; Velasco, Riccardo; Ramina, Angelo

2009-08-01

Apple Malus X domestica fruitlet abscission is preceded by a stimulation of ethylene biosynthesis and a gain in sensitivity to the hormone. This phase was studied by a differential screening carried out by cDNA-AFLP in abscising (AF) and non-abscising (NAF) fruitlet populations. Fifty-three primer combinations allowed for the isolation of 131, 66 and 30 differentially expressed bands from cortex, peduncle and seed, respectively. All sequences were then classified as up- or down-regulated by comparing the profile in AFs and NAFs. Almost all of these sequences showed significant homology to genes encoding proteins with known or putative function. The gene ontology analysis of the TDFs isolated indicated a deep change in metabolism, plastid and hormonal status, especially auxin. Furthermore, some common elements between abscission and senescence were identified. The isolation of the full length of one of these TDFs allowed for the identification of a gene encoding an auxin hydrogen symporter (MdAHS). Bioinformatic analysis indicated that the deduced protein shares some features with other auxin efflux carriers, which include PINs. Nevertheless the 3D structure pointed out substantial differences and a conformation largely dissimilar from canonical ion transporters. The expression analysis demonstrated that this gene is regulated by light and development but not affected by ethylene or auxin.

Enhanced determination of abscisic acid (ABA) and abscisic acid glucose ester (ABA-GE) in Cistus albidus plants by liquid chromatography-mass spectrometry in tandem mode.

PubMed

López-Carbonell, Marta; Gabasa, Marta; Jáuregui, Olga

2009-04-01

An improved, quick and simple method for the extraction and quantification of the phytohormones (+)-abscisic acid (ABA) and its major glucose conjugate, abscisic acid glucose ester (ABA-GE) in plant samples is described. The method includes the addition of deuterium-labeled internal standards to the leaves at the beginning of the extraction for quantification, a simple extraction/centrifugation process and the injection into the liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS-MS) system in multiple reaction monitoring mode (MRM). Quality parameters of the method (detection limits, repeatability, reproducibility and linearity) have been studied. The objective of this work is to show the applicability of this method for quantifying the endogenous content of both ABA and ABA-GE in Cistus albidus plants that have been grown during an annual cycle under Mediterranean field conditions. Leaf samples from winter plants have low levels of ABA which increase in spring and summer showing two peaks that corresponded to April and August. These increases are coincident with the high temperature and solar radiation and the low RWC and RH registered along the year. On the other hand, the endogenous levels of ABA-GE increase until maximum values in July just before the ABA content reaches its highest concentration, decreasing in August and during autumn and winter. Our results suggest that the method is useful for quantifying both compounds in this plant material and represents the advantage of a short-time sample preparation with a high accuracy and viability.

Very-Long-Chain Fatty Acids Are Involved in Polar Auxin Transport and Developmental Patterning in Arabidopsis[W

PubMed Central

Roudier, François; Gissot, Lionel; Beaudoin, Frédéric; Haslam, Richard; Michaelson, Louise; Marion, Jessica; Molino, Diana; Lima, Amparo; Bach, Liên; Morin, Halima; Tellier, Frédérique; Palauqui, Jean-Christophe; Bellec, Yannick; Renne, Charlotte; Miquel, Martine; DaCosta, Marco; Vignard, Julien; Rochat, Christine; Markham, Jonathan E.; Moreau, Patrick; Napier, Johnathan; Faure, Jean-Denis

2010-01-01

Very-long-chain fatty acids (VLCFAs) are essential for many aspects of plant development and necessary for the synthesis of seed storage triacylglycerols, epicuticular waxes, and sphingolipids. Identification of the acetyl-CoA carboxylase PASTICCINO3 and the 3-hydroxy acyl-CoA dehydratase PASTICCINO2 revealed that VLCFAs are important for cell proliferation and tissue patterning. Here, we show that the immunophilin PASTICCINO1 (PAS1) is also required for VLCFA synthesis. Impairment of PAS1 function results in reduction of VLCFA levels that particularly affects the composition of sphingolipids, known to be important for cell polarity in animals. Moreover, PAS1 associates with several enzymes of the VLCFA elongase complex in the endoplasmic reticulum. The pas1 mutants are deficient in lateral root formation and are characterized by an abnormal patterning of the embryo apex, which leads to defective cotyledon organogenesis. Our data indicate that in both tissues, defective organogenesis is associated with the mistargeting of the auxin efflux carrier PIN FORMED1 in specific cells, resulting in local alteration of polar auxin distribution. Furthermore, we show that exogenous VLCFAs rescue lateral root organogenesis and polar auxin distribution, indicating their direct involvement in these processes. Based on these data, we propose that PAS1 acts as a molecular scaffold for the fatty acid elongase complex in the endoplasmic reticulum and that the resulting VLCFAs are required for polar auxin transport and tissue patterning during plant development. PMID:20145257

Rewiring of auxin signaling under persistent shade.

PubMed

Pucciariello, Ornella; Legris, Martina; Costigliolo Rojas, Cecilia; Iglesias, María José; Hernando, Carlos Esteban; Dezar, Carlos; Vazquez, Martín; Yanovsky, Marcelo J; Finlayson, Scott A; Prat, Salomé; Casal, Jorge J

2018-05-22

Light cues from neighboring vegetation rapidly initiate plant shade-avoidance responses. Despite our detailed knowledge of the early steps of this response, the molecular events under prolonged shade are largely unclear. Here we show that persistent neighbor cues reinforce growth responses in addition to promoting auxin-responsive gene expression in Arabidopsis and soybean. However, while the elevation of auxin levels is well established as an early event, in Arabidopsis , the response to prolonged shade occurs when auxin levels have declined to the prestimulation values. Remarkably, the sustained low activity of phytochrome B under prolonged shade led to ( i ) decreased levels of PHYTOCHROME INTERACTING FACTOR 4 (PIF4) in the cotyledons (the organs that supply auxin) along with increased levels in the vascular tissues of the stem, ( ii ) elevated expression of the PIF4 targets INDOLE-3-ACETIC ACID 19 ( IAA19 ) and IAA29 , which in turn reduced the expression of the growth-repressive IAA17 regulator, ( iii ) reduced abundance of AUXIN RESPONSE FACTOR 6, ( iv ) reduced expression of MIR393 and increased abundance of its targets, the auxin receptors, and ( v ) elevated auxin signaling as indicated by molecular markers. Mathematical and genetic analyses support the physiological role of this system-level rearrangement. We propose that prolonged shade rewires the connectivity between light and auxin signaling to sustain shade avoidance without enhanced auxin levels.

Response of Cultured Maize Cells to (+)-Abscisic Acid, (-)-Abscisic Acid, and Their Metabolites.

PubMed Central

Balsevich, J. J.; Cutler, A. J.; Lamb, N.; Friesen, L. J.; Kurz, E. U.; Perras, M. R.; Abrams, S. R.

1994-01-01

The metabolism and effects of (+)-S- and (-)-R-abscisic acid (ABA) and some metabolites were studied in maize (Zea mays L. cv Black Mexican Sweet) suspension-cultured cells. Time-course studies of metabolite formation were performed in both cells and medium via analytical high-performance liquid chromatography. Metabolites were isolated and identified using physical and chemical methods. At 10 [mu]M concentration and 28[deg] C, (+)-ABA was metabolized within 24 h, yielding natural (-)-phaseic acid [(-)-PA] as the major product. The unnatural enantiomer (-)-ABA was less than 50% metabolized within 24 h and gave primarily (-)-7[prime]-hydroxyABA [(-)-7[prime]-HOABA], together with (+)-PA and ABA glucose ester. The distribution of metabolites in cells and medium was different, reflecting different sites of metabolism and membrane permeabilities of conjugated and nonconjugated metabolites. The results imply that (+)-ABA was oxidized to (-)-PA inside the cell, whereas (-)-ABA was converted to (-)-7[prime]-HOABA at the cell surface. Growth of maize cells was inhibited by both (+)- and (-)-ABA, with only weak contributions from their metabolites. The concentration of (+)-ABA that caused a 50% inhibition of growth of maize cells was approximately 1 [mu]M, whereas that for its metabolite (-)-PA was approximately 50 [mu]M. (-)-ABA was less active than (+)-ABA, with 50% growth inhibition observed at about 10 [mu]M. (-)-7[prime]-HOABA was only weakly active, with 50% inhibition caused by approximately 500 [mu]M. Time-course studies of medium pH indicated that (+)-ABA caused a transient pH increase (+0.3 units) at 6 h after addition that was not observed in controls or in samples treated with (-)-PA. The effect of (-)-ABA on medium Ph was marginal. No racemization at C-1[prime] of (+)-ABA, (-)-ABA, or metabolites was observed during the studies. PMID:12232311

Exogenous abscisic acid significantly affects proteome in tea plant (Camellia sinensis) exposed to drought stress

USDA-ARS?s Scientific Manuscript database

Tea [Camellia sinensis (L.) O. Kuntze] is an important economic crop, and drought is the most important abiotic stress affecting yield and quality. Abscisic acid (ABA) is an important phytohormone responsible for activating drought resistance. Increased understanding of ABA effects on tea plant unde...

Auxin increases the hydraulic conductivity of auxin-sensitive hypocotyl tissue.

PubMed

Boyer, J S; Wu, G

1978-01-01

The ability of water to enter the cells of growing hypocotyl tissue was determined in etiolated soybean (Glycine max (L.) Merr.) seedlings. Water uptake was restricted to that for cell enlargement, and the seedlings were kept intact insofar as possible. Tissue water potentials (ψ w) were measured at thermodynamic equilibrium with an isopiestic thermocouple psychrometer. ψ wwas below the water potential of the environment by as much as 3.1 bars when the tissue was enlarging rapidly. However, ψ w was similar to the water potential of the environment when cell enlargement was not occurring. The low ψ w in enlarging tissue indicates that there was a low conductivity for water entering the cells.The ability of water to enter the enlarging cells was defined as the apparent hydraulic conductivity of the tissue (L'p). Despite the low L'p of growing cells, L'p decreased further as cell enlargement decreased when intact hypocotyl tissue was deprived of endogenous auxin (indole-3-acetic acid) by removal of the hypocotyl hook. Cell enlargement resumed and L'p increased when auxin was resupplied exogenously. The auxin-induced increase in L'p was correlated with the magnitude of the growth enhancement caused by auxin, and it was observed during the earliest phase of the growth response to auxin. The increase in L'p appeared to be caused by an increase in the hydraulic conductivity of the cell protoplasm, since other factors contributing to L'p remained constant. The rapidity of the response is consistent with a cellular site of action at the plasmalemma, although other sites are not precluded.Because the experiments involved only short times, auxin-induced changes in cell enlargement could not be attributed to changes in cell osmotic potentials. Neither could they be attributed to changes in turgor, which increased when the rate of enlargement decreased. Rather, auxin appeared to act by altering the extensibility of the cell walls and by simultaneously altering the ability

Investigating a Potential Auxin-Related Mode of Hormetic/Inhibitory Action of the Phytotoxin Parthenin.

PubMed

Belz, Regina G

2016-01-01

Parthenin is a metabolite of Parthenium hysterophorus and is believed to contribute to the weed's invasiveness via allelopathy. Despite the potential of parthenin to suppress competitors, low doses stimulate plant growth. This biphasic action was hypothesized to be auxin-like and, therefore, an auxin-related mode of parthenin action was investigated using two approaches: joint action experiments with Lactuca sativa, and dose-response experiments with auxin/antiauxin-resistant Arabidopsis thaliana genotypes. The joint action approach comprised binary mixtures of subinhibitory doses of the auxin 3-indoleacetic acid (IAA) mixed with parthenin or one of three reference compounds [indole-3-butyric acid (IBA), 2,3,5-triiodobenzoic acid (TIBA), 2-(p-chlorophenoxy)-2-methylpropionic acid (PCIB)]. The reference compounds significantly interacted with IAA at all doses, but parthenin interacted only at low doses indicating that parthenin hormesis may be auxin-related, in contrast to its inhibitory action. The genetic approach investigated the response of four auxin/antiauxin-resistant mutants and a wildtype to parthenin or two reference compounds (IAA, PCIB). The responses of mutant plants to the reference compounds confirmed previous reports, but differed from the responses observed for parthenin. Parthenin stimulated and inhibited all mutants independent of resistance. This provided no indication for an auxin-related action of parthenin. Therefore, the hypothesis of an auxin-related inhibitory action of parthenin was rejected in two independent experimental approaches, while the hypothesis of an auxin-related stimulatory effect could not be rejected.

Auxin-induced growth of Avena coleoptiles involves two mechanisms with different pH optima

NASA Technical Reports Server (NTRS)

Cleland, R. E.

1992-01-01

Although rapid auxin-induced growth of coleoptile sections can persist for at least 18 hours, acid-induced growth lasts for a much shorter period of time. Three theories have been proposed to explain this difference in persistence. To distinguish between these theories, the pH dependence for auxin-induced growth of oat (Avena sativa L.) coleoptiles has been determined early and late in the elongation process. Coleoptile sections from which the outer epidermis was removed to facilitate buffer entry were incubated, with or without 10 micromolar indoleacetic acid, in 20 millimolar buffers at pH 4.5 to 7.0 to maintain a fixed wall pH. During the first 1 to 2 hours after addition of auxin, elongation occurs by acid-induced extension (i.e. the pH optimum is <5 and the elongation varies inversely with the solution pH). Auxin causes no additional elongation because the buffers prevent further changes in wall pH. After 60 to 90 minutes, a second mechanism of auxin-induced growth, whose pH optimum is 5.5 to 6.0, predominates. It is proposed that rapid growth responses to changes in auxin concentration are mediated by auxin-induced changes in wall pH, whereas the prolonged, steady-state growth rate is controlled by a second, auxin-mediated process whose pH optimum is less acidic.

Gibberellic Acid-Stimulated Arabidopsis6 Serves as an Integrator of Gibberellin, Abscisic Acid, and Glucose Signaling during Seed Germination in Arabidopsis.

PubMed

Zhong, Chunmei; Xu, Hao; Ye, Siting; Wang, Shiyi; Li, Lingfei; Zhang, Shengchun; Wang, Xiaojing

2015-11-01

The DELLA protein REPRESSOR OF ga1-3-LIKE2 (RGL2) plays an important role in seed germination under different conditions through a number of transcription factors. However, the functions of the structural genes associated with RGL2-regulated germination are less defined. Here, we report the role of an Arabidopsis (Arabidopsis thaliana) cell wall-localized protein, Gibberellic Acid-Stimulated Arabidopsis6 (AtGASA6), in functionally linking RGL2 and a cell wall loosening expansin protein (Arabidopsis expansin A1 [AtEXPA1]), resulting in the control of embryonic axis elongation and seed germination. AtGASA6-overexpressing seeds showed precocious germination, whereas transfer DNA and RNA interference mutant seeds displayed delayed seed germination under abscisic acid, paclobutrazol, and glucose (Glc) stress conditions. The differences in germination rates resulted from corresponding variation in cell elongation in the hypocotyl-radicle transition region of the embryonic axis. AtGASA6 was down-regulated by RGL2, GLUCOSE INSENSITIVE2, and ABSCISIC ACID-INSENSITIVE5 genes, and loss of AtGASA6 expression in the gasa6 mutant reversed the insensitivity shown by the rgl2 mutant to paclobutrazol and the gin2 mutant to Glc-induced stress, suggesting that it is involved in regulating both the gibberellin and Glc signaling pathways. Furthermore, it was found that the promotion of seed germination and length of embryonic axis by AtGASA6 resulted from a promotion of cell elongation at the embryonic axis mediated by AtEXPA1. Taken together, the data indicate that AtGASA6 links RGL2 and AtEXPA1 functions and plays a role as an integrator of gibberellin, abscisic acid, and Glc signaling, resulting in the regulation of seed germination through a promotion of cell elongation. © 2015 American Society of Plant Biologists. All Rights Reserved.

Large-scale proteome analysis of abscisic acid and ABSCISIC ACID INSENSITIVE3-dependent proteins related to desiccation tolerance in Physcomitrella patens.

PubMed

Yotsui, Izumi; Serada, Satoshi; Naka, Tetsuji; Saruhashi, Masashi; Taji, Teruaki; Hayashi, Takahisa; Quatrano, Ralph S; Sakata, Yoichi

2016-03-18

Desiccation tolerance is an ancestral feature of land plants and is still retained in non-vascular plants such as bryophytes and some vascular plants. However, except for seeds and spores, this trait is absent in vegetative tissues of vascular plants. Although many studies have focused on understanding the molecular basis underlying desiccation tolerance using transcriptome and proteome approaches, the critical molecular differences between desiccation tolerant plants and non-desiccation plants are still not clear. The moss Physcomitrella patens cannot survive rapid desiccation under laboratory conditions, but if cells of the protonemata are treated by the phytohormone abscisic acid (ABA) prior to desiccation, it can survive 24 h exposure to desiccation and regrow after rehydration. The desiccation tolerance induced by ABA (AiDT) is specific to this hormone, but also depends on a plant transcription factor ABSCISIC ACID INSENSITIVE3 (ABI3). Here we report the comparative proteomic analysis of AiDT between wild type and ABI3 deleted mutant (Δabi3) of P. patens using iTRAQ (Isobaric Tags for Relative and Absolute Quantification). From a total of 1980 unique proteins that we identified, only 16 proteins are significantly altered in Δabi3 compared to wild type after desiccation following ABA treatment. Among this group, three of the four proteins that were severely affected in Δabi3 tissue were Arabidopsis orthologous genes, which were expressed in maturing seeds under the regulation of ABI3. These included a Group 1 late embryogenesis abundant (LEA) protein, a short-chain dehydrogenase, and a desiccation-related protein. Our results suggest that at least three of these proteins expressed in desiccation tolerant cells of both Arabidopsis and the moss are very likely to play important roles in acquisition of desiccation tolerance in land plants. Furthermore, our results suggest that the regulatory machinery of ABA- and ABI3-mediated gene expression for desiccation

Effect of exogenous abscisic acid on morphology, growth and nutrient uptake of rice (Oryza sativa) roots under simulated acid rain stress.

PubMed

Liu, Hongyue; Ren, Xiaoqian; Zhu, Jiuzheng; Wu, Xi; Liang, Chanjuan

2018-05-31

Application of proper ABA can improve acid tolerance of rice roots by balancing endogenous hormones and promoting nutrient uptake. Abscisic acid (ABA) has an important signaling role in enhancing plant tolerance to environmental stress. To alleviate the inhibition on plant growth and productivity caused by acid rain, it is crucial to clarify the regulating mechanism of ABA on adaptation of plants to acid rain. Here, we studied the effects of exogenously applied ABA on nutrients uptake of rice roots under simulated acid rain (SAR) stress from physiological, biochemical and molecular aspects. Compared to the single SAR treatment (pH 4.5 or 3.5), exogenous 10 μM ABA alleviated the SAR-induced inhibition of root growth by balancing endogenous hormones (abscisic acid, indole-3-acetic acid, gibberellic acid and zeatin), promoting nutrient uptake (nitrate, P, K and Mg) in rice roots, and increasing the activity of the plasma membrane H + -ATPase by up-regulating expression levels of genes (OSA2, OSA4, OSA9 and OSA10). However, exogenous 100 μM ABA exacerbated the SAR-caused inhibition of root growth by disrupting the balance of endogenous hormones, and inhibiting nutrient uptake (nitrate, P, K, Ca and Mg) through decreasing the activity of the plasma membrane H + -ATPase. These results indicate that proper concentration of exogenous ABA could enhance tolerance of rice roots to SAR stress by promoting nutrients uptake and balancing endogenous hormones.

Early embryo development in Fucus distichus is auxin sensitive

NASA Technical Reports Server (NTRS)

Basu, Swati; Sun, Haiguo; Brian, Leigh; Quatrano, Ralph L.; Muday, Gloria K.

2002-01-01

Auxin and polar auxin transport have been implicated in controlling embryo development in land plants. The goal of these studies was to determine if auxin and auxin transport are also important during the earliest stages of development in embryos of the brown alga Fucus distichus. Indole-3-acetic acid (IAA) was identified in F. distichus embryos and mature tissues by gas chromatography-mass spectroscopy. F. distichus embryos accumulate [(3)H]IAA and an inhibitor of IAA efflux, naphthylphthalamic acid (NPA), elevates IAA accumulation, suggesting the presence of an auxin efflux protein complex similar to that found in land plants. F. distichus embryos normally develop with a single unbranched rhizoid, but growth on IAA leads to formation of multiple rhizoids and growth on NPA leads to formation of embryos with branched rhizoids, at concentrations that are active in auxin accumulation assays. The effects of IAA and NPA are complete before 6 h after fertilization (AF), which is before rhizoid germination and cell division. The maximal effects of IAA and NPA are between 3.5 and 5 h AF and 4 and 5.5 h AF, respectively. Although, the location of the planes of cell division was significantly altered in NPA- and IAA-treated embryos, these abnormal divisions occurred after abnormal rhizoid initiation and branching was observed. The results of this study suggest that auxin acts in the formation of apical basal patterns in F. distichus embryo development.

Abscisic acid induces biosynthesis of bisbibenzyls and tolerance to UV-C in the liverwort Marchantia polymorpha.

PubMed

Kageyama, Akito; Ishizaki, Kimitsune; Kohchi, Takayuki; Matsuura, Hideyuki; Takahashi, Kosaku

2015-09-01

Environmental stresses are effective triggers for the biosynthesis of various secondary metabolites in plants, and phytohormones such as jasmonic acid and abscisic acid are known to mediate such responses in flowering plants. However, the detailed mechanism underlying the regulation of secondary metabolism in bryophytes remains unclear. In this study, the induction mechanism of secondary metabolites in the model liverwort Marchantia polymorpha was investigated. Abscisic acid (ABA) and ultraviolet irradiation (UV-C) were found to induce the biosynthesis of isoriccardin C, marchantin C, and riccardin F, which are categorized as bisbibenzyls, characteristic metabolites of liverworts. UV-C led to the significant accumulation of ABA. Overexpression of MpABI1, which encodes protein phosphatase 2C (PP2C) as a negative regulator of ABA signaling, suppressed accumulation of bisbibenzyls in response to ABA and UV-C irradiation and conferred susceptibility to UV-C irradiation. These data show that ABA plays a significant role in the induction of bisbibenzyl biosynthesis, which might confer tolerance against UV-C irradiation in M. polymorpha. Copyright © 2015 Elsevier Ltd. All rights reserved.

[Aerobic methylobacteria are capable of synthesizing auxins].

PubMed

Ivanova, E G; Doronina, N V; Trotsenko, Iu A

2001-01-01

Obligately and facultatively methylotrophic bacteria with different pathways of C1 metabolism were found to be able to produce auxins, particularly indole-3-acetic acid (IAA), in amounts of 3-100 micrograms/ml. Indole-3-pyruvic acid and indole-3-acetamide were detected only in methylobacteria with the serine pathway of C1 metabolism, Methylobacterium mesophilicum and Aminobacter aminovorans. The production of auxins by methylobacteria was stimulated by the addition of tryptophan to the growth medium and was inhibited by ammonium ions. The methylobacteria under study lacked tryptophan decarboxylase and tryptophan side-chain oxidase. At the same time, they were found to contain several aminotransferases. IAA is presumably synthesized by methylobacteria through indole-3-pyruvic acid.

YUCCA9-Mediated Auxin Biosynthesis and Polar Auxin Transport Synergistically Regulate Regeneration of Root Systems Following Root Cutting

PubMed Central

Xu, Dongyang; Miao, Jiahang; Yumoto, Emi; Yokota, Takao; Asahina, Masashi; Watahiki, Masaaki

2017-01-01

Abstract Recovery of the root system following physical damage is an essential issue for plant survival. An injured root system is able to regenerate by increases in lateral root (LR) number and acceleration of root growth. The horticultural technique of root pruning (root cutting) is an application of this response and is a common garden technique for controlling plant growth. Although root pruning is widely used, the molecular mechanisms underlying the subsequent changes in the root system are poorly understood. In this study, root pruning was employed as a model system to study the molecular mechanisms of root system regeneration. Notably, LR defects in wild-type plants treated with inhibitors of polar auxin transport (PAT) or in the auxin signaling mutant auxin/indole-3-acetic acid19/massugu2 were recovered by root pruning. Induction of IAA19 following root pruning indicates an enhancement of auxin signaling by root pruning. Endogenous levels of IAA increased after root pruning, and YUCCA9 was identified as the primary gene responsible. PAT-related genes were induced after root pruning, and the YUCCA inhibitor yucasin suppressed root regeneration in PAT-related mutants. Therefore, we demonstrate the crucial role of YUCCA9, along with other redundant YUCCA family genes, in the enhancement of auxin biosynthesis following root pruning. This further enhances auxin transport and activates downstream auxin signaling genes, and thus increases LR number. PMID:29016906

Auxins and tropisms

NASA Technical Reports Server (NTRS)

Muday, G. K.; Brown, C. S. (Principal Investigator)

2001-01-01

Differential growth of plants in response to the changes in the light and gravity vectors requires a complex signal transduction cascade. Although many of the details of the mechanisms by which these differential growth responses are induced are as yet unknown, auxin has been implicated in both gravitropism and phototropism. Specifically, the redistribution of auxin across gravity or light-stimulated tissues has been detected and shown to be required for this process. The approaches by which auxin has been implicated in tropisms include isolation of mutants altered in auxin transport or response with altered gravitropic or phototropic response, identification of auxin gradients with radiolabeled auxin and auxin-inducible gene reporter systems, and by use of inhibitors of auxin transport that block gravitropism and phototropism. Proteins that transport auxin have been identified and the mechanisms which determine auxin transport polarity have been explored. In addition, recent evidence that reversible protein phosphorylation controls this process is summarized. Finally, the data in support of several hypotheses for mechanisms by which auxin transport could be differentially regulated during gravitropism are examined. Although many details of the mechanisms by which plants respond to gravity and light are not yet clear, numerous recent studies demonstrate the role of auxin in these processes.

Abscisic acid form, concentration, and application timing influence phenology and bud cold hardiness in Merlot grapevines

USDA-ARS?s Scientific Manuscript database

The effects of abscisic acid (ABA) form, concentration and application timing on bud cold hardiness, phenology and fruiting performance on ‘Merlot’ grapevines (Vitis vinifera) were evaluated in a three year field trial with site locations in British Columbia Canada, Ontario Canada, Washington U.S. ...

Auxin crosstalk to plant immune networks: a plant-pathogen interaction perspective.

PubMed

Naseem, Muhammad; Srivastava, Mugdha; Tehseen, Muhammad; Ahmed, Nazeer

2015-01-01

The plant hormone auxin regulates a whole repertoire of plant growth and development. Many plant-associated microorganisms, by virtue of their auxin production capability, mediate phytostimulation effects on plants. Recent studies, however, demonstrate diverse mechanisms whereby plant pathogens manipulate auxin biosynthesis, signaling and transport pathways to promote host susceptibility. Auxin responses have been coupled to their antagonistic and synergistic interactions with salicylic acid and jasmonate mediated defenses, respectively. Here, we discuss that a better understanding of auxin crosstalk to plant immune networks would enable us to engineer crop plants with higher protection and low unintended yield losses.

The Basic Leucine Zipper Transcription Factor ABSCISIC ACID RESPONSE ELEMENT-BINDING FACTOR2 Is an Important Transcriptional Regulator of Abscisic Acid-Dependent Grape Berry Ripening Processes1[W][OPEN

PubMed Central

Nicolas, Philippe; Lecourieux, David; Kappel, Christian; Cluzet, Stéphanie; Cramer, Grant; Delrot, Serge; Lecourieux, Fatma

2014-01-01

In grape (Vitis vinifera), abscisic acid (ABA) accumulates during fruit ripening and is thought to play a pivotal role in this process, but the molecular basis of this control is poorly understood. This work characterizes ABSCISIC ACID RESPONSE ELEMENT-BINDING FACTOR2 (VvABF2), a grape basic leucine zipper transcription factor belonging to a phylogenetic subgroup previously shown to be involved in ABA and abiotic stress signaling in other plant species. VvABF2 transcripts mainly accumulated in the berry, from the onset of ripening to the harvesting stage, and were up-regulated by ABA. Microarray analysis of transgenic grape cells overexpressing VvABF2 showed that this transcription factor up-regulates and/or modifies existing networks related to ABA responses. In addition, grape cells overexpressing VvABF2 exhibited enhanced responses to ABA treatment compared with control cells. Among the VvABF2-mediated responses highlighted in this study, the synthesis of phenolic compounds and cell wall softening were the most strongly affected. VvABF2 overexpression strongly increased the accumulation of stilbenes that play a role in plant defense and human health (resveratrol and piceid). In addition, the firmness of fruits from tomato (Solanum lycopersicum) plants overexpressing VvABF2 was strongly reduced. These data indicate that VvABF2 is an important transcriptional regulator of ABA-dependent grape berry ripening. PMID:24276949

Clathrin-Mediated Auxin Efflux and Maxima Regulate Hypocotyl Hook Formation and Light-Stimulated Hook Opening in Arabidopsis.

PubMed

Yu, Qinqin; Zhang, Ying; Wang, Juan; Yan, Xu; Wang, Chao; Xu, Jian; Pan, Jianwei

2016-01-04

The establishment of auxin maxima by PIN-FORMED 3 (PIN3)- and AUXIN RESISTANT 1/LIKE AUX1 (LAX) 3 (AUX1/LAX3)-mediated auxin transport is essential for hook formation in Arabidopsis hypocotyls. Until now, however, the underlying regulatory mechanism has remained poorly understood. Here, we show that loss of function of clathrin light chain CLC2 and CLC3 genes enhanced auxin maxima and thereby hook curvature, alleviated the inhibitory effect of auxin overproduction on auxin maxima and hook curvature, and delayed blue light-stimulated auxin maxima reduction and hook opening. Moreover, pharmacological experiments revealed that auxin maxima formation and hook curvature in clc2 clc3 were sensitive to auxin efflux inhibitors 1-naphthylphthalamic acid and 2,3,5-triiodobenzoic acid but not to the auxin influx inhibitor 1-naphthoxyacetic acid. Live-cell imaging analysis further uncovered that loss of CLC2 and CLC3 function impaired PIN3 endocytosis and promoted its lateralization in the cortical cells but did not affect AUX1 localization. Taken together, these results suggest that clathrin regulates auxin maxima and thereby hook formation through modulating PIN3 localization and auxin efflux, providing a novel mechanism that integrates developmental signals and environmental cues to regulate plant skotomorphogenesis and photomorphogenesis. Copyright © 2016 The Author. Published by Elsevier Inc. All rights reserved.

The Role of Auxin in Cell Wall Expansion.

PubMed

Majda, Mateusz; Robert, Stéphanie

2018-03-22

Plant cells are surrounded by cell walls, which are dynamic structures displaying a strictly regulated balance between rigidity and flexibility. Walls are fairly rigid to provide support and protection, but also extensible, to allow cell growth, which is triggered by a high intracellular turgor pressure. Wall properties regulate the differential growth of the cell, resulting in a diversity of cell sizes and shapes. The plant hormone auxin is well known to stimulate cell elongation via increasing wall extensibility. Auxin participates in the regulation of cell wall properties by inducing wall loosening. Here, we review what is known on cell wall property regulation by auxin. We focus particularly on the auxin role during cell expansion linked directly to cell wall modifications. We also analyze downstream targets of transcriptional auxin signaling, which are related to the cell wall and could be linked to acid growth and the action of wall-loosening proteins. All together, this update elucidates the connection between hormonal signaling and cell wall synthesis and deposition.

Early Embryo Development in Fucus distichus Is Auxin Sensitive1

PubMed Central

Basu, Swati; Sun, Haiguo; Brian, Leigh; Quatrano, Ralph L.; Muday, Gloria K.

2002-01-01

Auxin and polar auxin transport have been implicated in controlling embryo development in land plants. The goal of these studies was to determine if auxin and auxin transport are also important during the earliest stages of development in embryos of the brown alga Fucus distichus. Indole-3-acetic acid (IAA) was identified in F. distichus embryos and mature tissues by gas chromatography-mass spectroscopy. F. distichus embryos accumulate [3H]IAA and an inhibitor of IAA efflux, naphthylphthalamic acid (NPA), elevates IAA accumulation, suggesting the presence of an auxin efflux protein complex similar to that found in land plants. F. distichus embryos normally develop with a single unbranched rhizoid, but growth on IAA leads to formation of multiple rhizoids and growth on NPA leads to formation of embryos with branched rhizoids, at concentrations that are active in auxin accumulation assays. The effects of IAA and NPA are complete before 6 h after fertilization (AF), which is before rhizoid germination and cell division. The maximal effects of IAA and NPA are between 3.5 and 5 h AF and 4 and 5.5 h AF, respectively. Although, the location of the planes of cell division was significantly altered in NPA- and IAA-treated embryos, these abnormal divisions occurred after abnormal rhizoid initiation and branching was observed. The results of this study suggest that auxin acts in the formation of apical basal patterns in F. distichus embryo development. PMID:12226509

Involvement of a lipoxygenase-like enzyme in abscisic Acid biosynthesis.

PubMed

Creelman, R A; Bell, E; Mullet, J E

1992-07-01

Several lines of evidence indicate that abscisic acid (ABA) is derived from 9'-cis-neoxanthin or 9'-cis-violaxanthin with xanthoxin as an intermediate. (18)O-labeling experiments show incorporation primarily into the side chain carboxyl group of ABA, suggesting that oxidative cleavage occurs at the 11, 12 (11', 12') double bond of xanthophylls. Carbon monoxide, a strong inhibitor of heme-containing P-450 monooxygenases, did not inhibit ABA accumulation, suggesting that the oxygenase catalyzing the carotenoid cleavage step did not contain heme. This observation, plus the ability of lipoxygenase to make xanthoxin from violaxanthin, suggested that a lipoxygenase-like enzyme is involved in ABA biosynthesis. To test this idea, the ability of several soybean (Glycine max L.) lipoxygenase inhibitors (5,8,11-eicosatriynoic acid, 5,8,11,14-eicosatetraynoic acid, nordihydroguaiaretic acid, and naproxen) to inhibit stress-induced ABA accumulation in soybean cell culture and soybean seedlings was determined. All lipoxygenase inhibitors significantly inhibited ABA accumulation in response to stress. These results suggest that the in vivo oxidative cleavage reaction involved in ABA biosynthesis requires activity of a nonheme oxygenase having lipoxygenase-like properties.

Antisense suppression of phospholipase D alpha retards abscisic acid- and ethylene-promoted senescence of postharvest Arabidopsis leaves.

PubMed Central

Fan, L; Zheng, S; Wang, X

1997-01-01

Membrane disruption has been proposed to be a key event in plant senescence, and phospholipase D (PLD; EC 3.1.4.4) has been thought to play an important role in membrane deterioration. We recently cloned and biochemically characterized three different PLDs from Arabidopsis. In this study, we investigated the role of the most prevalent phospholipid-hydrolyzing enzyme, PLD alpha, in membrane degradation and senescence in Arabidopsis. The expression of PLD alpha was suppressed by introducing a PLD alpha antisense cDNA fragment into Arabidopsis. When incubated with abscisic acid and ethylene, leaves detached from the PLD alpha-deficient transgenic plants showed a slower rate of senescence than did those from wild-type and transgenic control plants. The retardation of senescence was demonstrated by delayed leaf yellowing, lower ion leakage, greater photosynthetic activity, and higher content of chlorophyll and phospholipids in the PLD alpha antisense leaves than in those of the wild type. Treatment of detached leaves with abscisic acid and ethylene stimulated PLD alpha expression, as indicated by increases in PLD alpha mRNA, protein, and activity. In the absence of abscisic acid and ethylene, however, detached leaves from the PLD alpha-deficient and wild-type plants showed a similar rate of senescence. In addition, the suppression of PLD alpha did not alter natural plant growth and development. These data suggest that PLD alpha is an important mediator in phytohormone-promoted senescence in detached leaves but is not a direct promoter of natural senescence. The physiological relevance of these findings is discussed. PMID:9437863

Regulatory elements in vivo in the promoter of the abscisic acid responsive gene rab17 from maize.

PubMed

Busk, P K; Jensen, A B; Pagès, M

1997-06-01

The rab17 gene from maize is transcribed in late embryonic development and is responsive to abscisic acid and water stress in embryo and vegetative tissues. In vivo footprinting and transient transformation of rab17 were performed in embryos and vegetative tissues to characterize the cis-elements involved in regulation of the gene. By in vivo footprinting, protein binding was observed to nine elements in the promoter, which correspond to five putative ABREs (abscisic acid responsive elements) and four other sequences. The footprints indicated that distinct proteins interact with these elements in the two developmental stages. In transient transformation, six of the elements were important for high level expression of the rab17 promoter in embryos, whereas only three elements were important in leaves. The cis-acting sequences can be divided in embryo-specific, ABA-specific and leaf-specific elements on the basis of protein binding and the ability to confer expression of rab17. We found one positive, new element, called GRA, with the sequence CACTGGCCGCCC. This element was important for transcription in leaves but not in embryos. Two other non-ABRE elements that stimulated transcription from the rab17 promoter resemble previously described abscisic acid and drought-inducible elements. There were differences in protein binding and function of the five ABREs in the rab17 promoter. The possible reasons for these differences are discussed. The in vivo data obtained suggest that an embryo-specific pathway regulates transcription of the rab genes during development, whereas another pathway is responsible for induction in response to ABA and drought in vegetative tissues.

Effect of asymmetric auxin application on Helianthus hypocotyl curvature

NASA Technical Reports Server (NTRS)

Migliaccio, F.; Rayle, D. L.

1989-01-01

Indole-3-acetic acid was applied asymmetrically to the hypocotyls of sunflower (Helianthus annuus L.) seedlings. After 5 hours on a clinostat, auxin gradients as small as 1 to 1.3 produced substantial (more than 60 degrees) hypocotyl curvature. This result suggests the asymmetric growth underlying hypocotyl gravitropism can be explained by lateral auxin redistribution.

Leaf expansion in Phaseolus: transient auxin-induced growth increase

PubMed Central

Keller, Christopher P.

2017-01-01

Control of leaf expansion by auxin is not well understood. Evidence from short term exogenous applications and from treatment of excised tissues suggests auxin positively influences growth. Manipulations of endogenous leaf auxin content, however, suggests that, long-term, auxin suppresses leaf expansion. This study attempts to clarify the growth effects of auxin on unifoliate (primary) leaves of the common bean (Phaseolus vulgaris) by reexamining the response to auxin treatment of both excised leaf strips and attached leaves. Leaf strips, incubated in culture conditions that promoted steady elongation for up to 48 h, treated with 10 μM NAA responded with an initial surge of elongation growth complete within 10 hours followed by insensitivity. A range of NAA concentrations from 0.1 μM to 300 μM induced increased strip elongation after 24 hours and 48 hours. Increased elongation and epinastic curvature of leaf strips was found specific to active auxins. Expanding attached unifoliates treated once with aqueous auxin α-naphthalene acetic acid (NAA) at 1.0 mM showed both an initial surge in growth lasting 4–6 hours followed by growth inhibition sustained at least as long as 24 hours post treatment. Auxin-induced inhibition of leaf expansion was associated with smaller epidermal cell area. Together the results suggest increasing leaf auxin first increases growth then slows growth through inhibition of cell expansion. Excised leaf strips, retain only the initial increased growth response to auxin and not the subsequent growth inhibition, either as a consequence of wounding or of isolation from the plant. PMID:29200506

Role of Auxin-Induced Reactive Oxygen Species in Root Gravitropism1

PubMed Central

Joo, Jung Hee; Bae, Yun Soo; Lee, June Seung

2001-01-01

We report our studies on root gravitropism indicating that reactive oxygen species (ROS) may function as a downstream component in auxin-mediated signal transduction. A transient increase in the intracellular concentration of ROS in the convex endodermis resulted from either gravistimulation or unilateral application of auxin to vertical roots. Root bending was also brought about by unilateral application of ROS to vertical roots pretreated with the auxin transport inhibitor N-1-naphthylphthalamic acid. Furthermore, the scavenging of ROS by antioxidants (N-acetylcysteine, ascorbic acid, and Trolox) inhibited root gravitropism. These results indicate that the generation of ROS plays a role in root gravitropism. PMID:11457956

Abscisic acid is not necessary for gravitropism in primary roots of Zea mays

NASA Technical Reports Server (NTRS)

Moore, R.

1990-01-01

Primary roots of Zea mays L. cv. Tx 5855 treated with fluridone are strongly graviresponsive, but have undetectable levels of abscisic acid (ABA). Primary roots of the carotenoid-deficient w-3, vp-5, and vp-7 mutants of Z. mays are also graviresponsive despite having undetectable amounts of ABA. Graviresponsive roots of untreated and wild-type seedlings contain 286 to 317 ng ABA g-1 f. wt, respectively. These results indicate that ABA is not necessary for root gravicurvature.

Gibberellic Acid-Stimulated Arabidopsis6 Serves as an Integrator of Gibberellin, Abscisic Acid, and Glucose Signaling during Seed Germination in Arabidopsis1[OPEN

PubMed Central

Zhong, Chunmei; Xu, Hao; Ye, Siting; Wang, Shiyi; Li, Lingfei; Zhang, Shengchun; Wang, Xiaojing

2015-01-01

The DELLA protein REPRESSOR OF ga1-3-LIKE2 (RGL2) plays an important role in seed germination under different conditions through a number of transcription factors. However, the functions of the structural genes associated with RGL2-regulated germination are less defined. Here, we report the role of an Arabidopsis (Arabidopsis thaliana) cell wall-localized protein, Gibberellic Acid-Stimulated Arabidopsis6 (AtGASA6), in functionally linking RGL2 and a cell wall loosening expansin protein (Arabidopsis expansin A1 [AtEXPA1]), resulting in the control of embryonic axis elongation and seed germination. AtGASA6-overexpressing seeds showed precocious germination, whereas transfer DNA and RNA interference mutant seeds displayed delayed seed germination under abscisic acid, paclobutrazol, and glucose (Glc) stress conditions. The differences in germination rates resulted from corresponding variation in cell elongation in the hypocotyl-radicle transition region of the embryonic axis. AtGASA6 was down-regulated by RGL2, GLUCOSE INSENSITIVE2, and ABSCISIC ACID-INSENSITIVE5 genes, and loss of AtGASA6 expression in the gasa6 mutant reversed the insensitivity shown by the rgl2 mutant to paclobutrazol and the gin2 mutant to Glc-induced stress, suggesting that it is involved in regulating both the gibberellin and Glc signaling pathways. Furthermore, it was found that the promotion of seed germination and length of embryonic axis by AtGASA6 resulted from a promotion of cell elongation at the embryonic axis mediated by AtEXPA1. Taken together, the data indicate that AtGASA6 links RGL2 and AtEXPA1 functions and plays a role as an integrator of gibberellin, abscisic acid, and Glc signaling, resulting in the regulation of seed germination through a promotion of cell elongation. PMID:26400990

Evolutionarily conserved regulatory mechanisms of abscisic acid signaling in land plants: characterization of ABSCISIC ACID INSENSITIVE1-like type 2C protein phosphatase in the liverwort Marchantia polymorpha.

PubMed

Tougane, Ken; Komatsu, Kenji; Bhyan, Salma Begum; Sakata, Yoichi; Ishizaki, Kimitsune; Yamato, Katsuyuki T; Kohchi, Takayuki; Takezawa, Daisuke

2010-03-01

Abscisic acid (ABA) is postulated to be a ubiquitous hormone that plays a central role in seed development and responses to environmental stresses of vascular plants. However, in liverworts (Marchantiophyta), which represent the oldest extant lineage of land plants, the role of ABA has been least emphasized; thus, very little information is available on the molecular mechanisms underlying ABA responses. In this study, we isolated and characterized MpABI1, an ortholog of ABSCISIC ACID INSENSITIVE1 (ABI1), from the liverwort Marchantia polymorpha. The MpABI1 cDNA encoded a 568-amino acid protein consisting of the carboxy-terminal protein phosphatase 2C (PP2C) domain and a novel amino-terminal regulatory domain. The MpABI1 transcript was detected in the gametophyte, and its expression level was increased by exogenous ABA treatment in the gemma, whose growth was strongly inhibited by ABA. Experiments using green fluorescent protein fusion constructs indicated that MpABI1 was mainly localized in the nucleus and that its nuclear localization was directed by the amino-terminal domain. Transient overexpression of MpABI1 in M. polymorpha and Physcomitrella patens cells resulted in suppression of ABA-induced expression of the wheat Em promoter fused to the beta -glucuronidase gene. Transgenic P. patens expressing MpABI1 and its mutant construct, MpABI1-d2, lacking the amino-terminal domain, had reduced freezing and osmotic stress tolerance, and associated with reduced accumulation of ABA-induced late embryogenesis abundant-like boiling-soluble proteins. Furthermore, ABA-induced morphological changes leading to brood cells were not prominent in these transgenic plants. These results suggest that MpABI1 is a negative regulator of ABA signaling, providing unequivocal molecular evidence of PP2C-mediated ABA response mechanisms functioning in liverworts.

Synthesis and Biological Activity of 2',3'-iso-Aryl-abscisic Acid Analogs.

PubMed

Wan, Chuan; Wang, Mingan; Yang, Dongyan; Han, Xiaoqiang; Che, Chuanliang; Ding, Shanshan; Xiao, Yumei; Qin, Zhaohai

2017-12-15

2',3'- iso -Benzoabscisic acid ( iso -PhABA), an excellent selective abscisic acid (ABA) analog, was developed in our previous work. In order to find its more structure-activity information, some structural modifications were completed in this paper, including the substitution of phenyl ring and replacing the ring with heterocycles. Thus, 16 novel analogs of iso -PhABA were synthesized and screened with three bioassays, Arabidopsis and lettuce seed germination and rice seedling elongation. Some of them, i.e., 2',3'- iso -pyridoabscisic acid ( iso -PyABA) and 2',3'- iso -franoabscisic acid ( iso -FrABA), displayed good bioactivities that closed to iso -PhABA and natural (+)-ABA. Some others, for instance, substituted- iso -PhABA, exhibited certain selectivity to different physiological process when compared to iso -PhABA or (+)-ABA. These analogs not only provided new candidates of ABA-like synthetic plant growth regulators (PGRs) for practical application, but also new potential selective agonist/antagonist for probing the specific function of ABA receptors.

Functional Characterization of PaLAX1, a Putative Auxin Permease, in Heterologous Plant Systems1[W][OA

PubMed Central

Hoyerová, Klára; Perry, Lucie; Hand, Paul; Laňková, Martina; Kocábek, Tomáš; May, Sean; Kottová, Jana; Pačes, Jan; Napier, Richard; Zažímalová, Eva

2008-01-01

We have isolated the cDNA of the gene PaLAX1 from a wild cherry tree (Prunus avium). The gene and its product are highly similar in sequences to both the cDNAs and the corresponding protein products of AUX/LAX-type genes, coding for putative auxin influx carriers. We have prepared and characterized transformed Nicotiana tabacum and Arabidopsis thaliana plants carrying the gene PaLAX1. We have proved that constitutive overexpression of PaLAX1 is accompanied by changes in the content and distribution of free indole-3-acetic acid, the major endogenous auxin. The increase in free indole-3-acetic acid content in transgenic plants resulted in various phenotype changes, typical for the auxin-overproducing plants. The uptake of synthetic auxin, 2,4-dichlorophenoxyacetic acid, was 3 times higher in transgenic lines compared to the wild-type lines and the treatment with the auxin uptake inhibitor 1-naphthoxyacetic acid reverted the changes caused by the expression of PaLAX1. Moreover, the agravitropic response could be restored by expression of PaLAX1 in the mutant aux1 plants, which are deficient in auxin influx carrier activity. Based on our data, we have concluded that the product of the gene PaLAX1 promotes the uptake of auxin into cells, and, as a putative auxin influx carrier, it affects the content and distribution of free endogenous auxin in transgenic plants. PMID:18184737

Effects of mechanical stress or abscisic acid on growth, water status and leaf abscisic acid content of eggplant seedlings

NASA Technical Reports Server (NTRS)

Latimer, J. G.; Mitchell, C. A.

1988-01-01

Container-grown eggplant (Solanum melongena L. var esculentum Nees. 'Burpee's Black Beauty') seedlings were conditioned with brief, periodic mechanical stress or abscisic acid (ABA) in a greenhouse prior to outdoor exposure. Mechanical stress consisted of seismic (shaking) or thigmic (stem flexing) treatment. Exogenous ABA (10(-3) or 10(-4)M) was applied as a soil drench 3 days prior to outdoor transfer. During conditioning, only thigmic stress reduced stem elongation and only 10(-3) M ABA reduced relative growth rate (RGR). Both conditioning treatments increased leaf specific chlorophyll content, but mechanical stress did not affect leaf ABA content. Outdoor exposure of unconditioned eggplant seedlings decreased RGR and leaf-specific chlorophyll content, but tended to increase leaf ABA content relative to that of plants maintained in the greenhouse. Conditioning did not affect RGR of plants subsequently transferred outdoors, but did reduce stem growth. Seismic stress applied in the greenhouse reduced dry weight gain by plants subsequently transferred outdoors. Mechanical stress treatments increased leaf water potential by 18-25% relative to that of untreated plants.

The homeodomain-leucine zipper (HD-Zip) class I transcription factors ATHB7 and ATHB12 modulate abscisic acid signalling by regulating protein phosphatase 2C and abscisic acid receptor gene activities.

PubMed

Valdés, Ana Elisa; Overnäs, Elin; Johansson, Henrik; Rada-Iglesias, Alvaro; Engström, Peter

2012-11-01

Plants perceiving drought activate multiple responses to improve survival, including large-scale alterations in gene expression. This article reports on the roles in the drought response of two Arabidopsis thaliana homeodomain-leucine zipper class I genes; ATHB7 and ATHB12, both strongly induced by water-deficit and abscisic acid (ABA). ABA-mediated transcriptional regulation of both genes is shown to depend on the activity of protein phosphatases type 2C (PP2C). ATHB7 and ATHB12 are, thus, targets of the ABA signalling mechanism defined by the PP2Cs and the PYR/PYL family of ABA receptors, with which the PP2C proteins interact. Our results from chromatin immunoprecipitation and gene expression analyses demonstrate that ATHB7 and ATHB12 act as positive transcriptional regulators of PP2C genes, and thereby as negative regulators of abscisic acid signalling. In support of this notion, our results also show that ATHB7 and ATHB12 act to repress the transcription of genes encoding the ABA receptors PYL5 and PYL8 in response to an ABA stimulus. In summary, we demonstrate that ATHB7 and ATHB12 have essential functions in the primary response to drought, as mediators of a negative feedback effect on ABA signalling in the plant response to water deficit.

The Arabidopsis WRINKLED1 transcription factor affects auxin homeostasis in roots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kong, Que; Ma, Wei; Yang, Haibing

WRINKLED1 (WRI1) is a key transcriptional regulator of fatty acid biosynthesis genes in diverse oil-containing tissues. Loss of function of Arabidopsis WRI1 leads to a reduction in the expression of genes for fatty acid biosynthesis and glycolysis, and concomitant strong reduction of seed oil content. The wri1-1 loss-of-function mutant shows reduced primary root growth and decreased acidification of the growth medium. The content of a conjugated form of the plant growth hormone auxin, indole-3-acetic acid (IAA)-Asp, was higher in wri1-1 plants compared with the wild-type. GH3.3, a gene encoding an enzyme involved in auxin degradation, displayed higher expression in themore » wri1-1 mutant. EMSAs demonstrated that AtWRI1 bound to the promoter of GH3.3. Specific AtWRI1-binding motifs were identified in the promoter of GH3.3. In addition, wri1-1 displayed decreased auxin transport. Expression of some PIN genes, which encode IAA carrier proteins, was reduced in wri1-1 plants as well. Correspondingly, AtWRI1 bound to the promoter regions of some PIN genes. It is well known that auxin exerts its maximum effects at a specific, optimal concentration in roots requiring a finely balanced auxin homeostasis. This process appears to be disrupted when the expression of WRI1 and in turn a subset of its target genes are misregulated, highlighting a role for WRI1 in root auxin homeostasis.« less

The Arabidopsis WRINKLED1 transcription factor affects auxin homeostasis in roots

DOE PAGES

Kong, Que; Ma, Wei; Yang, Haibing; ...

2017-08-26

WRINKLED1 (WRI1) is a key transcriptional regulator of fatty acid biosynthesis genes in diverse oil-containing tissues. Loss of function of Arabidopsis WRI1 leads to a reduction in the expression of genes for fatty acid biosynthesis and glycolysis, and concomitant strong reduction of seed oil content. The wri1-1 loss-of-function mutant shows reduced primary root growth and decreased acidification of the growth medium. The content of a conjugated form of the plant growth hormone auxin, indole-3-acetic acid (IAA)-Asp, was higher in wri1-1 plants compared with the wild-type. GH3.3, a gene encoding an enzyme involved in auxin degradation, displayed higher expression in themore » wri1-1 mutant. EMSAs demonstrated that AtWRI1 bound to the promoter of GH3.3. Specific AtWRI1-binding motifs were identified in the promoter of GH3.3. In addition, wri1-1 displayed decreased auxin transport. Expression of some PIN genes, which encode IAA carrier proteins, was reduced in wri1-1 plants as well. Correspondingly, AtWRI1 bound to the promoter regions of some PIN genes. It is well known that auxin exerts its maximum effects at a specific, optimal concentration in roots requiring a finely balanced auxin homeostasis. This process appears to be disrupted when the expression of WRI1 and in turn a subset of its target genes are misregulated, highlighting a role for WRI1 in root auxin homeostasis.« less

The Role of Auxin in Cell Wall Expansion

PubMed Central

2018-01-01

Plant cells are surrounded by cell walls, which are dynamic structures displaying a strictly regulated balance between rigidity and flexibility. Walls are fairly rigid to provide support and protection, but also extensible, to allow cell growth, which is triggered by a high intracellular turgor pressure. Wall properties regulate the differential growth of the cell, resulting in a diversity of cell sizes and shapes. The plant hormone auxin is well known to stimulate cell elongation via increasing wall extensibility. Auxin participates in the regulation of cell wall properties by inducing wall loosening. Here, we review what is known on cell wall property regulation by auxin. We focus particularly on the auxin role during cell expansion linked directly to cell wall modifications. We also analyze downstream targets of transcriptional auxin signaling, which are related to the cell wall and could be linked to acid growth and the action of wall-loosening proteins. All together, this update elucidates the connection between hormonal signaling and cell wall synthesis and deposition. PMID:29565829

Antagonism between salicylic and abscisic acid reflects early host-pathogen conflict and moulds plant defence responses.

PubMed

de Torres Zabala, Marta; Bennett, Mark H; Truman, William H; Grant, Murray R

2009-08-01

The importance of phytohormone balance is increasingly recognized as central to the outcome of plant-pathogen interactions. Recently it has been demonstrated that abscisic acid signalling pathways are utilized by the bacterial phytopathogen Pseudomonas syringae to promote pathogenesis. In this study, we examined the dynamics, inter-relationship and impact of three key acidic phytohormones, salicylic acid, abscisic acid and jasmonic acid, and the bacterial virulence factor, coronatine, during progression of P. syringae infection of Arabidopsis thaliana. We show that levels of SA and ABA, but not JA, appear to play important early roles in determining the outcome of the infection process. SA is required in order to mount a full innate immune responses, while bacterial effectors act rapidly to activate ABA biosynthesis. ABA suppresses inducible innate immune responses by down-regulating SA biosynthesis and SA-mediated defences. Mutant analyses indicated that endogenous ABA levels represent an important reservoir that is necessary for effector suppression of plant-inducible innate defence responses and SA synthesis prior to subsequent pathogen-induced increases in ABA. Enhanced susceptibility due to loss of SA-mediated basal resistance is epistatically dominant over acquired resistance due to ABA deficiency, although ABA also contributes to symptom development. We conclude that pathogen-modulated ABA signalling rapidly antagonizes SA-mediated defences. We predict that hormonal perturbations, either induced or as a result of environmental stress, have a marked impact on pathological outcomes, and we provide a mechanistic basis for understanding priming events in plant defence.

Specificity determinants for the abscisic acid response element.

PubMed

Sarkar, Aditya Kumar; Lahiri, Ansuman

2013-01-01

Abscisic acid (ABA) response elements (ABREs) are a group of cis-acting DNA elements that have been identified from promoter analysis of many ABA-regulated genes in plants. We are interested in understanding the mechanism of binding specificity between ABREs and a class of bZIP transcription factors known as ABRE binding factors (ABFs). In this work, we have modeled the homodimeric structure of the bZIP domain of ABRE binding factor 1 from Arabidopsis thaliana (AtABF1) and studied its interaction with ACGT core motif-containing ABRE sequences. We have also examined the variation in the stability of the protein-DNA complex upon mutating ABRE sequences using the protein design algorithm FoldX. The high throughput free energy calculations successfully predicted the ability of ABF1 to bind to alternative core motifs like GCGT or AAGT and also rationalized the role of the flanking sequences in determining the specificity of the protein-DNA interaction.

Clathrin regulates blue light-triggered lateral auxin distribution and hypocotyl phototropism in Arabidopsis.

PubMed

Zhang, Ying; Yu, Qinqin; Jiang, Nan; Yan, Xu; Wang, Chao; Wang, Qingmei; Liu, Jianzhong; Zhu, Muyuan; Bednarek, Sebastian Y; Xu, Jian; Pan, Jianwei

2017-01-01

Phototropism is the process by which plants grow towards light in order to maximize the capture of light for photosynthesis, which is particularly important for germinating seedlings. In Arabidopsis, hypocotyl phototropism is predominantly triggered by blue light (BL), which has a profound effect on the establishment of asymmetric auxin distribution, essential for hypocotyl phototropism. Two auxin efflux transporters ATP-binding cassette B19 (ABCB19) and PIN-formed 3 (PIN3) are known to mediate the effect of BL on auxin distribution in the hypocotyl, but the details for how BL triggers PIN3 lateralization remain poorly understood. Here, we report a critical role for clathrin in BL-triggered, PIN3-mediated asymmetric auxin distribution in hypocotyl phototropism. We show that unilateral BL induces relocalization of clathrin in the hypocotyl. Loss of clathrin light chain 2 (CLC2) and CLC3 affects endocytosis and lateral distribution of PIN3 thereby impairing BL-triggered establishment of asymmetric auxin distribution and consequently, phototropic bending. Conversely, auxin efflux inhibitors N-1-naphthylphthalamic acid and 2,3,5-triiodobenzoic acid affect BL-induced relocalization of clathrin, endocytosis and lateralization of PIN3 as well as asymmetric distribution of auxin. These results together demonstrate an important interplay between auxin and clathrin function that dynamically regulates BL-triggered hypocotyl phototropism in Arabidopsis. © 2016 John Wiley & Sons Ltd.

Cell wall pH and auxin transport velocity

NASA Technical Reports Server (NTRS)

Hasenstein, K. H.; Rayle, D.

1984-01-01

According to the chemiosmotic polar diffusion hypothesis, auxin pulse velocity and basal secretion should increase with decreasing cell wall pH. Experiments were designed to test this prediction. Avena coleoptile sections were preincubated in either fusicoccin (FC), cycloheximide, pH 4.0, or pH 8.0 buffer and subsequently their polar transport capacities were determined. Relative to controls, FC enhanced auxin (IAA) uptake while CHI and pH 8.0 buffer reduced IAA uptake. Nevertheless, FC reduced IAA pulse velocity while cycloheximide increased velocity. Additional experiments showed that delivery of auxin to receivers is enhanced by increased receiver pH. This phenomenon was overcome by a pretreatment of the tissue with IAA. Our data suggest that while acidic wall pH values facilitate cellular IAA uptake, they do not enhance pulse velocity or basal secretion. These findings are inconsistent with the chemiosmotic hypothesis for auxin transport.

Abscisic acid and sucrose regulate tomato and strawberry fruit ripening through the abscisic acid-stress-ripening transcription factor.

PubMed

Jia, Haifeng; Jiu, Songtao; Zhang, Cheng; Wang, Chen; Tariq, Pervaiz; Liu, Zhongjie; Wang, Baoju; Cui, Liwen; Fang, Jinggui

2016-10-01

Although great progress has been made towards understanding the role of abscisic acid (ABA) and sucrose in fruit ripening, the mechanisms underlying the ABA and sucrose signalling pathways remain elusive. In this study, transcription factor ABA-stress-ripening (ASR), which is involved in the transduction of ABA and sucrose signalling pathways, was isolated and analysed in the nonclimacteric fruit, strawberry and the climacteric fruit, tomato. We have identified four ASR isoforms in tomato and one in strawberry. All ASR sequences contained the ABA stress- and ripening-induced proteins and water-deficit stress-induced proteins (ABA/WDS) domain and all ASR transcripts showed increased expression during fruit development. The expression of the ASR gene was influenced not only by sucrose and ABA, but also by jasmonic acid (JA) and indole-3-acetic acid (IAA), and these four factors were correlated with each other during fruit development. ASR bound the hexose transporter (HT) promoter, which contained a sugar box that activated downstream gene expression. Overexpression of the ASR gene promoted fruit softening and ripening, whereas RNA interference delayed fruit ripening, as well as affected fruit physiological changes. Change in ASR gene expression influenced the expression of several ripening-related genes such as CHS, CHI, F3H, DFR, ANS, UFGT, PG, PL, EXP1/2, XET16, Cel1/2 and PME. Taken together, this study may provide new evidence on the important role of ASR in cross-signalling between ABA and sucrose to regulate tomato and strawberry fruit ripening. The findings of this study also provide new insights into the regulatory mechanism underlying fruit development. © 2016 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

A role for the root cap in root branching revealed by the non-auxin probe naxillin.

PubMed

De Rybel, Bert; Audenaert, Dominique; Xuan, Wei; Overvoorde, Paul; Strader, Lucia C; Kepinski, Stefan; Hoye, Rebecca; Brisbois, Ronald; Parizot, Boris; Vanneste, Steffen; Liu, Xing; Gilday, Alison; Graham, Ian A; Nguyen, Long; Jansen, Leentje; Njo, Maria Fransiska; Inzé, Dirk; Bartel, Bonnie; Beeckman, Tom

2012-09-01

The acquisition of water and nutrients by plant roots is a fundamental aspect of agriculture and strongly depends on root architecture. Root branching and expansion of the root system is achieved through the development of lateral roots and is to a large extent controlled by the plant hormone auxin. However, the pleiotropic effects of auxin or auxin-like molecules on root systems complicate the study of lateral root development. Here we describe a small-molecule screen in Arabidopsis thaliana that identified naxillin as what is to our knowledge the first non-auxin-like molecule that promotes root branching. By using naxillin as a chemical tool, we identified a new function for root cap-specific conversion of the auxin precursor indole-3-butyric acid into the active auxin indole-3-acetic acid and uncovered the involvement of the root cap in root branching. Delivery of an auxin precursor in peripheral tissues such as the root cap might represent an important mechanism shaping root architecture.

A role for the root cap in root branching revealed by the non-auxin probe naxillin

PubMed Central

De Rybel, Bert; Audenaert, Dominique; Xuan, Wei; Overvoorde, Paul; Strader, Lucia C; Kepinski, Stefan; Hoye, Rebecca; Brisbois, Ronald; Parizot, Boris; Vanneste, Steffen; Liu, Xing; Gilday, Alison; Graham, Ian A; Nguyen, Long; Jansen, Leentje; Njo, Maria Fransiska; Inzé, Dirk; Bartel, Bonnie; Beeckman, Tom

2013-01-01

The acquisition of water and nutrients by plant roots is a fundamental aspect of agriculture and strongly depends on root architecture. Root branching and expansion of the root system is achieved through the development of lateral roots and is to a large extent controlled by the plant hormone auxin. However, the pleiotropic effects of auxin or auxin-like molecules on root systems complicate the study of lateral root development. Here we describe a small-molecule screen in Arabidopsis thaliana that identified naxillin as what is to our knowledge the first non-auxin-like molecule that promotes root branching. By using naxillin as a chemical tool, we identified a new function for root cap-specific conversion of the auxin precursor indole-3-butyric acid into the active auxin indole-3-acetic acid and uncovered the involvement of the root cap in root branching. Delivery of an auxin precursor in peripheral tissues such as the root cap might represent an important mechanism shaping root architecture. PMID:22885787

Auxin as an inducer of asymmetrical division generating the subsidiary cells in stomatal complexes of Zea mays.

PubMed

Livanos, Pantelis; Giannoutsou, Eleni; Apostolakos, Panagiotis; Galatis, Basil

2015-01-01

The data presented in this work revealed that in Zea mays the exogenously added auxins indole-3-acetic acid (IAA) and 1-napthaleneacetic acid (NAA), promoted the establishment of subsidiary cell mother cell (SMC) polarity and the subsequent subsidiary cell formation, while treatment with auxin transport inhibitors 2,3,5-triiodobenzoic acid (TIBA) and 1-napthoxyacetic acid (NOA) specifically blocked SMC polarization and asymmetrical division. Furthermore, in young guard cell mother cells (GMCs) the PIN1 auxin efflux carriers were mainly localized in the transverse GMC faces, while in the advanced GMCs they appeared both in the transverse and the lateral ones adjacent to SMCs. Considering that phosphatidyl-inositol-3-kinase (PI3K) is an active component of auxin signal transduction and that phospholipid signaling contributes in the establishment of polarity, treatments with the specific inhibitor of the PI3K LY294002 were carried out. The presence of LY294002 suppressed polarization of SMCs and prevented their asymmetrical division, whereas combined treatment with exogenously added NAA and LY294002 restricted the promotional auxin influence on subsidiary cell formation. These findings support the view that auxin is involved in Z. mays subsidiary cell formation, probably functioning as inducer of the asymmetrical SMC division. Collectively, the results obtained from treatments with auxin transport inhibitors and the appearance of PIN1 proteins in the lateral GMC faces indicate a local transfer of auxin from GMCs to SMCs. Moreover, auxin signal transduction seems to be mediated by the catalytic function of PI3K.

Auxin as an inducer of asymmetrical division generating the subsidiary cells in stomatal complexes of Zea mays

PubMed Central

Livanos, Pantelis; Giannoutsou, Eleni; Apostolakos, Panagiotis; Galatis, Basil

2015-01-01

The data presented in this work revealed that in Zea mays the exogenously added auxins indole-3-acetic acid (IAA) and 1-napthaleneacetic acid (NAA), promoted the establishment of subsidiary cell mother cell (SMC) polarity and the subsequent subsidiary cell formation, while treatment with auxin transport inhibitors 2,3,5-triiodobenzoic acid (TIBA) and 1-napthoxyacetic acid (NOA) specifically blocked SMC polarization and asymmetrical division. Furthermore, in young guard cell mother cells (GMCs) the PIN1 auxin efflux carriers were mainly localized in the transverse GMC faces, while in the advanced GMCs they appeared both in the transverse and the lateral ones adjacent to SMCs. Considering that phosphatidyl-inositol-3-kinase (PI3K) is an active component of auxin signal transduction and that phospholipid signaling contributes in the establishment of polarity, treatments with the specific inhibitor of the PI3K LY294002 were carried out. The presence of LY294002 suppressed polarization of SMCs and prevented their asymmetrical division, whereas combined treatment with exogenously added NAA and LY294002 restricted the promotional auxin influence on subsidiary cell formation. These findings support the view that auxin is involved in Z. mays subsidiary cell formation, probably functioning as inducer of the asymmetrical SMC division. Collectively, the results obtained from treatments with auxin transport inhibitors and the appearance of PIN1 proteins in the lateral GMC faces indicate a local transfer of auxin from GMCs to SMCs. Moreover, auxin signal transduction seems to be mediated by the catalytic function of PI3K. PMID:25831267

The Allelochemical MDCA Inhibits Lignification and Affects Auxin Homeostasis1[OPEN

PubMed Central

Steenackers, Ward; Corneillie, Sander; Van de Wouwer, Dorien; Zažímalová, Eva

2016-01-01

The phenylpropanoid 3,4-(methylenedioxy)cinnamic acid (MDCA) is a plant-derived compound first extracted from roots of Asparagus officinalis and further characterized as an allelochemical. Later on, MDCA was identified as an efficient inhibitor of 4-COUMARATE-CoA LIGASE (4CL), a key enzyme of the general phenylpropanoid pathway. By blocking 4CL, MDCA affects the biosynthesis of many important metabolites, which might explain its phytotoxicity. To decipher the molecular basis of the allelochemical activity of MDCA, we evaluated the effect of this compound on Arabidopsis thaliana seedlings. Metabolic profiling revealed that MDCA is converted in planta into piperonylic acid (PA), an inhibitor of CINNAMATE-4-HYDROXYLASE (C4H), the enzyme directly upstream of 4CL. The inhibition of C4H was also reflected in the phenolic profile of MDCA-treated plants. Treatment of in vitro grown plants resulted in an inhibition of primary root growth and a proliferation of lateral and adventitious roots. These observed growth defects were not the consequence of lignin perturbation, but rather the result of disturbing auxin homeostasis. Based on DII-VENUS quantification and direct measurement of cellular auxin transport, we concluded that MDCA disturbs auxin gradients by interfering with auxin efflux. In addition, mass spectrometry was used to show that MDCA triggers auxin biosynthesis, conjugation, and catabolism. A similar shift in auxin homeostasis was found in the c4h mutant ref3-2, indicating that MDCA triggers a cross talk between the phenylpropanoid and auxin biosynthetic pathways independent from the observed auxin efflux inhibition. Altogether, our data provide, to our knowledge, a novel molecular explanation for the phytotoxic properties of MDCA. PMID:27506238

The Protein Kinase CK2 Mediates Cross-Talk between Auxin- and Salicylic Acid-Signaling Pathways in the Regulation of PINOID Transcription

PubMed Central

Armengot, Laia; Caldarella, Eleonora; Marquès-Bueno, Maria Mar; Martínez, M. Carmen

2016-01-01

The protein kinase CK2 is a ubiquitous and highly conserved enzyme, the activity of which is vital for eukaryotic cells. We recently demonstrated that CK2 modulates salicylic acid (SA) homeostasis in Arabidopsis thaliana, and that functional interplay between CK2 and SA sustains transcriptional expression of PIN-FORMED (PIN) genes. In this work, we show that CK2 also plays a key role in the transcriptional regulation of PINOID (PID), an AGC protein kinase that modulates the apical/basal localization of auxin-efflux transporters. We show that PID transcription is up-regulated by auxin and by SA and that CK2 is involved in both pathways. On the one hand, CK2 activity is required for proteosome-dependent degradation of AXR3, a member of the AUX/IAA family of auxin transcriptional repressors that must be degraded to activate auxin-responsive gene expression. On the other hand, the role of CK2 in SA homeostasis and, indirectly, in SA-driven PID transcription, was confirmed by using Arabidopsis NahG transgenic plants, which cannot accumulate SA. In conclusion, our results evidence a role for CK2 as a functional link in the negative cross-talk between auxin- and SA-signaling. PMID:27275924

Induction of phytic acid synthesis by abscisic acid in suspension-cultured cells of rice.

PubMed

Matsuno, Koya; Fujimura, Tatsuhito

2014-03-01

A pathway of phytic acid (PA) synthesis in plants has been revealed via investigations of low phytic acid mutants. However, the regulation of this pathway is not well understood because it is difficult to control the environments of cells in the seeds, where PA is mainly synthesized. We modified a rice suspension culture system in order to study the regulation of PA synthesis. Rice cells cultured with abscisic acid (ABA) accumulate PA at higher levels than cells cultured without ABA, and PA accumulation levels increase with ABA concentration. On the other hand, higher concentrations of sucrose or inorganic phosphorus do not affect PA accumulation. Mutations in the genes RINO1, OsMIK, OsIPK1 and OsLPA1 have each been reported to confer low phytic acid phenotypes in seeds. Each of these genes is upregulated in cells cultured with ABA. OsITPK4 and OsITPK6 are upregulated in cells cultured with ABA and in developing seeds. These results suggest that the regulation of PA synthesis is similar between developing seeds and cells in this suspension culture system. This system will be a powerful tool for elucidating the regulation of PA synthesis. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Single-cell-based system to monitor carrier driven cellular auxin homeostasis

PubMed Central

2013-01-01

Background Abundance and distribution of the plant hormone auxin play important roles in plant development. Besides other metabolic processes, various auxin carriers control the cellular level of active auxin and, hence, are major regulators of cellular auxin homeostasis. Despite the developmental importance of auxin transporters, a simple medium-to-high throughput approach to assess carrier activities is still missing. Here we show that carrier driven depletion of cellular auxin correlates with reduced nuclear auxin signaling in tobacco Bright Yellow-2 (BY-2) cell cultures. Results We developed an easy to use transient single-cell-based system to detect carrier activity. We use the relative changes in signaling output of the auxin responsive promoter element DR5 to indirectly visualize auxin carrier activity. The feasibility of the transient approach was demonstrated by pharmacological and genetic interference with auxin signaling and transport. As a proof of concept, we provide visual evidence that the prominent auxin transport proteins PIN-FORMED (PIN)2 and PIN5 regulate cellular auxin homeostasis at the plasma membrane and endoplasmic reticulum (ER), respectively. Our data suggest that PIN2 and PIN5 have different sensitivities to the auxin transport inhibitor 1-naphthylphthalamic acid (NPA). Also the putative PIN-LIKES (PILS) auxin carrier activity at the ER is insensitive to NPA in our system, indicating that NPA blocks intercellular, but not intracellular auxin transport. Conclusions This single-cell-based system is a useful tool by which the activity of putative auxin carriers, such as PINs, PILS and WALLS ARE THIN1 (WAT1), can be indirectly visualized in a medium-to-high throughput manner. Moreover, our single cell system might be useful to investigate also other hormonal signaling pathways, such as cytokinin. PMID:23379388

Gravitropism in higher plant shoots. VI. Changing sensitivity to auxin in gravistimulated soybean hypocotyls

NASA Technical Reports Server (NTRS)

Rorabaugh, P. A.; Salisbury, F. B.

1989-01-01

Although the Cholodny-Went model of auxin redistribution has been used to explain the transduction phase of gravitropism for over 60 years, problems are apparent, especially with dicot stems. An alternative to an auxin gradient is a physiological gradient in which lower tissues of a horizontal stem become more sensitive than upper tissues to auxin already present. Changes in tissue sensitivity to auxin were tested by immersing marked Glycine max Merrill (soybean) hypocotyl sections in buffered auxin solutions (0, 10(-8) to 10(-2) molar indoleacetic acid) and observing bending and growth of upper and lower surfaces. The two surfaces of horizontal hypocotyl sections responded differently to the same applied auxin stimulus; hypocotyls bent up (lower half grew more) in buffer alone or in low auxin levels, but bent down (upper half grew more) in high auxin. Dose-response curves were evaluated with Michaelis-Menten kinetics, with auxin-receptor binding analogous to enzyme-substrate binding. Vmax for the lower half was usually greater than that for the upper half, which could indicate more binding sites in the lower half. Km of the upper half was always greater than that of the lower half (unmeasurably low), which could indicate that upper-half binding sites had a much lower affinity for auxin than lower-half sites. Dose-response curves were also obtained for sections scrubbed' (cuticle abraded) on top or bottom before immersion in auxin, and gravitropic memory' experiments of L. Brauner and A. Hagar (1958 Planta 51: 115-147) were duplicated. [1-14C]Indoleacetic acid penetration was equal into the two halves, and endogenous plus exogenously supplied (not radiolabeled) free auxin in the two halves (by gas chromatography-selected ion monitoring-mass spectrometry) was also equal. Thus, differential growth occurred without free auxin redistribution, contrary to Cholodny-Went but in agreement with a sensitivity model.

Pavement cells: a model system for non-transcriptional auxin signalling and crosstalks

PubMed Central

Chen, Jisheng; Wang, Fei; Zheng, Shiqin; Xu, Tongda; Yang, Zhenbiao

2015-01-01

Auxin (indole acetic acid) is a multifunctional phytohormone controlling various developmental patterns, morphogenetic processes, and growth behaviours in plants. The transcription-based pathway activated by the nuclear TRANSPORT INHIBITOR RESISTANT 1/auxin-related F-box auxin receptors is well established, but the long-sought molecular mechanisms of non-transcriptional auxin signalling remained enigmatic until very recently. Along with the establishment of the Arabidopsis leaf epidermal pavement cell (PC) as an exciting and amenable model system in the past decade, we began to gain insight into non-transcriptional auxin signalling. The puzzle-piece shape of PCs forms from intercalated or interdigitated cell growth, requiring local intra- and inter-cellular coordination of lobe and indent formation. Precise coordination of this interdigitated pattern requires auxin and an extracellular auxin sensing system that activates plasma membrane-associated Rho GTPases from plants and subsequent downstream events regulating cytoskeletal reorganization and PIN polarization. Apart from auxin, mechanical stress and cytokinin have been shown to affect PC interdigitation, possibly by interacting with auxin signals. This review focuses upon signalling mechanisms for cell polarity formation in PCs, with an emphasis on non-transcriptional auxin signalling in polarized cell expansion and pattern formation and how different auxin pathways interplay with each other and with other signals. PMID:26047974

Genome-wide identification and transcriptional profiling analysis of auxin response-related gene families in cucumber

PubMed Central

2014-01-01

Background Auxin signaling has a vital function in the regulation of plant growth and development, both which are known to be mediated by auxin-responsive genes. So far, significant progress has been made toward the identification and characterization of auxin-response genes in several model plants, while no systematic analysis for these families was reported in cucumber (Cucumis sativus L.), a reference species for Cucurbitaceae crops. The comprehensive analyses will help design experiments for functional validation of their precise roles in plant development and stress responses. Results A genome-wide search for auxin-response gene homologues identified 16 auxin-response factors (ARFs), 27 auxin/indole acetic acids (Aux/IAAs), 10 Gretchen Hagen 3 (GH3s), 61 small auxin-up mRNAs (SAURs), and 39 lateral organ boundaries (LBDs) in cucumber. Sequence analysis together with the organization of putative motifs indicated the potential diverse functions of these five auxin-related family members. The distribution and density of auxin response-related genes on chromosomes were not uniform. Evolutionary analysis showed that the chromosomal segment duplications mainly contributed to the expansion of the CsARF, CsIAA, CsGH3, and CsLBD gene families. Quantitative real-time RT-PCR analysis demonstrated that many ARFs, AUX/IAAs, GH3s, SAURs, and LBD genes were expressed in diverse patterns within different organs/tissues and during different development stages. They were also implicated in IAA, methyl jasmonic acid, or salicylic acid response, which is consistent with the finding that a great number of diverse cis-elements are present in their promoter regions involving a variety of signaling transduction pathways. Conclusion Genome-wide comparative analysis of auxin response-related family genes and their expression analysis provide new evidence for the potential role of auxin in development and hormone response of plants. Our data imply that the auxin response genes may be

Regulation of the Osem gene by abscisic acid and the transcriptional activator VP1: analysis of cis-acting promoter elements required for regulation by abscisic acid and VP1.

PubMed

Hattori, T; Terada, T; Hamasuna, S

1995-06-01

Osem, a rice gene homologous to the wheat Em gene, which encodes one of the late-embryogenesis abundant proteins was isolated. The gene was characterized with respect to control of transcription by abscisic acid (ABA) and the transcriptional activator VP1, which is involved in the ABA-regulated gene expression during late embryo-genesis. A fusion gene (Osem-GUS) consisting of the Osem promoter and the bacterial beta-glucuronidase (GUS) gene was constructed and tested in a transient expression system, using protoplasts derived from a suspension-cultured line of rice cells, for activation by ABA and by co-transfection with an expression vector (35S-Osvp1) for the rice VP1 (OSVP1) cDNA. The expression of Osem-GUS was strongly (40- to 150-fold) activated by externally applied ABA and by over-expression of (OS)VP1. The Osem promoter has three ACGTG-containing sequences, motif A, motif B and motif A', which resemble the abscisic acid-responsive element (ABRE) that was previously identified in the wheat Em and the rice Rab16. There is also a CATGCATG sequence, which is known as the Sph box and is shown to be essential for the regulation by VP1 of the maize anthocyanin regulatory gene C1. Focusing on these sequence elements, various mutant derivatives of the Osem promoter in the transient expression system were assayed. The analysis revealed that motif A functions not only as an ABRE but also as a sequence element required for the regulation by (OS)VP1.

Tomato root growth, gravitropism, and lateral development: correlation with auxin transport

NASA Technical Reports Server (NTRS)

Muday, G. K.; Haworth, P.

1994-01-01

Tomato (Lycopersicon esculentum, Mill.) roots were analyzed during growth on agar plates. Growth of these roots was inhibited by the auxin transport inhibitors naphthylphthalamic acid (NPA) and semicarbazone derivative I (SCB-1). The effect of auxin transport inhibitors on root gravitropism was analyzed by measurement of the angle of gravitropic curvature after the roots were reoriented 90 degrees from the vertical. NPA and SCB-1 abolished both the response of these roots to gravity and the formation of lateral roots, with SCB-1 being the more effective at inhibition. Auxins also inhibited root growth. Both auxins tested has a slight effect on the gravity response, but this effect is probably indirect, since auxins reduced the growth rate. Auxins also stimulated lateral root growth at concentration where primary root growth was inhibited. When roots were treated with both IAA and NPA simultaneously, a cumulative inhibition of root growth was found. When both compounds were applied together, analysis of gravitropism and lateral root formation indicated that the dominant effect was exerted by auxin transport inhibitors. Together, these data suggest a model for the role of auxin transport in controlling both primary and lateral root growth.

Involvement of a Lipoxygenase-Like Enzyme in Abscisic Acid Biosynthesis 1

PubMed Central

Creelman, Robert A.; Bell, Erin; Mullet, John E.

1992-01-01

Several lines of evidence indicate that abscisic acid (ABA) is derived from 9′-cis-neoxanthin or 9′-cis-violaxanthin with xanthoxin as an intermediate. 18O-labeling experiments show incorporation primarily into the side chain carboxyl group of ABA, suggesting that oxidative cleavage occurs at the 11, 12 (11′, 12′) double bond of xanthophylls. Carbon monoxide, a strong inhibitor of heme-containing P-450 monooxygenases, did not inhibit ABA accumulation, suggesting that the oxygenase catalyzing the carotenoid cleavage step did not contain heme. This observation, plus the ability of lipoxygenase to make xanthoxin from violaxanthin, suggested that a lipoxygenase-like enzyme is involved in ABA biosynthesis. To test this idea, the ability of several soybean (Glycine max L.) lipoxygenase inhibitors (5,8,11-eicosatriynoic acid, 5,8,11,14-eicosatetraynoic acid, nordihydroguaiaretic acid, and naproxen) to inhibit stress-induced ABA accumulation in soybean cell culture and soybean seedlings was determined. All lipoxygenase inhibitors significantly inhibited ABA accumulation in response to stress. These results suggest that the in vivo oxidative cleavage reaction involved in ABA biosynthesis requires activity of a nonheme oxygenase having lipoxygenase-like properties. PMID:16668998

Calcium dependence of rapid auxin action in maize roots

NASA Technical Reports Server (NTRS)

Hasenstein, K. H.; Evans, M. L.

1986-01-01

We investigated the interaction of Ca2+ and auxin on root elongation in seedlings of Zea mays L. The seedlings were raised either in the presence of Ca2+ (high calcium; HC = imbibed and raised in 10 millimolar CaCl2), in the absence of additional Ca2+ (intermediate calcium; IC = imbibed and raised in distilled H2O, calcium supply from seed only), or without additional Ca2+ and subsequently depleting them of Ca2+ (low calcium; LC = imbibed and raised in distilled H2O and subsequently treated with 1 millimolar ethyleneglycol-bis-[beta-aminoethylether]-N,N,N',N'-tetraacetic acid [EGTA]). Exposure of roots of either HC or IC seedlings to auxin concentrations from 0.1 to 10 micromolar resulted in strong inhibition of elongation. In roots of LC seedlings, on the other hand, auxin concentrations as high as 10 micromolar caused only slight inhibition of elongation. Adding 0.5 millimolar Ca2+ to LC roots in the presence of IAA allowed normal expression of the inhibitory action of the hormone. Inhibition of elongation in IC roots by indoleacetic acid was reversible upon treatment of the roots with 1 millimolar EGTA. The inhibitory action of auxin could then be re-established by supplying 0.5 millimolar Ca2+. The data indicate that Ca2+ may be necessary to the growth-regulating action of auxin. The significance of this finding is discussed with respect to the potential role of Ca2+ as a second messenger of auxin action and the relevance of this model to recent evidence for gravi-induced redistribution of Ca2+ and its role in establishing gravitropic curvature.

Lipoxygenase in Caragana jubata responds to low temperature, abscisic acid, methyl jasmonate and salicylic acid.

PubMed

Bhardwaj, Pardeep Kumar; Kaur, Jagdeep; Sobti, Ranbir Chander; Ahuja, Paramvir Singh; Kumar, Sanjay

2011-09-01

Lipoxygenase (LOX) catalyses oxygenation of free polyunsaturated fatty acids into oxylipins, and is a critical enzyme of the jasmonate signaling pathway. LOX has been shown to be associated with biotic and abiotic stress responses in diverse plant species, though limited data is available with respect to low temperature and the associated cues. Using rapid amplification of cDNA ends, a full-length cDNA (CjLOX) encoding lipoxygenase was cloned from apical buds of Caragana jubata, a temperate plant species that grows under extreme cold. The cDNA obtained was 2952bp long consisting of an open reading frame of 2610bp encoding 869 amino acids protein. Multiple alignment of the deduced amino acid sequence with those of other plants demonstrated putative LH2/ PLAT domain, lipoxygenase iron binding catalytic domain and lipoxygenase_2 signature sequences. CjLOX exhibited up- and down-regulation of gene expression pattern in response to low temperature (LT), abscisic acid (ABA), methyl jasmonate (MJ) and salicylic acid (SA). Among all the treatments, a strong up-regulation was observed in response to MJ. Data suggests an important role of jasmonate signaling pathway in response to LT in C. jubata. Copyright © 2011 Elsevier B.V. All rights reserved.

Selection and Characterization of Single Stranded DNA Aptamers for the Hormone Abscisic Acid

PubMed Central

Gonzalez, Victor M.; Millo, Enrico; Sturla, Laura; Vigliarolo, Tiziana; Bagnasco, Luca; Guida, Lucrezia; D'Arrigo, Cristina; De Flora, Antonio; Salis, Annalisa; Martin, Elena M.; Bellotti, Marta; Zocchi, Elena

2013-01-01

The hormone abscisic acid (ABA) is a small molecule involved in pivotal physiological functions in higher plants. Recently, ABA has been also identified as an endogenous hormone in mammals, regulating different cell functions including inflammatory processes, stem cell expansion, insulin release, and glucose uptake. Aptamers are short, single-stranded (ss) oligonucleotidesable to recognize target molecules with high affinity. The small size of the ABA molecule represented a challenge for aptamer development and the aim of this study was to develop specific anti-ABA DNA aptamers. Biotinylated abscisic acid (bio-ABA) was immobilized on streptavidin-coated magnetic beads. DNA aptamers against bio-ABA were selected with 7 iterative rounds of the systematic evolution of ligands by exponential enrichment method (SELEX), each round comprising incubation of the ABA-binding beads with the ssDNA sequences, DNA elution, electrophoresis, and polymerase chain reaction (PCR) amplification. The PCR product was cloned and sequenced. The binding affinity of several clones was determined using bio-ABA immobilized on streptavidin-coated plates. Aptamer 2 and aptamer 9 showed the highest binding affinity, with dissociation constants values of 0.98±0.14 μM and 0.80±0.07 μM, respectively. Aptamers 2 and 9 were also able to bind free, unmodified ABA and to discriminate between different ABA enantiomers and isomers. Our findings indicate that ssDNA aptamers can selectively bind ABA and could be used for the development of ABA quantitation assays. PMID:23971905

Localized surface plasmon resonance-based abscisic acid biosensor using aptamer-functionalized gold nanoparticles

PubMed Central

Wang, Shun; Li, Wei; Chang, Keke; Liu, Juan; Guo, Qingqian; Sun, Haifeng; Jiang, Min; Zhang, Hao; Chen, Jing

2017-01-01

Abscisic acid (ABA) plays an important role in abiotic stress response and physiological signal transduction resisting to the adverse environment. Therefore, it is very essential for the quantitative detection of abscisic acid (ABA) due to its indispensable role in plant physiological activities. Herein, a new detection method based on localized surface plasmon resonance (LSPR) using aptamer-functionalized gold nanoparticles (AuNPs) is developed without using expensive instrument and antibody. In the presence of ABA, ABA specifically bind with their aptamers to form the ABA-aptamer complexes with G-quadruplex-like structure and lose the ability to stabilize AuNPs against NaCl-induced aggregation. Meanwhile, the changes of the LSPR spectra of AuNP solution occur and therefore the detection of ABA achieved. Under optimized conditions, this method showed a good linear range covering from 5×10−7 M to 5×10−5 M with a detection limit of 0.33 μM. In practice, the usage of this novel method has been demonstrated by its application to detect ABA from fresh leaves of rice with the relative error of 6.59%-7.93% compared with ELISA bioassay. The experimental results confirmed that this LSPR-based biosensor is simple, selective and sensitive for the detection of ABA. The proposed LSPR method could offer a new analytical platform for the detection of other plant hormones by changing the corresponding aptamer. PMID:28953934

Linking hormonal profiles with variations in sugar and anthocyanin contents during the natural development and ripening of sweet cherries.

PubMed

Teribia, Natalia; Tijero, Verónica; Munné-Bosch, Sergi

2016-12-25

Sweet cherries are highly appreciated by consumers worldwide and are usually cold-stored during postharvest to prevent over-ripening before distribution to the market. Sweet cherry is a non-climacteric fruit, for which ripening is known to be regulated by abscisic acid. Here we aimed to examine the hormone profiles, including measurements of abscisic acid, auxins, cytokinins and gibberellins by ultrahigh performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS), in relation to variations in sugar and anthocyanin contents, during growth and ripening of this fruit. Hormonal profiling revealed that indole-3-acetic acid, GA 1 and trans-zeatin levels decreased at early stages of fruit development, while GA 3 levels decreased at early stages but also later, once anthocyanin accumulation started. Conversely, abscisic acid levels rose significantly once the fruit started to synthetize anthocyanins, and isopentenyladenosine levels also increased during the ripening of sweet cherries. A strong negative correlation was found between GA 4 levels and both fruit biomass and anthocyanin levels, and between the levels of trans-zeatin and both fruit biomass and total sugar contents. In contrast, abscisic acid and isopentenyladenosine levels correlated positively with fruit biomass, anthocyanin and total soluble sugar content. Results suggest that auxins, cytokinins and gibberellins may act coordinately with abscisic acid in the regulation of sweet cherry development and ripening. Furthermore, it is shown that hormonal profile measurements by UHPLC-MS/MS may be a helpful tool to elucidate the timing of action of each specific hormonal compound during ripening, which has important applications in the agri-food biotechnological sector. Copyright © 2016 Elsevier B.V. All rights reserved.

Auxin and the integration of environmental signals into plant root development.

PubMed

Kazan, Kemal

2013-12-01

Auxin is a versatile plant hormone with important roles in many essential physiological processes. In recent years, significant progress has been made towards understanding the roles of this hormone in plant growth and development. Recent evidence also points to a less well-known but equally important role for auxin as a mediator of environmental adaptation in plants. This review briefly discusses recent findings on how plants utilize auxin signalling and transport to modify their root system architecture when responding to diverse biotic and abiotic rhizosphere signals, including macro- and micro-nutrient starvation, cold and water stress, soil acidity, pathogenic and beneficial microbes, nematodes and neighbouring plants. Stress-responsive transcription factors and microRNAs that modulate auxin- and environment-mediated root development are also briefly highlighted. The auxin pathway constitutes an essential component of the plant's biotic and abiotic stress tolerance mechanisms. Further understanding of the specific roles that auxin plays in environmental adaptation can ultimately lead to the development of crops better adapted to stressful environments.

Large-scale proteome analysis of abscisic acid and ABSCISIC ACID INSENSITIVE3-dependent proteins related to desiccation tolerance in Physcomitrella patens

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yotsui, Izumi, E-mail: izumi.yotsui@riken.jp; Serada, Satoshi, E-mail: serada@nibiohn.go.jp; Naka, Tetsuji, E-mail: tnaka@nibiohn.go.jp

2016-03-18

Desiccation tolerance is an ancestral feature of land plants and is still retained in non-vascular plants such as bryophytes and some vascular plants. However, except for seeds and spores, this trait is absent in vegetative tissues of vascular plants. Although many studies have focused on understanding the molecular basis underlying desiccation tolerance using transcriptome and proteome approaches, the critical molecular differences between desiccation tolerant plants and non-desiccation plants are still not clear. The moss Physcomitrella patens cannot survive rapid desiccation under laboratory conditions, but if cells of the protonemata are treated by the phytohormone abscisic acid (ABA) prior to desiccation,more » it can survive 24 h exposure to desiccation and regrow after rehydration. The desiccation tolerance induced by ABA (AiDT) is specific to this hormone, but also depends on a plant transcription factor ABSCISIC ACID INSENSITIVE3 (ABI3). Here we report the comparative proteomic analysis of AiDT between wild type and ABI3 deleted mutant (Δabi3) of P. patens using iTRAQ (Isobaric Tags for Relative and Absolute Quantification). From a total of 1980 unique proteins that we identified, only 16 proteins are significantly altered in Δabi3 compared to wild type after desiccation following ABA treatment. Among this group, three of the four proteins that were severely affected in Δabi3 tissue were Arabidopsis orthologous genes, which were expressed in maturing seeds under the regulation of ABI3. These included a Group 1 late embryogenesis abundant (LEA) protein, a short-chain dehydrogenase, and a desiccation-related protein. Our results suggest that at least three of these proteins expressed in desiccation tolerant cells of both Arabidopsis and the moss are very likely to play important roles in acquisition of desiccation tolerance in land plants. Furthermore, our results suggest that the regulatory machinery of ABA- and ABI3-mediated gene expression for

Ethylene Inhibits Root Elongation during Alkaline Stress through AUXIN1 and Associated Changes in Auxin Accumulation.

PubMed

Li, Juan; Xu, Heng-Hao; Liu, Wen-Cheng; Zhang, Xiao-Wei; Lu, Ying-Tang

2015-08-01

Soil alkalinity causes major reductions in yield and quality of crops worldwide. The plant root is the first organ sensing soil alkalinity, which results in shorter primary roots. However, the mechanism underlying alkaline stress-mediated inhibition of root elongation remains to be further elucidated. Here, we report that alkaline conditions inhibit primary root elongation of Arabidopsis (Arabidopsis thaliana) seedlings by reducing cell division potential in the meristem zones and that ethylene signaling affects this process. The ethylene perception antagonist silver (Ag(+)) alleviated the inhibition of root elongation by alkaline stress. Moreover, the ethylene signaling mutants ethylene response1-3 (etr1-3), ethylene insensitive2 (ein2), and ein3-1 showed less reduction in root length under alkaline conditions, indicating a reduced sensitivity to alkalinity. Ethylene biosynthesis also was found to play a role in alkaline stress-mediated root inhibition; the ethylene overproducer1-1 mutant, which overproduces ethylene because of increased stability of 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID SYNTHASE5, was hypersensitive to alkaline stress. In addition, the ethylene biosynthesis inhibitor cobalt (Co(2+)) suppressed alkaline stress-mediated inhibition of root elongation. We further found that alkaline stress caused an increase in auxin levels by promoting expression of auxin biosynthesis-related genes, but the increase in auxin levels was reduced in the roots of the etr1-3 and ein3-1 mutants and in Ag(+)/Co(2+)-treated wild-type plants. Additional genetic and physiological data showed that AUXIN1 (AUX1) was involved in alkaline stress-mediated inhibition of root elongation. Taken together, our results reveal that ethylene modulates alkaline stress-mediated inhibition of root growth by increasing auxin accumulation by stimulating the expression of AUX1 and auxin biosynthesis-related genes. © 2015 American Society of Plant Biologists. All Rights Reserved.

Hydrogen bonding in phytohormone-auxin (IAA) and its derivatives

NASA Astrophysics Data System (ADS)

Kojić-Prodić, Biserka; Kroon, Jan; Puntarec, Vitomir

1994-06-01

The significant importance of hydrogen bonds in biological structures and enzymatic reactions has been demonstrated in many examples. As a part of the molecular recognition study of auxins (plant growth hormones) the influence of hydrogen bonding on molecular conformation, particularly of the carboxyl group, which is one of the biologically active ligand sites, has been studied by X-ray diffraction and computational chemistry methods. The survey includes about 40 crystal structures of free auxins such as indol-3-ylacetic acid and its n-alkylated and halogenated derivatives but also bound auxins such as N-(indol-3-ylacetyl)- L-amino acids, and carbohydrate conjugates. The study includes hydrogen bonds of the NH⋯O and OH⋯O types. The classification of hydrogen bond patterns based on the discrimination between the centrosymmetric and non-centrosymmetric space groups and several examples of hydrogen bond systematics on graph set analysis are also shown.

Role of abscisic acid in strigolactone-induced salt stress tolerance in arbuscular mycorrhizal Sesbania cannabina seedlings.

PubMed

Ren, Cheng-Gang; Kong, Cun-Cui; Xie, Zhi-Hong

2018-05-03

Strigolactones (SLs) are considered to be a novel class of phytohormone involved in plant defense responses. Currently, their relationships with other plant hormones, such as abscisic acid (ABA), during responses to salinity stress are largely unknown. In this study, the relationship between SL and ABA during the induction of H 2 O 2 - mediated tolerance to salt stress were studied in arbuscular mycorrhizal (AM) Sesbania cannabina seedlings. The SL levels increased after ABA treatments and decreased when ABA biosynthesis was inhibited in AM plants. Additionally, the expression levels of SL-biosynthesis genes in AM plants increased following treatments with exogenous ABA and H 2 O 2 . Furthermore, ABA-induced SL production was blocked by a pre-treatment with dimethylthiourea, which scavenges H 2 O 2 . In contrast, ABA production was unaffected by dimethylthiourea. Abscisic acid induced only partial and transient increases in the salt tolerance of TIS108 (a SL synthesis inhibitor) treated AM plants, whereas SL induced considerable and prolonged increases in salt tolerance after a pre-treatment with tungstate. These results strongly suggest that ABA is regulating the induction of salt tolerance by SL in AM S. cannabina seedlings.

Salicylic acid antagonizes abscisic acid inhibition of shoot growth and cell cycle progression in rice

NASA Astrophysics Data System (ADS)

Meguro, Ayano; Sato, Yutaka

2014-04-01

We analysed effects of abscisic acid (ABA, a negative regulatory hormone), alone and in combination with positive or neutral hormones, including salicylic acid (SA), on rice growth and expression of cell cycle-related genes. ABA significantly inhibited shoot growth and induced expression of OsKRP4, OsKRP5, and OsKRP6. A yeast two-hybrid assay showed that OsKRP4, OsKRP5, and OsKRP6 interacted with OsCDKA;1 and/or OsCDKA;2. When SA was simultaneously supplied with ABA, the antagonistic effect of SA completely blocked ABA inhibition. SA also blocked ABA inhibition of DNA replication and thymidine incorporation in the shoot apical meristem. These results suggest that ABA arrests cell cycle progression by inducing expression of OsKRP4, OsKRP5, and OsKRP6, which inhibit the G1/S transition, and that SA antagonizes ABA by blocking expression of OsKRP genes.

Suppression of the auxin response pathway enhances susceptibility to Phytophthora cinnamomi while phosphite-mediated resistance stimulates the auxin signalling pathway

PubMed Central

2014-01-01

Background Phytophthora cinnamomi is a devastating pathogen worldwide and phosphite (Phi), an analogue of phosphate (Pi) is highly effective in the control of this pathogen. Phi also interferes with Pi starvation responses (PSR), of which auxin signalling is an integral component. In the current study, the involvement of Pi and the auxin signalling pathways in host and Phi-mediated resistance to P. cinnamomi was investigated by screening the Arabidopsis thaliana ecotype Col-0 and several mutants defective in PSR and the auxin response pathway for their susceptibility to this pathogen. The response to Phi treatment was also studied by monitoring its effect on Pi- and the auxin response pathways. Results Here we demonstrate that phr1-1 (phosphate starvation response 1), a mutant defective in response to Pi starvation was highly susceptible to P. cinnamomi compared to the parental background Col-0. Furthermore, the analysis of the Arabidopsis tir1-1 (transport inhibitor response 1) mutant, deficient in the auxin-stimulated SCF (Skp1 − Cullin − F-Box) ubiquitination pathway was also highly susceptible to P. cinnamomi and the susceptibility of the mutants rpn10 and pbe1 further supported a role for the 26S proteasome in resistance to P. cinnamomi. The role of auxin was also supported by a significant (P < 0.001) increase in susceptibility of blue lupin (Lupinus angustifolius) to P. cinnamomi following treatment with the inhibitor of auxin transport, TIBA (2,3,5-triiodobenzoic acid). Given the apparent involvement of auxin and PSR signalling in the resistance to P. cinnamomi, the possible involvement of these pathways in Phi mediated resistance was also investigated. Phi (especially at high concentrations) attenuates the response of some Pi starvation inducible genes such as AT4, AtACP5 and AtPT2 in Pi starved plants. However, Phi enhanced the transcript levels of PHR1 and the auxin responsive genes (AUX1, AXR1and AXR2), suppressed the primary root

Abscisic Acid and abiotic stress signaling.

PubMed

Tuteja, Narendra

2007-05-01

Abiotic stress is severe environmental stress, which impairs crop production on irrigated land worldwide. Overall, the susceptibility or tolerance to the stress in plants is a coordinated action of multiple stress responsive genes, which also cross-talk with other components of stress signal transduction pathways. Plant responses to abiotic stress can be determined by the severity of the stress and by the metabolic status of the plant. Abscisic acid (ABA) is a phytohormone critical for plant growth and development and plays an important role in integrating various stress signals and controlling downstream stress responses. Plants have to adjust ABA levels constantly in responce to changing physiological and environmental conditions. To date, the mechanisms for fine-tuning of ABA levels remain elusive. The mechanisms by which plants respond to stress include both ABA-dependent and ABA-independent processes. Various transcription factors such as DREB2A/2B, AREB1, RD22BP1 and MYC/MYB are known to regulate the ABA-responsive gene expression through interacting with their corrosponding cis-acting elements such as DRE/CRT, ABRE and MYCRS/MYBRS, respectively. Understanding these mechanisms is important to improve stress tolerance in crops plants. This article first describes the general pathway for plant stress response followed by roles of ABA and transcription factors in stress tolerance including the regulation of ABA biosynthesis.

Abscisic Acid and Abiotic Stress Signaling

PubMed Central

2007-01-01

Abiotic stress is severe environmental stress, which impairs crop production on irrigated land worldwide. Overall, the susceptibility or tolerance to the stress in plants is a coordinated action of multiple stress responsive genes, which also cross-talk with other components of stress signal transduction pathways. Plant responses to abiotic stress can be determined by the severity of the stress and by the metabolic status of the plant. Abscisic acid (ABA) is a phytohormone critical for plant growth and development and plays an important role in integrating various stress signals and controlling downstream stress responses. Plants have to adjust ABA levels constantly in responce to changing physiological and environmental conditions. To date, the mechanisms for fine-tuning of ABA levels remain elusive. The mechanisms by which plants respond to stress include both ABA-dependent and ABA-independent processes. Various transcription factors such as DREB2A/2B, AREB1, RD22BP1 and MYC/MYB are known to regulate the ABA-responsive gene expression through interacting with their corrosponding cis-acting elements such as DRE/CRT, ABRE and MYCRS/MYBRS, respectively. Understanding these mechanisms is important to improve stress tolerance in crops plants. This article first describes the general pathway for plant stress response followed by roles of ABA and transcription factors in stress tolerance including the regulation of ABA biosynthesis. PMID:19516981

Ntann12 annexin expression is induced by auxin in tobacco roots

PubMed Central

Baucher, Marie; Oukouomi Lowe, Yves; Vandeputte, Olivier M.; Mukoko Bopopi, Johnny; Moussawi, Jihad; Vermeersch, Marjorie; Mol, Adeline; El Jaziri, Mondher; Homblé, Fabrice; Pérez-Morga, David

2011-01-01

Ntann12, encoding a polypeptide homologous to annexins, was found previously to be induced upon infection of tobacco with the bacterium Rhodococcus fascians. In this study, Ntann12 is shown to bind negatively charged phospholipids in a Ca2+-dependent manner. In plants growing in light conditions, Ntann12 is principally expressed in roots and the corresponding protein was mainly immunolocalized in the nucleus. Ntann12 expression was inhibited following plant transfer to darkness and in plants lacking the aerial part. However, an auxin (indole-3-acetic acid) treatment restored the expression of Ntann12 in the root system in dark conditions. Conversely, polar auxin transport inhibitors such as 1-naphthylphthalamic acid (NPA) or 2,3,5-triiodobenzoic acid (TIBA) inhibited Ntann12 expression in light condition. These results indicate that the expression of Ntann12 in the root is linked to the perception of a signal in the aerial part of the plant that is transmitted to the root via polar auxin transport. PMID:21543519

Auxin enhances grafting success in Carya cathayensis (Chinese hickory).

PubMed

Saravana Kumar, R M; Gao, Liu Xiao; Yuan, Hu Wei; Xu, Dong Bin; Liang, Zhao; Tao, Shen Chen; Guo, Wen Bin; Yan, Dao Liang; Zheng, Bing Song; Edqvist, Johan

2018-03-01

Application of auxin to root stock and scion increases the success rate of grafting in Chinese hickory. The nuts of the Chinese hickory (Carya cathayensis) tree are considered both delicious and healthy. The popularity and high demand result is that the hickory nuts are of very high economical value for horticulture. This is particularly true for the Zhejiang province in eastern China where this tree is widely cultivated. However, there are several difficulties surrounding the hickory cultivation, such as for example long vegetative growth, tall trees, labour-intensive nut picking, and slow variety improvements. These complications form a great bottleneck in the expansion of the hickory industry. The development of an efficient grafting procedure could surpass at least some of these problems. In this study, we demonstrate that application of the auxin indole-3-acetic acid promotes the grafting process in hickory, whereas application of the auxin transport inhibitor 1-N-naphthylphthalamic acid inhibits the grafting process. Furthermore, we have identified hickory genes in the PIN, ABCB, and AUX/LAX-families known to encode influx and efflux carriers in the polar transport of auxin. We show that increased expression of several of these genes, such as CcPIN1b and CcLAX3, is correlating with successful grafting.

RNA-Seq analysis of Citrus reticulata in the early stages of Xylella fastidiosa infection reveals auxin-related genes as a defense response.

PubMed

Rodrigues, Carolina M; de Souza, Alessandra A; Takita, Marco A; Kishi, Luciano T; Machado, Marcos A

2013-10-03

Citrus variegated chlorosis (CVC), caused by Xylella fastidiosa, is one the most important citrus diseases, and affects all varieties of sweet orange (Citrus sinensis L. Osb). On the other hand, among the Citrus genus there are different sources of resistance against X. fastidiosa. For these species identifying these defense genes could be an important step towards obtaining sweet orange resistant varieties through breeding or genetic engineering. To assess these genes we made use of mandarin (C. reticulata Blanco) that is known to be resistant to CVC and shares agronomical characteristics with sweet orange. Thus, we investigated the gene expression in Ponkan mandarin at one day after infection with X. fastidiosa, using RNA-seq. A set of genes considered key elements in the resistance was used to confirm its regulation in mandarin compared with the susceptible sweet orange. Gene expression analysis of mock inoculated and infected tissues of Ponkan mandarin identified 667 transcripts repressed and 724 significantly induced in the later. Among the induced transcripts, we identified genes encoding proteins similar to Pattern Recognition Receptors. Furthermore, many genes involved in secondary metabolism, biosynthesis and cell wall modification were upregulated as well as in synthesis of abscisic acid, jasmonic acid and auxin. This work demonstrated that the defense response to the perception of bacteria involves cell wall modification and activation of hormone pathways, which probably lead to the induction of other defense-related genes. We also hypothesized the induction of auxin-related genes indicates that resistant plants initially recognize X. fastidiosa as a necrotrophic pathogen.

RNA-Seq analysis of Citrus reticulata in the early stages of Xylella fastidiosa infection reveals auxin-related genes as a defense response

PubMed Central

2013-01-01

Background Citrus variegated chlorosis (CVC), caused by Xylella fastidiosa, is one the most important citrus diseases, and affects all varieties of sweet orange (Citrus sinensis L. Osb). On the other hand, among the Citrus genus there are different sources of resistance against X. fastidiosa. For these species identifying these defense genes could be an important step towards obtaining sweet orange resistant varieties through breeding or genetic engineering. To assess these genes we made use of mandarin (C. reticulata Blanco) that is known to be resistant to CVC and shares agronomical characteristics with sweet orange. Thus, we investigated the gene expression in Ponkan mandarin at one day after infection with X. fastidiosa, using RNA-seq. A set of genes considered key elements in the resistance was used to confirm its regulation in mandarin compared with the susceptible sweet orange. Results Gene expression analysis of mock inoculated and infected tissues of Ponkan mandarin identified 667 transcripts repressed and 724 significantly induced in the later. Among the induced transcripts, we identified genes encoding proteins similar to Pattern Recognition Receptors. Furthermore, many genes involved in secondary metabolism, biosynthesis and cell wall modification were upregulated as well as in synthesis of abscisic acid, jasmonic acid and auxin. Conclusions This work demonstrated that the defense response to the perception of bacteria involves cell wall modification and activation of hormone pathways, which probably lead to the induction of other defense-related genes. We also hypothesized the induction of auxin-related genes indicates that resistant plants initially recognize X. fastidiosa as a necrotrophic pathogen. PMID:24090429

Ethylene Inhibits Root Elongation during Alkaline Stress through AUXIN1 and Associated Changes in Auxin Accumulation1

PubMed Central

Li, Juan; Xu, Heng-Hao; Liu, Wen-Cheng; Zhang, Xiao-Wei

2015-01-01

Soil alkalinity causes major reductions in yield and quality of crops worldwide. The plant root is the first organ sensing soil alkalinity, which results in shorter primary roots. However, the mechanism underlying alkaline stress-mediated inhibition of root elongation remains to be further elucidated. Here, we report that alkaline conditions inhibit primary root elongation of Arabidopsis (Arabidopsis thaliana) seedlings by reducing cell division potential in the meristem zones and that ethylene signaling affects this process. The ethylene perception antagonist silver (Ag+) alleviated the inhibition of root elongation by alkaline stress. Moreover, the ethylene signaling mutants ethylene response1-3 (etr1-3), ethylene insensitive2 (ein2), and ein3-1 showed less reduction in root length under alkaline conditions, indicating a reduced sensitivity to alkalinity. Ethylene biosynthesis also was found to play a role in alkaline stress-mediated root inhibition; the ethylene overproducer1-1 mutant, which overproduces ethylene because of increased stability of 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID SYNTHASE5, was hypersensitive to alkaline stress. In addition, the ethylene biosynthesis inhibitor cobalt (Co2+) suppressed alkaline stress-mediated inhibition of root elongation. We further found that alkaline stress caused an increase in auxin levels by promoting expression of auxin biosynthesis-related genes, but the increase in auxin levels was reduced in the roots of the etr1-3 and ein3-1 mutants and in Ag+/Co2+-treated wild-type plants. Additional genetic and physiological data showed that AUXIN1 (AUX1) was involved in alkaline stress-mediated inhibition of root elongation. Taken together, our results reveal that ethylene modulates alkaline stress-mediated inhibition of root growth by increasing auxin accumulation by stimulating the expression of AUX1 and auxin biosynthesis-related genes. PMID:26109425

Evolutionarily Conserved Regulatory Mechanisms of Abscisic Acid Signaling in Land Plants: Characterization of ABSCISIC ACID INSENSITIVE1-Like Type 2C Protein Phosphatase in the Liverwort Marchantia polymorpha1[C][OA

PubMed Central

Tougane, Ken; Komatsu, Kenji; Bhyan, Salma Begum; Sakata, Yoichi; Ishizaki, Kimitsune; Yamato, Katsuyuki T.; Kohchi, Takayuki; Takezawa, Daisuke

2010-01-01

Abscisic acid (ABA) is postulated to be a ubiquitous hormone that plays a central role in seed development and responses to environmental stresses of vascular plants. However, in liverworts (Marchantiophyta), which represent the oldest extant lineage of land plants, the role of ABA has been least emphasized; thus, very little information is available on the molecular mechanisms underlying ABA responses. In this study, we isolated and characterized MpABI1, an ortholog of ABSCISIC ACID INSENSITIVE1 (ABI1), from the liverwort Marchantia polymorpha. The MpABI1 cDNA encoded a 568-amino acid protein consisting of the carboxy-terminal protein phosphatase 2C (PP2C) domain and a novel amino-terminal regulatory domain. The MpABI1 transcript was detected in the gametophyte, and its expression level was increased by exogenous ABA treatment in the gemma, whose growth was strongly inhibited by ABA. Experiments using green fluorescent protein fusion constructs indicated that MpABI1 was mainly localized in the nucleus and that its nuclear localization was directed by the amino-terminal domain. Transient overexpression of MpABI1 in M. polymorpha and Physcomitrella patens cells resulted in suppression of ABA-induced expression of the wheat Em promoter fused to the β -glucuronidase gene. Transgenic P. patens expressing MpABI1 and its mutant construct, MpABI1-d2, lacking the amino-terminal domain, had reduced freezing and osmotic stress tolerance, and associated with reduced accumulation of ABA-induced late embryogenesis abundant-like boiling-soluble proteins. Furthermore, ABA-induced morphological changes leading to brood cells were not prominent in these transgenic plants. These results suggest that MpABI1 is a negative regulator of ABA signaling, providing unequivocal molecular evidence of PP2C-mediated ABA response mechanisms functioning in liverworts. PMID:20097789

Detection of phytohormones in temperate forest fungi predicts consistent abscisic acid production and a common pathway for cytokinin biosynthesis.

PubMed

Morrison, Erin N; Knowles, Sarah; Hayward, Allison; Thorn, R Greg; Saville, Barry J; Emery, R J N

2015-01-01

The phytohormones, abscisic acid and cytokinin, once were thought to be present uniquely in plants, but increasing evidence suggests that these hormones are present in a wide variety of organisms. Few studies have examined fungi for the presence of these "plant" hormones or addressed whether their levels differ based on the nutrition mode of the fungus. This study examined 20 temperate forest fungi of differing nutritional modes (ectomycorrhizal, wood-rotting, saprotrophic). Abscisic acid and cytokinin were present in all fungi sampled; this indicated that the sampled fungi have the capacity to synthesize these two classes of phytohormones. Of the 27 cytokinins analyzed by HPLC-ESI MS/MS, seven were present in all fungi sampled. This suggested the existence of a common cytokinin metabolic pathway in fungi that does not vary among different nutritional modes. Predictions regarding the source of isopentenyl, cis-zeatin and methylthiol CK production stemming from the tRNA degradation pathway among fungi are discussed. © 2015 by The Mycological Society of America.

The auxin-resistant diageotropica mutant of tomato responds to gravity via an auxin-mediated pathway

NASA Technical Reports Server (NTRS)

Rice, M. S.; Lomax, T. L.

2000-01-01

Hypocotyls of the diageotropica (dgt) mutant of tomato (Lycopersicon esculentum Mill.) do not elongate in response to exogenous auxin, but can respond to gravity. This appears paradoxical in light of the Cholodny-Went hypothesis, which states that shoot gravicurvature results from asymmetric stimulation of elongation by auxin. While light-grown dgt seedlings can achieve correct gravitropic reorientation, the response is slow compared to wild-type seedlings. The sensitivity of dgt seedlings to inhibition of gravicurvature by immersion in auxin or auxin-transport inhibitors is similar to that of wild-type plants, indicating that both an auxin gradient and auxin transport are required for the gravitropic response and that auxin uptake, efflux, and at least one auxin receptor are functional in dgt. Furthermore, dgt gravicurvature is the result of asymmetrically increased elongation as would be expected for an auxin-mediated response. Our results suggest differences between elongation in response to exogenous auxin (absent in dgt) and elongation in response to gravistimulation (present but attenuated in dgt) and confirm the presence of two phases during the gravitropic response, both of which are dependent on functional auxin transport.

The IBO germination quantitative trait locus encodes a phosphatase 2C-related variant with a nonsynonymous amino acid change that interferes with abscisic acid signaling.

PubMed

Amiguet-Vercher, Amélia; Santuari, Luca; Gonzalez-Guzman, Miguel; Depuydt, Stephen; Rodriguez, Pedro L; Hardtke, Christian S

2015-02-01

Natural genetic variation is crucial for adaptability of plants to different environments. Seed dormancy prevents precocious germination in unsuitable conditions and is an adaptation to a major macro-environmental parameter, the seasonal variation in temperature and day length. Here we report the isolation of IBO, a quantitative trait locus (QTL) that governs c. 30% of germination rate variance in an Arabidopsis recombinant inbred line (RIL) population derived from the parental accessions Eilenburg-0 (Eil-0) and Loch Ness-0 (Lc-0). IBO encodes an uncharacterized phosphatase 2C-related protein, but neither the Eil-0 nor the Lc-0 variant, which differ in a single amino acid, have any appreciable phosphatase activity in in vitro assays. However, we found that the amino acid change in the Lc-0 variant of the IBO protein confers reduced germination rate. Moreover, unlike the Eil-0 variant of the protein, the Lc-0 variant can interfere with the activity of the phosphatase 2C ABSCISIC ACID INSENSITIVE 1 in vitro. This suggests that the Lc-0 variant possibly interferes with abscisic acid signaling, a notion that is supported by physiological assays. Thus, we isolated an example of a QTL allele with a nonsynonymous amino acid change that might mediate local adaptation of seed germination timing. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Pavement cells: a model system for non-transcriptional auxin signalling and crosstalks.

PubMed

Chen, Jisheng; Wang, Fei; Zheng, Shiqin; Xu, Tongda; Yang, Zhenbiao

2015-08-01

Auxin (indole acetic acid) is a multifunctional phytohormone controlling various developmental patterns, morphogenetic processes, and growth behaviours in plants. The transcription-based pathway activated by the nuclear TRANSPORT INHIBITOR RESISTANT 1/auxin-related F-box auxin receptors is well established, but the long-sought molecular mechanisms of non-transcriptional auxin signalling remained enigmatic until very recently. Along with the establishment of the Arabidopsis leaf epidermal pavement cell (PC) as an exciting and amenable model system in the past decade, we began to gain insight into non-transcriptional auxin signalling. The puzzle-piece shape of PCs forms from intercalated or interdigitated cell growth, requiring local intra- and inter-cellular coordination of lobe and indent formation. Precise coordination of this interdigitated pattern requires auxin and an extracellular auxin sensing system that activates plasma membrane-associated Rho GTPases from plants and subsequent downstream events regulating cytoskeletal reorganization and PIN polarization. Apart from auxin, mechanical stress and cytokinin have been shown to affect PC interdigitation, possibly by interacting with auxin signals. This review focuses upon signalling mechanisms for cell polarity formation in PCs, with an emphasis on non-transcriptional auxin signalling in polarized cell expansion and pattern formation and how different auxin pathways interplay with each other and with other signals. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Auxin and the integration of environmental signals into plant root development

PubMed Central

Kazan, Kemal

2013-01-01

Background Auxin is a versatile plant hormone with important roles in many essential physiological processes. In recent years, significant progress has been made towards understanding the roles of this hormone in plant growth and development. Recent evidence also points to a less well-known but equally important role for auxin as a mediator of environmental adaptation in plants. Scope This review briefly discusses recent findings on how plants utilize auxin signalling and transport to modify their root system architecture when responding to diverse biotic and abiotic rhizosphere signals, including macro- and micro-nutrient starvation, cold and water stress, soil acidity, pathogenic and beneficial microbes, nematodes and neighbouring plants. Stress-responsive transcription factors and microRNAs that modulate auxin- and environment-mediated root development are also briefly highlighted. Conclusions The auxin pathway constitutes an essential component of the plant's biotic and abiotic stress tolerance mechanisms. Further understanding of the specific roles that auxin plays in environmental adaptation can ultimately lead to the development of crops better adapted to stressful environments. PMID:24136877

Abscisic acid perception and signaling: structural mechanisms and applications

PubMed Central

Ng, Ley Moy; Melcher, Karsten; Teh, Bin Tean; Xu, H Eric

2014-01-01

Adverse environmental conditions are a threat to agricultural yield and therefore exert a global effect on livelihood, health and the economy. Abscisic acid (ABA) is a vital plant hormone that regulates abiotic stress tolerance, thereby allowing plants to cope with environmental stresses. Previously, attempts to develop a complete understanding of the mechanisms underlying ABA signaling have been hindered by difficulties in the identification of bona fide ABA receptors. The discovery of the PYR/PYL/RCAR family of ABA receptors therefore represented a major milestone in the effort to overcome these roadblocks; since then, many structural and functional studies have provided detailed insights into processes ranging from ABA perception to the activation of ABA-responsive gene transcription. This understanding of the mechanisms of ABA perception and signaling has served as the basis for recent, preliminary developments in the genetic engineering of stress-resistant crops as well as in the design of new synthetic ABA agonists, which hold great promise for the agricultural enhancement of stress tolerance. PMID:24786231

Flavonoids and Auxin Transport Inhibitors Rescue Symbiotic Nodulation in the Medicago truncatula Cytokinin Perception Mutant cre1

PubMed Central

Ng, Jason Liang Pin; Hassan, Samira; Truong, Thy T.; Hocart, Charles H.; Laffont, Carole; Frugier, Florian; Mathesius, Ulrike

2015-01-01

Initiation of symbiotic nodules in legumes requires cytokinin signaling, but its mechanism of action is largely unknown. Here, we tested whether the failure to initiate nodules in the Medicago truncatula cytokinin perception mutant cre1 (cytokinin response1) is due to its altered ability to regulate auxin transport, auxin accumulation, and induction of flavonoids. We found that in the cre1 mutant, symbiotic rhizobia cannot locally alter acro- and basipetal auxin transport during nodule initiation and that these mutants show reduced auxin (indole-3-acetic acid) accumulation and auxin responses compared with the wild type. Quantification of flavonoids, which can act as endogenous auxin transport inhibitors, showed a deficiency in the induction of free naringenin, isoliquiritigenin, quercetin, and hesperetin in cre1 roots compared with wild-type roots 24 h after inoculation with rhizobia. Coinoculation of roots with rhizobia and the flavonoids naringenin, isoliquiritigenin, and kaempferol, or with the synthetic auxin transport inhibitor 2,3,5,-triiodobenzoic acid, rescued nodulation efficiency in cre1 mutants and allowed auxin transport control in response to rhizobia. Our results suggest that CRE1-dependent cytokinin signaling leads to nodule initiation through the regulation of flavonoid accumulation required for local alteration of polar auxin transport and subsequent auxin accumulation in cortical cells during the early stages of nodulation. PMID:26253705

Ethylene Upregulates Auxin Biosynthesis in Arabidopsis Seedlings to Enhance Inhibition of Root Cell Elongation[W

PubMed Central

Swarup, Ranjan; Perry, Paula; Hagenbeek, Dik; Van Der Straeten, Dominique; Beemster, Gerrit T.S.; Sandberg, Göran; Bhalerao, Rishikesh; Ljung, Karin; Bennett, Malcolm J.

2007-01-01

Ethylene represents an important regulatory signal for root development. Genetic studies in Arabidopsis thaliana have demonstrated that ethylene inhibition of root growth involves another hormone signal, auxin. This study investigated why auxin was required by ethylene to regulate root growth. We initially observed that ethylene positively controls auxin biosynthesis in the root apex. We subsequently demonstrated that ethylene-regulated root growth is dependent on (1) the transport of auxin from the root apex via the lateral root cap and (2) auxin responses occurring in multiple elongation zone tissues. Detailed growth studies revealed that the ability of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid to inhibit root cell elongation was significantly enhanced in the presence of auxin. We conclude that by upregulating auxin biosynthesis, ethylene facilitates its ability to inhibit root cell expansion. PMID:17630275

Abscisic Acid Regulates Early Seed Development in Arabidopsis by ABI5-Mediated Transcription of SHORT HYPOCOTYL UNDER BLUE1[C][W][OPEN

PubMed Central

Cheng, Zhi Juan; Zhao, Xiang Yu; Shao, Xing Xing; Wang, Fei; Zhou, Chao; Liu, Ying Gao; Zhang, Yan; Zhang, Xian Sheng

2014-01-01

Seed development includes an early stage of endosperm proliferation and a late stage of embryo growth at the expense of the endosperm in Arabidopsis thaliana. Abscisic acid (ABA) has known functions during late seed development, but its roles in early seed development remain elusive. In this study, we report that ABA-deficient mutants produced seeds with increased size, mass, and embryo cell number but delayed endosperm cellularization. ABSCISIC ACID DEFICIENT2 (ABA2) encodes a unique short-chain dehydrogenase/reductase that functions in ABA biosynthesis, and its expression pattern overlaps that of SHORT HYPOCOTYL UNDER BLUE1 (SHB1) during seed development. SHB1 RNA accumulation was significantly upregulated in the aba2-1 mutant and was downregulated by the application of exogenous ABA. Furthermore, RNA accumulation of the basic/region leucine zipper transcription factor ABSCISIC ACID-INSENSITIVE5 (ABI5), involved in ABA signaling, was decreased in aba2-1. Consistent with this, seed size was also increased in abi5. We further show that ABI5 directly binds to two discrete regions in the SHB1 promoter. Our results suggest that ABA negatively regulates SHB1 expression, at least in part, through the action of its downstream signaling component ABI5. Our findings provide insights into the molecular mechanisms by which ABA regulates early seed development. PMID:24619610

Arabidopsis YAK1 regulates abscisic acid response and drought resistance.

PubMed

Kim, Dongjin; Ntui, Valentine Otang; Xiong, Liming

2016-07-01

Abscisic acid (ABA) is an important phytohormone that controls several plant processes such as seed germination, seedling growth, and abiotic stress response. Here, we report that AtYak1 plays an important role in ABA signaling and postgermination growth in Arabidopsis. AtYak1 knockout mutant plants were hyposensitive to ABA inhibition of seed germination, cotyledon greening, seedling growth, and stomatal movement. atyak1-1 mutant plants display reduced drought stress resistance, as evidenced by water loss rate and survival rate. Molecular genetic analysis revealed that AtYak1 deficiency led to elevated expression of stomatal-related gene, MYB60, and down-regulation of several stress-responsive genes. Altogether, these results indicate that AtYak1 plays a role as a positive regulator in ABA-mediated drought response in Arabidopsis. © 2016 Federation of European Biochemical Societies.

Halogenated auxins affect microtubules and root elongation in Lactuca sativa

NASA Technical Reports Server (NTRS)

Zhang, N.; Hasenstein, K. H.

2000-01-01

We studied the effect of 4,4,4-trifluoro-3-(indole-3-)butyric acid (TFIBA), a recently described root growth stimulator, and 5,6-dichloro-indole-3-acetic acid (DCIAA) on growth and microtubule (MT) organization in roots of Lactuca sativa L. DCIAA and indole-3-butyric acid (IBA) inhibited root elongation and depolymerized MTs in the cortex of the elongation zone, inhibited the elongation of stele cells, and promoted xylem maturation. Both auxins caused the plane of cell division to shift from anticlinal to periclinal. In contrast, TFIBA (100 micromolar) promoted elongation of primary roots by 40% and stimulated the elongation of lateral roots, even in the presence of IBA, the microtubular inhibitors oryzalin and taxol, or the auxin transport inhibitor naphthylphthalamic acid. However, TFIBA inhibited the formation of lateral root primordia. Immunostaining showed that TFIBA stabilized MTs orientation perpendicular to the root axis, doubled the cortical cell length, but delayed xylem maturation. The data indicate that the auxin-induced inhibition of elongation and swelling of roots results from reoriented phragmoplasts, the destabilization of MTs in elongating cells, and promotion of vessel formation. In contrast, TFIBA induced promotion of root elongation by enhancing cell length, prolonging transverse MT orientation, delaying cell and xylem maturation.

Abscisic acid is involved in the iron-induced synthesis of maize ferritin.

PubMed Central

Lobréaux, S; Hardy, T; Briat, J F

1993-01-01

The ubiquitous iron storage protein ferritin has a highly conserved structure in plants and animals, but a distinct cytological location and a different level of control in response to iron excess. Plant ferritins are plastid-localized and transcriptionally regulated in response to iron, while animal ferritins are found in the cytoplasm and have their expression mainly controlled at the translational level. In order to understand the basis of these differences, we developed hydroponic cultures of maize plantlets which allowed an increase in the intracellular iron concentration, leading to a transient accumulation of ferritin mRNA and protein (Lobréaux,S., Massenet,O. and Briat,J.F., 1992, Plant Mol. Biol., 19, 563-575). Here, it is shown that iron induces ferritin and RAB (Responsive to Abscisic Acid) mRNA accumulation relatively with abscisic acid (ABA) accumulation. Ferritin mRNA also accumulates in response to exogenous ABA. Synergistic experiments demonstrate that the ABA and iron responses are linked, although full expression of the ferritin genes cannot be entirely explained by an increase in ABA concentration. Inducibility of ferritin mRNA accumulation by iron is dramatically decreased in the maize ABA-deficient mutant vp2 and can be rescued by addition of exogenous ABA, confirming the involvement of ABA in the iron response in plants. Therefore, it is concluded that a major part of the iron-induced biosynthesis of ferritin is achieved through a pathway involving an increase in the level of the plant hormone ABA. The general conclusion of this work is that the synthesis of the same protein in response to the same environmental signal can be controlled by separate and distinct mechanisms in plants and animals. Images PMID:8440255

Asymmetric Auxin Distribution is Not Required to Establish Root Phototropism in Arabidopsis.

PubMed

Kimura, Taro; Haga, Ken; Shimizu-Mitao, Yasushi; Takebayashi, Yumiko; Kasahara, Hiroyuki; Hayashi, Ken-Ichiro; Kakimoto, Tatsuo; Sakai, Tatsuya

2018-04-01

An asymmetric auxin distribution pattern is assumed to underlie the tropic responses of seed plants. It is unclear, however, whether this pattern is required for root negative phototropism. We here demonstrate that asymmetric auxin distribution is not required to establish root phototropism in Arabidopsis. Our detailed analyses of auxin reporter genes indicate that auxin accumulates on the irradiated side of roots in response to an incidental gravitropic stimulus caused by phototropic bending. Further, an agravitropic mutant showed a suppression of this accumulation with an enhancement of the phototropic response. In this context, our pharmacological and genetic analyses revealed that both polar auxin transport and auxin biosynthesis are critical for the establishment of root gravitropism, but not for root phototropism, and that defects in these processes actually enhance phototropic responses in roots. The auxin response factor double mutant arf7 arf19 and the auxin receptor mutant tir1 showed a slight reduction in phototropic curvatures in roots, suggesting that the transcriptional regulation by some specific ARF proteins and their regulators is at least partly involved in root phototropism. However, the auxin antagonist PEO-IAA [α-(phenylethyl-2-one)-indole-3-acetic acid] suppressed root gravitropism and enhanced root phototropism, suggesting that the TIR1/AFB auxin receptors and ARF transcriptional factors play minor roles in root phototropism. Taken together, we conclude from our current data that the phototropic response in Arabidopsis roots is induced by an unknown mechanism that does not require asymmetric auxin distribution and that the Cholodny-Went hypothesis probably does not apply to root phototropism.

Control of cytokinin and auxin homeostasis in cyanobacteria and algae.

PubMed

Žižková, Eva; Kubeš, Martin; Dobrev, Petre I; Přibyl, Pavel; Šimura, Jan; Zahajská, Lenka; Záveská Drábková, Lenka; Novák, Ondřej; Motyka, Václav

2017-01-01

The metabolism of cytokinins (CKs) and auxins in vascular plants is relatively well understood, but data concerning their metabolic pathways in non-vascular plants are still rather rare. With the aim of filling this gap, 20 representatives of taxonomically major lineages of cyanobacteria and algae from Cyanophyceae, Xanthophyceae, Eustigmatophyceae, Porphyridiophyceae, Chlorophyceae, Ulvophyceae, Trebouxiophyceae, Zygnematophyceae and Klebsormidiophyceae were analysed for endogenous profiles of CKs and auxins and some of them were used for studies of the metabolic fate of exogenously applied radiolabelled CK, [ 3 H]trans-zeatin (transZ) and auxin ([ 3 H]indole-3-acetic acid (IAA)), and the dynamics of endogenous CK and auxin pools during algal growth and cell division. Quantification of phytohormone levels was performed by high-performance or ultrahigh-performance liquid chromatography-electrospray tandem mass spectrometry (HPLC-MS/MS, UHPLC-MS/MS). The dynamics of exogenously applied [ 3 H]transZ and [ 3 H]IAA in cell cultures were monitored by HPLC with on-line radioactivity detection. The comprehensive screen of selected cyanobacteria and algae for endogenous CKs revealed a predominance of bioactive and phosphate CK forms while O- and N-glucosides evidently did not contribute greatly to the total CK pool. The abundance of cis-zeatin-type CKs and occurrence of CK 2-methylthio derivatives pointed to the tRNA pathway as a substantial source of CKs. The importance of the tRNA biosynthetic pathway was proved by the detection of tRNA-bound CKs during the course of Scenedesmus obliquus growth. Among auxins, free IAA and its oxidation catabolite 2-oxindole-3-acetic acid represented the prevailing endogenous forms. After treatment with [ 3 H]IAA, IAA-aspartate and indole-3-acetyl-1-glucosyl ester were detected as major auxin metabolites. Moreover, different dynamics of endogenous CKs and auxin profiles during S. obliquus culture clearly demonstrated diverse roles of both

Control of cytokinin and auxin homeostasis in cyanobacteria and algae

PubMed Central

Žižková, Eva; Kubeš, Martin; Dobrev, Petre I.; Přibyl, Pavel; Šimura, Jan; Zahajská, Lenka; Záveská Drábková, Lenka; Novák, Ondřej; Motyka, Václav

2017-01-01

Background and Aims The metabolism of cytokinins (CKs) and auxins in vascular plants is relatively well understood, but data concerning their metabolic pathways in non-vascular plants are still rather rare. With the aim of filling this gap, 20 representatives of taxonomically major lineages of cyanobacteria and algae from Cyanophyceae, Xanthophyceae, Eustigmatophyceae, Porphyridiophyceae, Chlorophyceae, Ulvophyceae, Trebouxiophyceae, Zygnematophyceae and Klebsormidiophyceae were analysed for endogenous profiles of CKs and auxins and some of them were used for studies of the metabolic fate of exogenously applied radiolabelled CK, [3H]trans-zeatin (transZ) and auxin ([3H]indole-3-acetic acid (IAA)), and the dynamics of endogenous CK and auxin pools during algal growth and cell division. Methods Quantification of phytohormone levels was performed by high-performance or ultrahigh-performance liquid chromatography–electrospray tandem mass spectrometry (HPLC-MS/MS, UHPLC-MS/MS). The dynamics of exogenously applied [3H]transZ and [3H]IAA in cell cultures were monitored by HPLC with on-line radioactivity detection. Key Results The comprehensive screen of selected cyanobacteria and algae for endogenous CKs revealed a predominance of bioactive and phosphate CK forms while O- and N-glucosides evidently did not contribute greatly to the total CK pool. The abundance of cis-zeatin-type CKs and occurrence of CK 2-methylthio derivatives pointed to the tRNA pathway as a substantial source of CKs. The importance of the tRNA biosynthetic pathway was proved by the detection of tRNA-bound CKs during the course of Scenedesmus obliquus growth. Among auxins, free IAA and its oxidation catabolite 2-oxindole-3-acetic acid represented the prevailing endogenous forms. After treatment with [3H]IAA, IAA-aspartate and indole-3-acetyl-1-glucosyl ester were detected as major auxin metabolites. Moreover, different dynamics of endogenous CKs and auxin profiles during S. obliquus culture clearly

Role for apyrases in polar auxin transport in Arabidopsis.

PubMed

Liu, Xing; Wu, Jian; Clark, Greg; Lundy, Stacey; Lim, Minhui; Arnold, David; Chan, Jing; Tang, Wenqiang; Muday, Gloria K; Gardner, Gary; Roux, Stanley J

2012-12-01

Recent evidence indicates that extracellular nucleotides regulate plant growth. Exogenous ATP has been shown to block auxin transport and gravitropic growth in primary roots of Arabidopsis (Arabidopsis thaliana). Cells limit the concentration of extracellular ATP in part through the activity of ectoapyrases (ectonucleoside triphosphate diphosphohydrolases), and two nearly identical Arabidopsis apyrases, APY1 and APY2, appear to share this function. These findings, plus the fact that suppression of APY1 and APY2 blocks growth in Arabidopsis, suggested that the expression of these apyrases could influence auxin transport. This report tests that hypothesis. The polar movement of [(3)H]indole-3-acetic acid in both hypocotyl sections and primary roots of Arabidopsis seedlings was measured. In both tissues, polar auxin transport was significantly reduced in apy2 null mutants when they were induced by estradiol to suppress the expression of APY1 by RNA interference. In the hypocotyl assays, the basal halves of APY-suppressed hypocotyls contained considerably lower free indole-3-acetic acid levels when compared with wild-type plants, and disrupted auxin transport in the APY-suppressed roots was reflected by their significant morphological abnormalities. When a green fluorescent protein fluorescence signal encoded by a DR5:green fluorescent protein construct was measured in primary roots whose apyrase expression was suppressed either genetically or chemically, the roots showed no signal asymmetry following gravistimulation, and both their growth and gravitropic curvature were inhibited. Chemicals that suppress apyrase activity also inhibit gravitropic curvature and, to a lesser extent, growth. Taken together, these results indicate that a critical step connecting apyrase suppression to growth suppression is the inhibition of polar auxin transport.

The promoting effects of alginate oligosaccharides on root development in Oryza sativa L. mediated by auxin signaling.

PubMed

Zhang, Yunhong; Yin, Heng; Zhao, Xiaoming; Wang, Wenxia; Du, Yuguang; He, Ailing; Sun, Kegang

2014-11-26

Alginate oligosaccharides (AOS), which are marine oligosaccharides, are involved in regulating plant root growth, but the promotion mechanism for AOS remains unclear. Here, AOS (10-80 mg/L) induced the expression of auxin-related gene (OsYUCCA1, OsYUCCA5, OsIAA11 and OsPIN1) in rice (Oryza sativa L.) tissues to accelerate auxin biosynthesis and transport, and reduced indole-3-acetic acid (IAA) oxidase activity in rice roots. These changes resulted in the increase of 37.8% in IAA concentration in rice roots, thereby inducing the expression of root development-related genes, promoting root growth in a dose-dependent manner, which were inhibited by auxin transport inhibitor 2,3,5-triiodo benzoic acid (TIBA) and calcium-chelating agent ethylene glycol bis (2-aminoethyl) tetraacetic acid (EGTA). AOS also induced calcium signaling generation in rice roots. Those results indicated that auxin mediated AOS regulation of root development, and calcium signaling may act mainly in the upstream of auxin in the regulation of AOS on rice root development. Copyright © 2014 Elsevier Ltd. All rights reserved.

Abscisic acid and other plant hormones: Methods to visualize distribution and signaling

PubMed Central

Waadt, Rainer; Hsu, Po-Kai; Schroeder, Julian I.

2015-01-01

The exploration of plant behavior on a cellular scale in a minimal invasive manner is key to understanding plant adaptations to their environment. Plant hormones regulate multiple aspects of growth and development and mediate environmental responses to ensure a successful life cycle. To monitor the dynamics of plant hormone actions in intact tissue, we need qualitative and quantitative tools with high temporal and spatial resolution. Here, we describe a set of biological instruments (reporters) for the analysis of the distribution and signaling of various plant hormones. Furthermore, we provide examples of their utility for gaining novel insights into plant hormone action with a deeper focus on the drought hormone abscisic acid. PMID:26577078

Ultra-rapid auxin metabolite profiling for high-throughput mutant screening in Arabidopsis.

PubMed

Pencík, Aleš; Casanova-Sáez, Rubén; Pilarová, Veronika; Žukauskaite, Asta; Pinto, Rui; Micol, José Luis; Ljung, Karin; Novák, Ondrej

2018-04-27

Auxin (indole-3-acetic acid, IAA) plays fundamental roles as a signalling molecule during numerous plant growth and development processes. The formation of local auxin gradients and auxin maxima/minima, which is very important for these processes, is regulated by auxin metabolism (biosynthesis, degradation, and conjugation) as well as transport. When studying auxin metabolism pathways it is crucial to combine data obtained from genetic investigations with the identification and quantification of individual metabolites. Thus, to facilitate efforts to elucidate auxin metabolism and its roles in plants, we have developed a high-throughput method for simultaneously quantifying IAA and its key metabolites in minute samples (<10 mg FW) of Arabidopsis thaliana tissues by in-tip micro solid-phase extraction and fast LC-tandem MS. As a proof of concept, we applied the method to a collection of Arabidopsis mutant lines and identified lines with altered IAA metabolite profiles using multivariate data analysis. Finally, we explored the correlation between IAA metabolite profiles and IAA-related phenotypes. The developed rapid analysis of large numbers of samples (>100 samples d-1) is a valuable tool to screen for novel regulators of auxin metabolism and homeostasis among large collections of genotypes.

The microtubule cytoskeleton does not integrate auxin transport and gravitropism in maize roots

NASA Technical Reports Server (NTRS)

Hasenstein, K. H.; Blancaflor, E. B.; Lee, J. S.

1999-01-01

The Cholodny-Went hypothesis of gravitropism suggests that the graviresponse is controlled by the distribution of auxin. However, the mechanism of auxin transport during the graviresponse of roots is still unresolved. To determine whether the microtubule (MT) cytoskeleton is participating in auxin transport, the cytoskeleton was examined and the movement of 3H-IAA measured in intact and excised taxol, oryzalin, and naphthylphthalamic acid (NPA)-treated roots of Zea mays cv. Merit. Taxol and oryzalin did not inhibit the graviresponse of roots but the auxin transport inhibitor NPA greatly inhibited both auxin transport and graviresponse. NPA had no effect on MT organization in vertical roots, but caused MT reorientation in horizontally placed roots. Regardless of treatment, the organization of MTs in intact roots differed from that in root segments. The MT inhibitors, taxol and oryzalin had opposite effects on the MTs, namely, depolymerization (oryzalin) and stabilization and thickening (taxol), but both treatments caused swelling of the roots. The data indicate that the MT cytoskeleton does not directly interfere with auxin transport or auxin-mediated growth responses in maize roots.

SOS2-LIKE PROTEIN KINASE5, an SNF1-RELATED PROTEIN KINASE3-Type Protein Kinase, Is Important for Abscisic Acid Responses in Arabidopsis through Phosphorylation of ABSCISIC ACID-INSENSITIVE51[OPEN

PubMed Central

Zhou, Xiaona; Hao, Hongmei; Zhang, Yuguo; Bai, Yili; Zhu, Wenbo; Qin, Yunxia; Yuan, Feifei; Zhao, Feiyi; Wang, Mengyao; Hu, Jingjiang; Xu, Hong; Guo, Aiguang; Zhao, Huixian; Zhao, Yang; Cao, Cuiling; Yang, Yongqing; Schumaker, Karen S.; Guo, Yan; Xie, Chang Gen

2015-01-01

Abscisic acid (ABA) plays an essential role in seed germination. In this study, we demonstrate that one SNF1-RELATED PROTEIN KINASE3-type protein kinase, SOS2-LIKE PROTEIN KINASE5 (PKS5), is involved in ABA signal transduction via the phosphorylation of an interacting protein, ABSCISIC ACID-INSENSITIVE5 (ABI5). We found that pks5-3 and pks5-4, two previously identified PKS5 superactive kinase mutants with point mutations in the PKS5 FISL/NAF (a conserved peptide that is necessary for interaction with SOS3 or SOS3-LIKE CALCIUM BINDING PROTEINs) motif and the kinase domain, respectively, are hypersensitive to ABA during seed germination. PKS5 was found to interact with ABI5 in yeast (Saccharomyces cerevisiae), and this interaction was further confirmed in planta using bimolecular fluorescence complementation. Genetic studies revealed that ABI5 is epistatic to PKS5. PKS5 phosphorylates a serine (Ser) residue at position 42 in ABI5 and regulates ABA-responsive gene expression. This phosphorylation was induced by ABA in vivo and transactivated ABI5. Expression of ABI5, in which Ser-42 was mutated to alanine, could not fully rescue the ABA-insensitive phenotypes of the abi5-8 and pks5-4abi5-8 mutants. In contrast, mutating Ser-42 to aspartate rescued the ABA insensitivity of these mutants. These data demonstrate that PKS5-mediated phosphorylation of ABI5 at Ser-42 is critical for the ABA regulation of seed germination and gene expression in Arabidopsis (Arabidopsis thaliana). PMID:25858916

Effects of abscisic acid, gibberellin, ethylene and their interactions on production of phenolic acids in salvia miltiorrhiza bunge hairy roots.

PubMed

Liang, Zongsuo; Ma, Yini; Xu, Tao; Cui, Beimi; Liu, Yan; Guo, Zhixin; Yang, Dongfeng

2013-01-01

Salvia miltiorrhiza is one of the most important traditional Chinese medicinal plants because of its excellent performance in treating coronary heart disease. Phenolic acids mainly including caffeic acid, rosmarinic acid and salvianolic acid B are a group of active ingredients in S. miltiorrhiza. Abscisic acid (ABA), gibberellin (GA) and ethylene are three important phytohormones. In this study, effects of the three phytohormones and their interactions on phenolic production in S. miltiorrhiza hairy roots were investigated. The results showed that ABA, GA and ethylene were all effective to induce production of phenolic acids and increase activities of PAL and TAT in S. miltiorrhiza hairy roots. Effects of phytohormones were reversed by their biosynthetic inhibitors. Antagonistic actions between the three phytohormones played important roles in the biosynthesis of phenolic acids. GA signaling is necessary for ABA and ethylene-induced phenolic production. Yet, ABA and ethylene signaling is probably not necessary for GA3-induced phenolic production. The complex interactions of phytohormones help us reveal regulation mechanism of secondary metabolism and scale-up production of active ingredients in plants.

Effects of Abscisic Acid, Gibberellin, Ethylene and Their Interactions on Production of Phenolic Acids in Salvia miltiorrhiza Bunge Hairy Roots

PubMed Central

Xu, Tao; Cui, Beimi; Liu, Yan; Guo, Zhixin; Yang, Dongfeng

2013-01-01

Salvia miltiorrhiza is one of the most important traditional Chinese medicinal plants because of its excellent performance in treating coronary heart disease. Phenolic acids mainly including caffeic acid, rosmarinic acid and salvianolic acid B are a group of active ingredients in S. miltiorrhiza. Abscisic acid (ABA), gibberellin (GA) and ethylene are three important phytohormones. In this study, effects of the three phytohormones and their interactions on phenolic production in S. miltiorrhiza hairy roots were investigated. The results showed that ABA, GA and ethylene were all effective to induce production of phenolic acids and increase activities of PAL and TAT in S. miltiorrhiza hairy roots. Effects of phytohormones were reversed by their biosynthetic inhibitors. Antagonistic actions between the three phytohormones played important roles in the biosynthesis of phenolic acids. GA signaling is necessary for ABA and ethylene-induced phenolic production. Yet, ABA and ethylene signaling is probably not necessary for GA3-induced phenolic production. The complex interactions of phytohormones help us reveal regulation mechanism of secondary metabolism and scale-up production of active ingredients in plants. PMID:24023778

Abscisic-acid-induced cellular apoptosis and differentiation in glioma via the retinoid acid signaling pathway.

PubMed

Zhou, Nan; Yao, Yu; Ye, Hongxing; Zhu, Wei; Chen, Liang; Mao, Ying

2016-04-15

Retinoid acid (RA) plays critical roles in regulating differentiation and apoptosis in a variety of cancer cells. Abscisic acid (ABA) and RA are direct derivatives of carotenoids and share structural similarities. Here we proposed that ABA may also play a role in cellular differentiation and apoptosis by sharing a similar signaling pathway with RA that may be involved in glioma pathogenesis. We reported for the first time that the ABA levels were twofold higher in low-grade gliomas compared with high-grade gliomas. In glioma tissues, there was a positive correlation between the ABA levels and the transcription of cellular retinoic acid-binding protein 2 (CRABP2) and a negative correlation between the ABA levels and transcription of fatty acid-binding protein 5 (FABP5). ABA treatment induced a significant increase in the expression of CRABP2 and a decrease in the expression of peroxisome proliferator-activated receptor (PPAR) in glioblastoma cells. Remarkably, both cellular apoptosis and differentiation were increased in the glioblastoma cells after ABA treatment. ABA-induced cellular apoptosis and differentiation were significantly reduced by selectively silencing RAR-α, while RAR-α overexpression exaggerated the ABA-induced effects. These results suggest that ABA may play a role in the pathogenesis of glioma by promoting cellular apoptosis and differentiation through the RA signaling pathway. © 2015 UICC.

Arabidopsis thaliana GH3.15 acyl acid amido synthetase has a highly specific substrate preference for the auxin precursor indole-3-butyric acid.

PubMed

Sherp, Ashley M; Westfall, Corey S; Alvarez, Sophie; Jez, Joseph M

2018-03-23

Various phytohormones control plant growth and development and mediate biotic and abiotic stress responses. Gretchen Hagen 3 (GH3) acyl acid amido synthetases are plant enzymes that typically conjugate amino acids to indole-3-acetic acid (IAA) or jasmonic acid (JA) to inactivate or activate these phytohormones, respectively; however, the physiological and biological roles of many of these enzymes remain unclear. Using a biochemical approach, we found that the Arabidopsis thaliana GH3.15 (AtGH3.15) preferentially uses indole-3-butyric acid (IBA) and glutamine as substrates. The X-ray crystal structure of the AtGH3.15·AMP complex, modeling of IBA in the active site, and biochemical analysis of site-directed mutants provide insight on active site features that lead to AtGH3.15's preference for IBA. Assay-based in planta analysis of AtGH3.15-overexpressing lines indicated that their root elongation and lateral root density were resistant to IBA treatment but not to treatment with either IAA or JA. These findings suggest that AtGH3.15 may play a role in auxin homeostasis by modulating the levels of IBA for peroxisomal conversion to IAA. Analysis of AtGH3.15 promoter-driven yellow fluorescent protein reporter lines revealed that AtGH3.15 is expressed at significant levels in seedlings, roots, and parts of the siliques. We conclude that AtGH3.15 is unique in the GH3 protein family for its role in modifying IBA in auxin homeostasis and that it is the first GH3 protein shown to primarily modify a plant growth regulator other than IAA and JA. © 2018 Sherp et al.

Analysis of defense signals in Arabidopsis thaliana leaves by ultra-performance liquid chromatography/tandem mass spectrometry: jasmonates, salicylic acid, abscisic acid.

PubMed

Stingl, Nadja; Krischke, Markus; Fekete, Agnes; Mueller, Martin J

2013-01-01

Defense signaling compounds and phytohormones play an essential role in the regulation of plant responses to various environmental abiotic and biotic stresses. Among the most severe stresses are herbivory, pathogen infection, and drought stress. The major hormones involved in the regulation of these responses are 12-oxo-phytodienoic acid (OPDA), the pro-hormone jasmonic acid (JA) and its biologically active isoleucine conjugate (JA-Ile), salicylic acid (SA), and abscisic acid (ABA). These signaling compounds are present and biologically active at very low concentrations from ng/g to μg/g dry weight. Accurate and sensitive quantification of these signals has made a significant contribution to the understanding of plant stress responses. Ultra-performance liquid chromatography (UPLC) coupled with a tandem quadrupole mass spectrometer (MS/MS) has become an essential technique for the analysis and quantification of these compounds.

FERONIA interacts with ABI2-type phosphatases to facilitate signaling cross-talk between abscisic acid and RALF peptide in Arabidopsis

PubMed Central

Chen, Jia; Yu, Feng; Liu, Ying; Du, Changqing; Li, Xiushan; Zhu, Sirui; Wang, Xianchun; Lan, Wenzhi; Rodriguez, Pedro L.; Liu, Xuanming; Li, Dongping; Chen, Liangbi; Luan, Sheng

2016-01-01

Receptor-like kinase FERONIA (FER) plays a crucial role in plant response to small molecule hormones [e.g., auxin and abscisic acid (ABA)] and peptide signals [e.g., rapid alkalinization factor (RALF)]. It remains unknown how FER integrates these different signaling events in the control of cell growth and stress responses. Under stress conditions, increased levels of ABA will inhibit cell elongation in the roots. In our previous work, we have shown that FER, through activation of the guanine nucleotide exchange factor 1 (GEF1)/4/10-Rho of Plant 11 (ROP11) pathway, enhances the activity of the phosphatase ABA Insensitive 2 (ABI2), a negative regulator of ABA signaling, thereby inhibiting ABA response. In this study, we found that both RALF and ABA activated FER by increasing the phosphorylation level of FER. The FER loss-of-function mutant displayed strong hypersensitivity to both ABA and abiotic stresses such as salt and cold conditions, indicating that FER plays a key role in ABA and stress responses. We further showed that ABI2 directly interacted with and dephosphorylated FER, leading to inhibition of FER activity. Several other ABI2-like phosphatases also function in this pathway, and ABA-dependent FER activation required PYRABACTIN RESISTANCE (PYR)/PYR1-LIKE (PYL)/REGULATORY COMPONENTS OF ABA RECEPTORS (RCAR)–A-type protein phosphatase type 2C (PP2CA) modules. Furthermore, suppression of RALF1 gene expression, similar to disruption of the FER gene, rendered plants hypersensitive to ABA. These results formulated a mechanism for ABA activation of FER and for cross-talk between ABA and peptide hormone RALF in the control of plant growth and responses to stress signals. PMID:27566404

SCFTIR1/AFB-auxin signalling regulates PIN vacuolar trafficking and auxin fluxes during root gravitropism

PubMed Central

Baster, Paweł; Robert, Stéphanie; Kleine-Vehn, Jürgen; Vanneste, Steffen; Kania, Urszula; Grunewald, Wim; De Rybel, Bert; Beeckman, Tom; Friml, Jiří

2013-01-01

The distribution of the phytohormone auxin regulates many aspects of plant development including growth response to gravity. Gravitropic root curvature involves coordinated and asymmetric cell elongation between the lower and upper side of the root, mediated by differential cellular auxin levels. The asymmetry in the auxin distribution is established and maintained by a spatio-temporal regulation of the PIN-FORMED (PIN) auxin transporter activity. We provide novel insights into the complex regulation of PIN abundance and activity during root gravitropism. We show that PIN2 turnover is differentially regulated on the upper and lower side of gravistimulated roots by distinct but partially overlapping auxin feedback mechanisms. In addition to regulating transcription and clathrin-mediated internalization, auxin also controls PIN abundance at the plasma membrane by promoting their vacuolar targeting and degradation. This effect of elevated auxin levels requires the activity of SKP-Cullin-F-boxTIR1/AFB (SCFTIR1/AFB)-dependent pathway. Importantly, also suboptimal auxin levels mediate PIN degradation utilizing the same signalling pathway. These feedback mechanisms are functionally important during gravitropic response and ensure fine-tuning of auxin fluxes for maintaining as well as terminating asymmetric growth. PMID:23211744

Insights into the origin and evolution of the plant hormone signaling machinery.

PubMed

Wang, Chunyang; Liu, Yang; Li, Si-Shen; Han, Guan-Zhu

2015-03-01

Plant hormones modulate plant growth, development, and defense. However, many aspects of the origin and evolution of plant hormone signaling pathways remain obscure. Here, we use a comparative genomic and phylogenetic approach to investigate the origin and evolution of nine major plant hormone (abscisic acid, auxin, brassinosteroid, cytokinin, ethylene, gibberellin, jasmonate, salicylic acid, and strigolactone) signaling pathways. Our multispecies genome-wide analysis reveals that: (1) auxin, cytokinin, and strigolactone signaling pathways originated in charophyte lineages; (2) abscisic acid, jasmonate, and salicylic acid signaling pathways arose in the last common ancestor of land plants; (3) gibberellin signaling evolved after the divergence of bryophytes from land plants; (4) the canonical brassinosteroid signaling originated before the emergence of angiosperms but likely after the split of gymnosperms and angiosperms; and (5) the origin of the canonical ethylene signaling pathway postdates shortly the emergence of angiosperms. Our findings might have important implications in understanding the molecular mechanisms underlying the emergence of land plants. © 2015 American Society of Plant Biologists. All Rights Reserved.

Interaction of galactoglucomannan oligosaccharides with auxin involves changes in flavonoid accumulation.

PubMed

Kučerová, Danica; Kollárová, Karin; Vatehová, Zuzana; Lišková, Desana

2016-01-01

Galactoglucomannan oligosaccharides (GGMOs) are signalling molecules originating from plant cell walls influencing plant growth and defence reactions. The present study focused on their interaction with exogenous IAA (indole-3-acetic acid). GGMOs acted as auxin antagonists and diminished the effect of IAA on Arabidopsis primary root growth. Their effect is associated with meristem enlargement and prolongation of the elongation zone. Reduction of the elongation zone was a consequence of the IAA action, but IAA did not affect the size of the meristem. In the absence of auxin, GGMOs stimulated root growth, meristem enlargement and elongation zone prolongation. It is assumed that the effect of GGMOs in the absence of exogenous auxin resulted from their interaction with the endogenous form. In the presence of auxin transport inhibitor GGMOs did not affect root growth. It is known that flavonoids are auxin transport modulators but this is the first study suggesting the role of flavonoids in GGMOs' signalling. The accumulation of flavonoids in the meristem and elongation zone decreased in GGMOs' treatments in comparison with the control. These oligosaccharides also diminished the effect of IAA on the flavonoids' elevation. The fact that GGMOs decreased the accumulation of flavonoids, known to be modulators of auxin transport, and the loss of GGMOs' activity in the presence of the auxin transport inhibitor indicates that the root growth stimulation caused by GGMOs could be related to changes in auxin transport, possibly mediated by flavonoids. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Block of ATP-binding cassette B19 ion channel activity by 5-nitro-2-(3-phenylpropylamino)-benzoic acid impairs polar auxin transport and root gravitropism.

PubMed

Cho, Misuk; Henry, Elizabeth M; Lewis, Daniel R; Wu, Guosheng; Muday, Gloria K; Spalding, Edgar P

2014-12-01

Polar transport of the hormone auxin through tissues and organs depends on membrane proteins, including some B-subgroup members of the ATP-binding cassette (ABC) transporter family. The messenger RNA level of at least one B-subgroup ABCB gene in Arabidopsis (Arabidopsis thaliana), ABCB19, increases upon treatment with the anion channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), possibly to compensate for an inhibitory effect of the drug on ABCB19 activity. Consistent with this hypothesis, NPPB blocked ion channel activity associated with ABCB19 expressed in human embryonic kidney cells as measured by patch-clamp electrophysiology. NPPB inhibited polar auxin transport through Arabidopsis seedling roots similarly to abcb19 mutations. NPPB also inhibited shootward auxin transport, which depends on the related ABCB4 protein. NPPB substantially decreased ABCB4 and ABCB19 protein levels when cycloheximide concomitantly inhibited new protein synthesis, indicating that blockage by NPPB enhances the degradation of ABCB transporters. Impairing the principal auxin transport streams in roots with NPPB caused aberrant patterns of auxin signaling reporters in root apices. Formation of the auxin-signaling gradient across the tips of gravity-stimulated roots, and its developmental consequence (gravitropism), were inhibited by micromolar concentrations of NPPB that did not affect growth rate. These results identify ion channel activity of ABCB19 that is blocked by NPPB, a compound that can now be considered an inhibitor of polar auxin transport with a defined molecular target. © 2014 American Society of Plant Biologists. All Rights Reserved.

Accumulation of eicosapolyenoic acids enhances sensitivity to abscisic acid and mitigates the effects of drought in transgenic Arabidopsis thaliana

PubMed Central

Qi, Baoxiu

2014-01-01

IgASE1, a C18 Δ9-specific polyunsaturated fatty acid elongase from the marine microalga Isochrysis galbana, is able to convert linoleic acid and α-linolenic acid to eicosadienoic acid and eicosatrienoic acid in Arabidopsis. Eicosadienoic acid and eicosatrienoic acid are precursors of arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, which are synthesized via the Δ8 desaturation biosynthetic pathways. This study shows that the IgASE1-expressing transgenic Arabidopsis exhibited altered morphology (decreased leaf area and biomass) and enhanced drought resistance compared to wild-type plants. The transgenic Arabidopsis were hypersensitive to abscisic acid (ABA) during seed germination, post-germination growth, and seedling development. They had elevated leaf ABA levels under well-watered and dehydrated conditions and their stomata were more sensitive to ABA. Exogenous application of eicosadienoic acid and eicosatrienoic acid can mimic ABA and drought responses in the wild type plants, similar to that found in the transgenic ones. The transcript levels of genes involved in the biosynthesis of ABA (NCED3, ABA1, AAO3) as well as other stress-related genes were upregulated in this transgenic line upon osmotic stress (300mM mannitol). Taken together, these results indicate that these two eicosapolyenoic acids or their derived metabolites can mitigate the effects of drought in transgenic Arabidopsis, at least in part, through the action of ABA. PMID:24609499

Accumulation of eicosapolyenoic acids enhances sensitivity to abscisic acid and mitigates the effects of drought in transgenic Arabidopsis thaliana.

PubMed

Yuan, Xiaowei; Li, Yaxiao; Liu, Shiyang; Xia, Fei; Li, Xinzheng; Qi, Baoxiu

2014-04-01

IgASE1, a C₁₈ Δ(9)-specific polyunsaturated fatty acid elongase from the marine microalga Isochrysis galbana, is able to convert linoleic acid and α-linolenic acid to eicosadienoic acid and eicosatrienoic acid in Arabidopsis. Eicosadienoic acid and eicosatrienoic acid are precursors of arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid, which are synthesized via the Δ(8) desaturation biosynthetic pathways. This study shows that the IgASE1-expressing transgenic Arabidopsis exhibited altered morphology (decreased leaf area and biomass) and enhanced drought resistance compared to wild-type plants. The transgenic Arabidopsis were hypersensitive to abscisic acid (ABA) during seed germination, post-germination growth, and seedling development. They had elevated leaf ABA levels under well-watered and dehydrated conditions and their stomata were more sensitive to ABA. Exogenous application of eicosadienoic acid and eicosatrienoic acid can mimic ABA and drought responses in the wild type plants, similar to that found in the transgenic ones. The transcript levels of genes involved in the biosynthesis of ABA (NCED3, ABA1, AAO3) as well as other stress-related genes were upregulated in this transgenic line upon osmotic stress (300 mM mannitol). Taken together, these results indicate that these two eicosapolyenoic acids or their derived metabolites can mitigate the effects of drought in transgenic Arabidopsis, at least in part, through the action of ABA.

OsABCB14 functions in auxin transport and iron homeostasis in rice (Oryza sativa L.).

PubMed

Xu, Yanxia; Zhang, Saina; Guo, Haipeng; Wang, Suikang; Xu, Ligen; Li, Chuanyou; Qian, Qian; Chen, Fan; Geisler, Markus; Qi, Yanhua; Jiang, De An

2014-07-01

Members of the ATP Binding Cassette B/Multidrug-Resistance/P-glyco-protein (ABCB/MDR/PGP) subfamily were shown to function primarily in Oryza sativa (rice) auxin transport; however, none of the rice ABCB transporters have been functionally characterized. Here, we describe that a knock-down of OsABCB14 confers decreased auxin concentrations and polar auxin transport rates, conferring insensitivity to 2,4-dichlorophenoxyacetic acid (2,4-D) and indole-3-acetic acid (IAA). OsABCB14 displays enhanced specific auxin influx activity in yeast and protoplasts prepared from rice knock-down alleles. OsABCB14 is localized at the plasma membrane, pointing to an important directionality under physiological conditions. osabcb14 mutants were surprisingly found to be insensitive to iron deficiency treatment (-Fe). Their Fe concentration is higher and upregulation of Fe deficiency-responsive genes is lower in osabcb14 mutants than in wild-type rice (Nipponbare, NIP). Taken together, our results strongly support the role of OsABCB14 as an auxin influx transporter involved in Fe homeostasis. The functional characterization of OsABCB14 provides insights in monocot auxin transport and its relationship to Fe nutrition. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

Abscisic Acid and Abiotic Stress Tolerance in Crop Plants

PubMed Central

Sah, Saroj K.; Reddy, Kambham R.; Li, Jiaxu

2016-01-01

Abiotic stress is a primary threat to fulfill the demand of agricultural production to feed the world in coming decades. Plants reduce growth and development process during stress conditions, which ultimately affect the yield. In stress conditions, plants develop various stress mechanism to face the magnitude of stress challenges, although that is not enough to protect them. Therefore, many strategies have been used to produce abiotic stress tolerance crop plants, among them, abscisic acid (ABA) phytohormone engineering could be one of the methods of choice. ABA is an isoprenoid phytohormone, which regulates various physiological processes ranging from stomatal opening to protein storage and provides adaptation to many stresses like drought, salt, and cold stresses. ABA is also called an important messenger that acts as the signaling mediator for regulating the adaptive response of plants to different environmental stress conditions. In this review, we will discuss the role of ABA in response to abiotic stress at the molecular level and ABA signaling. The review also deals with the effect of ABA in respect to gene expression. PMID:27200044

Novel Abscisic Acid Antagonists Identified with Chemical Array Screening.

PubMed

Ito, Takuya; Kondoh, Yasumitsu; Yoshida, Kazuko; Umezawa, Taishi; Shimizu, Takeshi; Shinozaki, Kazuo; Osada, Hiroyuki

2015-11-01

Abscisic acid (ABA) signaling is involved in multiple processes in plants, such as water stress control and seed dormancy. Major regulators of ABA signaling are the PYR/PYL/RCAR family receptor proteins, group A protein phosphatases 2C (PP2Cs), and subclass III of SNF1-related protein kinase 2 (SnRK2). Novel ABA agonists and antagonists to modulate the functions of these proteins would not only contribute to clarification of the signaling mechanisms but might also be used to improve crop yields. To obtain small molecules that interact with Arabidopsis ABA receptor PYR1, we screened 24 275 compounds from a chemical library at the RIKEN Natural Products Depository by using a chemical array platform. Subsequent SnRK2 and PP2C assays narrowed down the candidates to two molecules. One antagonized ABA in a competitive manner and inhibited the formation of the PYR1-ABA-PP2C ternary complex. These compounds might have potential as bioprobes to analyze ABA signaling. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cyclic GMP is involved in auxin signalling during Arabidopsis root growth and development.

PubMed

Nan, Wenbin; Wang, Xiaomin; Yang, Lei; Hu, Yanfeng; Wei, Yuantao; Liang, Xiaolei; Mao, Lina; Bi, Yurong

2014-04-01

The second messenger cyclic guanosine 3',5'-monophosphate (cGMP) plays an important role in plant development and responses to stress. Recent studies indicated that cGMP is a secondary signal generated in response to auxin stimulation. cGMP also mediates auxin-induced adventitious root formation in mung bean and gravitropic bending in soybean. Nonetheless, the mechanism of the participation of cGMP in auxin signalling to affect these growth and developmental processes is largely unknown. In this report we provide evidence that indole-3-acetic acid (IAA) induces cGMP accumulation in Arabidopsis roots through modulation of the guanylate cyclase activity. Application of 8-bromo-cGMP (a cell-permeable cGMP derivative) increases auxin-dependent lateral root formation, root hair development, primary root growth, and gene expression. In contrast, inhibitors of endogenous cGMP synthesis block these processes induced by auxin. Data also showed that 8-bromo-cGMP enhances auxin-induced degradation of Aux/IAA protein modulated by the SCF(TIR1) ubiquitin-proteasome pathway. Furthermore, it was found that 8-bromo-cGMP is unable to directly influence the auxin-dependent TIR1-Aux/IAA interaction as evidenced by pull-down and yeast two-hybrid assays. In addition, we provide evidence for cGMP-mediated modulation of auxin signalling through cGMP-dependent protein kinase (PKG). Our results suggest that cGMP acts as a mediator to participate in auxin signalling and may govern this process by PKG activity via its influence on auxin-regulated gene expression and auxin/IAA degradation.

Antagonism between abscisic acid and gibberellins is partially mediated by ascorbic acid during seed germination in rice.

PubMed

Ye, Nenghui; Zhang, Jianhua

2012-05-01

The antagonism between abscisic acid (ABA) and gibberellin (GA) plays a key role in controlling seed germination, but the mechanism of antagonism during this process is not known. In the associated study, we investigated the relationship among ABA, reactive oxygen species (ROS), ascorbic acid (ASC) and GA during rice seed germination. ROS production is reduced by ABA, which hence results in decreasing ASC accumulation during imbibition. GA accumulation was also suppressed by a reduced ROS and ASC level, whereas application of exogenous ASC can partially rescue seed germination from ABA treatment. Further results show that production of ASC, which acts as a substrate in GA biosynthesis, was significantly inhibited by lycorine which thus suppressed the accumulation of GA. Consequently, expression of GA biosynthesis genes was suppressed by the low levels of ROS and ASC in ABA-treated seeds. These studies reveal a new role for ASC in mediating the antagonism between ABA and GA during seed germination in rice.

PIN6 auxin transporter at endoplasmic reticulum and plasma membrane mediates auxin homeostasis and organogenesis in Arabidopsis.

PubMed

Simon, Sibu; Skůpa, Petr; Viaene, Tom; Zwiewka, Marta; Tejos, Ricardo; Klíma, Petr; Čarná, Mária; Rolčík, Jakub; De Rycke, Riet; Moreno, Ignacio; Dobrev, Petre I; Orellana, Ariel; Zažímalová, Eva; Friml, Jiří

2016-07-01

Plant development mediated by the phytohormone auxin depends on tightly controlled cellular auxin levels at its target tissue that are largely established by intercellular and intracellular auxin transport mediated by PIN auxin transporters. Among the eight members of the Arabidopsis PIN family, PIN6 is the least characterized candidate. In this study we generated functional, fluorescent protein-tagged PIN6 proteins and performed comprehensive analysis of their subcellular localization and also performed a detailed functional characterization of PIN6 and its developmental roles. The localization study of PIN6 revealed a dual localization at the plasma membrane (PM) and endoplasmic reticulum (ER). Transport and metabolic profiling assays in cultured cells and Arabidopsis strongly suggest that PIN6 mediates both auxin transport across the PM and intracellular auxin homeostasis, including the regulation of free auxin and auxin conjugates levels. As evidenced by the loss- and gain-of-function analysis, the complex function of PIN6 in auxin transport and homeostasis is required for auxin distribution during lateral and adventitious root organogenesis and for progression of these developmental processes. These results illustrate a unique position of PIN6 within the family of PIN auxin transporters and further add complexity to the developmentally crucial process of auxin transport. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

AUX1 regulates root gravitropism in Arabidopsis by facilitating auxin uptake within root apical tissues.

PubMed Central

Marchant, A; Kargul, J; May, S T; Muller, P; Delbarre, A; Perrot-Rechenmann, C; Bennett, M J

1999-01-01

Plants employ a specialized transport system composed of separate influx and efflux carriers to mobilize the plant hormone auxin between its site(s) of synthesis and action. Mutations within the permease-like AUX1 protein significantly reduce the rate of carrier-mediated auxin uptake within Arabidopsis roots, conferring an agravitropic phenotype. We are able to bypass the defect within auxin uptake and restore the gravitropic root phenotype of aux1 by growing mutant seedlings in the presence of the membrane-permeable synthetic auxin, 1-naphthaleneacetic acid. We illustrate that AUX1 expression overlaps that previously described for the auxin efflux carrier, AtPIN2, using transgenic lines expressing an AUX1 promoter::uidA (GUS) gene. Finally, we demonstrate that AUX1 regulates gravitropic curvature by acting in unison with the auxin efflux carrier to co-ordinate the localized redistribution of auxin within the Arabidopsis root apex. Our results provide the first example of a developmental role for the auxin influx carrier within higher plants and supply new insight into the molecular basis of gravitropic signalling. PMID:10205161

Overexpression of Poplar Pyrabactin Resistance-Like Abscisic Acid Receptors Promotes Abscisic Acid Sensitivity and Drought Resistance in Transgenic Arabidopsis.

PubMed

Yu, Jingling; Yang, Lei; Liu, Xiaobing; Tang, Renjie; Wang, Yuan; Ge, Haiman; Wu, Mengting; Zhang, Jiang; Zhao, Fugeng; Luan, Sheng; Lan, Wenzhi

2016-01-01

Drought stress is an important environmental factor limiting productivity of plants, especially fast growing species with high water consumption like poplar. Abscisic acid (ABA) is a phytohormone that positively regulates seed dormancy and drought resistance. The PYR1 (Pyrabactin Resistance 1)/ PYRL (PYR-Like)/ RCAR (Regulatory Component of ABA Receptor) (PYR/PYL/RCAR) ABA receptor family has been identified and widely characterized in Arabidopsis thaliana. However, their functions in poplars remain unknown. Here, we report that 2 of 14 PYR/PYL/RCAR orthologues in poplar (Populus trichocarpa) (PtPYRLs) function as a positive regulator of the ABA signal transduction pathway. The Arabidopsis transient expression and yeast two-hybrid assays showed the interaction among PtPYRL1 and PtPYRL5, a clade A protein phosphatase 2C, and a SnRK2, suggesting that a core signalling complex for ABA signaling pathway exists in poplars. Phenotypic analysis of PtPYRL1 and PtPYRL5 transgenic Arabidopsis showed that these two genes positively regulated the ABA responses during the seed germination. More importantly, the overexpression of PtPYRL1 and PtPYRL5 substantially improved ABA sensitivity and drought stress tolerance in transgenic plants. In summary, we comprehensively uncovered the properties of PtPYRL1 and PtPYRL5, which might be good target genes to genetically engineer drought-Resistant plants.

Abscisic acid and pyrabactin improve vitamin C contents in raspberries.

PubMed

Miret, Javier A; Munné-Bosch, Sergi

2016-07-15

Abscisic acid (ABA) is a plant growth regulator with roles in senescence, fruit ripening and environmental stress responses. ABA and pyrabactin (a non-photosensitive ABA agonist) effects on red raspberry (Rubus idaeus L.) fruit development (including ripening) were studied, with a focus on vitamin and antioxidant composition. Application of ABA and/or pyrabactin just after fruit set did not affect the temporal pattern of fruit development and ripening; neither provitamin A (carotenoids) nor vitamin E contents were modified. In contrast, ABA and pyrabactin altered the vitamin C redox state at early stages of fruit development and more than doubled vitamin C contents at the end of fruit ripening. These were partially explained by changes in ascorbate oxidation and recycling. Therefore, ABA and pyrabactin applications may be used to increase vitamin C content of ripe fruits, increasing fruit quality and value. However, treatments containing pyrabactin-combined with ABA or alone-diminished protein content, thus partially limiting its potential applicability. Copyright © 2016 Elsevier Ltd. All rights reserved.

SCF(TIR1/AFB)-auxin signalling regulates PIN vacuolar trafficking and auxin fluxes during root gravitropism.

PubMed

Baster, Paweł; Robert, Stéphanie; Kleine-Vehn, Jürgen; Vanneste, Steffen; Kania, Urszula; Grunewald, Wim; De Rybel, Bert; Beeckman, Tom; Friml, Jiří

2013-01-23

The distribution of the phytohormone auxin regulates many aspects of plant development including growth response to gravity. Gravitropic root curvature involves coordinated and asymmetric cell elongation between the lower and upper side of the root, mediated by differential cellular auxin levels. The asymmetry in the auxin distribution is established and maintained by a spatio-temporal regulation of the PIN-FORMED (PIN) auxin transporter activity. We provide novel insights into the complex regulation of PIN abundance and activity during root gravitropism. We show that PIN2 turnover is differentially regulated on the upper and lower side of gravistimulated roots by distinct but partially overlapping auxin feedback mechanisms. In addition to regulating transcription and clathrin-mediated internalization, auxin also controls PIN abundance at the plasma membrane by promoting their vacuolar targeting and degradation. This effect of elevated auxin levels requires the activity of SKP-Cullin-F-box(TIR1/AFB) (SCF(TIR1/AFB))-dependent pathway. Importantly, also suboptimal auxin levels mediate PIN degradation utilizing the same signalling pathway. These feedback mechanisms are functionally important during gravitropic response and ensure fine-tuning of auxin fluxes for maintaining as well as terminating asymmetric growth.

A Central Role of Abscisic Acid in Stress-Regulated Carbohydrate Metabolism

PubMed Central

Kempa, Stefan; Krasensky, Julia; Dal Santo, Silvia; Kopka, Joachim; Jonak, Claudia

2008-01-01

Background Abiotic stresses adversely affect plant growth and development. The hormone abscisic acid (ABA) plays a central role in the response and adaptation to environmental constraints. However, apart from the well established role of ABA in regulating gene expression programmes, little is known about its function in plant stress metabolism. Principal Findings Using an integrative multiparallel approach of metabolome and transcriptome analyses, we studied the dynamic response of the model glyophyte Arabidopsis thaliana to ABA and high salt conditions. Our work shows that salt stress induces complex re-adjustment of carbohydrate metabolism and that ABA triggers the initial steps of carbon mobilisation. Significance These findings open new perspectives on how high salinity and ABA impact on central carbohydrate metabolism and highlight the power of iterative combinatorial approaches of non-targeted and hypothesis-driven experiments in stress biology. PMID:19081841

Up-regulation of abscisic acid signaling pathway facilitates aphid xylem absorption and osmoregulation under drought stress.

PubMed

Guo, Huijuan; Sun, Yucheng; Peng, Xinhong; Wang, Qinyang; Harris, Marvin; Ge, Feng

2016-02-01

The activation of the abscisic acid (ABA) signaling pathway reduces water loss from plants challenged by drought stress. The effect of drought-induced ABA signaling on the defense and nutrition allocation of plants is largely unknown. We postulated that these changes can affect herbivorous insects. We studied the effects of drought on different feeding stages of pea aphids in the wild-type A17 of Medicago truncatula and ABA signaling pathway mutant sta-1. We examined the impact of drought on plant water status, induced plant defense signaling via the abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA) pathways, and on the host nutritional quality in terms of leaf free amino acid content. During the penetration phase of aphid feeding, drought decreased epidermis/mesophyll resistance but increased mesophyll/phloem resistance of A17 but not sta-1 plants. Quantification of transcripts associated with ABA, JA and SA signaling indicated that the drought-induced up-regulation of ABA signaling decreased the SA-dependent defense but increased the JA-dependent defense in A17 plants. During the phloem-feeding phase, drought had little effect on the amino acid concentrations and the associated aphid phloem-feeding parameters in both plant genotypes. In the xylem absorption stage, drought decreased xylem absorption time of aphids in both genotypes because of decreased water potential. Nevertheless, the activation of the ABA signaling pathway increased water-use efficiency of A17 plants by decreasing the stomatal aperture and transpiration rate. In contrast, the water potential of sta-1 plants (unable to close stomata) was too low to support xylem absorption activity of aphids; the aphids on sta-1 plants had the highest hemolymph osmolarity and lowest abundance under drought conditions. Taken together this study illustrates the significance of cross-talk between biotic-abiotic signaling pathways in plant-aphid interaction, and reveals the mechanisms leading to alter

Up-regulation of abscisic acid signaling pathway facilitates aphid xylem absorption and osmoregulation under drought stress

PubMed Central

Guo, Huijuan; Sun, Yucheng; Peng, Xinhong; Wang, Qinyang; Harris, Marvin; Ge, Feng

2016-01-01

The activation of the abscisic acid (ABA) signaling pathway reduces water loss from plants challenged by drought stress. The effect of drought-induced ABA signaling on the defense and nutrition allocation of plants is largely unknown. We postulated that these changes can affect herbivorous insects. We studied the effects of drought on different feeding stages of pea aphids in the wild-type A17 of Medicago truncatula and ABA signaling pathway mutant sta-1. We examined the impact of drought on plant water status, induced plant defense signaling via the abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA) pathways, and on the host nutritional quality in terms of leaf free amino acid content. During the penetration phase of aphid feeding, drought decreased epidermis/mesophyll resistance but increased mesophyll/phloem resistance of A17 but not sta-1 plants. Quantification of transcripts associated with ABA, JA and SA signaling indicated that the drought-induced up-regulation of ABA signaling decreased the SA-dependent defense but increased the JA-dependent defense in A17 plants. During the phloem-feeding phase, drought had little effect on the amino acid concentrations and the associated aphid phloem-feeding parameters in both plant genotypes. In the xylem absorption stage, drought decreased xylem absorption time of aphids in both genotypes because of decreased water potential. Nevertheless, the activation of the ABA signaling pathway increased water-use efficiency of A17 plants by decreasing the stomatal aperture and transpiration rate. In contrast, the water potential of sta-1 plants (unable to close stomata) was too low to support xylem absorption activity of aphids; the aphids on sta-1 plants had the highest hemolymph osmolarity and lowest abundance under drought conditions. Taken together this study illustrates the significance of cross-talk between biotic-abiotic signaling pathways in plant-aphid interaction, and reveals the mechanisms leading to alter

C2-domain abscisic acid-related proteins mediate the interaction of PYR/PYL/RCAR abscisic acid receptors with the plasma membrane and regulate abscisic acid sensitivity in Arabidopsis.

PubMed

Rodriguez, Lesia; Gonzalez-Guzman, Miguel; Diaz, Maira; Rodrigues, Americo; Izquierdo-Garcia, Ana C; Peirats-Llobet, Marta; Fernandez, Maria A; Antoni, Regina; Fernandez, Daniel; Marquez, Jose A; Mulet, Jose M; Albert, Armando; Rodriguez, Pedro L

2014-12-01

Membrane-delimited abscisic acid (ABA) signal transduction plays a critical role in early ABA signaling, but the molecular mechanisms linking core signaling components to the plasma membrane are unclear. We show that transient calcium-dependent interactions of PYR/PYL ABA receptors with membranes are mediated through a 10-member family of C2-domain ABA-related (CAR) proteins in Arabidopsis thaliana. Specifically, we found that PYL4 interacted in an ABA-independent manner with CAR1 in both the plasma membrane and nucleus of plant cells. CAR1 belongs to a plant-specific gene family encoding CAR1 to CAR10 proteins, and bimolecular fluorescence complementation and coimmunoprecipitation assays showed that PYL4-CAR1 as well as other PYR/PYL-CAR pairs interacted in plant cells. The crystal structure of CAR4 was solved, which revealed that, in addition to a classical calcium-dependent lipid binding C2 domain, a specific CAR signature is likely responsible for the interaction with PYR/PYL receptors and their recruitment to phospholipid vesicles. This interaction is relevant for PYR/PYL function and ABA signaling, since different car triple mutants affected in CAR1, CAR4, CAR5, and CAR9 genes showed reduced sensitivity to ABA in seedling establishment and root growth assays. In summary, we identified PYR/PYL-interacting partners that mediate a transient Ca(2+)-dependent interaction with phospholipid vesicles, which affects PYR/PYL subcellular localization and positively regulates ABA signaling. © 2014 American Society of Plant Biologists. All rights reserved.

Regulation of auxin transport during gravitropism

NASA Astrophysics Data System (ADS)

Rashotte, A.; Brady, S.; Kirpalani, N.; Buer, C.; Muday, G.

Plants respond to changes in the gravity vector by differential growth across the gravity-stimulated organ. The plant hormone auxin, which is normally basipetally transported, changes in direction and auxin redistribution has been suggested to drive this differential growth or gravitropism. The mechanisms by which auxin transport directionality changes in response to a change in gravity vector are largely unknown. Using the model plant, Arabidopsis thaliana, we have been exploring several regulatory mechanisms that may control auxin transport. Mutations that alter protein phosphorylation suggest that auxin transport in arabidopsis roots may be controlled via phosphorylation and this signal may facilitate gravitropic bending. The protein kinase mutant pinoid (pid9) has reduced auxin transport; whereas the protein phosphatase mutant, rcn1, has elevated transport, suggesting reciprocal regulation of auxin transport by reversible protein phosphorylation. In both of these mutants, the auxin transport defects are accompanied by gravitropic defects, linking phosphorylation signaling to gravity-induced changes in auxin transport. Additionally, auxin transport may be regulated during gravity response by changes in an endogenous auxin efflux inhibitor. Flavonoids, such as quercetin and kaempferol, have been implicated in regulation of auxin transport in vivo and in vitro. Mutants that make no flavonoids have reduced root gravitropic bending. Furthermore, changes in auxin-induced gene expression and flavonoid accumulation patterns have been observed during gravity stimulation. Current studies are examining whether there are spatial and temporal changes in flavonoid accumulation that precede gravitropic bending and whether the absence of these changes are the cause of the altered gravity response in plants with mutations that block flavonoid synthesis. These results support the idea that auxin transport may be regulated during gravity response by several mechanisms including

Two New Alleles of the abscisic aldehyde oxidase 3 Gene Reveal Its Role in Abscisic Acid Biosynthesis in Seeds1

PubMed Central

González-Guzmán, Miguel; Abia, David; Salinas, Julio; Serrano, Ramón; Rodríguez, Pedro L.

2004-01-01

The abscisic aldehyde oxidase 3 (AAO3) gene product of Arabidopsis catalyzes the final step in abscisic acid (ABA) biosynthesis. An aao3-1 mutant in a Landsberg erecta genetic background exhibited a wilty phenotype in rosette leaves, whereas seed dormancy was not affected (Seo et al., 2000a). Therefore, it was speculated that a different aldehyde oxidase would be the major contributor to ABA biosynthesis in seeds (Seo et al., 2000a). Through a screening based on germination under high-salt concentration, we isolated two mutants in a Columbia genetic background, initially named sre2-1 and sre2-2 (for salt resistant). Complementation tests with different ABA-deficient mutants indicated that sre2-1 and sre2-2 mutants were allelic to aao3-1, and therefore they were renamed as aao3-2 and aao3-3, respectively. Indeed, molecular characterization of the aao3-2 mutant revealed a T-DNA insertional mutation that abolished the transcription of AAO3 gene, while sequence analysis of AAO3 in aao3-3 mutant revealed a deletion of three nucleotides and several missense mutations. Physiological characterization of aao3-2 and aao3-3 mutants revealed a wilty phenotype and osmotolerance in germination assays. In contrast to aao3-1, both aao3-2 and aao3-3 mutants showed a reduced dormancy. Accordingly, ABA levels were reduced in dry seeds and rosette leaves of both aao3-2 and aao3-3. Taken together, these results indicate that AAO3 gene product plays a major role in seed ABA biosynthesis. PMID:15122034

Transcriptomics of shading-induced and NAA-induced abscission in apple (Malus domestica) reveals a shared pathway involving reduced photosynthesis, alterations in carbohydrate transport and signaling and hormone crosstalk

USDA-ARS?s Scientific Manuscript database

Naphthaleneacetic acid (NAA), a synthetic auxin analogue, is widely used as an effective thinner in apple orchards. When applied shortly after fruit set, some fruit abscise leading to improved fruit size and quality. However, the thinning results of NAA are inconsistent and difficult to predict, s...

Inhibition of auxin movement from the shoot into the root inhibits lateral root development in Arabidopsis

NASA Technical Reports Server (NTRS)

Reed, R. C.; Brady, S. R.; Muday, G. K.

1998-01-01

In roots two distinct polar movements of auxin have been reported that may control different developmental and growth events. To test the hypothesis that auxin derived from the shoot and transported toward the root controls lateral root development, the two polarities of auxin transport were uncoupled in Arabidopsis. Local application of the auxin-transport inhibitor naphthylphthalamic acid (NPA) at the root-shoot junction decreased the number and density of lateral roots and reduced the free indoleacetic acid (IAA) levels in the root and [3H]IAA transport into the root. Application of NPA to the basal half of or at several positions along the root only reduced lateral root density in regions that were in contact with NPA or in regions apical to the site of application. Lateral root development was restored by application of IAA apical to NPA application. Lateral root development in Arabidopsis roots was also inhibited by excision of the shoot or dark growth and this inhibition was reversible by IAA. Together, these results are consistent with auxin transport from the shoot into the root controlling lateral root development.

Auxins differentially regulate root system architecture and cell cycle protein levels in maize seedlings.

PubMed

Martínez-de la Cruz, Enrique; García-Ramírez, Elpidio; Vázquez-Ramos, Jorge M; Reyes de la Cruz, Homero; López-Bucio, José

2015-03-15

Maize (Zea mays) root system architecture has a complex organization, with adventitious and lateral roots determining its overall absorptive capacity. To generate basic information about the earlier stages of root development, we compared the post-embryonic growth of maize seedlings germinated in water-embedded cotton beds with that of plants obtained from embryonic axes cultivated in liquid medium. In addition, the effect of four different auxins, namely indole-3-acetic acid (IAA), 1-naphthaleneacetic acid (NAA), indole-3-butyric acid (IBA) and 2,4-dichlorophenoxyacetic acid (2,4-D) on root architecture and levels of the heat shock protein HSP101 and the cell cycle proteins CKS1, CYCA1 and CDKA1 were analyzed. Our data show that during the first days after germination, maize seedlings develop several root types with a simultaneous and/or continuous growth. The post-embryonic root development started with the formation of the primary root (PR) and seminal scutellar roots (SSR) and then continued with the formation of adventitious crown roots (CR), brace roots (BR) and lateral roots (LR). Auxins affected root architecture in a dose-response fashion; whereas NAA and IBA mostly stimulated crown root formation, 2,4-D showed a strong repressing effect on growth. The levels of HSP101, CKS1, CYCA1 and CDKA in root and leaf tissues were differentially affected by auxins and interestingly, HSP101 registered an auxin-inducible and root specific expression pattern. Taken together, our results show the timing of early branching patterns of maize and indicate that auxins regulate root development likely through modulation of the HSP101 and cell cycle proteins. Copyright © 2014 Elsevier GmbH. All rights reserved.

Block of ATP-Binding Cassette B19 Ion Channel Activity by 5-Nitro-2-(3-Phenylpropylamino)-Benzoic Acid Impairs Polar Auxin Transport and Root Gravitropism1[OPEN

PubMed Central

Cho, Misuk; Henry, Elizabeth M.; Lewis, Daniel R.; Wu, Guosheng; Muday, Gloria K.

2014-01-01

Polar transport of the hormone auxin through tissues and organs depends on membrane proteins, including some B-subgroup members of the ATP-binding cassette (ABC) transporter family. The messenger RNA level of at least one B-subgroup ABCB gene in Arabidopsis (Arabidopsis thaliana), ABCB19, increases upon treatment with the anion channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), possibly to compensate for an inhibitory effect of the drug on ABCB19 activity. Consistent with this hypothesis, NPPB blocked ion channel activity associated with ABCB19 expressed in human embryonic kidney cells as measured by patch-clamp electrophysiology. NPPB inhibited polar auxin transport through Arabidopsis seedling roots similarly to abcb19 mutations. NPPB also inhibited shootward auxin transport, which depends on the related ABCB4 protein. NPPB substantially decreased ABCB4 and ABCB19 protein levels when cycloheximide concomitantly inhibited new protein synthesis, indicating that blockage by NPPB enhances the degradation of ABCB transporters. Impairing the principal auxin transport streams in roots with NPPB caused aberrant patterns of auxin signaling reporters in root apices. Formation of the auxin-signaling gradient across the tips of gravity-stimulated roots, and its developmental consequence (gravitropism), were inhibited by micromolar concentrations of NPPB that did not affect growth rate. These results identify ion channel activity of ABCB19 that is blocked by NPPB, a compound that can now be considered an inhibitor of polar auxin transport with a defined molecular target. PMID:25324509

FORMATION OF AUXIN IN YEAST CULTURES.

PubMed

Robinson, T W; Stier, T J

1941-07-20

We have found far more auxin in the culture media of bakers' yeast than was obtained by Kögl and Kostermans from the cells themselves. The production of auxin by yeast cells resembles the formation observed in other organisms such as Rhizopus and Rhizobium which also form auxins in their culture media. The auxin yield was found to increase with the concentration of sucrose and to decrease with the concentration of peptone. An inverse relation with the rate of cell multiplication was observed. Enlarged and elongated cells appeared only in those media which contained considerable amounts of auxin. The total auxin yield in the various cultures was found to be directly proportional, below pH 5, to the hydrogen ion concentration. Thus, it was proposed that certain growth conditions favor the breakage of the link between auxin and its protein carrier (Skoog and Thimann) 1940) and consequently accelerate the rate of excretion of auxin into the growth medium.

C2-Domain Abscisic Acid-Related Proteins Mediate the Interaction of PYR/PYL/RCAR Abscisic Acid Receptors with the Plasma Membrane and Regulate Abscisic Acid Sensitivity in Arabidopsis[C][W

PubMed Central

Rodriguez, Lesia; Diaz, Maira; Rodrigues, Americo; Izquierdo-Garcia, Ana C.; Peirats-Llobet, Marta; Fernandez, Maria A.; Antoni, Regina; Fernandez, Daniel; Marquez, Jose A.; Mulet, Jose M.; Albert, Armando; Rodriguez, Pedro L.

2014-01-01

Membrane-delimited abscisic acid (ABA) signal transduction plays a critical role in early ABA signaling, but the molecular mechanisms linking core signaling components to the plasma membrane are unclear. We show that transient calcium-dependent interactions of PYR/PYL ABA receptors with membranes are mediated through a 10-member family of C2-domain ABA-related (CAR) proteins in Arabidopsis thaliana. Specifically, we found that PYL4 interacted in an ABA-independent manner with CAR1 in both the plasma membrane and nucleus of plant cells. CAR1 belongs to a plant-specific gene family encoding CAR1 to CAR10 proteins, and bimolecular fluorescence complementation and coimmunoprecipitation assays showed that PYL4-CAR1 as well as other PYR/PYL-CAR pairs interacted in plant cells. The crystal structure of CAR4 was solved, which revealed that, in addition to a classical calcium-dependent lipid binding C2 domain, a specific CAR signature is likely responsible for the interaction with PYR/PYL receptors and their recruitment to phospholipid vesicles. This interaction is relevant for PYR/PYL function and ABA signaling, since different car triple mutants affected in CAR1, CAR4, CAR5, and CAR9 genes showed reduced sensitivity to ABA in seedling establishment and root growth assays. In summary, we identified PYR/PYL-interacting partners that mediate a transient Ca2+-dependent interaction with phospholipid vesicles, which affects PYR/PYL subcellular localization and positively regulates ABA signaling. PMID:25465408

40 CFR 180.1158 - Auxins; exemption from the requirement of a tolerance.

Code of Federal Regulations, 2013 CFR

2013-07-01

... requirement of a tolerance is established for residues of auxins (specifically: indole-3-acetic acid and indole-3-butyric acid) in or on all food commodities when used as plant regulators on plants, seeds, or...

40 CFR 180.1158 - Auxins; exemption from the requirement of a tolerance.

Code of Federal Regulations, 2012 CFR

2012-07-01

... requirement of a tolerance is established for residues of auxins (specifically: indole-3-acetic acid and indole-3-butyric acid) in or on all food commodities when used as plant regulators on plants, seeds, or...

40 CFR 180.1158 - Auxins; exemption from the requirement of a tolerance.

Code of Federal Regulations, 2011 CFR

2011-07-01

... requirement of a tolerance is established for residues of auxins (specifically: indole-3-acetic acid and indole-3-butyric acid) in or on all food commodities when used as plant regulators on plants, seeds, or...

40 CFR 180.1158 - Auxins; exemption from the requirement of a tolerance.

Code of Federal Regulations, 2010 CFR

2010-07-01

... requirement of a tolerance is established for residues of auxins (specifically: indole-3-acetic acid and indole-3-butyric acid) in or on all food commodities when used as plant regulators on plants, seeds, or...

40 CFR 180.1158 - Auxins; exemption from the requirement of a tolerance.

Code of Federal Regulations, 2014 CFR

2014-07-01

... requirement of a tolerance is established for residues of auxins (specifically: indole-3-acetic acid and indole-3-butyric acid) in or on all food commodities when used as plant regulators on plants, seeds, or...

Evolution of Abscisic Acid Synthesis and Signaling Mechanisms

PubMed Central

Hauser, Felix; Waadt, Rainer; Schroeder, Julian I.

2011-01-01

The plant hormone abscisic acid (ABA) mediates seed dormancy, controls seedling development and triggers tolerance to abiotic stresses, including drought. Core ABA signaling components consist of a recently identified group of ABA receptor proteins of the PYRABACTIN RESISTANCE (PYR)/REGULATORY COMPONENT OF ABA RECEPTOR (RCAR) family that act as negative regulators of members of the PROTEIN PHOSPHATASE 2C (PP2C) family. Inhibition of PP2C activity enables activation of SNF1-RELATED KINASE 2 (SnRK2) protein kinases, which target downstream components, including transcription factors, ion channels and NADPH oxidases. These and other components form a complex ABA signaling network. Here, an in depth analysis of the evolution of components in this ABA signaling network shows that (i) PYR/RCAR ABA receptor and ABF-type transcription factor families arose during land colonization of plants and are not found in algae and other species, (ii) ABA biosynthesis enzymes have evolved to plant- and fungal-specific forms, leading to different ABA synthesis pathways, (iii) existing stress signaling components, including PP2C phosphatases and SnRK kinases, were adapted for novel roles in this plant-specific network to respond to water limitation. In addition, evolutionarily conserved secondary structures in the PYR/RCAR ABA receptor family are visualized. PMID:21549957

Abscisic acid enhances cold tolerance in honeybee larvae

PubMed Central

Sturla, Laura; Guida, Lucrezia; Vigliarolo, Tiziana; Maggi, Matías; Eguaras, Martín; Zocchi, Elena; Lamattina, Lorenzo

2017-01-01

The natural composition of nutrients present in food is a key factor determining the immune function and stress responses in the honeybee (Apis mellifera). We previously demonstrated that a supplement of abscisic acid (ABA), a natural component of nectar, pollen, and honey, increases honeybee colony survival overwinter. Here we further explored the role of ABA in in vitro-reared larvae exposed to low temperatures. Four-day-old larvae (L4) exposed to 25°C for 3 days showed lower survival rates and delayed development compared to individuals growing at a standard temperature (34°C). Cold-stressed larvae maintained higher levels of ABA for longer than do larvae reared at 34°C, suggesting a biological significance for ABA. Larvae fed with an ABA-supplemented diet completely prevent the low survival rate due to cold stress and accelerate adult emergence. ABA modulates the expression of genes involved in metabolic adjustments and stress responses: Hexamerin 70b, Insulin Receptor Substrate, Vitellogenin, and Heat Shock Proteins 70. AmLANCL2, the honeybee ABA receptor, is also regulated by cold stress and ABA. These results support a role for ABA increasing the tolerance of honeybee larvae to low temperatures through priming effects. PMID:28381619

Abscisic acid enhances cold tolerance in honeybee larvae.

PubMed

Ramirez, Leonor; Negri, Pedro; Sturla, Laura; Guida, Lucrezia; Vigliarolo, Tiziana; Maggi, Matías; Eguaras, Martín; Zocchi, Elena; Lamattina, Lorenzo

2017-04-12

The natural composition of nutrients present in food is a key factor determining the immune function and stress responses in the honeybee ( Apis mellifera ). We previously demonstrated that a supplement of abscisic acid (ABA), a natural component of nectar, pollen, and honey, increases honeybee colony survival overwinter. Here we further explored the role of ABA in in vitro -reared larvae exposed to low temperatures. Four-day-old larvae (L4) exposed to 25°C for 3 days showed lower survival rates and delayed development compared to individuals growing at a standard temperature (34°C). Cold-stressed larvae maintained higher levels of ABA for longer than do larvae reared at 34°C, suggesting a biological significance for ABA. Larvae fed with an ABA-supplemented diet completely prevent the low survival rate due to cold stress and accelerate adult emergence. ABA modulates the expression of genes involved in metabolic adjustments and stress responses: Hexamerin 70b, Insulin Receptor Substrate, Vitellogenin , and Heat Shock Proteins 70. AmLANCL2, the honeybee ABA receptor, is also regulated by cold stress and ABA. These results support a role for ABA increasing the tolerance of honeybee larvae to low temperatures through priming effects. © 2017 The Author(s).

Abscisic acid metabolite profiling as indicators of plastic responses to drought in grasses from arid Patagonian Monte (Argentina).

PubMed

Cenzano, Ana M; Masciarelli, O; Luna, M Virginia

2014-10-01

The identification of hormonal and biochemical traits that play functional roles in the adaptation to drought is necessary for the conservation and planning of rangeland management. The aim of this study was to evaluate the effects of drought on i) the water content (WC) of different plant organs, ii) the endogenous level of abscisic acid (ABA) and metabolites (phaseic acid-PA, dihydrophaseic acid-DPA and abscisic acid conjugated with glucose ester-ABA-GE), iii) the total carotenoid concentration and iv) to compare the traits of two desert perennial grasses (Pappostipa speciosa and Poa ligularis) with contrasting morphological and functional drought resistance traits and life-history strategies. Both species were subjected to two levels of gravimetric soil moisture (the highest near field capacity during autumn-winter and the lowest corresponding to summer drought). Drought significantly increased the ABA and DPA levels in the green leaves of P. speciosa and P. ligularis. Drought decreased ABA in the roots of P. speciosa while it increased ABA in the roots of P. ligularis. P. ligularis had the highest ABA level and WC in green leaves. While P. speciosa had the highest DPA levels in leaves. In conclusion, we found the highest ABA level in the mesophytic species P. ligularis and the lowest ABA level in the xerophytic species P. speciosa, revealing that the ABA metabolite profile in each grass species is a plastic response to drought resistance. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Study on the extraction, purification and quantification of jasmonic acid, abscisic acid and indole-3-acetic acid in plants.

PubMed

Zhang, Feng Juan; Jin, You Ju; Xu, Xing You; Lu, Rong Chun; Chen, Hua Jun

2008-01-01

Jasmonic acid (JA), abscisic acid (ABA) and indole-3-acetic acid (IAA) are important plant hormones. Plant hormones are difficult to analyse because they occur in small concentrations and other substances in the plant interfere with their detection. To develop a new, inexpensive procedure for the rapid extraction and purification of IAA, ABA and JA from various plant species. Samples were prepared by extraction of plant tissues with methanol and ethyl acetate. Then the extracts were further purified and enriched with C(18) cartridges. The final extracts were derivatised with diazomethane and then measured by GC-MS. The results of the new methodology were compared with those of the Creelman and Mullet procedure. Sequential elution of the assimilates from the C(18 )cartridges revealed that IAA and ABA eluted in 40% methanol, while JA subsequently eluted in 60% methanol. The new plant hormone extraction and purification procedure produced results that were comparable to those obtained with the Creelman and Mullet's procedure. This new procedure requires only 0.5 g leaf samples to quantify these compounds with high reliability and can simultaneously determine the concentrations of the three plant hormones. A simple, inexpensive method was developed for determining endogenous IAA, ABA and JA concentrations in plant tissue.

Flavonols Accumulate Asymmetrically and Affect Auxin Transport in Arabidopsis1[C][W][OA

PubMed Central

Kuhn, Benjamin M.; Geisler, Markus; Bigler, Laurent; Ringli, Christoph

2011-01-01

Flavonoids represent a class of secondary metabolites with diverse functions in plants including ultraviolet protection, pathogen defense, and interspecies communication. They are also known as modulators of signaling processes in plant and animal systems and therefore are considered to have beneficial effects as nutraceuticals. The rol1-2 (for repressor of lrx1) mutation of Arabidopsis (Arabidopsis thaliana) induces aberrant accumulation of flavonols and a cell-growth phenotype in the shoot. The hyponastic cotyledons, aberrant shape of pavement cells, and deformed trichomes in rol1-2 mutants are suppressed by blocking flavonoid biosynthesis, suggesting that the altered flavonol accumulation in these plants induces the shoot phenotype. Indeed, the identification of several transparent testa, myb, and fls1 (for flavonol synthase1) alleles in a rol1-2 suppressor screen provides genetic evidence that flavonols interfere with shoot development in rol1-2 seedlings. The increased accumulation of auxin in rol1-2 seedlings appears to be caused by a flavonol-induced modification of auxin transport. Quantification of auxin export from mesophyll protoplasts revealed that naphthalene-1-acetic acid but not indole-3-acetic acid transport is affected by the rol1-2 mutation. Inhibition of flavonol biosynthesis in rol1-2 fls1-3 restores naphthalene-1-acetic acid transport to wild-type levels, indicating a very specific mode of action of flavonols on the auxin transport machinery. PMID:21502189

Acyl substrate preferences of an IAA-amido synthetase account for variations in grape (Vitis vinifera L.) berry ripening caused by different auxinic compounds indicating the importance of auxin conjugation in plant development

PubMed Central

Böttcher, Christine; Boss, Paul K.; Davies, Christopher

2011-01-01

Nine Gretchen Hagen (GH3) genes were identified in grapevine (Vitis vinifera L.) and six of these were predicted on the basis of protein sequence similarity to act as indole-3-acetic acid (IAA)-amido synthetases. The activity of these enzymes is thought to be important in controlling free IAA levels and one auxin-inducible grapevine GH3 protein, GH3-1, has previously been implicated in the berry ripening process. Ex planta assays showed that the expression of only one other GH3 gene, GH3-2, increased following the treatment of grape berries with auxinic compounds. One of these was the naturally occurring IAA and the other two were synthetic, α-naphthalene acetic acid (NAA) and benzothiazole-2-oxyacetic acid (BTOA). The determination of steady-state kinetic parameters for the recombinant GH3-1 and GH3-2 proteins revealed that both enzymes efficiently conjugated aspartic acid (Asp) to IAA and less well to NAA, while BTOA was a poor substrate. GH3-2 gene expression was induced by IAA treatment of pre-ripening berries with an associated increase in levels of IAA-Asp and a decrease in free IAA levels. This indicates that GH3-2 responded to excess auxin to maintain low levels of free IAA. Grape berry ripening was not affected by IAA application prior to veraison (ripening onset) but was considerably delayed by NAA and even more so by BTOA. The differential effects of the three auxinic compounds on berry ripening can therefore be explained by the induction and acyl substrate specificity of GH3-2. These results further indicate an important role for GH3 proteins in controlling auxin-related plant developmental processes. PMID:21543520

Acyl substrate preferences of an IAA-amido synthetase account for variations in grape (Vitis vinifera L.) berry ripening caused by different auxinic compounds indicating the importance of auxin conjugation in plant development.

PubMed

Böttcher, Christine; Boss, Paul K; Davies, Christopher

2011-08-01

Nine Gretchen Hagen (GH3) genes were identified in grapevine (Vitis vinifera L.) and six of these were predicted on the basis of protein sequence similarity to act as indole-3-acetic acid (IAA)-amido synthetases. The activity of these enzymes is thought to be important in controlling free IAA levels and one auxin-inducible grapevine GH3 protein, GH3-1, has previously been implicated in the berry ripening process. Ex planta assays showed that the expression of only one other GH3 gene, GH3-2, increased following the treatment of grape berries with auxinic compounds. One of these was the naturally occurring IAA and the other two were synthetic, α-naphthalene acetic acid (NAA) and benzothiazole-2-oxyacetic acid (BTOA). The determination of steady-state kinetic parameters for the recombinant GH3-1 and GH3-2 proteins revealed that both enzymes efficiently conjugated aspartic acid (Asp) to IAA and less well to NAA, while BTOA was a poor substrate. GH3-2 gene expression was induced by IAA treatment of pre-ripening berries with an associated increase in levels of IAA-Asp and a decrease in free IAA levels. This indicates that GH3-2 responded to excess auxin to maintain low levels of free IAA. Grape berry ripening was not affected by IAA application prior to veraison (ripening onset) but was considerably delayed by NAA and even more so by BTOA. The differential effects of the three auxinic compounds on berry ripening can therefore be explained by the induction and acyl substrate specificity of GH3-2. These results further indicate an important role for GH3 proteins in controlling auxin-related plant developmental processes.

Sites of abscisic acid synthesis and metabolism in Ricinus communis L

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeevaart, J.A.D.

1977-05-01

The sites of abscisic acid (ABA) synthesis and metabolism in Ricinus communis L. were investigated by analyzing the levels of ABA and its two metabolites phaseic acid (PA) and dihydrophaseic acid (DPA) in the shoot tips, mature leaves, and phloem sap of stressed and nonstressed plants. Water stress increased the concentration of ABA, PA, and DPA in phloem exudate and also increased the levels of all three compounds in mature leaves and in shoot tips. The latter had a very high DPA content (18.7 ..mu..g/g fresh weight) even in plants not subjected to water stress. When young and mature leavesmore » were excised and allowed to wilt, the level of ABA increased in both, demonstrating that leaves at an early stage of development have the capacity to produce ABA. These results have been interpreted to mean that in mature leaves of nonstressed Ricinus plants, ABA is synthesized and metabolized, and that ABA itself, as well as its metabolites, are translocated in the phloem to the shoot tips (sinks). Since DPA, but not ABA, accumulates in the shoot tips, it follows that ABA is metabolized rapidly in the apical region. To what extent ABA present in young leaves of nonstressed plants is the consequence of synthesis in situ and of import from older leaves remains to be determined.« less

Deliberate ROS production and auxin synergistically trigger the asymmetrical division generating the subsidiary cells in Zea mays stomatal complexes.

PubMed

Livanos, Pantelis; Galatis, Basil; Apostolakos, Panagiotis

2016-07-01

Subsidiary cell generation in Poaceae is an outstanding example of local intercellular stimulation. An inductive stimulus emanates from the guard cell mother cells (GMCs) towards their laterally adjacent subsidiary cell mother cells (SMCs) and triggers the asymmetrical division of the latter. Indole-3-acetic acid (IAA) immunolocalization in Zea mays protoderm confirmed that the GMCs function as local sources of auxin and revealed that auxin is polarly accumulated between GMCs and SMCs in a timely-dependent manner. Besides, staining techniques showed that reactive oxygen species (ROS) exhibit a closely similar, also time-dependent, pattern of appearance suggesting ROS implication in subsidiary cell formation. This phenomenon was further investigated by using the specific NADPH-oxidase inhibitor diphenylene iodonium, the ROS scavenger N-acetyl-cysteine, menadione which leads to ROS overproduction, and H2O2. Treatments with diphenylene iodonium, N-acetyl-cysteine, and menadione specifically blocked SMC polarization and asymmetrical division. In contrast, H2O2 promoted the establishment of SMC polarity and subsequently subsidiary cell formation in "younger" protodermal areas. Surprisingly, H2O2 favored the asymmetrical division of the intervening cells of the stomatal rows leading to the creation of extra apical subsidiary cells. Moreover, H2O2 altered IAA localization, whereas synthetic auxin analogue 1-napthaleneacetic acid enhanced ROS accumulation. Combined treatments with ROS modulators along with 1-napthaleneacetic acid or 2,3,5-triiodobenzoic acid, an auxin efflux inhibitor, confirmed the crosstalk between ROS and auxin functioning during subsidiary cell generation. Collectively, our results demonstrate that ROS are critical partners of auxin during development of Z. mays stomatal complexes. The interplay between auxin and ROS seems to be spatially and temporarily regulated.

A survey of the pyrabactin resistance-like abscisic acid receptor gene family in poplar.

PubMed

Yu, Jingling; Li, Hejuan; Peng, Yajing; Yang, Lei; Zhao, Fugeng; Luan, Sheng; Lan, Wenzhi

2017-08-03

The conserved PYR/PYL/RCAR family acts as abscisic acid (ABA) receptors for land plants to adapt to terrestrial environments. Our recent study reported that the exogenous overexpression of poplar PtPYRL1 and PtPYRL5, the PYR/PYL/RCAR orthologs, promoted the sensitivity of transgenic Arabidopsis to ABA responses. Here, we surveyed the PtPYRL family in poplar, and revealed that although the sequence and structure are relatively conserved among these receptors, PtPYRL members have differential expression patterns and the sensitivity to ABA or drought treatment, suggesting that PtPYRLs might be good candidates to a future biotechnological use to enhance poplar resistance to water-stress environments.

Mechanistic Basis for Plant Responses to Drought Stress : Regulatory Mechanism of Abscisic Acid Signaling

NASA Astrophysics Data System (ADS)

Miyakawa, Takuya; Tanokura, Masaru

The phytohormone abscisic acid (ABA) plays a key role in the rapid adaptation of plants to environmental stresses such as drought and high salinity. Accumulated ABA in plant cells promotes stomatal closure in guard cells and transcription of stress-tolerant genes. Our understanding of ABA responses dramatically improved by the discovery of both PYR/PYL/RCAR as a soluble ABA receptor and inhibitory complex of a protein phospatase PP2C and a protein kinase SnRK2. Moreover, several structural analyses of PYR/PYL/RCAR revealed the mechanistic basis for the regulatory mechanism of ABA signaling, which provides a rational framework for the design of alternative agonists in future.

Biological activities of indoleacetylamino acids and their use as auxins in tissue culture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hangarter, R.P.; Peterson, M.D.; Good, N.E.

1980-05-01

The auxin activities of a number of indoleacetylamino acid conjugates have been determined in three test systems: growth of tomato hypocotyl explants (Lycopersicon esculentum Mill. cv. Marglobe); growth of tobacco callus cultures (Nicotiana tabacum L. cv. Wisconsin 38); and ethylene production from pea stems (Pisum sativum L. cv. Alaska). The activities of the conjugates differ greatly depending on the amino acid moiety. Indoleacetyl-L-alanine supports rapid callus growth from the tomato hypocotyls while inhibiting growth of shoots and roots. Indoleacetlyglycine behaves in a similar manner but is somewhat less effective in supporting callus growth and in inhibiting growth of shoots andmore » roots. Indoleacetylglycine behaves in a similar manner but is somewhat less effective in supporting callus growth and in inhibiting shoot formation. The other amino acid conjugates tested (valine, leucine, aspartic acid, threonine, methionine, phenylalanine, and proline) support shoot formation without supporting root formation or much callus growth. The tobacco callus system, which forms abundant shoots in the presence or absence of free indoleacetic acid, produces only rapid undifferentiated growth in the presence of indoleacetyl-L-alanine and indoleacetylglycine. The other conjugates inhibit shoot formatin weakly if at all. Most of the conjugates induce sustained ethylene production from the pea stems but at rates well below the initial rates observed with free indoleacetic acid. Many, but not all of the effects of conjugates such as indoleacetyl-L-alanine can be mimicked by frequent renewals of the supply of free indoleacetic acid.« less

Sensory role of actin in auxin-dependent responses of tobacco BY-2.

PubMed

Huang, Xiang; Maisch, Jan; Nick, Peter

2017-11-01

Polar auxin transport depends on the polar localization of auxin-efflux carriers. The cycling of these carriers between cell interior and plasma membrane depends on actin. The dynamic of actin not only affects auxin transport, but also changes the auxin-responsiveness. To study the potential link between auxin responsiveness and actin dynamics, we investigated developmental responses of the non-transformed BY-2 (Nicotiana tabacum L. cv Bright Yellow 2) cell line and the transgenic BY-2 strain GF11 (stably transformed BY-2 cells with a GFP-fimbrin actin-binding domain 2 construct). The developmental process was divided into three distinct stages: cell cycling, cell elongation and file disintegration. Several phenotypes were measured to monitor the cellular responses to different concentrations of exogenous natural auxin (Indole-3-acetic acid, IAA). We found that auxin stimulated and prolonged the mitotic activity, and delayed the exit from the proliferation phase. However, both responses were suppressed in the GF11 line. At the stationary phase of the cultivation cycle, auxin strongly accelerated the cell file disintegration. Interestingly, it was not suppressed but progressed to a more complete disintegration in the GF11 line. During the cultivation cycle, we also followed the organization of actin in the GF11 line and did not detect any significant difference in actin organization from untreated control or exogenous IAA treatment. Therefore, our findings indicate that the specific differences observed in the GF11 line must be linked with a function of actin that is not structural. It means that there is a sensory role of actin for auxin signaling. Copyright © 2017 Elsevier GmbH. All rights reserved.

New auxin analogs with growth-promoting effects in intact plants reveal a chemical strategy to improve hormone delivery.

PubMed

Savaldi-Goldstein, Sigal; Baiga, Thomas J; Pojer, Florence; Dabi, Tsegeye; Butterfield, Cristina; Parry, Geraint; Santner, Aaron; Dharmasiri, Nihal; Tao, Yi; Estelle, Mark; Noel, Joseph P; Chory, Joanne

2008-09-30

Plant growth depends on the integration of environmental cues and phytohormone-signaling pathways. During seedling emergence, elongation of the embryonic stem (hypocotyl) serves as a readout for light and hormone-dependent responses. We screened 10,000 chemicals provided exogenously to light-grown seedlings and identified 100 compounds that promote hypocotyl elongation. Notably, one subset of these chemicals shares structural characteristics with the synthetic auxins, 2,4-dichlorophenoxyacetic acid (2,4-D), and 1-naphthaleneacetic acid (1-NAA); however, traditional auxins (e.g., indole-3-acetic acid [IAA], 2,4-D, 1-NAA) have no effect on hypocotyl elongation. We show that the new compounds act as "proauxins" akin to prodrugs. Our data suggest that these compounds diffuse efficiently to the hypocotyls, where they undergo cleavage at varying rates, releasing functional auxins. To investigate this principle, we applied a masking strategy and designed a pro-2,4-D. Unlike 2,4-D alone, this pro-2,4-D enhanced hypocotyl elongation. We further demonstrated the utility of the proauxins by characterizing auxin responses in light-grown hypocotyls of several auxin receptor mutants. These new compounds thus provide experimental access to a tissue previously inaccessible to exogenous application of auxins. Our studies exemplify the combined power of chemical genetics and biochemical analyses for discovering and refining prohormone analogs with selective activity in specific plant tissues. In addition to the utility of these compounds for addressing questions related to auxin and light-signaling interactions, one can envision using these simple principles to study other plant hormone and small molecule responses in temporally and spatially controlled ways.

Red light-regulated growth. I. Changes in the abundance of indoleacetic acid and a 22-kilodalton auxin-binding protein in the maize mesocotyl

NASA Technical Reports Server (NTRS)

Jones, A. M.; Cochran, D. S.; Lamerson, P. M.; Evans, M. L.; Cohen, J. D.

1991-01-01

We examined the changes in the levels of indoleacetic acid (IAA), IAA esters, and a 22-kilodalton subunit auxin-binding protein (ABP1) in apical mesocotyl tissue of maize (Zea mays L.) during continuous red light (R) irradiation. These changes were compared with the kinetics of R-induced growth inhibition in the same tissue. Upon the onset of continuous irradiation, growth decreased in a continuous manner following a brief lag period. The decrease in growth continued for 5 hours, then remained constant at 25% of the dark rate. The abundance of ABP1 and the level of free IAA both decreased in the mesocotyl. Only the kinetics of the decrease in IAA within the apical mesocotyl correlated with the initial change in growth, although growth continued to decrease even after IAA content reached its final level, 50% of the dark control. This decrease in IAA within the mesocotyl probably occurs primarily by a change in its transport within the shoot since auxin applied as a pulse move basipetally in R-irradiated tissue at the same rate but with half the area as dark control tissue. In situ localization of auxin in etiolated maize shoots revealed that R-irradiated shoots contained less auxin in the epidermis than the dark controls. Irradiated mesocotyl grew 50% less than the dark controls even when incubated in an optimal level of auxin. However, irradiated and dark tissue contained essentially the same amount of radioactivity after incubation in [14C]IAA indicating that the light treatment does not affect the uptake into the tissue through the cut end, although it is possible that a small subset of cells within the mesocotyl is affected. These observations support the hypothesis that R causes a decrease in the level of auxin in epidermal cells of the mesocotyl, consequently constraining the growth of the entire mesocotyl.

Emerging roles of protein kinase CK2 in abscisic acid signaling.

PubMed

Vilela, Belmiro; Pagès, Montserrat; Riera, Marta

2015-01-01

The phytohormone abscisic acid (ABA) regulates many aspects of plant growth and development as well as responses to multiple stresses. Post-translational modifications such as phosphorylation or ubiquitination have pivotal roles in the regulation of ABA signaling. In addition to the positive regulator sucrose non-fermenting-1 related protein kinase 2 (SnRK2), the relevance of the role of other protein kinases, such as CK2, has been recently highlighted. We have recently established that CK2 phosphorylates the maize ortholog of open stomata 1 OST1, ZmOST1, suggesting a role of CK2 phosphorylation in the control of ZmOST1 protein degradation (Vilela et al., 2015). CK2 is a pleiotropic enzyme involved in multiple developmental and stress-responsive pathways. This review summarizes recent advances that taken together suggest a prominent role of protein kinase CK2 in ABA signaling and related processes.

A novel root gravitropism mutant of Arabidopsis thaliana exhibiting altered auxin physiology

NASA Technical Reports Server (NTRS)

Simmons, C.; Migliaccio, F.; Masson, P.; Caspar, T.; Soll, D.

1995-01-01

A root gravitropism mutant was isolated from the DuPont Arabidopsis thaliana T-DNA insertional mutagenesis collection. This mutant has reduced root gravitropism, hence the name rgr1. Roots of rgr1 are shorter than those of wild-type, and they have reduced lateral root formation. In addition, roots of rgr1 coil clockwise on inclined agar plates, unlike wild-type roots which grow in a wavy pattern. The rgr1 mutant has increased resistance, as measured by root elongation, to exogenously applied auxins (6-fold to indole-3-acetic acid, 3-fold to 2,4-dichlorophenoxyacetic acid, and 2-fold to napthyleneacetic acid). It is also resistant to polar auxin transport inhibitors (2-fold to triiodobenzoic acid and 3- to 5-fold to napthylphthalamic acid). The rgr1 mutant does not appear to be resistant to other plant hormone classes. When grown in the presence of 10(-7) M 2,4-dichlorophenoxyacetic acid, rgr1 roots have fewer root hairs than wild type. All these rgr1 phenotypes are Mendelian recessives. Complementation tests indicate that rgr1 is not allelic to previously characterized agravitropic or auxin-resistant mutants. The rgr1 locus was mapped using visible markers to 1.4 +/- 0.6 map units from the CH1 locus at 1-65.4. The rgr1 mutation and the T-DNA cosegregate, suggesting that rgr1 was caused by insertional gene inactivation.

The Maize (Zea mays L.) AUXIN/INDOLE-3-ACETIC ACID Gene Family: Phylogeny, Synteny, and Unique Root-Type and Tissue-Specific Expression Patterns during Development

PubMed Central

Ludwig, Yvonne; Zhang, Yanxiang; Hochholdinger, Frank

2013-01-01

The plant hormone auxin plays a key role in the coordination of many aspects of growth and development. AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) genes encode instable primary auxin responsive regulators of plant development that display a protein structure with four characteristic domains. In the present study, a comprehensive analysis of the 34 members of the maize Aux/IAA gene family was performed. Phylogenetic reconstructions revealed two classes of Aux/IAA proteins that can be distinguished by alterations in their domain III. Seven pairs of paralogous maize Aux/IAA proteins were discovered. Comprehensive root-type and tissue-specific expression profiling revealed unique expression patterns of the diverse members of the gene family. Remarkably, five of seven pairs of paralogous genes displayed highly correlated expression patterns in roots. All but one (ZmIAA23) tested maize Aux/IAA genes were auxin inducible, displaying two types of auxin induction within three hours of treatment. Moreover, 51 of 55 (93%) differential Aux/IAA expression patterns between different root-types followed the expression tendency: crown roots > seminal roots > primary roots > lateral roots. This pattern might imply root-type-specific regulation of Aux/IAA transcript abundance. In summary, the detailed analysis of the maize Aux/IAA gene family provides novel insights in the evolution and developmental regulation and thus the function of these genes in different root-types and tissues. PMID:24223858

The maize (Zea mays L.) AUXIN/INDOLE-3-ACETIC ACID gene family: phylogeny, synteny, and unique root-type and tissue-specific expression patterns during development.

PubMed

Ludwig, Yvonne; Zhang, Yanxiang; Hochholdinger, Frank

2013-01-01

The plant hormone auxin plays a key role in the coordination of many aspects of growth and development. AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) genes encode instable primary auxin responsive regulators of plant development that display a protein structure with four characteristic domains. In the present study, a comprehensive analysis of the 34 members of the maize Aux/IAA gene family was performed. Phylogenetic reconstructions revealed two classes of Aux/IAA proteins that can be distinguished by alterations in their domain III. Seven pairs of paralogous maize Aux/IAA proteins were discovered. Comprehensive root-type and tissue-specific expression profiling revealed unique expression patterns of the diverse members of the gene family. Remarkably, five of seven pairs of paralogous genes displayed highly correlated expression patterns in roots. All but one (ZmIAA23) tested maize Aux/IAA genes were auxin inducible, displaying two types of auxin induction within three hours of treatment. Moreover, 51 of 55 (93%) differential Aux/IAA expression patterns between different root-types followed the expression tendency: crown roots > seminal roots > primary roots > lateral roots. This pattern might imply root-type-specific regulation of Aux/IAA transcript abundance. In summary, the detailed analysis of the maize Aux/IAA gene family provides novel insights in the evolution and developmental regulation and thus the function of these genes in different root-types and tissues.

Metabolic pathways regulated by abscisic acid, salicylic acid and γ-aminobutyric acid in association with improved drought tolerance in creeping bentgrass (Agrostis stolonifera).

PubMed

Li, Zhou; Yu, Jingjin; Peng, Yan; Huang, Bingru

2017-01-01

Abscisic acid (ABA), salicylic acid (SA) and γ-aminobutyric acid (GABA) are known to play roles in regulating plant stress responses. This study was conducted to determine metabolites and associated pathways regulated by ABA, SA and GABA that could contribute to drought tolerance in creeping bentgrass (Agrostis stolonifera). Plants were foliar sprayed with ABA (5 μM), GABA (0.5 mM) and SA (10 μM) or water (untreated control) prior to 25 days drought stress in controlled growth chambers. Application of ABA, GABA or SA had similar positive effects on alleviating drought damages, as manifested by the maintenance of lower electrolyte leakage and greater relative water content in leaves of treated plants relative to the untreated control. Metabolic profiling showed that ABA, GABA and SA induced differential metabolic changes under drought stress. ABA mainly promoted the accumulation of organic acids associated with tricarboxylic acid cycle (aconitic acid, succinic acid, lactic acid and malic acid). SA strongly stimulated the accumulation of amino acids (proline, serine, threonine and alanine) and carbohydrates (glucose, mannose, fructose and cellobiose). GABA enhanced the accumulation of amino acids (GABA, glycine, valine, proline, 5-oxoproline, serine, threonine, aspartic acid and glutamic acid) and organic acids (malic acid, lactic acid, gluconic acid, malonic acid and ribonic acid). The enhanced drought tolerance could be mainly due to the enhanced respiration metabolism by ABA, amino acids and carbohydrates involved in osmotic adjustment (OA) and energy metabolism by SA, and amino acid metabolism related to OA and stress-defense secondary metabolism by GABA. © 2016 Scandinavian Plant Physiology Society.

Basipetal auxin transport is required for gravitropism in roots of Arabidopsis

NASA Technical Reports Server (NTRS)

Rashotte, A. M.; Brady, S. R.; Reed, R. C.; Ante, S. J.; Muday, G. K.; Davies, E. (Principal Investigator)

2000-01-01

Auxin transport has been reported to occur in two distinct polarities, acropetally and basipetally, in two different root tissues. The goals of this study were to determine whether both polarities of indole-3-acetic acid (IAA) transport occur in roots of Arabidopsis and to determine which polarity controls the gravity response. Global application of the auxin transport inhibitor naphthylphthalamic acid (NPA) to roots blocked the gravity response, root waving, and root elongation. Immediately after the application of NPA, the root gravity response was completely blocked, as measured by an automated video digitizer. Basipetal [(3)H]IAA transport in Arabidopsis roots was inhibited by NPA, whereas the movement of [(14)C]benzoic acid was not affected. Inhibition of basipetal IAA transport by local application of NPA blocked the gravity response. Inhibition of acropetal IAA transport by application of NPA at the root-shoot junction only partially reduced the gravity response at high NPA concentrations. Excised root tips, which do not receive auxin from the shoot, exhibited a normal response to gravity. The Arabidopsis mutant eir1, which has agravitropic roots, exhibited reduced basipetal IAA transport but wild-type levels of acropetal IAA transport. These results support the hypothesis that basipetally transported IAA controls root gravitropism in Arabidopsis.

The diageotropica mutant of tomato lacks high specific activity auxin binding sites

NASA Technical Reports Server (NTRS)

Hicks, G. R.; Rayle, D. L.; Lomax, T. L.

1989-01-01

Tomato plants homozygous for the diageotropica (dgt) mutation exhibit morphological and physiological abnormalities which suggest that they are unable to respond to the plant growth hormone auxin (indole-3-acetic acid). The photoaffinity auxin analog [3H]5N3-IAA specifically labels a polypeptide doublet of 40 and 42 kilodaltons in membrane preparations from stems of the parental variety, VFN8, but not from stems of plants containing the dgt mutation. In roots of the mutant plants, however, labeling is indistinguishable from that in VFN8. These data suggest that the two polypeptides are part of a physiologically important auxin receptor system, which is altered in a tissue-specific manner in the mutant.

Abscisic acid analogs as chemical probes for dissection of abscisic acid responses in Arabidopsis thaliana.

PubMed

Benson, Chantel L; Kepka, Michal; Wunschel, Christian; Rajagopalan, Nandhakishore; Nelson, Ken M; Christmann, Alexander; Abrams, Suzanne R; Grill, Erwin; Loewen, Michele C

2015-05-01

Abscisic acid (ABA) is a phytohormone known to mediate numerous plant developmental processes and responses to environmental stress. In Arabidopsis thaliana, ABA acts, through a genetically redundant family of ABA receptors entitled Regulatory Component of ABA Receptor (RCAR)/Pyrabactin Resistant 1 (PYR1)/Pyrabactin Resistant-Like (PYL) receptors comprised of thirteen homologues acting in concert with a seven-member set of phosphatases. The individual contributions of A. thaliana RCARs and their binding partners with respect to specific physiological functions are as yet poorly understood. Towards developing efficacious plant growth regulators selective for specific ABA functions and tools for elucidating ABA perception, a panel of ABA analogs altered specifically on positions around the ABA ring was assembled. These analogs have been used to probe thirteen RCARs and four type 2C protein phosphatases (PP2Cs) and were also screened against representative physiological assays in the model plant Arabidopsis. The 1'-O methyl ether of (S)-ABA was identified as selective in that, at physiologically relevant levels, it regulates stomatal aperture and improves drought tolerance, but does not inhibit germination or root growth. Analogs with the 7'- and 8'-methyl groups of the ABA ring replaced with bulkier groups generally retained the activity and stereoselectivity of (S)- and (R)-ABA, while alteration of the 9'-methyl group afforded an analog that substituted for ABA in inhibiting germination but neither root growth nor stomatal closure. Further in vitro testing indicated differences in binding of analogs to individual RCARs, as well as differences in the enzyme activity resulting from specific PP2Cs bound to RCAR-analog complexes. Ultimately, these findings highlight the potential of a broader chemical genetics approach for dissection of the complex network mediating ABA-perception, signaling and functionality within a given species and modifications in the future design

Preliminary evidence that abscisic acid improves spatial memory in rats.

PubMed

Qi, Cong-Cong; Ge, Jin-Fang; Zhou, Jiang-Ning

2015-02-01

Abscisic acid (ABA) is a crucial phytohormone that exists in a wide range of animals, including humans, and has multiple bioactivities. As direct derivatives of carotenoids, ABA and retinoic acid (RA) share similar molecular structures, and RA has been reported to improve spatial memory in rodents. To explore the potential effects of ABA on spatial learning and memory in rodents, 20mg/kg ABA was administered to young rats for 6weeks, and its effects on behaviour performance were evaluated through a series of behavioural tests. ABA pharmacokinetic analysis revealed that the exogenous ABA was distributed widely in the rat brain, characterised by rapid absorption and slow elimination. The behavioural tests showed that ABA increased both the duration spent in the target quadrant and the frequency it was entered in the probe test of the Morris water maze (MWM) and decreased the latency to locate the target quadrant. Moreover, ABA decreased the latency to enter the novel arm in the Y-maze test, accompanied by increases in the total entries and distance travelled in the three arms. However, there were no significant differences between the ABA-treated and control rats in the open field test and elevated plus-maze test. These results preliminarily indicate that ABA improves spatial memory in MWM and exploratory activity in Y-maze in young rats. Copyright © 2014 Elsevier Inc. All rights reserved.

Tomato ASR1 abrogates the response to abscisic acid and glucose in Arabidopsis by competing with ABI4 for DNA binding.

PubMed

Shkolnik, Doron; Bar-Zvi, Dudy

2008-05-01

The manipulation of transacting factors is commonly used to achieve a wide change in the expression of a large number of genes in transgenic plants as a result of a change in the expression of a single gene product. This is mostly achieved by the overexpression of transactivator or repressor proteins. In this study, it is demonstrated that the overexpression of an exogenous DNA-binding protein can be used to compete with the expression of an endogenous transcription factor sharing the same DNA-binding sequence. Arabidopsis was transformed with cDNA encoding tomato abscisic acid stress ripening 1 (ASR1), a sequence-specific DNA protein that has no orthologues in the Arabidopsis genome. ASR1-overexpressing (ASR1-OE) plants display an abscisic acid-insensitive 4 (abi4) phenotype: seed germination is not sensitive to inhibition by abscisic acid (ABA), glucose, NaCl and paclobutrazol. ASR1 binds coupling element 1 (CE1), a cis-acting element bound by the ABI4 transcription factor, located in the ABI4-regulated promoters, including that of the ABI4 gene. Chromatin immunoprecipitation demonstrates that ASR1 is bound in vivo to the promoter of the ABI4 gene in ASR1-OE plants, but not to promoters of genes known to be regulated by the transcription factors ABI3 or ABI5. Real-time polymerase chain reaction (PCR) analysis confirmed that the expression of ABI4 and ABI4-regulated genes is markedly reduced in ASR1-OE plants. Therefore, it is concluded that the abi4 phenotype of ASR1-OE plants is the result of competition between the foreign ASR1 and the endogenous ABI4 on specific promoter DNA sequences. The biotechnological advantage of using this approach in crop plants from the Brassicaceae family to reduce the transactivation activity of ABI4 is discussed.

Maternal synthesis of abscisic acid controls seed development and yield in Nicotiana plumbaginifolia.

PubMed

Frey, Anne; Godin, Béatrice; Bonnet, Magda; Sotta, Bruno; Marion-Poll, Annie

2004-04-01

The role of maternally derived abscisic acid (ABA) during seed development has been studied using ABA-deficient mutants of Nicotiana plumbaginifolia Viviani. ABA deficiency induced seed abortion, resulting in reduced seed yield, and delayed growth of the remaining embryos. Mutant grafting onto wild-type stocks and reciprocal crosses indicated that maternal ABA, synthesized in maternal vegetative tissues and translocated to the seed, promoted early seed development and growth. Moreover ABA deficiency delayed both seed coat pigmentation and capsule dehiscence. Mutant grafting did not restore these phenotypes, indicating that ABA synthesized in the seed coat and capsule envelope may have a positive effect on capsule and testa maturation. Together these results shed light on the positive role of maternal ABA during N. plumbaginifolia seed development.

Ethylene signaling triggered by low concentrations of ascorbic acid regulates biomass accumulation in Arabidopsis thaliana.

PubMed

Caviglia, M; Mazorra Morales, L M; Concellón, A; Gergoff Grozeff, G E; Wilson, M; Foyer, C H; Bartoli, C G

2018-02-02

Ascorbic acid (AA) is a major redox buffer in plant cells. The role of ethylene in the redox signaling pathways that influence photosynthesis and growth was explored in two independent AA deficient Arabidopsis thaliana mutants (vtc2-1 and vtc2-4). Both mutants, which are defective in the AA biosynthesis gene GDP-L-galactose phosphorylase, produce higher amounts of ethylene than wt plants. In contrast to the wt, the inhibition of ethylene signaling increased leaf conductance, photosynthesis and dry weight in both vtc2 mutant lines. The AA-deficient mutants showed altered expression of genes encoding proteins involved in the synthesis/responses to phytohormones that control growth, particularly auxin, cytokinins, abscisic acid, brassinosterioids, ethylene and salicylic acid. These results demonstrate that AA deficiency modifies hormone signaling in plants, redox-ethylene interactions providing a regulatory node controlling shoot biomass accumulation. Copyright © 2018 Elsevier Inc. All rights reserved.

Effect of Exogenous Abscisic Acid and Methyl Jasmonate on Anthocyanin Composition, Fatty Acids, and Volatile Compounds of Cabernet Sauvignon (Vitis vinifera L.) Grape Berries.

PubMed

Ju, Yan-Lun; Liu, Min; Zhao, Hui; Meng, Jiang-Fei; Fang, Yu-Lin

2016-10-12

The anthocyanin composition, fatty acids, and volatile aromas are important for Cabernet Sauvignon grape quality. This study evaluated the effect of exogenous abscisic acid (ABA) and methyl jasmonate (MeJA) on the anthocyanin composition, fatty acids, lipoxygenase activity, and the volatile compounds of Cabernet Sauvignon grape berries. Exogenous ABA and MeJA improved the content of total anthocyanins (TAC) and individual anthocyanins. Lipoxygenase (LOX) activity also increased after treatment. Furthermore, 16 fatty acids were detected. The linoleic acid concentration gradually increased with ABA concentration. The fatty acid content decreased with increasing MeJA concentration and then increased again, with the exception of linoleic acid. After exogenous ABA and MeJA treatment, the C6 aroma content increased significantly. Interestingly, the exogenous ABA and MeJA treatments improved mainly the content of 1-hexanol, hexanal, and 2-heptanol. These results provide insight into the effect of plant hormones on wine grapes, which is useful for grape quality improvement.

Extracellular ATP inhibits root gravitropism at concentrations that inhibit polar auxin transport

NASA Technical Reports Server (NTRS)

Tang, Wenqiang; Brady, Shari R.; Sun, Yu; Muday, Gloria K.; Roux, Stanley J.

2003-01-01

Raising the level of extracellular ATP to mM concentrations similar to those found inside cells can block gravitropism of Arabidopsis roots. When plants are grown in Murashige and Skoog medium supplied with 1 mM ATP, their roots grow horizontally instead of growing straight down. Medium with 2 mM ATP induces root curling, and 3 mM ATP stimulates lateral root growth. When plants are transferred to medium containing exogenous ATP, the gravity response is reduced or in some cases completely blocked by ATP. Equivalent concentrations of ADP or inorganic phosphate have slight but usually statistically insignificant effects, suggesting the specificity of ATP in these responses. The ATP effects may be attributable to the disturbance of auxin distribution in roots by exogenously applied ATP, because extracellular ATP can alter the pattern of auxin-induced gene expression in DR5-beta-glucuronidase transgenic plants and increase the response sensitivity of plant roots to exogenously added auxin. The presence of extracellular ATP also decreases basipetal auxin transport in a dose-dependent fashion in both maize (Zea mays) and Arabidopsis roots and increases the retention of [(3)H]indole-3-acetic acid in root tips of maize. Taken together, these results suggest that the inhibitory effects of extracellular ATP on auxin distribution may happen at the level of auxin export. The potential role of the trans-plasma membrane ATP gradient in auxin export and plant root gravitropism is discussed.

Abscisic Acid–Responsive Guard Cell Metabolomes of Arabidopsis Wild-Type and gpa1 G-Protein Mutants[C][W

PubMed Central

Jin, Xiaofen; Wang, Rui-Sheng; Zhu, Mengmeng; Jeon, Byeong Wook; Albert, Reka; Chen, Sixue; Assmann, Sarah M.

2013-01-01

Individual metabolites have been implicated in abscisic acid (ABA) signaling in guard cells, but a metabolite profile of this specialized cell type is lacking. We used liquid chromatography–multiple reaction monitoring mass spectrometry for targeted analysis of 85 signaling-related metabolites in Arabidopsis thaliana guard cell protoplasts over a time course of ABA treatment. The analysis utilized ∼350 million guard cell protoplasts from ∼30,000 plants of the Arabidopsis Columbia accession (Col) wild type and the heterotrimeric G-protein α subunit mutant, gpa1, which has ABA-hyposensitive stomata. These metabolomes revealed coordinated regulation of signaling metabolites in unrelated biochemical pathways. Metabolites clustered into different temporal modules in Col versus gpa1, with fewer metabolites showing ABA-altered profiles in gpa1. Ca2+-mobilizing agents sphingosine-1-phosphate and cyclic adenosine diphosphate ribose exhibited weaker ABA-stimulated increases in gpa1. Hormone metabolites were responsive to ABA, with generally greater responsiveness in Col than in gpa1. Most hormones also showed different ABA responses in guard cell versus mesophyll cell metabolomes. These findings suggest that ABA functions upstream to regulate other hormones, and are also consistent with G proteins modulating multiple hormonal signaling pathways. In particular, indole-3-acetic acid levels declined after ABA treatment in Col but not gpa1 guard cells. Consistent with this observation, the auxin antagonist α-(phenyl ethyl-2-one)-indole-3-acetic acid enhanced ABA-regulated stomatal movement and restored partial ABA sensitivity to gpa1. PMID:24368793

TWISTED DWARF1 Mediates the Action of Auxin Transport Inhibitors on Actin Cytoskeleton Dynamics

PubMed Central

Bailly, Aurelien; Zwiewka, Marta; Sovero, Valpuri; Ge, Pei; Aryal, Bibek; Hao, Pengchao; Linnert, Miriam; Burgardt, Noelia Inés; Lücke, Christian; Weiwad, Matthias; Michel, Max; Weiergräber, Oliver H.; Pollmann, Stephan; Azzarello, Elisa; Fukao, Yoichiro; Hoffmann, Céline; Wedlich-Söldner, Roland

2016-01-01

Plant growth and architecture is regulated by the polar distribution of the hormone auxin. Polarity and flexibility of this process is provided by constant cycling of auxin transporter vesicles along actin filaments, coordinated by a positive auxin-actin feedback loop. Both polar auxin transport and vesicle cycling are inhibited by synthetic auxin transport inhibitors, such as 1-N-naphthylphthalamic acid (NPA), counteracting the effect of auxin; however, underlying targets and mechanisms are unclear. Using NMR, we map the NPA binding surface on the Arabidopsis thaliana ABCB chaperone TWISTED DWARF1 (TWD1). We identify ACTIN7 as a relevant, although likely indirect, TWD1 interactor, and show TWD1-dependent regulation of actin filament organization and dynamics and that TWD1 is required for NPA-mediated actin cytoskeleton remodeling. The TWD1-ACTIN7 axis controls plasma membrane presence of efflux transporters, and as a consequence act7 and twd1 share developmental and physiological phenotypes indicative of defects in auxin transport. These can be phenocopied by NPA treatment or by chemical actin (de)stabilization. We provide evidence that TWD1 determines downstream locations of auxin efflux transporters by adjusting actin filament debundling and dynamizing processes and mediating NPA action on the latter. This function appears to be evolutionary conserved since TWD1 expression in budding yeast alters actin polarization and cell polarity and provides NPA sensitivity. PMID:27053424

Interactions between red light, abscisic acid, and calcium in gravitropism

NASA Technical Reports Server (NTRS)

Leopold, A. C.; LaFavre, A. K.

1989-01-01

The effect of red light on orthogravitropism of Merit corn (Zea mays L.) roots has been attributed to its effects on the transduction phase of gravitropism (AC Leopold, SH Wettlaufer [1988] Plant Physiol 87:803-805). In an effort to characterize the orthogravitropic transduction system, comparative experiments have been carried out on the effects of red light, calcium, and abscisic acid (ABA). The red light effect can be completely satisfied with added ABA (100 micromolar) or with osmotic shock, which is presumed to increase endogenous ABA. The decay of the red light effect is closely paralleled by the decay of the ABA effect. ABA and exogenous calcium show strong additive effects when applied to either Merit or a line of corn which does not require red light for orthogravitropism. Measurements of the ABA content show marked increases in endogenous ABA in the growing region of the roots after red light. The interpretation is offered that red light or ABA may serve to increase the cytoplasmic concentrations of calcium, and that this may be an integral part of orthogravitropic transduction.

Activation of Big Grain1 significantly improves grain size by regulating auxin transport in rice.

PubMed

Liu, Linchuan; Tong, Hongning; Xiao, Yunhua; Che, Ronghui; Xu, Fan; Hu, Bin; Liang, Chengzhen; Chu, Jinfang; Li, Jiayang; Chu, Chengcai

2015-09-01

Grain size is one of the key factors determining grain yield. However, it remains largely unknown how grain size is regulated by developmental signals. Here, we report the identification and characterization of a dominant mutant big grain1 (Bg1-D) that shows an extra-large grain phenotype from our rice T-DNA insertion population. Overexpression of BG1 leads to significantly increased grain size, and the severe lines exhibit obviously perturbed gravitropism. In addition, the mutant has increased sensitivities to both auxin and N-1-naphthylphthalamic acid, an auxin transport inhibitor, whereas knockdown of BG1 results in decreased sensitivities and smaller grains. Moreover, BG1 is specifically induced by auxin treatment, preferentially expresses in the vascular tissue of culms and young panicles, and encodes a novel membrane-localized protein, strongly suggesting its role in regulating auxin transport. Consistent with this finding, the mutant has increased auxin basipetal transport and altered auxin distribution, whereas the knockdown plants have decreased auxin transport. Manipulation of BG1 in both rice and Arabidopsis can enhance plant biomass, seed weight, and yield. Taking these data together, we identify a novel positive regulator of auxin response and transport in a crop plant and demonstrate its role in regulating grain size, thus illuminating a new strategy to improve plant productivity.

Abscisic-acid-dependent basic leucine zipper (bZIP) transcription factors in plant abiotic stress.

PubMed

Banerjee, Aditya; Roychoudhury, Aryadeep

2017-01-01

One of the major causes of significant crop loss throughout the world is the myriad of environmental stresses including drought, salinity, cold, heavy metal toxicity, and ultraviolet-B (UV-B) rays. Plants as sessile organisms have evolved various effective mechanism which enable them to withstand this plethora of stresses. Most of such regulatory mechanisms usually follow the abscisic-acid (ABA)-dependent pathway. In this review, we have primarily focussed on the basic leucine zipper (bZIP) transcription factors (TFs) activated by the ABA-mediated signalosome. Upon perception of ABA by specialized receptors, the signal is transduced via various groups of Ser/Thr kinases, which phosphorylate the bZIP TFs. Following such post-translational modification of TFs, they are activated so that they bind to specific cis-acting sequences called abscisic-acid-responsive elements (ABREs) or GC-rich coupling elements (CE), thereby influencing the expression of their target downstream genes. Several in silico techniques have been adopted so far to predict the structural features, recognize the regulatory modification sites, undergo phylogenetic analyses, and facilitate genome-wide survey of TF under multiple stresses. Current investigations on the epigenetic regulation that controls greater accessibility of the inducible regions of DNA of the target gene to the bZIP TFs exclusively under stress situations, along with the evolved stress memory responses via genomic imprinting mechanism, have been highlighted. The potentiality of overexpression of bZIP TFs, either in a homologous or in a heterologous background, in generating transgenic plants tolerant to various abiotic stressors have also been addressed by various groups. The present review will provide a coherent documentation on the functional characterization and regulation of bZIP TFs under multiple environmental stresses, with the major goal of generating multiple-stress-tolerant plant cultivars in near future.

New auxin analogs with growth-promoting effects in intact plants reveal a chemical strategy to improve hormone delivery

PubMed Central

Savaldi-Goldstein, Sigal; Baiga, Thomas J.; Pojer, Florence; Dabi, Tsegeye; Butterfield, Cristina; Parry, Geraint; Santner, Aaron; Dharmasiri, Nihal; Tao, Yi; Estelle, Mark; Noel, Joseph P.; Chory, Joanne

2008-01-01

Plant growth depends on the integration of environmental cues and phytohormone-signaling pathways. During seedling emergence, elongation of the embryonic stem (hypocotyl) serves as a readout for light and hormone-dependent responses. We screened 10,000 chemicals provided exogenously to light-grown seedlings and identified 100 compounds that promote hypocotyl elongation. Notably, one subset of these chemicals shares structural characteristics with the synthetic auxins, 2,4-dichlorophenoxyacetic acid (2,4-D), and 1-naphthaleneacetic acid (1-NAA); however, traditional auxins (e.g., indole-3-acetic acid [IAA], 2,4-D, 1-NAA) have no effect on hypocotyl elongation. We show that the new compounds act as “proauxins” akin to prodrugs. Our data suggest that these compounds diffuse efficiently to the hypocotyls, where they undergo cleavage at varying rates, releasing functional auxins. To investigate this principle, we applied a masking strategy and designed a pro-2,4-D. Unlike 2,4-D alone, this pro-2,4-D enhanced hypocotyl elongation. We further demonstrated the utility of the proauxins by characterizing auxin responses in light-grown hypocotyls of several auxin receptor mutants. These new compounds thus provide experimental access to a tissue previously inaccessible to exogenous application of auxins. Our studies exemplify the combined power of chemical genetics and biochemical analyses for discovering and refining prohormone analogs with selective activity in specific plant tissues. In addition to the utility of these compounds for addressing questions related to auxin and light-signaling interactions, one can envision using these simple principles to study other plant hormone and small molecule responses in temporally and spatially controlled ways. PMID:18818305

Jasmonic Acid, Abscisic Acid, and Salicylic Acid Are Involved in the Phytoalexin Responses of Rice to Fusarium fujikuroi, a High Gibberellin Producer Pathogen.

PubMed

Siciliano, Ilenia; Amaral Carneiro, Greice; Spadaro, Davide; Garibaldi, Angelo; Gullino, Maria Lodovica

2015-09-23

Fusarium fujikuroi, the causal agent of bakanae disease, is the main seedborne pathogen on rice. To understand the basis of rice resistance, a quantitative method to simultaneously detect phytohormones and phytoalexins was developed by using HPLC-MS/MS. With this method dynamic profiles and possible interactions of defense-related phytohormones and phytoalexins were investigated on two rice cultivars, inoculated or not with F. fujikuroi. In the resistant cultivar Selenio, the presence of pathogen induced high production of phytoalexins, mainly sakuranetin, and symptoms of bakanae were not observed. On the contrary, in the susceptible genotype Dorella, the pathogen induced the production of gibberellin and abscisic acid and inhibited jasmonic acid production, phytoalexins were very low, and bakanae symptoms were observed. The results suggested that a wide range of secondary metabolites are involved in plant defense against pathogens and phytoalexin synthesis could be an important factor for rice resistance against bakanae disease.

Synchronization of Somatic Embryogenesis in Date Palm Suspension Culture Using Abscisic Acid.

PubMed

Alwael, Hussain A; Naik, Poornananda M; Al-Khayri, Jameel M

2017-01-01

Somatic embryogenesis is considered the most effective method for commercial propagation of date palm. However, the limitation of obtaining synchronized development of somatic embryos remains an impediment. The synchronization of somatic embryo development is ideal for the applications to produce artificial seeds. Abscisic acid (ABA) is associated with stress response and influences in vitro growth and development. This chapter describes an effective method to achieve synchronized development of somatic embryos in date palm cell suspension culture. Among the ABA concentrations tested (0, 1, 10, 50, 100 μM), the best synchronized growth was obtained in response to 50-100 μM. Here we provide a comprehensive protocol for in vitro plant regeneration of date palm starting with shoot-tip explant, callus initiation and growth, cell suspension establishment, embryogenesis synchronization with ABA treatment, somatic embryo germination, and rooting as well as acclimatized plantlet establishment.

ACCERBATIN, a small molecule at the intersection of auxin and reactive oxygen species homeostasis with herbicidal properties.

PubMed

Hu, Yuming; Depaepe, Thomas; Smet, Dajo; Hoyerova, Klara; Klíma, Petr; Cuypers, Ann; Cutler, Sean; Buyst, Dieter; Morreel, Kris; Boerjan, Wout; Martins, José; Petrášek, Jan; Vandenbussche, Filip; Van Der Straeten, Dominique

2017-07-10

The volatile two-carbon hormone ethylene acts in concert with an array of signals to affect etiolated seedling development. From a chemical screen, we isolated a quinoline carboxamide designated ACCERBATIN (AEX) that exacerbates the 1-aminocyclopropane-1-carboxylic acid-induced triple response, typical for ethylene-treated seedlings in darkness. Phenotypic analyses revealed distinct AEX effects including inhibition of root hair development and shortening of the root meristem. Mutant analysis and reporter studies further suggested that AEX most probably acts in parallel to ethylene signaling. We demonstrated that AEX functions at the intersection of auxin metabolism and reactive oxygen species (ROS) homeostasis. AEX inhibited auxin efflux in BY-2 cells and promoted indole-3-acetic acid (IAA) oxidation in the shoot apical meristem and cotyledons of etiolated seedlings. Gene expression studies and superoxide/hydrogen peroxide staining further revealed that the disrupted auxin homeostasis was accompanied by oxidative stress. Interestingly, in light conditions, AEX exhibited properties reminiscent of the quinoline carboxylate-type auxin-like herbicides. We propose that AEX interferes with auxin transport from its major biosynthesis sites, either as a direct consequence of poor basipetal transport from the shoot meristematic region, or indirectly, through excessive IAA oxidation and ROS accumulation. Further investigation of AEX can provide new insights into the mechanisms connecting auxin and ROS homeostasis in plant development and provide useful tools to study auxin-type herbicides. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Postharvest Exogenous Application of Abscisic Acid Reduces Internal Browning in Pineapple.

PubMed

Zhang, Qin; Liu, Yulong; He, Congcong; Zhu, Shijiang

2015-06-10

Internal browning (IB) is a postharvest physiological disorder causing economic losses in pineapple, but there is no effective control measure. In this study, postharvest application of 380 μM abscisic acid (ABA) reduced IB incidence by 23.4-86.3% and maintained quality in pineapple fruit. ABA reduced phenolic contents and polyphenol oxidase and phenylalanine ammonia lyase activities; increased catalase and peroxidase activities; and decreased O2(·-), H2O2, and malondialdehyde levels. This suggests ABA could control IB through inhibiting phenolics biosynthesis and oxidation and enhancing antioxidant capability. Furthermore, the efficacy of IB control by ABA was not obviously affected by tungstate, ABA biosynthesis inhibitor, nor by diphenylene iodonium, NADPH oxidase inhibitor, nor by lanthanum chloride, calcium channel blocker, suggesting that ABA is sufficient for controlling IB. This process might not involve H2O2 generation, but could involve the Ca(2+) channels activation. These results provide potential for developing effective measures for controlling IB in pineapple.

Developmental priming of stomatal sensitivity to abscisic acid by leaf microclimate.

PubMed

Pantin, Florent; Renaud, Jeanne; Barbier, François; Vavasseur, Alain; Le Thiec, Didier; Rose, Christophe; Bariac, Thierry; Casson, Stuart; McLachlan, Deirdre H; Hetherington, Alistair M; Muller, Bertrand; Simonneau, Thierry

2013-09-23

Plant water loss and CO2 uptake are controlled by valve-like structures on the leaf surface known as stomata. Stomatal aperture is regulated by hormonal and environmental signals. We show here that stomatal sensitivity to the drought hormone abscisic acid (ABA) is acquired during leaf development by exposure to an increasingly dryer atmosphere in the rosette plant Arabidopsis. Young leaves, which develop in the center of the rosette, do not close in response to ABA. As the leaves increase in size, they are naturally exposed to increasingly dry air as a consequence of the spatial arrangement of the leaves, and this triggers the acquisition of ABA sensitivity. Interestingly, stomatal ABA sensitivity in young leaves is rapidly restored upon water stress. These findings shed new light on how plant architecture and stomatal physiology have coevolved to optimize carbon gain against water loss in stressing environments. Copyright © 2013 Elsevier Ltd. All rights reserved.

Mechanisms of action and medicinal applications of abscisic Acid.

PubMed

Bassaganya-Riera, J; Skoneczka, J; Kingston, D G J; Krishnan, A; Misyak, S A; Guri, A J; Pereira, A; Carter, A B; Minorsky, P; Tumarkin, R; Hontecillas, R

2010-01-01

Since its discovery in the early 1960's, abscisic acid (ABA) has received considerable attention as an important phytohormone, and more recently, as a candidate medicinal in humans. In plants it has been shown to regulate important physiological processes such as response to drought stress, and dormancy. The discovery of ABA synthesis in animal cells has generated interest in the possible parallels between its role in plant and animal systems. The importance of this molecule has prompted the development of several methods for the chemical synthesis of ABA, which differ significantly from the biosynthesis of ABA in plants through the mevalonic acid pathway. ABA recognition in plants has been shown to occur at both the intra- and extracellularly but little is known about the perception of ABA by animal cells. A few ABA molecular targets have been identified in vitro (e.g., calcium signaling, G protein-coupled receptors) in both plant and animal systems. A unique finding in mammalian systems, however, is that the peroxisome proliferator-activated receptor, PPAR gamma, is upregulated by ABA in both in vitro and in vivo studies. Comparison of the human PPAR gamma gene network with Arabidopsis ABA-related genes reveal important orthologs between these groups. Also, ABA can ameliorate the symptoms of type II diabetes, targeting PPAR gamma in a similar manner as the thiazolidinediones class of anti-diabetic drugs. The use of ABA in the treatment of type II diabetes, offers encouragement for further studies concerning the biomedical applications of ABA.

Abscisic acid deficiency increases defence responses against Myzus persicae in Arabidopsis.

PubMed

Hillwig, Melissa S; Chiozza, Mariana; Casteel, Clare L; Lau, Siau Ting; Hohenstein, Jessica; Hernández, Enrique; Jander, Georg; MacIntosh, Gustavo C

2016-02-01

Comparison of Arabidopsis thaliana (Arabidopsis) gene expression induced by Myzus persicae (green peach aphid) feeding, aphid saliva infiltration and abscisic acid (ABA) treatment showed a significant positive correlation. In particular, ABA-regulated genes are over-represented among genes that are induced by M. persicae saliva infiltration into Arabidopsis leaves. This suggests that the induction of ABA-related gene expression could be an important component of the Arabidopsis-aphid interaction. Consistent with this hypothesis, M. persicae populations induced ABA production in wild-type plants. Furthermore, aphid populations were smaller on Arabidopsis aba1-1 mutants, which cannot synthesize ABA, and showed a significant preference for wild-type plants compared with the mutant. Total free amino acids, which play an important role in aphid nutrition, were not altered in the aba1-1 mutant line, but the levels of isoleucine (Ile) and tryptophan (Trp) were differentially affected by aphids in wild-type and mutant plants. Recently, indole glucosinolates have been shown to promote aphid resistance in Arabidopsis. In this study, 4-methoxyindol-3-ylmethylglucosinolate was more abundant in the aba1-1 mutant than in wild-type Arabidopsis, suggesting that the induction of ABA signals that decrease the accumulation of defence compounds may be beneficial for aphids. © 2015 BSPP AND JOHN WILEY & SONS LTD.

To Stimulate or Inhibit? That Is the Question for the Function of Abscisic Acid.

PubMed

Humplík, Jan F; Bergougnoux, Véronique; Van Volkenburgh, Elizabeth

2017-10-01

Physiologically, abscisic acid (ABA) is believed to be a general inhibitor of plant growth, including during the crucial early development of seedlings. However, this view contradicts many reports of stimulatory effects of ABA that, so far, have not been considered in the debate concerning ABA's function in plant development. To address this apparent contradiction, we propose a hypothetical mechanism to explain how ABA might contribute to the promotion of cell expansion. We wish to overturn conventional views on ABA's role during juvenile plant development and put forward the idea that, as for other phytohormones, the role of ABA is determined by dose and sensitivity and ranges from stimulatory to inhibitory effects. Copyright © 2017 Elsevier Ltd. All rights reserved.

Auxin effects on in vitro and in vivo protein phosphorylation in pea. [Pisum sativum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gallagher, S.R.; Ray, P.M.

1987-04-01

Terminal 8mm sections from the third internode of dark grown 7 day old Pisum sativum cv Alaska seedlings were separated into membrane and soluble fractions. SDS gradient PAGE identified approximately 50 in vivo phosphorylated proteins and proved superior to 2-D SDS PAGE in terms of resolution and repeatability. Addition of indoleacetic acid (IAA), fusicoccin, or 2,4 dichlorophenoxyacetic acid to membranes resulted in no detectable change in the number or phosphorylation level of the labeled proteins during in vitro phosphorylation in the presence of submicromolar concentrations of calcium. Similar results were obtained with soluble proteins. In the absence of calcium, themore » level of in vitro protein phosphorylation was much less, but not auxin effects could be identified. Furthermore, treatment of the sections with IAA in vivo followed by cell fractionation and in vitro phosphorylation failed to identify auxin responsive proteins. Lastly, when sections were labeled with /sup 32/P inorganic phosphate in the presence of 17 uM IAA, no auxin specific changes were found in the level of phosphorylation or in the number of phosphorylated proteins. Auxin effects on phosphorylation are thus slight or below their detection limit.« less

The interaction and integration of auxin signaling components.

PubMed

Hayashi, Ken-ichiro

2012-06-01

IAA, a naturally occurring auxin, is a simple signaling molecule that regulates many diverse steps of plant development. Auxin essentially coordinates plant development through transcriptional regulation. Auxin binds to TIR1/AFB nuclear receptors, which are F-box subunits of the SCF ubiquitin ligase complex. The auxin signal is then modulated by the quantitative and qualitative responses of the Aux/IAA repressors and the auxin response factor (ARF) transcription factors. The specificity of the auxin-regulated gene expression profile is defined by several factors, such as the expression of these regulatory proteins, their post-transcriptional regulation, their stability and the affinity between these regulatory proteins. Auxin-binding protein 1 (ABP1) is a candidate protein for an auxin receptor that is implicated in non-transcriptional auxin signaling. ABP1 also affects TIR1/AFB-mediated auxin-responsive gene expression, implying that both the ABP1 and TIR1/AFB signaling machineries coordinately control auxin-mediated physiological events. Systematic approaches using the comprehensive mapping of the expression and interaction of signaling modules and computational modeling would be valuable for integrating our knowledge of auxin signals and responses.

Inducible knock-down of GNOM during root formation reveals tissue-specific response to auxin transport and its modulation of local auxin biosynthesis

PubMed Central

Sun, Meng-Xiang

2014-01-01

In plants, active transport of auxin plays an essential role in root development. Localization of the PIN1 auxin transporters to the basal membrane of cells directs auxin flow and depends on the trafficking mediator GNOM. GNOM-dependent auxin transport is vital for root development and thus offers a useful tool for the investigation of a possible tissue-specific response to dynamic auxin transport. To avoid pleiotropic effects, DEX-inducible expression of GNOM antisense RNA was used to disrupt GNOM expression transiently or persistently during embryonic root development. It was found that the elongation zone and the pericycle layer are the most sensitive to GNOM-dependent auxin transport variations, which is shown by the phenotypes in cell elongation and the initiation of lateral root primordia, respectively. This suggests that auxin dynamics is critical to cell differentiation and cell fate transition, but not to cell division. The results also reveal that GNOM-dependent auxin transport could affect local auxin biosynthesis. This suggests that local auxin biosynthesis may also contribute to the establishment of GNOM-dependent auxin gradients in specific tissues, and that auxin transport and local auxin biosynthesis may function together in the regulatory network for initiation and development of lateral root primordia. Thus, the data reveal a tissue-specific response to auxin transport and modulation of local auxin biosynthesis by auxin transport. PMID:24453227

The actin cytoskeleton may control the polar distribution of an auxin transport protein

NASA Technical Reports Server (NTRS)

Muday, G. K.; Hu, S.; Brady, S. R.; Davies, E. (Principal Investigator)

2000-01-01

The gravitropic bending of plants has long been linked to the changes in the transport of the plant hormone auxin. To understand the mechanism by which gravity alters auxin movement, it is critical to know how polar auxin transport is initially established. In shoots, polar auxin transport is basipetal (i.e., from the shoot apex toward the base). It is driven by the basal localization of the auxin efflux carrier complex. One mechanism for localizing this efflux carrier complex to the basal membrane may be through attachment to the actin cytoskeleton. The efflux carrier protein complex is believed to consist of several polypeptides, including a regulatory subunit that binds auxin transport inhibitors, such as naphthylphthalamic acid (NPA). Several lines of experimentation have been used to determine if the NPA binding protein interacts with actin filaments. The NPA binding protein has been shown to partition with the actin cytoskeleton during detergent extraction. Agents that specifically alter the polymerization state of the actin cytoskeleton change the amount of NPA binding protein and actin recovered in these cytoskeletal pellets. Actin-affinity columns were prepared with polymers of actin purified from zucchini hypocotyl tissue. NPA binding activity was eluted in a single peak from the actin filament column. Cytochalasin D, which fragments the actin cytoskeleton, was shown to reduce polar auxin transport in zucchini hypocotyls. The interaction of the NPA binding protein with the actin cytoskeleton may localize it in one plane of the plasma membrane, and thereby control the polarity of auxin transport.

The actin cytoskeleton may control the polar distribution of an auxin transport protein.

PubMed

Muday, G K; Hu, S; Brady, S R

2000-06-01

The gravitropic bending of plants has long been linked to the changes in the transport of the plant hormone auxin. To understand the mechanism by which gravity alters auxin movement, it is critical to know how polar auxin transport is initially established. In shoots, polar auxin transport is basipetal (i.e., from the shoot apex toward the base). It is driven by the basal localization of the auxin efflux carrier complex. One mechanism for localizing this efflux carrier complex to the basal membrane may be through attachment to the actin cytoskeleton. The efflux carrier protein complex is believed to consist of several polypeptides, including a regulatory subunit that binds auxin transport inhibitors, such as naphthylphthalamic acid (NPA). Several lines of experimentation have been used to determine if the NPA binding protein interacts with actin filaments. The NPA binding protein has been shown to partition with the actin cytoskeleton during detergent extraction. Agents that specifically alter the polymerization state of the actin cytoskeleton change the amount of NPA binding protein and actin recovered in these cytoskeletal pellets. Actin-affinity columns were prepared with polymers of actin purified from zucchini hypocotyl tissue. NPA binding activity was eluted in a single peak from the actin filament column. Cytochalasin D, which fragments the actin cytoskeleton, was shown to reduce polar auxin transport in zucchini hypocotyls. The interaction of the NPA binding protein with the actin cytoskeleton may localize it in one plane of the plasma membrane, and thereby control the polarity of auxin transport.

Early steps of adventitious rooting: morphology, hormonal profiling and carbohydrate turnover in carnation stem cuttings.

PubMed

Agulló-Antón, María Ángeles; Ferrández-Ayela, Almudena; Fernández-García, Nieves; Nicolás, Carlos; Albacete, Alfonso; Pérez-Alfocea, Francisco; Sánchez-Bravo, José; Pérez-Pérez, José Manuel; Acosta, Manuel

2014-03-01

The rooting of stem cuttings is a common vegetative propagation practice in many ornamental species. A detailed analysis of the morphological changes occurring in the basal region of cultivated carnation cuttings during the early stages of adventitious rooting was carried out and the physiological modifications induced by exogenous auxin application were studied. To this end, the endogenous concentrations of five major classes of plant hormones [auxin, cytokinin (CK), abscisic acid, salicylic acid (SA) and jasmonic acid] and the ethylene precursor 1-aminocyclopropane-1-carboxylic acid were analyzed at the base of stem cuttings and at different stages of adventitious root formation. We found that the stimulus triggering the initiation of adventitious root formation occurred during the first hours after their excision from the donor plant, due to the breakdown of the vascular continuum that induces auxin accumulation near the wounding. Although this stimulus was independent of exogenously applied auxin, it was observed that the auxin treatment accelerated cell division in the cambium and increased the sucrolytic activities at the base of the stem, both of which contributed to the establishment of the new root primordia at the stem base. Further, several genes involved in auxin transport were upregulated in the stem base either with or without auxin application, while endogenous CK and SA concentrations were specially affected by exogenous auxin application. Taken together our results indicate significant crosstalk between auxin levels, stress hormone homeostasis and sugar availability in the base of the stem cuttings in carnation during the initial steps of adventitious rooting. © 2013 Scandinavian Plant Physiology Society.

The cotton transcription factor TCP14 functions in auxin-mediated epidermal cell differentiation and elongation.

PubMed

Wang, Miao-Ying; Zhao, Pi-Ming; Cheng, Huan-Qing; Han, Li-Bo; Wu, Xiao-Min; Gao, Peng; Wang, Hai-Yun; Yang, Chun-Lin; Zhong, Nai-Qin; Zuo, Jian-Ru; Xia, Gui-Xian

2013-07-01

Plant-specific TEOSINTE-BRANCHED1/CYCLOIDEA/PCF (TCP) transcription factors play crucial roles in development, but their functional mechanisms remain largely unknown. Here, we characterized the cellular functions of the class I TCP transcription factor GhTCP14 from upland cotton (Gossypium hirsutum). GhTCP14 is expressed predominantly in fiber cells, especially at the initiation and elongation stages of development, and its expression increased in response to exogenous auxin. Induced heterologous overexpression of GhTCP14 in Arabidopsis (Arabidopsis thaliana) enhanced initiation and elongation of trichomes and root hairs. In addition, root gravitropism was severely affected, similar to mutant of the auxin efflux carrier PIN-FORMED2 (PIN2) gene. Examination of auxin distribution in GhTCP14-expressing Arabidopsis by observation of auxin-responsive reporters revealed substantial alterations in auxin distribution in sepal trichomes and root cortical regions. Consistent with these changes, expression of the auxin uptake carrier AUXIN1 (AUX1) was up-regulated and PIN2 expression was down-regulated in the GhTCP14-expressing plants. The association of GhTCP14 with auxin responses was also evidenced by the enhanced expression of auxin response gene IAA3, a gene in the AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) family. Electrophoretic mobility shift assays showed that GhTCP14 bound the promoters of PIN2, IAA3, and AUX1, and transactivation assays indicated that GhTCP14 had transcription activation activity. Taken together, these results demonstrate that GhTCP14 is a dual-function transcription factor able to positively or negatively regulate expression of auxin response and transporter genes, thus potentially acting as a crucial regulator in auxin-mediated differentiation and elongation of cotton fiber cells.

A new look at stress: abscisic acid patterns and dynamics at high-resolution.

PubMed

Jones, Alexander M

2016-04-01

Abscisic acid (ABA) is a key phytohormone promoting abiotic stress tolerance as well as developmental processes such as seed dormancy. A spatiotemporal map of ABA concentrations would greatly advance our understanding of the cell type and timing of ABA action. Organ and tissue-level ABA measurements, as well as indirect in vivo measurements such as cell-specific transcriptional analysis of ABA metabolic enzymes and ABA-responsive promoters, have all contributed to current views of the localization and timing of ABA accumulations. Recently developed Förster resonance energy transfer (FRET) biosensors for ABA that sense ABA levels directly promise to add unprecedented resolution to in vivo ABA spatiotemporal mapping and expand our knowledge of the mechanisms controlling ABA levels in space and time. © 2015 Carnegie Institution for Science New Phytologist © 2015 New Phytologist Trust.

Maize LAZY1 mediates shoot gravitropism and inflorescence development through regulating auxin transport, auxin signaling, and light response.

PubMed

Dong, Zhaobin; Jiang, Chuan; Chen, Xiaoyang; Zhang, Tao; Ding, Lian; Song, Weibin; Luo, Hongbing; Lai, Jinsheng; Chen, Huabang; Liu, Renyi; Zhang, Xiaolan; Jin, Weiwei

2013-11-01

Auxin is a plant hormone that plays key roles in both shoot gravitropism and inflorescence development. However, these two processes appear to be parallel and to be regulated by distinct players. Here, we report that the maize (Zea mays) prostrate stem1 mutant, which is allelic to the classic mutant lazy plant1 (la1), displays prostrate growth with reduced shoot gravitropism and defective inflorescence development. Map-based cloning identified maize ZmLA1 as the functional ortholog of LAZY1 in rice (Oryza sativa) and Arabidopsis (Arabidopsis thaliana). It has a unique role in inflorescence development and displays enriched expression in reproductive organs such as tassels and ears. Transcription of ZmLA1 responds to auxin and is repressed by light. Furthermore, ZmLA1 physically interacts with a putative auxin transport regulator in the plasma membrane and a putative auxin signaling protein in the nucleus. RNA-SEQ data showed that dozens of auxin transport, auxin response, and light signaling genes were differentially expressed in la1 mutant stems. Therefore, ZmLA1 might mediate the cross talk between shoot gravitropism and inflorescence development by regulating auxin transport, auxin signaling, and probably light response in maize.

Structural basis and functions of abscisic acid receptors PYLs

PubMed Central

Zhang, Xing L.; Jiang, Lun; Xin, Qi; Liu, Yang; Tan, Jian X.; Chen, Zhong Z.

2015-01-01

Abscisic acid (ABA) plays a key role in many developmental processes and responses to adaptive stresses in plants. Recently, a new family of nucleocytoplasmic PYR/PYL/RCAR (PYLs) has been identified as bona fide ABA receptors. PYLs together with protein phosphatases type-2C (PP2Cs), Snf1 (Sucrose-non-fermentation 1)-related kinases subfamily 2 (SnRK2s) and downstream substrates constitute the core ABA signaling network. Generally, PP2Cs inactivate SnRK2s kinases by physical interaction and direct dephosphorylation. Upon ABA binding, PYLs change their conformations and then contact and inhibit PP2Cs, thus activating SnRK2s. Here, we reviewed the recent progress in research regarding the structures of the core signaling pathways of ABA, including the (+)-ABA, (−)-ABA and ABA analogs pyrabactin as well as 6AS perception by PYLs, SnRK2s mimicking PYLs in binding PP2Cs. PYLs inhibited PP2Cs in both the presence and absence of ABA and activated SnRK2s. The present review elucidates multiple ABA signal perception and transduction by PYLs, which might shed light on how to design small chemical compounds for improving plant performance in the future. PMID:25745428

Abscisic acid controlled sex before transpiration in vascular plants

PubMed Central

McAdam, Scott A. M.; Brodribb, Timothy J.; Hedrich, Rainer; Atallah, Nadia M.; Cai, Chao; Geringer, Michael A.; Lind, Christof; Nichols, David S.; Stachowski, Kye; Sussmilch, Frances C.

2016-01-01

Sexual reproduction in animals and plants shares common elements, including sperm and egg production, but unlike animals, little is known about the regulatory pathways that determine the sex of plants. Here we use mutants and gene silencing in a fern species to identify a core regulatory mechanism in plant sexual differentiation. A key player in fern sex differentiation is the phytohormone abscisic acid (ABA), which regulates the sex ratio of male to hermaphrodite tissues during the reproductive cycle. Our analysis shows that in the fern Ceratopteris richardii, a gene homologous to core ABA transduction genes in flowering plants [SNF1-related kinase2s (SnRK2s)] is primarily responsible for the hormonal control of sex determination. Furthermore, we provide evidence that this ABA–SnRK2 signaling pathway has transitioned from determining the sex of ferns to controlling seed dormancy in the earliest seed plants before being co-opted to control transpiration and CO2 exchange in derived seed plants. By tracing the evolutionary history of this ABA signaling pathway from plant reproduction through to its role in the global regulation of plant–atmosphere gas exchange during the last 450 million years, we highlight the extraordinary effect of the ABA–SnRK2 signaling pathway in plant evolution and vegetation function. PMID:27791082

Abscisic acid controlled sex before transpiration in vascular plants.

PubMed

McAdam, Scott A M; Brodribb, Timothy J; Banks, Jo Ann; Hedrich, Rainer; Atallah, Nadia M; Cai, Chao; Geringer, Michael A; Lind, Christof; Nichols, David S; Stachowski, Kye; Geiger, Dietmar; Sussmilch, Frances C

2016-10-26

Sexual reproduction in animals and plants shares common elements, including sperm and egg production, but unlike animals, little is known about the regulatory pathways that determine the sex of plants. Here we use mutants and gene silencing in a fern species to identify a core regulatory mechanism in plant sexual differentiation. A key player in fern sex differentiation is the phytohormone abscisic acid (ABA), which regulates the sex ratio of male to hermaphrodite tissues during the reproductive cycle. Our analysis shows that in the fern Ceratopteris richardii, a gene homologous to core ABA transduction genes in flowering plants [SNF1-related kinase2s (SnRK2s)] is primarily responsible for the hormonal control of sex determination. Furthermore, we provide evidence that this ABA-SnRK2 signaling pathway has transitioned from determining the sex of ferns to controlling seed dormancy in the earliest seed plants before being co-opted to control transpiration and CO 2 exchange in derived seed plants. By tracing the evolutionary history of this ABA signaling pathway from plant reproduction through to its role in the global regulation of plant-atmosphere gas exchange during the last 450 million years, we highlight the extraordinary effect of the ABA-SnRK2 signaling pathway in plant evolution and vegetation function.

Role of Auxin in Orchid Development

PubMed Central

Novak, Stacey D.; Luna, Lila J.; Gamage, Roshan N.

2014-01-01

Auxin's capacity to regulate aspects of plant development has been well characterized in model plant systems. In contrast, orchids have received considerably less attention, but the realization that many orchid species are endangered has led to culture-based propagation studies which have unveiled some functions for auxin in this system. This mini-review summarizes the many auxin-mediated developmental responses in orchids that are consistent with model systems; however, it also brings to the forefront auxin responses that are unique to orchid development, namely protocorm formation and ovary/ovule maturation. With regard to shoot establishment, we also assess auxin's involvement in orchid germination, PLB formation, and somatic embryogenesis. Further, it makes evident that auxin flow during germination of the undifferentiated, but mature, orchid embryo mirrors late embryogenesis of typical angiosperms. Also discussed is the use of orchid protocorms in future phytohormone studies to better understand the mechanisms behind meristem formation and organogenesis. PMID:25482818

Modulation of organic acids and sugar content in tomato fruits by an abscisic acid-regulated transcription factor.

PubMed

Bastías, Adriana; López-Climent, María; Valcárcel, Mercedes; Rosello, Salvador; Gómez-Cadenas, Aurelio; Casaretto, José A

2011-03-01

Growing evidence suggests that the phytohormone abscisic acid (ABA) plays a role in fruit development. ABA signaling components of developmental programs and responses to stress conditions include the group of basic leucine zipper transcriptional activators known as ABA-response element binding factors (AREBs/ABFs). AREB transcription factors mediate ABA-regulated gene expression involved in desiccation tolerance and are expressed mainly in seeds and in vegetative tissues under stress; however, they are also expressed in some fruits such as tomato. In order to get an insight into the role of ABA signaling in fruit development, the expression of two AREB-like factors were investigated during different developmental stages. In addition, tomato transgenic lines that overexpress and downregulate one AREB-like transcription factor, SlAREB1, were used to determine its effect on the levels of some metabolites determining fruit quality. Higher levels of citric acid, malic acid, glutamic acid, glucose and fructose were observed in SlAREB1-overexpressing lines compared with those in antisense suppression lines in red mature fruit pericarp. The higher hexose concentration correlated with increased expression of genes encoding a vacuolar invertase (EC 3.2.1.26) and a sucrose synthase (EC 2.4.1.13). No significant changes were found in ethylene content which agrees with the normal ripening phenotype observed in transgenic fruits. These results suggest that an AREB-mediated ABA signal affects the metabolism of these compounds during the fruit developmental program. Copyright © Physiologia Plantarum 2010.

A mutation in protein phosphatase 2A regulatory subunit A affects auxin transport in Arabidopsis

NASA Technical Reports Server (NTRS)

Garbers, C.; DeLong, A.; Deruere, J.; Bernasconi, P.; Soll, D.; Evans, M. L. (Principal Investigator)

1996-01-01

The phytohormone auxin controls processes such as cell elongation, root hair development and root branching. Tropisms, growth curvatures triggered by gravity, light and touch, are also auxin-mediated responses. Auxin is synthesized in the shoot apex and transported through the stem, but the molecular mechanism of auxin transport is not well understood. Naphthylphthalamic acid (NPA) and other inhibitors of auxin transport block tropic curvature responses and inhibit root and shoot elongation. We have isolated a novel Arabidopsis thaliana mutant designated roots curl in NPA (rcn1). Mutant seedlings exhibit altered responses to NPA in root curling and hypocotyl elongation. Auxin efflux in mutant seedlings displays increased sensitivity to NPA. The rcn1 mutation was transferred-DNA (T-DNA) tagged and sequences flanking the T-DNA insert were cloned. Analysis of the RCN1 cDNA reveals that the T-DNA insertion disrupts a gene for the regulatory A subunit of protein phosphatase 2A (PP2A-A). The RCN1 gene rescues the rcn1 mutant phenotype and also complements the temperature-sensitive phenotype of the Saccharomyces cerevisiae PP2A-A mutation, tpd3-1. These data implicate protein phosphatase 2A in the regulation of auxin transport in Arabidopsis.

Evidence That Chlorinated Auxin Is Restricted to the Fabaceae But Not to the Fabeae.

PubMed

Lam, Hong Kiat; McAdam, Scott A M; McAdam, Erin L; Ross, John J

2015-07-01

Auxin is a pivotal plant hormone, usually occurring in the form of indole-3-acetic acid (IAA). However, in maturing pea (Pisum sativum) seeds, the level of the chlorinated auxin, 4-chloroindole-3-acetic acid (4-Cl-IAA), greatly exceeds that of IAA. A key issue is how plants produce halogenated compounds such as 4-Cl-IAA. To better understand this topic, we investigated the distribution of the chlorinated auxin. We show for the first time, to our knowledge, that 4-Cl-IAA is found in the seeds of Medicago truncatula, Melilotus indicus, and three species of Trifolium. Furthermore, we found no evidence that Pinus spp. synthesize 4-Cl-IAA in seeds, contrary to a previous report. The evidence indicates a single evolutionary origin of 4-Cl-IAA synthesis in the Fabaceae, which may provide an ideal model system to further investigate the action and activity of halogenating enzymes in plants. © 2015 American Society of Plant Biologists. All Rights Reserved.

Reduced naphthylphthalamic acid binding in the tir3 mutant of Arabidopsis is associated with a reduction in polar auxin transport and diverse morphological defects

NASA Technical Reports Server (NTRS)

Ruegger, M.; Dewey, E.; Hobbie, L.; Brown, D.; Bernasconi, P.; Turner, J.; Muday, G.; Estelle, M.

1997-01-01

Polar auxin transport plays a key role in the regulation of plant growth and development. To identify genes involved in this process, we have developed a genetic procedure to screen for mutants of Arabidopsis that are altered in their response to auxin transport inhibitors. We recovered a total of 16 independent mutants that defined seven genes, called TRANSPORT INHIBITOR RESPONSE (TIR) genes. Recessive mutations in one of these genes, TIR3, result in altered responses to transport inhibitors, a reduction in polar auxin transport, and a variety of morphological defects that can be ascribed to changes in indole-3-acetic acid distribution. Most dramatically, tir3 seedlings are strongly deficient in lateral root production, a process that is known to depend on polar auxin transport from the shoot into the root. In addition, tir3 plants display a reduction in apical dominance as well as decreased elongation of siliques, pedicels, roots, and the inflorescence. Biochemical studies indicate that tir3 plants have a reduced number of N-1-naphthylphthalamic (NPA) binding sites, suggesting that the TIR3 gene is required for expression, localization, or stabilization of the NPA binding protein (NBP). Alternatively, the TIR3 gene may encode the NBP. Because the tir3 mutants have a substantial defect in NPA binding, their phenotype provides genetic evidence for a role for the NBP in plant growth and development.

Abscisic Acid Determines Basal Susceptibility of Tomato to Botrytis cinerea and Suppresses Salicylic Acid-Dependent Signaling Mechanisms1

PubMed Central

Audenaert, Kris; De Meyer, Geert B.; Höfte, Monica M.

2002-01-01

Abscisic acid (ABA) is one of the plant hormones involved in the interaction between plants and pathogens. In this work, we show that tomato (Lycopersicon esculentum Mill. cv Moneymaker) mutants with reduced ABA levels (sitiens plants) are much more resistant to the necrotrophic fungus Botrytis cinerea than wild-type (WT) plants. Exogenous application of ABA restored susceptibility to B. cinerea in sitiens plants and increased susceptibility in WT plants. These results indicate that ABA plays a major role in the susceptibility of tomato to B. cinerea. ABA appeared to interact with a functional plant defense response against B. cinerea. Experiments with transgenic NahG tomato plants and benzo(1,2,3)thiadiazole-7-carbothioic acid demonstrated the importance of salicylic acid in the tomato-B. cinerea interaction. In addition, upon infection with B. cinerea, sitiens plants showed a clear increase in phenylalanine ammonia lyase activity, which was not observed in infected WT plants, indicating that the ABA levels in healthy WT tomato plants partly repress phenylalanine ammonia lyase activity. In addition, sitiens plants became more sensitive to benzo(1,2,3)thiadiazole-7-carbothioic acid root treatment. The threshold values for PR1a gene expression declined with a factor 10 to 100 in sitiens compared with WT plants. Thus, ABA appears to negatively modulate the salicylic acid-dependent defense pathway in tomato, which may be one of the mechanisms by which ABA levels determine susceptibility to B. cinerea. PMID:11842153

Abscisic acid and osmoticum prevent germination of developing alfalfa embryos, but only osmoticum maintains the synthesis of developmental proteins.

PubMed

Xu, N; Coulter, K M; Derek Bewley, J

1990-10-01

Developing seeds of alfalfa (Medicago sativa L.) acquire the ability to germinate during the latter stages of development, the maturation drying phase. Isolated embryos placed on Murashige and Skoog medium germinate well during early and late development, but poorly during mid-development; however, when placed on water they germinate well only during the latter stage of development. Germination of isolated embryos is very slow and poor when they are incubated in the presence of surrounding seed structures (the endosperm or seed coat) taken from the mid-development stages. This inhibitory effect is also achieved by incubating embryos in 10(-5) M abscisic acid (ABA). Endogenous ABA attains a high level during mid-development, especially in the endosperm. Seeds developing in pods treated with fluridone (1-methyl-3-phenyl-5[3-(trifluoromethyl)-phenyl]-4(1H)-pyridinone) contain low levels of ABA during mid-development, and the endosperm and seed coat only weakly inhibit the germination of isolated embryos. However, intact seeds from fluridone-treated pods do not germinate viviparously, which is indicative that ABA alone is not responsible for maintaining seeds in a developing state. Application of osmoticum (e.g. 0.35 M sucrose) to isolated developing embryos prevents their germination. Also, in the developing seed in situ the osmotic potential is high. Thus internal levels of osmoticum may play a role in preventing germination of the embryo and maintaining development. Abscisic acid and osmoticum impart distinctly different metabolic responses on developing embryos, as demonstrated by their protein-synthetic capacity. Only in the presence of osmoticum do embryos synthesize proteins which are distinctly recognizable as those synthesized by developing embryos in situ, i.e. when inside the pod. Abscisic acid induces the synthesis of a few unique proteins, but these arise even in mature embryos treated with ABA. Thus while both osmoticum and ABA prevent precocious

Asymmetric gibberellin signaling regulates vacuolar trafficking of PIN auxin transporters during root gravitropism.

PubMed

Löfke, Christian; Zwiewka, Marta; Heilmann, Ingo; Van Montagu, Marc C E; Teichmann, Thomas; Friml, Jirí

2013-02-26

Gravitropic bending of plant organs is mediated by an asymmetric signaling of the plant hormone auxin between the upper and lower side of the respective organ. Here, we show that also another plant hormone, gibberellic acid (GA), shows asymmetric action during gravitropic responses. Immunodetection using an antibody against GA and monitoring GA signaling output by downstream degradation of DELLA proteins revealed an asymmetric GA distribution and response with the maximum at the lower side of gravistimulated roots. Genetic or pharmacological manipulation of GA levels or response affects gravity-mediated auxin redistribution and root bending response. The higher GA levels at the lower side of the root correlate with increased amounts of PIN-FORMED2 (PIN2) auxin transporter at the plasma membrane. The observed increase in PIN2 stability is caused by a specific GA effect on trafficking of PIN proteins to lytic vacuoles that presumably occurs downstream of brefeldin A-sensitive endosomes. Our results suggest that asymmetric auxin distribution instructive for gravity-induced differential growth is consolidated by the asymmetric action of GA that stabilizes the PIN-dependent auxin stream along the lower side of gravistimulated roots.

Morphophysiology, Phenotypic and Molecular Diversity of Auxin-induced Passiflora mucronata Lam. (Passifloraceae).

PubMed

França, Juliany M; Venial, Lucimara R; Costa, Eloá B; Schmildt, Edilson R; Schmildt, Omar; Bernardes, Paula M; Tatagiba, Sandro D; Lopes, José C; Ferreira, Marcia F S; Alexandre, Rodrigo S

2018-01-01

Genetic diversity allows identification of potential intraspecific genotypes in the genus Passiflora. The objective of this study was to examine the morphological and genetic diversity of auxin-induced Passiflora mucronata. The experiments were arranged in a complete randomized block design, with a 9 x 2 factorial arrangement (nine genotypes x presence and absence of auxin, indole-3-butyric acid (IBA)), with four replicates of 16 cuttings. The rooting and vegetative growth responses were variable. Genotype 5 was more responsive in the absence of IBA and genotypes 3, 8 and 9 were more responsive in the presence of IBA. Auxin increased rooting rate and percentage, reducing the average time of root protrusion in eight days. IBA also contributed to increase photosynthesis and dry root and shoot mass in 55.55 and 44.44% of the genotypes, respectively. The highest relative contribution to phenotypic diversity in the absence of auxin was rate (38.75%) and percentage (20.27%) of rooting, whereas in the presence of auxin was stomatal conductance (23.19%) and root dry mass (20.91%). Similarity was found for phenotypic and molecular divergence in the presence of IBA, in which genotypes 1 and 6; genotypes 5, 8 and 9; and genotype 3 were clustered in distinct groups.

Studies on the Role of RNA Synthesis in Auxin Induction of Cell Enlargement 1

PubMed Central

Nooden, Larry D.

1968-01-01

Selective inhibitors were used to study the connection between nucleic acid synthesis and indoleacetic acid (IAA) induction of cell enlargement. Actinomycin D (act D) and azaguanine (azaG) almost completely inhibit IAA-induced growth in aged artichoke tuber disks when they are added simultaneously with IAA. In contrast, when they are added 24 hours after the hormone, these inhibitors have little or no effect on the induced growth which continues for 48 hours or more with little or no inhibition. Inhibitors of protein synthesis still stop growth when applied 24 hours after the IAA, thus protein synthesis and presumably supporting metabolism are still essential. In corn coleoptile sections auxin-induced growth did not show any pronounced tendency to become less sensitive to act D as the IAA treatment progressed. Act D did not completely inhibit the response to IAA unless the sections were pretreated with act D for 6 hours. In contrast to act D, cordycepin produced almost complete inhibition of IAA-induced growth when added with the IAA. Although IAA has a very large and very rapid stimulatory effect (within 10 min) on incorporation of 32P-orthophosphate into RNA in disks, it did not cause a detectable change in the base composition of the RNA synthesized. Furthermore, the promotive effect could be accounted for through increased uptake of the 32P. That much of the RNA synthesis in these tissues is not necessary for auxin action is indicated by the results with fluorouracil (FU). FU strongly inhibits RNA synthesis, probably acting preferentially on ribosomal RNA synthesis, without inhibiting auxin-induced growth in the disks or coleoptile sections. FU also strongly inhibited respiration in auxin-treated disks indicating that the large promotion of respiration by auxin likewise may not be entirely necessary for growth. At least in the artichoke disks, RNA synthesis is required for auxin induction of cell enlargement and not for cell enlargement itself. The possible

PIF4 and PIF5 transcription factors link blue light and auxin to regulate the phototropic response in Arabidopsis.

PubMed

Sun, Jiaqiang; Qi, Linlin; Li, Yanan; Zhai, Qingzhe; Li, Chuanyou

2013-06-01

Both blue light (BL) and auxin are essential for phototropism in Arabidopsis thaliana. However, the mechanisms by which light is molecularly linked to auxin during phototropism remain elusive. Here, we report that phytochrome interacting factoR4 (PIF4) and PIF5 act downstream of the BL sensor phototropin1 (PHOT1) to negatively modulate phototropism in Arabidopsis. We also reveal that PIF4 and PIF5 negatively regulate auxin signaling. Furthermore, we demonstrate that PIF4 directly activates the expression of the auxin/indole-3-acetic acid (IAA) genes IAA19 and IAA29 by binding to the G-box (CACGTG) motifs in their promoters. Our genetic assays demonstrate that IAA19 and IAA29, which physically interact with auxin response factor7 (ARF7), are sufficient for PIF4 to negatively regulate auxin signaling and phototropism. This study identifies a key step of phototropic signaling in Arabidopsis by showing that PIF4 and PIF5 link light and auxin.

The influence of abscisic acid on the ethylene biosynthesis pathway in the functioning of the flower abscission zone in Lupinus luteus.

PubMed

Wilmowicz, Emilia; Frankowski, Kamil; Kućko, Agata; Świdziński, Michał; de Dios Alché, Juan; Nowakowska, Anna; Kopcewicz, Jan

2016-11-01

Flower abscission is a highly regulated developmental process activated in response to exogenous (e.g. changing environmental conditions) and endogenous stimuli (e.g. phytohormones). Ethylene (ET) and abscisic acid (ABA) are very effective stimulators of flower abortion in Lupinus luteus, which is a widely cultivated species in Poland, Australia and Mediterranean countries. In this paper, we show that artificial activation of abscission by flower removal caused an accumulation of ABA in the abscission zone (AZ). Moreover, the blocking of that phytohormone's biosynthesis by NDGA (nordihydroguaiaretic acid) decreased the number of abscised flowers. However, the application of NBD - an inhibitor of ET action - reversed the stimulatory effect of ABA on flower abscission, indicating that ABA itself is not sufficient to turn on the organ separation. Our analysis revealed that exogenous ABA significantly accelerated the transcriptional activity of the ET biosynthesis genes ACC synthase (LlACS) and oxidase (LlACO), and moreover, strongly increased the level of 1-aminocyclopropane-1-carboxylic acid (ACC) - ET precursor, which was specifically localized within AZ cells. We cannot exclude the possibility that ABA mediates flower abscission processes by enhancing the ET biosynthesis rate. The findings of our study will contribute to the overall basic knowledge on the phytohormone-regulated generative organs abscission in L. luteus. Copyright © 2016 Elsevier GmbH. All rights reserved.

α-Ketol linolenic acid (KODA) application affects endogenous abscisic acid, jasmonic acid and aromatic volatiles in grapes infected by a pathogen (Glomerella cingulata).

PubMed

Wang, Shanshan; Saito, Takanori; Ohkawa, Katsuya; Ohara, Hitoshi; Shishido, Masahiro; Ikeura, Hiromi; Takagi, Kazuteru; Ogawa, Shigeyuki; Yokoyama, Mineyuki; Kondo, Satoru

2016-03-15

Effects of α-ketol linolenic acid (KODA) application on endogenous abscisic acid (ABA), jasmonic acid (JA), and aromatic volatiles were investigated in 'Kyoho' grapes (Vitis labrusca×Vitis vinifera) infected by a pathogen (Glomerella cingulata). The expressions of 9-cis-epoxycarotenoid dioxygenase (VvNCED1), ABA 8'-hydroxylase (VvCYP707A1), lipoxygenase (VvLOX), and allene oxide synthase (VvAOS) were also examined. The grape berries were dipped in 0.1mM KODA solution before inoculation with the pathogen and stored at 25°C for 12 days. The development of infection was significantly suppressed upon KODA treatment. Endogenous ABA, JA and phaseic acid (PA) were induced in inoculated berries. KODA application before inoculation increased endogenous ABA, PA and JA through the activation of VvNCED1, VvCYP707A1 and VvAOS genes, respectively. In addition, terpenes, methyl salicylate (Me-SA) and C6-aldehydes such as (E)-2-hexenal and cis-3-hexenal associated with fungal resistance also increased in KODA-treated berries during storage. These results suggest that the synergistic effect of JA, ABA, and some aromatic volatiles induced by KODA application may provide resistance to pathogen infection in grape berries. Copyright © 2016 Elsevier GmbH. All rights reserved.

Reduced abscisic acid content is responsible for enhanced sucrose accumulation by potassium nutrition in vegetable soybean seeds.

PubMed

Tu, Bingjie; Liu, Changkai; Tian, Bowen; Zhang, Qiuying; Liu, Xiaobing; Herbert, Stephen J

2017-05-01

In order to understand the physiological mechanism of potassium (K) application in enhancing sugar content of vegetable soybean seeds, pot experiments were conducted in 2014 and 2015 with two vegetable soybean (Glycine max L. Merr.) cultivars (c.v. Zhongkemaodou 1 and c.v. 121) under normal rate of nitrogen and phosphorus application. Three potassium (K) fertilization treatments were imposed: No K application (K0), 120 kg K 2 SO 4 ha -1 at seeding (K1), and 120 kg K 2 SO 4 ha -1 at seedling + 1% K 2 SO 4 foliar application at flowering (K2). Contents of indole-3-acetic acid (IAA), gibberellins (GA), cytokinins (ZR) and abscisic acid (ABA) in seeds were determined from 4 to 8 weeks after flowering. K fertilization increased the contents of IAA, GA, ZR, soluble sugar, sucrose and fresh pod yield, but reduced ABA content consistently. When the contents of soluble sugar and sucrose reached the highest level at 7 weeks after flowering for the 2 cultivars, the contents of IAA、GA、ZR all reached the lowest level in general. The content of ABA in seed was negatively correlated with the sucrose content (P < 0.01, r = -0.749**, -0.768** in 2014 and -0.535**, -0.791** in 2015 for c.v.121 and c.v. Zhongkemaodou 1 respectively). The changes in ratio of the ABA to (IAA + GA + ZR) from 4 to 8 weeks after flowering affected by K application were coincident to the changes of sucrose accumulation. The reduced ratio of ABA/(IAA + GA + ZR) affected by K nutrition particularly reduced abscisic acid content plays a critical role in enhancing sucrose content, which might be a partial mechanism involved in K nutrition to improve the quality of vegetable soybean.

Regulation of Root Greening by Light and Auxin/Cytokinin Signaling in Arabidopsis[W

PubMed Central

Kobayashi, Koichi; Baba, Shinsuke; Obayashi, Takeshi; Sato, Mayuko; Toyooka, Kiminori; Keränen, Mika; Aro, Eva-Mari; Fukaki, Hidehiro; Ohta, Hiroyuki; Sugimoto, Keiko; Masuda, Tatsuru

2012-01-01

Tight coordination between plastid differentiation and plant development is best evidenced by the synchronized development of photosynthetic tissues and the biogenesis of chloroplasts. Here, we show that Arabidopsis thaliana roots demonstrate accelerated chlorophyll accumulation and chloroplast development when they are detached from shoots. However, this phenomenon is repressed by auxin treatment. Mutant analyses suggest that auxin transported from the shoot represses root greening via the function of INDOLE-3-ACETIC ACID14, AUXIN RESPONSE FACTOR7 (ARF7), and ARF19. Cytokinin signaling, on the contrary, is required for chlorophyll biosynthesis in roots. The regulation by auxin/cytokinin is dependent on the transcription factor LONG HYPOCOTYL5 (HY5), which is required for the expression of key chlorophyll biosynthesis genes in roots. The expression of yet another root greening transcription factor, GOLDEN2-LIKE2 (GLK2), was found to be regulated in opposing directions by auxin and cytokinin. Furthermore, both the hormone signaling and the GLK transcription factors modified the accumulation of HY5 in roots. Overexpression of GLKs in the hy5 mutant provided evidence that GLKs require HY5 to maximize their activities in root greening. We conclude that the combination of HY5 and GLKs, functioning downstream of light and auxin/cytokinin signaling pathways, is responsible for coordinated expression of the key genes in chloroplast biogenesis. PMID:22415275

Interactions between Auxin Transport and the Actin Cytoskeleton in Developmental Polarity of Fucus distichus Embryos in Response to Light and Gravity1

PubMed Central

Sun, Haiguo; Basu, Swati; Brady, Shari R.; Luciano, Randy L.; Muday, Gloria K.

2004-01-01

Land plants orient their growth relative to light and gravity through complex mechanisms that require auxin redistribution. Embryos of brown algae use similar environmental stimuli to orient their developmental polarity. These studies of the brown algae Fucus distichus examined whether auxin and auxin transport are also required during polarization in early embryos and to orient growth in already developed tissues. These embryos polarize with the gravity vector in the absence of a light cue. The auxin, indole-3-acetic acid (IAA), and auxin efflux inhibitors, such as naphthylphthalamic acid (NPA), reduced environmental polarization in response to gravity and light vectors. Young rhizoids are negatively phototropic, and NPA also inhibits rhizoid phototropism. The effect of IAA and NPA on gravity and photopolarization is maximal within 2.5 to 4.5 h after fertilization (AF). Over the first 6 h AF, auxin transport is relatively constant, suggesting that developmentally controlled sensitivity to auxin determines the narrow window during which NPA and IAA reduce environmental polarization. Actin patches were formed during the first hour AF and began to photolocalize within 3 h, coinciding with the time of NPA and IAA action. Treatment with NPA reduced the polar localization of actin patches but not patch formation. Latrunculin B prevented environmental polarization in a time frame that overlaps the formation of actin patches and IAA and NPA action. Latrunculin B also altered auxin transport. Together, these results indicate a role for auxin in the orientation of developmental polarity and suggest interactions between the actin cytoskeleton and auxin transport in F. distichus embryos. PMID:15122028

Polar auxin transport: controlling where and how much

NASA Technical Reports Server (NTRS)

Muday, G. K.; DeLong, A.; Brown, C. S. (Principal Investigator)

2001-01-01

Auxin is transported through plant tissues, moving from cell to cell in a unique polar manner. Polar auxin transport controls important growth and developmental processes in higher plants. Recent studies have identified several proteins that mediate polar auxin transport and have shown that some of these proteins are asymmetrically localized, paving the way for studies of the mechanisms that regulate auxin transport. New data indicate that reversible protein phosphorylation can control the amount of auxin transport, whereas protein secretion through Golgi-derived vesicles and interactions with the actin cytoskeleton might regulate the localization of auxin efflux complexes.

The arabidopsis thaliana AGRAVITROPIC 1 gene encodes a component of the polar-auxin-transport efflux carrier

NASA Technical Reports Server (NTRS)

Chen, R.; Hilson, P.; Sedbrook, J.; Rosen, E.; Caspar, T.; Masson, P. H.

1998-01-01

Auxins are plant hormones that mediate many aspects of plant growth and development. In higher plants, auxins are polarly transported from sites of synthesis in the shoot apex to their sites of action in the basal regions of shoots and in roots. Polar auxin transport is an important aspect of auxin functions and is mediated by cellular influx and efflux carriers. Little is known about the molecular identity of its regulatory component, the efflux carrier [Estelle, M. (1996) Current Biol. 6, 1589-1591]. Here we show that mutations in the Arabidopsis thaliana AGRAVITROPIC 1 (AGR1) gene involved in root gravitropism confer increased root-growth sensitivity to auxin and decreased sensitivity to ethylene and an auxin transport inhibitor, and cause retention of exogenously added auxin in root tip cells. We used positional cloning to show that AGR1 encodes a putative transmembrane protein whose amino acid sequence shares homologies with bacterial transporters. When expressed in Saccharomyces cerevisiae, AGR1 promotes an increased efflux of radiolabeled IAA from the cells and confers increased resistance to fluoro-IAA, a toxic IAA-derived compound. AGR1 transcripts were localized to the root distal elongation zone, a region undergoing a curvature response upon gravistimulation. We have identified several AGR1-related genes in Arabidopsis, suggesting a global role of this gene family in the control of auxin-regulated growth and developmental processes.

Supplementation with Abscisic Acid Reduces Malaria Disease Severity and Parasite Transmission

PubMed Central

Glennon, Elizabeth K. K.; Adams, L. Garry; Hicks, Derrick R.; Dehesh, Katayoon; Luckhart, Shirley

2016-01-01

Nearly half of the world's population is at risk for malaria. Increasing drug resistance has intensified the need for novel therapeutics, including treatments with intrinsic transmission-blocking properties. In this study, we demonstrate that the isoprenoid abscisic acid (ABA) modulates signaling in the mammalian host to reduce parasitemia and the formation of transmissible gametocytes and in the mosquito host to reduce parasite infection. Oral ABA supplementation in a mouse model of malaria was well tolerated and led to reduced pathology and enhanced gene expression in the liver and spleen consistent with infection recovery. Oral ABA supplementation also increased mouse plasma ABA to levels that can signal in the mosquito midgut upon blood ingestion. Accordingly, we showed that supplementation of a Plasmodium falciparum-infected blood meal with ABA increased expression of mosquito nitric oxide synthase and reduced infection prevalence in a nitric oxide-dependent manner. Identification of the mechanisms whereby ABA reduces parasite growth in mammals and mosquitoes could shed light on the balance of immunity and metabolism across eukaryotes and provide a strong foundation for clinical translation. PMID:27001761

Development of an indirect enzyme linked immunoassay for abscisic acid. [Pisum sativum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ross, G.S.; Elder, P.A.; McWha, J.A.

1987-09-01

AN INDIRECT METHOD OF ENZYME-LINKED-IMMUNOSORBENT-ASSAY (ELISA) IS REPORTED FOR ABSCISIC ACID (ABA), UTILIZING A THYROGLOBULIN-ABA CONJUGATE FOR COATING WELLS. THE ASSAY CAN USE COMMERCIALLY AVAILABLE MONOCLONAL ANTIBODIES, IS SENSITIVE TO AS LITTLE AS 20 PICOGRAMS ABA PER WELL, AND IS MUCH MORE CONSERVATIVE OF ANTIBODY THAN DIRECT METHODS. THE MOST DILUTE ABA STANDARDS DID NOT RETAIN THEIR ANTIGENICITY DURING STORAGE, SO ABA STANDARD SETS WERE DILUTED IMMEDIATELY PRIOR TO USE. THE INDIRECT ELISA WAS USED SUCCESSFULLY TO ESTIMATE ABA CONCENTRATIONS IN DEVELOPING COTYLEDONS OF PISUM SATIVUM L., AFTER ONLY LITTLE PRELIMINARY PURIFICATION. IT WAS VALIDATED FOR THIS TISSUE THROUGH THEmore » USE OF GAS CHROMATOGRAPHY-ELECTRON CAPTURE DETECTION (GC-EC), AND CAPILLARY GC-SELECTED ION MONITORING (GC-MS-SIM) USING LABELLED ABA AS AN INTERNAL STANDARD. FULL SPECTRUM GC-MASS SPECTROMETRY WAS ALSO USED TO VERIFY THAT ABA WAS PRESENT IN A SAMPLE ASSAYED QUANTITATIVELY BY BOTH ELISA AND GC-MS-SIM.« less

Abscisic acid ameliorates atherosclerosis by suppressing macrophage and CD4+ T cell recruitment into the aortic wall

PubMed Central

Guri, Amir J.; Misyak, Sarah A.; Hontecillas, Raquel; Hasty, Alyssa; Liu, Dongmin; Si, Hongwei; Bassaganya-Riera, Josep

2009-01-01

Abscisic acid (ABA) is a natural phytohormone which improves insulin sensitivity and reduces adipose tissue inflammation when supplemented into diets of obese mice. The objective of this study was to investigate the mechanisms by which abscisic acid (ABA) prevents or ameliorates atherosclerosis. Apolipoprotein E-deficient (ApoE −/−) mice were fed high-fat diets with or without ABA for 84 days. Systolic blood pressure was assessed on days 0, 28, 56, and 72. Gene expression, immune cell infiltration, and histological lesions were evaluated in the aortic root wall. Human aortic endothelial cells were used to examine the effect of ABA on 3’, 5’-cyclic adenosine monophosphate (cAMP) and nitric oxide (NO) production in vitro. We report that ABA-treated mice had significantly improved systolic blood pressure and decreased accumulation of F4/80+CD11b+ macrophages and CD4+ T cells in aortic root walls. At the molecular level, ABA significantly enhanced aortic endothelial nitric oxide synthase (eNOS) and tended to suppress aortic vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1 (MCP-1) expression and plasma MCP-1 concentrations. ABA also caused a dose-dependent increase in intracellular concentrations of cAMP and NO and upregulated eNOS mRNA expression in human aortic endothelial cells. This is the first report showing that ABA prevents or ameliorates atherosclerosis-induced hypertension, immune cell recruitment into the aortic root wall, and upregulates aortic eNOS expression in ApoE−/− mice. PMID:20092994

A genomics approach to understanding the role of auxin in apple (Malus x domestica) fruit size control.

PubMed

Devoghalaere, Fanny; Doucen, Thomas; Guitton, Baptiste; Keeling, Jeannette; Payne, Wendy; Ling, Toby John; Ross, John James; Hallett, Ian Charles; Gunaseelan, Kularajathevan; Dayatilake, G A; Diak, Robert; Breen, Ken C; Tustin, D Stuart; Costes, Evelyne; Chagné, David; Schaffer, Robert James; David, Karine Myriam

2012-01-13

Auxin is an important phytohormone for fleshy fruit development, having been shown to be involved in the initial signal for fertilisation, fruit size through the control of cell division and cell expansion, and ripening related events. There is considerable knowledge of auxin-related genes, mostly from work in model species. With the apple genome now available, it is possible to carry out genomics studies on auxin-related genes to identify genes that may play roles in specific stages of apple fruit development. High amounts of auxin in the seed compared with the fruit cortex were observed in 'Royal Gala' apples, with amounts increasing through fruit development. Injection of exogenous auxin into developing apples at the start of cell expansion caused an increase in cell size. An expression analysis screen of auxin-related genes involved in auxin reception, homeostasis, and transcriptional regulation showed complex patterns of expression in each class of gene. Two mapping populations were phenotyped for fruit size over multiple seasons, and multiple quantitative trait loci (QTLs) were observed. One QTL mapped to a region containing an Auxin Response Factor (ARF106). This gene is expressed during cell division and cell expansion stages, consistent with a potential role in the control of fruit size. The application of exogenous auxin to apples increased cell expansion, suggesting that endogenous auxin concentrations are at least one of the limiting factors controlling fruit size. The expression analysis of ARF106 linked to a strong QTL for fruit weight suggests that the auxin signal regulating fruit size could partially be modulated through the function of this gene. One class of gene (GH3) removes free auxin by conjugation to amino acids. The lower expression of these GH3 genes during rapid fruit expansion is consistent with the apple maximising auxin concentrations at this point.

A genomics approach to understanding the role of auxin in apple (Malus x domestica) fruit size control

PubMed Central

2012-01-01

Background Auxin is an important phytohormone for fleshy fruit development, having been shown to be involved in the initial signal for fertilisation, fruit size through the control of cell division and cell expansion, and ripening related events. There is considerable knowledge of auxin-related genes, mostly from work in model species. With the apple genome now available, it is possible to carry out genomics studies on auxin-related genes to identify genes that may play roles in specific stages of apple fruit development. Results High amounts of auxin in the seed compared with the fruit cortex were observed in 'Royal Gala' apples, with amounts increasing through fruit development. Injection of exogenous auxin into developing apples at the start of cell expansion caused an increase in cell size. An expression analysis screen of auxin-related genes involved in auxin reception, homeostasis, and transcriptional regulation showed complex patterns of expression in each class of gene. Two mapping populations were phenotyped for fruit size over multiple seasons, and multiple quantitative trait loci (QTLs) were observed. One QTL mapped to a region containing an Auxin Response Factor (ARF106). This gene is expressed during cell division and cell expansion stages, consistent with a potential role in the control of fruit size. Conclusions The application of exogenous auxin to apples increased cell expansion, suggesting that endogenous auxin concentrations are at least one of the limiting factors controlling fruit size. The expression analysis of ARF106 linked to a strong QTL for fruit weight suggests that the auxin signal regulating fruit size could partially be modulated through the function of this gene. One class of gene (GH3) removes free auxin by conjugation to amino acids. The lower expression of these GH3 genes during rapid fruit expansion is consistent with the apple maximising auxin concentrations at this point. PMID:22243694

Viability of Azotobacter consortium in auxin production

NASA Astrophysics Data System (ADS)

Zulaika, Enny; Solikhah, Farihatus; Alami, Nur Hidayatul; Kuswytasari, Nengah Dwianita; Shovitri, Maya

2017-06-01

Azotobacter is a kind of rhizobacteria which is abundant in soil and having beneficial for plants due to its ability to produce auxin. Each isolated Azotobacter from Eco Urban Farming ITS were able to produce auxin individually. However, the isolated Azotobacter consortium was prefer to produce more auxin than the individual one. Synergism test were carried out in order to verify non-antagonism among Azotobacter isolates. Auxin production test was conducted by inoculating 100 ml of Azotobacter consortium starter in 400 ml nutrient broth by addition of 1.000 ppm of L-tryptophan while shaking 100 rpm in rotary shaker at room temperature for 8 weeks. Auxin concentration was measured spectrophotometrically according to the Salkowski method. The Azotobacter consortium showed living synergistically and able to produce 1,82 ppm auxin in 2 hours incubation time although the concentration was tend to decrease periodically.

Control of seed dormancy in Nicotiana plumbaginifolia: post-imbibition abscisic acid synthesis imposes dormancy maintenance.

PubMed

Grappin, P; Bouinot, D; Sotta, B; Miginiac, E; Jullien, M

2000-01-01

The physiological characteristics of seed dormancy in Nicotiana plumbaginifolia Viv. are described. The level of seed dormancy is defined by the delay in seed germination (i.e the time required prior to germination) under favourable environmental conditions. A wild-type line shows a clear primary dormancy, which is suppressed by afterripening, whereas an abscisic acid (ABA)-deficient mutant shows a non-dormant phenotype. We have investigated the role of ABA and gibberellic acid (GA(3)) in the control of dormancy maintenance or breakage during imbibition in suitable conditions. It was found that fluridone, a carotenoid biosynthesis inhibitor, is almost as efficient as GA(3) in breaking dormancy. Dry dormant seeds contained more ABA than dry afterripened seeds and, during early imbibition, there was an accumulation of ABA in dormant seeds, but not in afterripened seeds. In addition, fluridone and exogenous GA(3) inhibited the accumulation of ABA in imbibed dormant seeds. This reveals an important role for ABA synthesis in dormancy maintenance in imbibed seeds.

Auxin modulates the enhanced development of root hairs in Arabidopsis thaliana (L.) Heynh. under elevated CO(2).

PubMed

Niu, Yaofang; Jin, Chongwei; Jin, Gulei; Zhou, Qingyan; Lin, Xianyong; Tang, Caixian; Zhang, Yongsong

2011-08-01

Root hairs may play a critical role in nutrient acquisition of plants grown under elevated CO(2) . This study investigated how elevated CO(2) enhanced the development of root hairs in Arabidopsis thaliana (L.) Heynh. The plants under elevated CO(2) (800 µL L(-1)) had denser and longer root hairs, and more H-positioned cells in root epidermis than those under ambient CO(2) (350 µL L(-1)). The elevated CO(2) increased auxin production in roots. Under elevated CO(2) , application of either 1-naphthoxyacetic acid (1-NOA) or N-1-naphthylphthalamic acid (NPA) blocked the enhanced development of root hairs. The opposite was true when the plants under ambient CO(2) were treated with 1-naphthylacetic acid (NAA), an auxin analogue. Furthermore, the elevated CO(2) did not enhance the development of root hairs in auxin-response mutants, axr1-3, and auxin-transporter mutants, axr4-1, aux1-7 and pin1-1. Both elevated CO(2) and NAA application increased expressions of caprice, triptychon and rho-related protein from plants 2, and decreased expressions of werewolf, GLABRA2, GLABRA3 and the transparent testa glabra 1, genes related to root-hair development, while 1-NOA and NPA application had an opposite effect. Our study suggests that elevated CO(2) enhanced the development of root hairs in Arabidopsis via the well-characterized auxin signalling and transport that modulate the initiation of root hairs and the expression of its specific genes. © 2011 Blackwell Publishing Ltd.

Mutations in the Arabidopsis Lst8 and Raptor genes encoding partners of the TOR complex, or inhibition of TOR activity decrease abscisic acid (ABA) synthesis.

PubMed

Kravchenko, Alena; Citerne, Sylvie; Jéhanno, Isabelle; Bersimbaev, Rakhmetkazhi I; Veit, Bruce; Meyer, Christian; Leprince, Anne-Sophie

2015-11-27

The Target of Rapamycin (TOR) kinase regulates essential processes in plant growth and development by modulation of metabolism and translation in response to environmental signals. In this study, we show that abscisic acid (ABA) metabolism is also regulated by the TOR kinase. Indeed ABA hormone level strongly decreases in Lst8-1 and Raptor3g mutant lines as well as in wild-type (WT) Arabidopsis plants treated with AZD-8055, a TOR inhibitor. However the growth and germination of these lines are more sensitive to exogenous ABA. The diminished ABA hormone accumulation is correlated with lower transcript levels of ZEP, NCED3 and AAO3 biosynthetic enzymes, and higher transcript amount of the CYP707A2 gene encoding a key-enzyme in abscisic acid catabolism. These results suggest that the TOR signaling pathway is implicated in the regulation of ABA accumulation in Arabidopsis. Copyright © 2015 Elsevier Inc. All rights reserved.

Seed-specific overexpression of an endogenous Arabidopsis phytoene synthase gene results in delayed germination and increased levels of carotenoids, chlorophyll, and abscisic acid.

PubMed

Lindgren, L Ove; Stålberg, Kjell G; Höglund, Anna-Stina

2003-06-01

Phytoene synthase catalyzes the dimerization of two molecules of geranylgeranyl pyrophosphate to phytoene and has been shown to be rate limiting for the synthesis of carotenoids. To elucidate if the capacity to produce phytoene is limiting also in the seed of Arabidopsis (Wassilewskija), a gene coding for an endogenous phytoene synthase was cloned and coupled to a seed-specific promoter, and the effects of the overexpression were examined. The resulting transgenic plants produced darker seeds, and extracts from the seed of five overexpressing plants had a 43-fold average increase of beta-carotene and a total average amount of beta-carotene of approximately 260 microg g-1 fresh weight. Lutein, violaxanthin, and chlorophyll were significantly increased, whereas the levels of zeaxanthin only increased by a factor 1.1. In addition, substantial levels of lycopene and alpha-carotene were produced in the seeds, whereas only trace amounts were found in the control plants. Seeds from the transgenic plants exhibited delayed germination, and the degree of delay was positively correlated with the increased levels of carotenoids. The abscisic acid levels followed the increase of the carotenoids, and plants having the highest carotenoid levels also had the highest abscisic acid content. Addition of gibberellic acid to the growth medium only partly restored germination of the transgenic seeds.

Characterization of the growth and auxin physiology of roots of the tomato mutant, diageotropica

NASA Technical Reports Server (NTRS)

Muday, G. K.; Lomax, T. L.; Rayle, D. L.

1995-01-01

Roots of the tomato (Lycopersicon esculentum, Mill.) mutant (diageotropica (dgt) exhibit an altered phenotype. These roots are agravitropic and lack lateral roots. Relative to wild-type (VFN8) roots, dgt roots are less sensitive to growth inhibition by exogenously applied IAA and auxin transport inhibitors (phytotropins), and the roots exhibit a reduction in maximal growth inhibition in response to ethylene. However, IAA transport through roots, binding of the phytotropin, tritiated naphthylphthalamic acid ([3H]NPA), to root microsomal membranes, NPA-sensitive IAA uptake by root segments, and uptake of [3H]NPA into root segments are all similar in mutant and wild-type roots. We speculate that the reduced sensitivity of dgt root growth to auxin-transport inhibitors and ethylene is an indirect result of the reduction in sensitivity to auxin in this single gene, recessive mutant. We conclude that dgt roots, like dgt shoots, exhibit abnormalities indicating they have a defect associated with or affecting a primary site of auxin perception or action.

A Simple Auxin Transcriptional Response System Regulates Multiple Morphogenetic Processes in the Liverwort Marchantia polymorpha

PubMed Central

Flores-Sandoval, Eduardo; Eklund, D. Magnus; Bowman, John L.

2015-01-01

In land plants comparative genomics has revealed that members of basal lineages share a common set of transcription factors with the derived flowering plants, despite sharing few homologous structures. The plant hormone auxin has been implicated in many facets of development in both basal and derived lineages of land plants. We functionally characterized the auxin transcriptional response machinery in the liverwort Marchantia polymorpha, a member of the basal lineage of extant land plants. All components known from flowering plant systems are present in M. polymorpha, but they exist as single orthologs: a single MpTOPLESS (TPL) corepressor, a single MpTRANSPORT INHIBITOR RESPONSE 1 auxin receptor, single orthologs of each class of AUXIN RESPONSE FACTOR (ARF; MpARF1, MpARF2, MpARF3), and a single negative regulator AUXIN/INDOLE-3-ACETIC ACID (MpIAA). Phylogenetic analyses suggest this simple system is the ancestral condition for land plants. We experimentally demonstrate that these genes act in an auxin response pathway — chimeric fusions of the MpTPL corepressor with heterodimerization domains of MpARF1, MpARF2, or their negative regulator, MpIAA, generate auxin insensitive plants that lack the capacity to pattern and transition into mature stages of development. Our results indicate auxin mediated transcriptional regulation acts as a facilitator of branching, differentiation and growth, rather than acting to determine or specify tissues during the haploid stage of the M. polymorpha life cycle. We hypothesize that the ancestral role of auxin is to modulate a balance of differentiated and pluri- or totipotent cell states, whose fates are determined by interactions with combinations of unrelated transcription factors. PMID:26020649

Identification and functional analysis of two alternatively spliced transcripts of ABSCISIC ACID INSENSITIVE3 (ABI3) in linseed flax (Linum usitatissimum L.).

PubMed

Wang, Yanyan; Zhang, Tianbao; Song, Xiaxia; Zhang, Jianping; Dang, Zhanhai; Pei, Xinwu; Long, Yan

2018-01-01

Alternative splicing is a popular phenomenon in different types of plants. It can produce alternative spliced transcripts that encode proteins with altered functions. Previous studies have shown that one transcription factor, ABSCISIC ACID INSENSITIVE3 (ABI3), which encodes an important component in abscisic acid (ABA) signaling, is subjected to alternative splicing in both mono- and dicotyledons. In the current study, we identified two homologs of ABI3 in the genome of linseed flax. We screened two alternatively spliced flax LuABI3 transcripts, LuABI3-2 and LuABI3-3, and one normal flax LuABI3 transcript, LuABI3-1. Sequence analysis revealed that one of the alternatively spliced transcripts, LuABI3-3, retained a 6 bp intron. RNA accumulation analysis showed that all three transcripts were expressed during seed development, while subcellular localization and transgene experiments showed that LuABI3-3 had no biological function. The two normal transcripts, LuABI3-1 and LuABI3-2, are the important functional isoforms in flax and play significant roles in the ABA regulatory pathway during seed development, germination, and maturation.

Gravity-stimulated changes in auxin and invertase gene expression in maize pulvinal cells

NASA Technical Reports Server (NTRS)

Long, Joanne C.; Zhao, Wei; Rashotte, Aaron M.; Muday, Gloria K.; Huber, Steven C.; Brown, C. S. (Principal Investigator)

2002-01-01

Maize (Zea mays) stem gravitropism involves differential elongation of cells within a highly specialized region, the stem internodal pulvinus. In the present study, we investigated factors that control gravitropic responses in this system. In the graviresponding pulvinus, hexose sugars (D-Glc and D-Fru) accumulated asymmetrically across the pulvinus. This correlated well with an asymmetric increase in acid invertase activity across the pulvinus. Northern analyses revealed asymmetric induction of one maize acid invertase gene, Ivr2, consistent with transcriptional regulation by gravistimulation. Several lines of evidence indicated that auxin redistribution, as a result of polar auxin transport, is necessary for gravity-stimulated Ivr2 transcript accumulation and differential cell elongation across the maize pulvinus. First, the auxin transport inhibitor, N-1-naphthylphthalamic acid, inhibited gravistimulated curvature and Ivr2 transcript accumulation. Second, a transient gradient of free indole-3-acetic acid (IAA) across the pulvinus was apparent shortly after initiation of gravistimulation. This temporarily free IAA gradient appears to be important for differential cell elongation and Ivr2 transcript accumulation. This is based on the observation that N-1-naphthylphthalamic acid will not inhibit gravitropic responses when applied to pulvinus tissue after the free IAA gradient peak has occurred. Third, IAA alone can stimulate Ivr2 transcript accumulation in non-gravistimulated pulvini. The gravity- and IAA-stimulated increase in Ivr2 transcripts was sensitive to the protein synthesis inhibitor, cycloheximide. Based on these results, a two-phase model describing possible relationships between gravitropic curvature, IAA redistribution, and Ivr2 expression is presented.

Influence of abscisic acid on growth, biomass and lipid yield of Scenedesmus quadricauda under nitrogen starved condition.

PubMed

Sulochana, Sujitha Balakrishnan; Arumugam, Muthu

2016-08-01

Scenedesmus quadricauda, accumulated more lipid but with a drastic reduction in biomass yield during nitrogen starvation. Abscisic acid (ABA) being a stress responsible hormone, its effect on growth and biomass with sustainable lipid yield during nitrogen depletion was studied. The result revealed that the ABA level shoots up at 24h (27.21pmol/L) during the onset of nitrogen starvation followed by a sharp decline. The external supplemented ABA showed a positive effect on growth pattern (38×10(6)cells/ml) at a lower concentration. The dry biomass yield is also increasing up to 2.1 fold compared to nitrogen deficient S. quadricauda. The lipid content sustains in 1 and 2μM concentration of ABA under nitrogen-deficient condition. The fatty acid composition of ABA treated S. quadricauda cultures with respect to nitrogen-starved cells showed 11.17% increment in saturated fatty acid content, the desired lipid composition for biofuel application. Copyright © 2016 Elsevier Ltd. All rights reserved.

PLETHORA gradient formation mechanism separates auxin responses.

PubMed

Mähönen, Ari Pekka; Ten Tusscher, Kirsten; Siligato, Riccardo; Smetana, Ondřej; Díaz-Triviño, Sara; Salojärvi, Jarkko; Wachsman, Guy; Prasad, Kalika; Heidstra, Renze; Scheres, Ben

2014-11-06

During plant growth, dividing cells in meristems must coordinate transitions from division to expansion and differentiation, thus generating three distinct developmental zones: the meristem, elongation zone and differentiation zone. Simultaneously, plants display tropisms, rapid adjustments of their direction of growth to adapt to environmental conditions. It is unclear how stable zonation is maintained during transient adjustments in growth direction. In Arabidopsis roots, many aspects of zonation are controlled by the phytohormone auxin and auxin-induced PLETHORA (PLT) transcription factors, both of which display a graded distribution with a maximum near the root tip. In addition, auxin is also pivotal for tropic responses. Here, using an iterative experimental and computational approach, we show how an interplay between auxin and PLTs controls zonation and gravitropism. We find that the PLT gradient is not a direct, proportionate readout of the auxin gradient. Rather, prolonged high auxin levels generate a narrow PLT transcription domain from which a gradient of PLT protein is subsequently generated through slow growth dilution and cell-to-cell movement. The resulting PLT levels define the location of developmental zones. In addition to slowly promoting PLT transcription, auxin also rapidly influences division, expansion and differentiation rates. We demonstrate how this specific regulatory design in which auxin cooperates with PLTs through different mechanisms and on different timescales enables both the fast tropic environmental responses and stable zonation dynamics necessary for coordinated cell differentiation.

Genetic and chemical reductions in protein phosphatase activity alter auxin transport, gravity response, and lateral root growth

NASA Technical Reports Server (NTRS)

Rashotte, A. M.; DeLong, A.; Muday, G. K.; Brown, C. S. (Principal Investigator)

2001-01-01

Auxin transport is required for important growth and developmental processes in plants, including gravity response and lateral root growth. Several lines of evidence suggest that reversible protein phosphorylation regulates auxin transport. Arabidopsis rcn1 mutant seedlings exhibit reduced protein phosphatase 2A activity and defects in differential cell elongation. Here we report that reduced phosphatase activity alters auxin transport and dependent physiological processes in the seedling root. Root basipetal transport was increased in rcn1 or phosphatase inhibitor-treated seedlings but showed normal sensitivity to the auxin transport inhibitor naphthylphthalamic acid (NPA). Phosphatase inhibition reduced root gravity response and delayed the establishment of differential auxin-induced gene expression across a gravity-stimulated root tip. An NPA treatment that reduced basipetal transport in rcn1 and cantharidin-treated wild-type plants also restored a normal gravity response and asymmetric auxin-induced gene expression, indicating that increased basipetal auxin transport impedes gravitropism. Increased auxin transport in rcn1 or phosphatase inhibitor-treated seedlings did not require the AGR1/EIR1/PIN2/WAV6 or AUX1 gene products. In contrast to basipetal transport, root acropetal transport was normal in phosphatase-inhibited seedlings in the absence of NPA, although it showed reduced NPA sensitivity. Lateral root growth also exhibited reduced NPA sensitivity in rcn1 seedlings, consistent with acropetal transport controlling lateral root growth. These results support the role of protein phosphorylation in regulating auxin transport and suggest that the acropetal and basipetal auxin transport streams are differentially regulated.

Auxin Does Not Alter the Permeability of Pea Segments to Tritium-labeled Water.

PubMed

Dowler, M J; Rayle, D L

1974-02-01

The possibility of an auxin effect on the permeability of pea (Pisum sativum L. ev. Alaska) segments to tritium-labeled water has been investigated by three separate laboratories, and the combined results are presented. We were unable to obtain any indication of a rapid effect of indoleacetic acid on the efflux of (3)HHO when pea segments previously "loaded" for 90 minutes with (3)HHO were transferred to unlabeled aqueous medium with indoleacetic acid. We were able to confirm that segments pretreated with (3)HHO plus indoleacetic acid for 60 to 90 minutes can show an enhanced (3)HHO release as compared with minus indoleacetic acid controls. However, this phenomenon appears to be due to an increased uptake of (3)HHO during the prolonged indoleacetic acid pretreatment, and therefore we conclude that auxin does not alter the permeability of pea segments to (3)HHO in either short term or long term tests. We confirm previous reports that the uptake of (3)HHO in pea segments proceeds largely through the cut surfaces, and that the cuticle is a potent barrier to (3)HHO flux.

Effects of ethylene on the kinetics of curvature and auxin redistribution in gravistimulated roots of Zea mays

NASA Technical Reports Server (NTRS)

Lee, J. S.; Evans, M. L.

1990-01-01

We tested the involvement of ethylene in maize (Zea mays L.) root gravitropism by measuring the kinetics of curvature and lateral auxin movement in roots treated with ethylene, inhibitors of ethylene synthesis, or inhibitors of ethylene action. In the presence of ethylene the latent period of gravitropic curvature appeared to be increased somewhat. However, ethylene-treated roots continued to curve after control roots had reached their final angle of curvature. Consequently, maximum curvature in the presence of ethylene was much greater in ethylene-treated roots than in controls. Inhibitors of ethylene biosynthesis or action had effects on the kinetics of curvature opposite to that of ethylene, i.e. the latent period appeared to be shortened somewhat while total curvature was reduced relative to that of controls. Label from applied 3H-indole-3-acetic acid was preferentially transported toward the lower side of stimulated roots. In parallel with effects on curvature, ethylene treatment delayed the development of gravity-induced asymmetric auxin movement across the root but extended its duration once initiated. The auxin transport inhibitor, 1-N-naphthylphthalamic acid reduced both gravitropic curvature and the effect of ethylene on curvature. Since neither ethylene nor inhibitors of ethylene biosynthesis or action prevented curvature, we conclude that ethylene does not mediate the primary differential growth response causing curvature. Because ethylene affects curvature and auxin transport in parallel, we suggest that ethylene modifies curvature by affecting gravity-induced lateral transport of auxin, perhaps by interfering with adaptation of the auxin transport system to the gravistimulus.

The effects of abscisic acid, salicylic acid and jasmonic acid on lipid accumulation in two freshwater Chlorella strains.

PubMed

Wu, Guanxun; Gao, Zhengquan; Du, Huanmin; Lin, Bin; Yan, Yuchen; Li, Guoqiang; Guo, Yanyun; Fu, Shenggui; Wei, Gongxiang; Wang, Miaomiao; Cui, Meng; Meng, Chunxiao

2018-03-27

Sustainable renewable energy is being hotly debated globally because the continued use of finite fossil fuels is now widely recognized as being unsustainable. Microalgae potentially offer great opportunities for resolving this challenge. Abscisic acid (ABA), jasmonic acid (JA) and salicylic acid (SA) are involved in regulating many physiological properties and have been widely used in higher plants. To test if phytohormones have an impact on accumulating lipid for microalgae, ABA, JA and SA were used to induce two Chlorella strains in the present study. The results showed 1.0 mg/L ABA, 10 mg/L SA, and 0.5 mg/L JA, led strain C. vulgaris ZF strain to produce a 45%, 42% and 49% lipid content that was 1.8-, 1.7- and 2.0-fold that of controls, respectively. For FACHB 31 (number 31 of the Freshwater Algae Culture Collection at the Institute of Hydrobiology, Chinese Academy of Sciences), the addition of 1.0 mg/L ABA, 10 mg/L SA, and 0.5 mg/L, JA produced 33%, 30% and 38% lipid content, which was 1.8-, 1.6- and 2.1-fold that of controls, respectively. As for lipid productivity, 1.0 mg/L ABA increased the lipid productivity of C. vulgaris ZF strain and FACHB-31 by 123% and 44%; 10 mg/L SA enhanced lipid productivity by 100% and 33%; the best elicitor, 0.5 mg/L JA, augmented lipid productivity by 127% and 75% compared to that of controls, respectively. The results above suggest that the three phytohormones at physiological concentrations play crucial roles in inducing lipid accumulation in Chlorella.

Abscisic acid negatively regulates elicitor-induced synthesis of capsidiol in wild tobacco.

PubMed

Mialoundama, Alexis Samba; Heintz, Dimitri; Debayle, Delphine; Rahier, Alain; Camara, Bilal; Bouvier, Florence

2009-07-01

In the Solanaceae, biotic and abiotic elicitors induce de novo synthesis of sesquiterpenoid stress metabolites known as phytoalexins. Because plant hormones play critical roles in the induction of defense-responsive genes, we have explored the effect of abscisic acid (ABA) on the synthesis of capsidiol, the major wild tobacco (Nicotiana plumbaginifolia) sesquiterpenoid phytoalexin, using wild-type plants versus nonallelic mutants Npaba2 and Npaba1 that are deficient in ABA synthesis. Npaba2 and Npaba1 mutants exhibited a 2-fold higher synthesis of capsidiol than wild-type plants when elicited with either cellulase or arachidonic acid or when infected by Botrytis cinerea. The same trend was observed for the expression of the capsidiol biosynthetic genes 5-epi-aristolochene synthase and 5-epi-aristolochene hydroxylase. Treatment of wild-type plants with fluridone, an inhibitor of the upstream ABA pathway, recapitulated the behavior of Npaba2 and Npaba1 mutants, while the application of exogenous ABA reversed the enhanced synthesis of capsidiol in Npaba2 and Npaba1 mutants. Concomitant with the production of capsidiol, we observed the induction of ABA 8'-hydroxylase in elicited plants. In wild-type plants, the induction of ABA 8'-hydroxylase coincided with a decrease in ABA content and with the accumulation of ABA catabolic products such as phaseic acid and dihydrophaseic acid, suggesting a negative regulation exerted by ABA on capsidiol synthesis. Collectively, our data indicate that ABA is not required per se for the induction of capsidiol synthesis but is essentially implicated in a stress-response checkpoint to fine-tune the amplification of capsidiol synthesis in challenged plants.

Alteration in Auxin Homeostasis and Signaling by Overexpression Of PINOID Kinase Causes Leaf Growth Defects in Arabidopsis thaliana

PubMed Central

Saini, Kumud; Markakis, Marios N.; Zdanio, Malgorzata; Balcerowicz, Daria M.; Beeckman, Tom; De Veylder, Lieven; Prinsen, Els; Beemster, Gerrit T. S.; Vissenberg, Kris

2017-01-01

In plants many developmental processes are regulated by auxin and its directional transport. PINOID (PID) kinase helps to regulate this transport by influencing polar recruitment of PIN efflux proteins on the cellular membranes. We investigated how altered auxin levels affect leaf growth in Arabidopsis thaliana. Arabidopsis mutants and transgenic plants with altered PID expression levels were used to study the effect on auxin distribution and leaf development. Single knockouts showed small pleiotropic growth defects. Contrastingly, several leaf phenotypes related to changes in auxin concentrations and transcriptional activity were observed in PID overexpression (PIDOE) lines. Unlike in the knockout lines, the leaves of PIDOE lines showed an elevation in total indole-3-acetic acid (IAA). Accordingly, enhanced DR5-visualized auxin responses were detected, especially along the leaf margins. Kinematic analysis revealed that ectopic expression of PID negatively affects cell proliferation and expansion rates, yielding reduced cell numbers and small-sized cells in the PIDOE leaves. We used PIDOE lines as a tool to study auxin dose effects on leaf development and demonstrate that auxin, above a certain threshold, has a negative affect on leaf growth. RNA sequencing further showed how subtle PIDOE-related changes in auxin levels lead to transcriptional reprogramming of cellular processes. PMID:28659952

Abscisic Acid as Pathogen Effector and Immune Regulator

PubMed Central

Lievens, Laurens; Pollier, Jacob; Goossens, Alain; Beyaert, Rudi; Staal, Jens

2017-01-01

Abscisic acid (ABA) is a sesquiterpene signaling molecule produced in all kingdoms of life. To date, the best known functions of ABA are derived from its role as a major phytohormone in plant abiotic stress resistance. Different organisms have developed different biosynthesis and signal transduction pathways related to ABA. Despite this, there are also intriguing common themes where ABA often suppresses host immune responses and is utilized by pathogens as an effector molecule. ABA also seems to play an important role in compatible mutualistic interactions such as mycorrhiza and rhizosphere bacteria with plants, and possibly also the animal gut microbiome. The frequent use of ABA in inter-species communication could be a possible reason for the wide distribution and re-invention of ABA as a signaling molecule in different organisms. In humans and animal models, it has been shown that ABA treatment or nutrient-derived ABA is beneficial in inflammatory diseases like colitis and type 2 diabetes, which confer potential to ABA as an interesting nutraceutical or pharmacognostic drug. The anti-inflammatory activity, cellular metabolic reprogramming, and other beneficial physiological and psychological effects of ABA treatment in humans and animal models has sparked an interest in this molecule and its signaling pathway as a novel pharmacological target. In contrast to plants, however, very little is known about the ABA biosynthesis and signaling in other organisms. Genes, tools and knowledge about ABA from plant sciences and studies of phytopathogenic fungi might benefit biomedical studies on the physiological role of endogenously generated ABA in humans. PMID:28469630

Abscisic Acid: A Novel Nutraceutical for Glycemic Control

PubMed Central

Zocchi, Elena; Hontecillas, Raquel; Leber, Andrew; Einerhand, Alexandra; Carbo, Adria; Bruzzone, Santina; Tubau-Juni, Nuria; Philipson, Noah; Zoccoli-Rodriguez, Victoria; Sturla, Laura; Bassaganya-Riera, Josep

2017-01-01

Abscisic acid is naturally present in fruits and vegetables, and it plays an important role in managing glucose homeostasis in humans. According to the latest U.S. dietary survey, about 92% of the population might have a deficient intake of ABA due to their deficient intake of fruits and vegetables. This review summarizes the in vitro, preclinical, mechanistic, and human translational findings obtained over the past 15 years in the study of the role of ABA in glycemic control. In 2007, dietary ABA was first reported to ameliorate glucose tolerance and obesity-related inflammation in mice. The most recent findings regarding the topic of ABA and its proposed receptor lanthionine synthetase C-like 2 in glycemic control and their interplay with insulin and glucagon-like peptide-1 suggest a major role for ABA in the physiological response to a glucose load in humans. Moreover, emerging evidence suggests that the ABA response might be dysfunctional in diabetic subjects. Follow on intervention studies in healthy individuals show that low-dose dietary ABA administration exerts a beneficial effect on the glycemia and insulinemia profiles after oral glucose load. These recent findings showing benefits in humans, together with extensive efficacy data in mouse models of diabetes and inflammatory disease, suggest the need for reference ABA values and its possible exploitation of the glycemia-lowering effects of ABA for preventative purposes. Larger clinical studies on healthy, prediabetic, and diabetic subjects are needed to determine whether addressing the widespread dietary ABA deficiency improves glucose control in humans. PMID:28660193

Growth and graviresponsiveness of primary roots of Zea mays seedlings deficient in abscisic acid and gibberellic acid

NASA Technical Reports Server (NTRS)

Moore, R.; Dickey, K.

1985-01-01

The objective of this research was to determine if gibberellic acid (GA) and/or abscisic acid (ABA) are necessary for graviresponsiveness by primary roots of Zea mays. To accomplish this objective we measured the growth and graviresponsiveness of primary roots of seedlings in which the synthesis of ABA and GA was inhibited collectively and individually by genetic and chemical means. Roots of seedlings treated with Fluridone (an inhibitor of ABA biosynthesis) and Ancymidol (an inhibitor of GA biosynthesis) were characterized by slower growth rates but not significantly different gravicultures as compared to untreated controls. Gravicurvatures of primary roots of d-5 mutants (having undetectable levels of GA) and vp-9 mutants (having undectable levels of ABA) were not significantly different from those of wild-type seedlings. Roots of seedlings in which the biosynthesis of ABA and GA was collectively inhibited were characterized by gravicurvatures not significantly different for those of controls. These results (1) indicate that drastic reductions in the amount of ABA and GA in Z. mays seedlings do not significantly alter root graviresponsiveness, (2) suggest that neither ABA nor GA is necessary for root gravicurvature, and (3) indicate that root gravicurvature is not necessarily proportional to root elongation.

A gradient of auxin and auxin-dependent transcription precedes tropic growth responses.

PubMed

Esmon, C Alex; Tinsley, Amanda G; Ljung, Karin; Sandberg, Goran; Hearne, Leonard B; Liscum, Emmanuel

2006-01-03

Plants, although sessile, can reorient growth axes in response to changing environmental conditions. Phototropism and gravitropism represent adaptive growth responses induced by changes in light direction and growth axis orientation relative to gravitational direction, respectively. The nearly 80-year-old Cholodny-Went theory [Went, F. W. & Thimann, K. V. (1937) Phytohormones (Macmillan, New York)] predicts that formation of a gradient of the plant morphogen auxin is central to the establishment of tropic curvature. Loss of tropic responses in seedling stems of Arabidopsis thaliana mutants lacking the auxin-regulated transcriptional activator NPH4/ARF7 has further suggested that a gradient of gene expression represents an essential output from the auxin gradient. Yet the molecular identities of such output components, which are likely to encode proteins directly involved in growth control, have remained elusive. Here we report the discovery of a suite of tropic stimulus-induced genes in Brassica oleracea that are responsive to an auxin gradient and exhibit morphologically graded expression concomitant with, or before, observable curvature responses. These results provide compelling molecular support for the Cholodny-Went theory and suggest that morphologically graded transcription represents an important mechanism for interpreting tropically stimulated gradients of auxin. Intriguingly, two of the tropic stimulus-induced genes, EXPA1 and EXPA8, encode enzymes involved in cell wall extension, a response prerequisite for differential growth leading to curvatures, and are up-regulated before curvature in the flank that will elongate. This observation suggests that morphologically graded transcription likely leads to the graded expression of proteins whose activities can directly regulate the establishment and modulation of tropic curvatures.

Low irradiances affect abscisic acid, indole-3-acidic acid, and cytokinin levels of wheat (Triticum aestivum L.) tissues

NASA Technical Reports Server (NTRS)

Nan, R.; Carman, J. G.; Salisbury, F. B.

1999-01-01

Wheat (Triticum aestivum L.) plants were grown under four irradiance levels: 1,400, 400, 200, and 100 micromol m-2 s-1. Leaves and roots were sampled before, during, and after the boot stage, and levels of abscisic acid (ABA), indole-3-acetic acid (IAA), zeatin, zeatin riboside, dihydrozeatin, dihydrozeatin riboside, isopentenyl adenine, and isopentenyl adenosine were quantified using noncompetitive indirect ELISA systems. Levels of IAA in leaves and roots of plants exposed to 100 micromol m-2 s-1 of irradiance were 0.7 and 2.9 micromol kg-1 dry mass (DM), respectively. These levels were 0.2 and 1.0 micromol kg-1 DM, respectively, when plants were exposed to 1,400 micromol m-2 s-1. Levels of ABA in leaves and roots of plants exposed to 100 micromol m-2 s-1 were 0.65 and 0.55 micromol kg-1 DM, respectively. They were 0.24 micromol kg-1 DM (both leaves and roots) when plants were exposed to 1,400 micromol m-2 s-1. Levels of isopentenyl adenosine in leaves (24.3 nmol kg-1 DM) and roots (29.9 nmol kg-1 DM) were not affected by differences in the irradiance regime. Similar values were obtained in a second experiment. Other cytokinins could not be detected (<10 nmol kg 1 DM) in either experiment with the sample sizes used (150-600 mg DM for roots and shoots, respectively).

A synthetic auxin (NAA) suppresses secondary wall cellulose synthesis and enhances elongation in cultured cotton fiber.

PubMed

Singh, Bir; Cheek, Hannah D; Haigler, Candace H

2009-07-01

Use of a synthetic auxin (naphthalene-1-acetic acid, NAA) to start (Gossypium hirsutum) ovule/fiber cultures hindered fiber secondary wall cellulose synthesis compared with natural auxin (indole-3-acetic acid, IAA). In contrast, NAA promoted fiber elongation and ovule weight gain, which resulted in larger ovule/fiber units. To reach these conclusions, fiber and ovule growth parameters were measured and cell wall characteristics were examined microscopically. The differences in fiber from NAA and IAA culture were underpinned by changes in the expression patterns of marker genes for three fiber developmental stages (elongation, the transition stage, and secondary wall deposition), and these gene expression patterns were also analyzed quantitatively in plant-grown fiber. The results demonstrate that secondary wall cellulose synthesis: (1) is under strong transcriptional control that is influenced by auxin; and (2) must be specifically characterized in the cotton ovule/fiber culture system given the many protocol variables employed in different laboratories.

Evidence That Chlorinated Auxin Is Restricted to the Fabaceae But Not to the Fabeae1[OPEN

PubMed Central

McAdam, Scott A.M.; McAdam, Erin L.

2015-01-01

Auxin is a pivotal plant hormone, usually occurring in the form of indole-3-acetic acid (IAA). However, in maturing pea (Pisum sativum) seeds, the level of the chlorinated auxin, 4-chloroindole-3-acetic acid (4-Cl-IAA), greatly exceeds that of IAA. A key issue is how plants produce halogenated compounds such as 4-Cl-IAA. To better understand this topic, we investigated the distribution of the chlorinated auxin. We show for the first time, to our knowledge, that 4-Cl-IAA is found in the seeds of Medicago truncatula, Melilotus indicus, and three species of Trifolium. Furthermore, we found no evidence that Pinus spp. synthesize 4-Cl-IAA in seeds, contrary to a previous report. The evidence indicates a single evolutionary origin of 4-Cl-IAA synthesis in the Fabaceae, which may provide an ideal model system to further investigate the action and activity of halogenating enzymes in plants. PMID:25971549

Spatio-temporal appearance of α-amylase and limit dextrinase in barley aleurone layer in response to gibberellic acid, abscisic acid and salicylic acid.

PubMed

Shahpiri, Azar; Talaei, Nasim; Finnie, Christine

2015-01-01

Cereal seed germination involves mobilization of storage reserves in the starchy endosperm to support seedling growth. In response to gibberellin produced by the embryo the aleurone layer synthesizes hydrolases that are secreted to the endosperm for degradation of storage products. In this study analysis of intracellular protein accumulation and release from barley aleurone layers is presented for the important enzymes in starch degradation: α-amylase and limit dextrinase (LD). Proteins were visualized by immunoblotting in aleurone layers and culture supernatants from dissected aleurone layers incubated up to 72 h with either gibberellic acid (GA), abscisic acid (ABA) or salicylic acid (SA). The results show that α-amylase is secreted from aleurone layer treated with GA soon after synthesis but the release of LD to culture supernatants was significantly delayed and coincided with a general loss of proteins from aleurone layers. Release of LD was found to differ from that of amylase and was suggested to depend on programmed cell death (PCD). Despite detection of intracellular amylase in untreated aleurone layers or aleurone layers treated with ABA or SA, α-amylase was not released from these samples. Nevertheless, the release of α-amylase was observed from aleurone layers treated with GA+ABA or GA+SA. © 2014 Society of Chemical Industry.

Time course and auxin sensitivity of cortical microtubule reorientation in maize roots

NASA Technical Reports Server (NTRS)

Blancaflor, E. B.; Hasenstein, K. H.

1995-01-01

The kinetics of MT [microtubule] reorientation in primary roots of Zea mays cv. Merit, were examined 15, 30, 45, and 60 min after horizontal positioning. Confocal microscopy of longitudinal tissue sections showed no change in MT orientation 15 and 30 min after horizontal placement. However, after 45 and 60 min, MTs of the outer 4-5 cortical cell layers along the lower side were reoriented. In order to test whether MT reorientation during graviresponse is caused by an auxin gradient, we examined the organization of MTs in roots that were incubated for 1 h in solutions containing 10(-9) to 10(-6) M IAA. IAA treatment at 10(-8) M or less showed no major or consistent changes but 10(-7) M IAA resulted in MT reorientation in the cortex. The auxin effect does not appear to be acid-induced since benzoic acid (10(-5) M) did not cause MT reorientation. The region closest to the maturation zone was most sensitive to IAA. The data indicate that early stages of gravity induced curvature occur in the absence of MT reorientation but sustained curvature leads to reoriented MTs in the outer cortex. Growth inhibition along the lower side of graviresponding roots appears to result from asymmetric distribution of auxin following gravistimulation.

Maize LAZY1 Mediates Shoot Gravitropism and Inflorescence Development through Regulating Auxin Transport, Auxin Signaling, and Light Response1[C][W

PubMed Central

Dong, Zhaobin; Jiang, Chuan; Chen, Xiaoyang; Zhang, Tao; Ding, Lian; Song, Weibin; Luo, Hongbing; Lai, Jinsheng; Chen, Huabang; Liu, Renyi; Zhang, Xiaolan; Jin, Weiwei

2013-01-01

Auxin is a plant hormone that plays key roles in both shoot gravitropism and inflorescence development. However, these two processes appear to be parallel and to be regulated by distinct players. Here, we report that the maize (Zea mays) prostrate stem1 mutant, which is allelic to the classic mutant lazy plant1 (la1), displays prostrate growth with reduced shoot gravitropism and defective inflorescence development. Map-based cloning identified maize ZmLA1 as the functional ortholog of LAZY1 in rice (Oryza sativa) and Arabidopsis (Arabidopsis thaliana). It has a unique role in inflorescence development and displays enriched expression in reproductive organs such as tassels and ears. Transcription of ZmLA1 responds to auxin and is repressed by light. Furthermore, ZmLA1 physically interacts with a putative auxin transport regulator in the plasma membrane and a putative auxin signaling protein in the nucleus. RNA-SEQ data showed that dozens of auxin transport, auxin response, and light signaling genes were differentially expressed in la1 mutant stems. Therefore, ZmLA1 might mediate the cross talk between shoot gravitropism and inflorescence development by regulating auxin transport, auxin signaling, and probably light response in maize. PMID:24089437

N-Acylethanolamine metabolism interacts with abscisic acid signaling in Arabidopsis thaliana seedlings.

PubMed

Teaster, Neal D; Motes, Christy M; Tang, Yuhong; Wiant, William C; Cotter, Matthew Q; Wang, Yuh-Shuh; Kilaru, Aruna; Venables, Barney J; Hasenstein, Karl H; Gonzalez, Gabriel; Blancaflor, Elison B; Chapman, Kent D

2007-08-01

N-Acylethanolamines (NAEs) are bioactive acylamides that are present in a wide range of organisms. In plants, NAEs are generally elevated in desiccated seeds, suggesting that they may play a role in seed physiology. NAE and abscisic acid (ABA) levels were depleted during seed germination, and both metabolites inhibited the growth of Arabidopsis thaliana seedlings within a similar developmental window. Combined application of low levels of ABA and NAE produced a more dramatic reduction in germination and growth than either compound alone. Transcript profiling and gene expression studies in NAE-treated seedlings revealed elevated transcripts for a number of ABA-responsive genes and genes typically enriched in desiccated seeds. The levels of ABI3 transcripts were inversely associated with NAE-modulated growth. Overexpression of the Arabidopsis NAE degrading enzyme fatty acid amide hydrolase resulted in seedlings that were hypersensitive to ABA, whereas the ABA-insensitive mutants, abi1-1, abi2-1, and abi3-1, exhibited reduced sensitivity to NAE. Collectively, our data indicate that an intact ABA signaling pathway is required for NAE action and that NAE may intersect the ABA pathway downstream from ABA. We propose that NAE metabolism interacts with ABA in the negative regulation of seedling development and that normal seedling establishment depends on the reduction of the endogenous levels of both metabolites.

The Cotton Transcription Factor TCP14 Functions in Auxin-Mediated Epidermal Cell Differentiation and Elongation1[C][W

PubMed Central

Wang, Miao-Ying; Zhao, Pi-Ming; Cheng, Huan-Qing; Han, Li-Bo; Wu, Xiao-Min; Gao, Peng; Wang, Hai-Yun; Yang, Chun-Lin; Zhong, Nai-Qin; Zuo, Jian-Ru; Xia, Gui-Xian

2013-01-01

Plant-specific TEOSINTE-BRANCHED1/CYCLOIDEA/PCF (TCP) transcription factors play crucial roles in development, but their functional mechanisms remain largely unknown. Here, we characterized the cellular functions of the class I TCP transcription factor GhTCP14 from upland cotton (Gossypium hirsutum). GhTCP14 is expressed predominantly in fiber cells, especially at the initiation and elongation stages of development, and its expression increased in response to exogenous auxin. Induced heterologous overexpression of GhTCP14 in Arabidopsis (Arabidopsis thaliana) enhanced initiation and elongation of trichomes and root hairs. In addition, root gravitropism was severely affected, similar to mutant of the auxin efflux carrier PIN-FORMED2 (PIN2) gene. Examination of auxin distribution in GhTCP14-expressing Arabidopsis by observation of auxin-responsive reporters revealed substantial alterations in auxin distribution in sepal trichomes and root cortical regions. Consistent with these changes, expression of the auxin uptake carrier AUXIN1 (AUX1) was up-regulated and PIN2 expression was down-regulated in the GhTCP14-expressing plants. The association of GhTCP14 with auxin responses was also evidenced by the enhanced expression of auxin response gene IAA3, a gene in the AUXIN/INDOLE-3-ACETIC ACID (Aux/IAA) family. Electrophoretic mobility shift assays showed that GhTCP14 bound the promoters of PIN2, IAA3, and AUX1, and transactivation assays indicated that GhTCP14 had transcription activation activity. Taken together, these results demonstrate that GhTCP14 is a dual-function transcription factor able to positively or negatively regulate expression of auxin response and transporter genes, thus potentially acting as a crucial regulator in auxin-mediated differentiation and elongation of cotton fiber cells. PMID:23715527

Molecular and biochemical evidence for the involvement of calcium/calmodulin in auxin action

NASA Technical Reports Server (NTRS)

Yang, T.; Poovaiah, B. W.

2000-01-01

The use of (35)S-labeled calmodulin (CaM) to screen a corn root cDNA expression library has led to the isolation of a CaM-binding protein, encoded by a cDNA with sequence similarity to small auxin up RNAs (SAURs), a class of early auxin-responsive genes. The cDNA designated as ZmSAUR1 (Zea mays SAURs) was expressed in Escherichia coli, and the recombinant protein was purified by CaM affinity chromatography. The CaM binding assay revealed that the recombinant protein binds to CaM in a calcium-dependent manner. Deletion analysis revealed that the CaM binding site was located at the NH(2)-terminal domain. A synthetic peptide of amino acids 20-45, corresponding to the potential CaM binding region, was used for calcium-dependent mobility shift assays. The synthetic peptide formed a stable complex with CaM only in the presence of calcium. The CaM affinity assay indicated that ZmSAUR1 binds to CaM with high affinity (K(d) approximately 15 nM) in a calcium-dependent manner. Comparison of the NH(2)-terminal portions of all of the characterized SAURs revealed that they all contain a stretch of the basic alpha-amphiphilic helix similar to the CaM binding region of ZmSAUR1. CaM binds to the two synthetic peptides from the NH(2)-terminal regions of Arabidopsis SAUR-AC1 and soybean 10A5, suggesting that this is a general phenomenon for all SAURs. Northern analysis was carried out using the total RNA isolated from auxin-treated corn coleoptile segments. ZmSAUR1 gene expression began within 10 min, increased rapidly between 10 and 60 min, and peaked around 60 min after 10 microM alpha-naphthaleneacetic acid treatment. These results indicate that ZmSAUR1 is an early auxin-responsive gene. The CaM antagonist N-(6-aminohexyl)5-chloro-1-naphthalenesulfonamide hydrochloride inhibited the auxin-induced cell elongation but not the auxin-induced expression of ZmSAUR1. This suggests that calcium/CaM do not regulate ZmSAUR1 at the transcriptional level. CaM binding to ZmSAUR1 in a calcium

Identification of Abscisic Acid in Tulipa gesneriana L. by Gas-Liquid Chromatography with Electron Capture and Combined Gas-Liquid Chromatography and Mass Spectrometry

PubMed Central

Terry, Paul H.; Aung, Louis H.; De Hertogh, August A.

1982-01-01

A major growth inhibitory substance of tulip bulbs (Tulipa gesneriana L. cv Paul Richter) has been unequivocally shown to be abscisic acid (ABA). The ABA methyl ester of the free ether-soluble acid fractions of tulip organs had the identical retention time on gas-liquid chromatography with electron capture detector as authentic ABA methyl ester. In addition, the mass spectra were the same. On a unit dry matter basis, the basalplate and floral shoot contained 3.6 and 2.6 times more ABA than the fleshy scales, respectively. PMID:16662721

Agrochemical control of plant water use using engineered abscisic acid receptors.

PubMed

Park, Sang-Youl; Peterson, Francis C; Mosquna, Assaf; Yao, Jin; Volkman, Brian F; Cutler, Sean R

2015-04-23

Rising temperatures and lessening fresh water supplies are threatening agricultural productivity and have motivated efforts to improve plant water use and drought tolerance. During water deficit, plants produce elevated levels of abscisic acid (ABA), which improves water consumption and stress tolerance by controlling guard cell aperture and other protective responses. One attractive strategy for controlling water use is to develop compounds that activate ABA receptors, but agonists approved for use have yet to be developed. In principle, an engineered ABA receptor that can be activated by an existing agrochemical could achieve this goal. Here we describe a variant of the ABA receptor PYRABACTIN RESISTANCE 1 (PYR1) that possesses nanomolar sensitivity to the agrochemical mandipropamid and demonstrate its efficacy for controlling ABA responses and drought tolerance in transgenic plants. Furthermore, crystallographic studies provide a mechanistic basis for its activity and demonstrate the relative ease with which the PYR1 ligand-binding pocket can be altered to accommodate new ligands. Thus, we have successfully repurposed an agrochemical for a new application using receptor engineering. We anticipate that this strategy will be applied to other plant receptors and represents a new avenue for crop improvement.

Copper mediates auxin signalling to control cell differentiation in the copper moss Scopelophila cataractae

PubMed Central

Nomura, Toshihisa; Itouga, Misao; Kojima, Mikiko; Kato, Yukari; Sakakibara, Hitoshi; Hasezawa, Seiichiro

2015-01-01

The copper (Cu) moss Scopelophila cataractae (Mitt.) Broth. is often found in Cu-enriched environments, but it cannot flourish under normal conditions in nature. Excess Cu is toxic to almost all plants, and therefore how this moss species thrives in regions with high Cu concentration remains unknown. In this study, we investigated the effect of Cu on gemma germination and protonemal development in S. cataractae. A high concentration of Cu (up to 800 µM) did not affect gemma germination. In the protonemal stage, a low concentration of Cu promoted protonemal gemma formation, which is the main strategy adopted by S. cataractae to expand its habitat to new locations. Cu-rich conditions promoted auxin accumulation and induced differentiation of chloronema into caulonema cells, whereas it repressed protonemal gemma formation. Under low-Cu conditions, auxin treatment mimicked the effects of high-Cu conditions. Furthermore, Cu-induced caulonema differentiation was severely inhibited in the presence of the auxin antagonist α-(phenylethyl-2-one)-indole-3-acetic acid, or the auxin biosynthesis inhibitor l-kynurenine. These results suggest that S. cataractae flourishes in Cu-rich environments via auxin-regulated cell differentiation. The copper moss might have acquired this mechanism during the evolutionary process to benefit from its advantageous Cu-tolerance ability. PMID:25428998

Auxin effects on ion transport in Chara corallina.

PubMed

Zhang, Suyun; de Boer, Albertus H; van Duijn, Bert

2016-04-01

The plant hormone auxin has been widely studied with regard to synthesis, transport, signaling and functions among the land plants while there is still a lack of knowledge about the possible role for auxin regulation mechanisms in algae with "plant-like" structures. Here we use the alga Chara corallina as a model to study aspects of auxin signaling. In this respect we measured auxin on membrane potential changes and different ion fluxes (K(+), H(+)) through the plasma membrane. Results showed that auxin, mainly IAA, could hyperpolarize the membrane potential of C. corallina internodal cells. Ion flux measurements showed that the auxin-induced membrane potential change may be based on the change of K(+) permeability and/or channel activity rather than through the activation of proton pumps as known in land plants. Copyright © 2016 Elsevier GmbH. All rights reserved.

Morphometric Analysis of Auxin-Mediated Development

NASA Astrophysics Data System (ADS)

Lewis, Daniel

Auxin controls many aspects of plant development through its effects on growth. Its distribution is controlled by specific tissue and organ level polar transport streams. The responses to environmental cues such as gravity light, nutrient availability are largely controlled by coordinated regulation of distinct auxin transport streams. Many plant responses to the environment involve changes in shape. Much can be learned about the underlying processes controlling plant form if the response is measured with sufficient resolution. Computer-aided analysis of digital images or 'machine vision' can be used to greatly increase the speed and consistency of data from a morphometric study of plant form. Advances in image acquisition and analysis pioneered at UW-Madison have allowed unprecedented resolution of the growth and gravitropism of Arabidopsis. A reverse genetic analysis was used to determine if the MDR-like ABC transporters influence auxin distribution important for plant development and the response to environmental cues in Arabidopsis. Mutations in MDR1 (At3g28860) reduce acropetal auxin transport in the root. This is correlated with deviation from the vertical axis. Mutations in MDR4 (At2g47000) reduce basipetal auxin transport in the root. This is correlated with hypergravitropism. It was theorized that reduced transport whithin the elongation zone is responsible for the increased curvature. Flavanols were found to regulate gravitropism upstream of MDR4. The mdr1 mdr4 double mutant showed additive but not synergistic phenotypes, suggesting that the two auxin transport streams are more independent than interdependent. MDR proteins seem to enhance auxin transport in situations where PIN-type effux alone is insufficient.

Auxology: when auxin meets plant evo-devo.

PubMed

Finet, Cédric; Jaillais, Yvon

2012-09-01

Auxin is implicated throughout plant growth and development. Although the effects of this plant hormone have been recognized for more than a century, it is only in the past two decades that light has been shed on the molecular mechanisms that regulate auxin homeostasis, signaling, transport, crosstalk with other hormonal pathways as well as its roles in plant development. These discoveries established a molecular framework to study the role of auxin in land plant evolution. Here, we review recent advances in auxin biology and their implications in both micro- and macro-evolution of plant morphology. By analogy to the term 'hoxology', which refers to the critical role of HOX genes in metazoan evolution, we propose to introduce the term 'auxology' to take into account the crucial role of auxin in plant evo-devo. Copyright © 2012 Elsevier Inc. All rights reserved.

Cytokinin-auxin crosstalk in cell type specification.

PubMed

Chandler, John William; Werr, Wolfgang

2015-05-01

Auxin and cytokinin affect cell fate specification transcriptionally and non-transcriptionally, and their roles have been characterised in several founder cell specification and activation contexts. Similarly to auxin, local cytokinin synthesis and response gradients are instructive, and the roles of ARABIDOPSIS RESPONSE REGULATOR 7/15 (ARR7/15) and the negative cytokinin response regulator ARABIDOPSIS HISTIDINE PHOSPHOTRANSFER PROTEIN 6, as well as auxin signalling via MONOPTEROS/BODENLOS, are functionally conserved across different developmental processes. Auxin and cytokinin crosstalk is tissue- and context-specific, and may be synergistic in the shoot apical meristem (SAM) but antagonistic in the root. We review recent advances in understanding the interactions between auxin and cytokinin in pivotal developmental processes, and show that feedback complexity and the multistep nature of specification processes argue against a single morphogenetic signal. Copyright © 2015 Elsevier Ltd. All rights reserved.

Auxin-dependent compositional change in Mediator in ARF7- and ARF19-mediated transcription.

PubMed

Ito, Jun; Fukaki, Hidehiro; Onoda, Makoto; Li, Lin; Li, Chuanyou; Tasaka, Masao; Furutani, Masahiko

2016-06-07

Mediator is a multiprotein complex that integrates the signals from transcription factors binding to the promoter and transmits them to achieve gene transcription. The subunits of Mediator complex reside in four modules: the head, middle, tail, and dissociable CDK8 kinase module (CKM). The head, middle, and tail modules form the core Mediator complex, and the association of CKM can modify the function of Mediator in transcription. Here, we show genetic and biochemical evidence that CKM-associated Mediator transmits auxin-dependent transcriptional repression in lateral root (LR) formation. The AUXIN/INDOLE 3-ACETIC ACID 14 (Aux/IAA14) transcriptional repressor inhibits the transcriptional activity of its binding partners AUXIN RESPONSE FACTOR 7 (ARF7) and ARF19 by making a complex with the CKM-associated Mediator. In addition, TOPLESS (TPL), a transcriptional corepressor, forms a bridge between IAA14 and the CKM component MED13 through the physical interaction. ChIP assays show that auxin induces the dissociation of MED13 but not the tail module component MED25 from the ARF7 binding region upstream of its target gene. These findings indicate that auxin-induced degradation of IAA14 changes the module composition of Mediator interacting with ARF7 and ARF19 in the upstream region of their target genes involved in LR formation. We suggest that this regulation leads to a quick switch of signal transmission from ARFs to target gene expression in response to auxin.

Isatin as an auxin source favoring floral and vegetative shoot regeneration from calli produced by thin layer explants of tomato pedicel

NASA Technical Reports Server (NTRS)

Applewhite, P. B.; K-Sawhney, R.; Galston, A. W.

1994-01-01

Thin layer explants taken from the pedicels and peduncles of flowering tomato plants yielded calli with great organogenetic potential. Of the 15 cultivars tested, 7 regenerated roots, shoots and eventually entire fruit-bearing plants. Calli grown on modified Murashige-Skoog medium responded to varied auxins and cytokinins with different morphogenetic patterns. Thus, naphthaleneacetic acid yielded root-producing calli, while the auxin precursor isatin (indole 2,3-dione) caused the production of calli with vegetative and floral shoots, rarely yielding roots. This may be related to isatin's slow, steady conversion to an active auxin (Plant Physiol 41:1485-1488, 1966) in contrast with naphthaleneacetic acid's immediate presentation of a high level of active auxin. The highest incidence of vegetative shoot (100%) and flower (50%) formation was obtained with 10 micromoles isatin and 3 micromoles zeatin. A few of the flowers developed into ripe fruits. The high frequency of induction of vegetative shoots and flowers before roots with isatin suggests its utility in micropropagation from plant tissue cultures.

[Graviresponse in higher plants and its regulation in molecular bases: relevance to growth and development, and auxin polar transport in etiolated pea seedlings].

PubMed

Ueda, Junichi; Miyamoto, Kensuke

2003-08-01

We review the graviresponse under true and simulated microgravity conditions on a clinostat in higher plants, and its regulation in molecular bases, especially on the aspect of auxin polar transport in etiolated pea (Pisum sativum L. cv. Alaska) seedlings which were the plant materials subjected to STS-95 space experiments. True and simulated microgravity conditions substantially affected growth and development in etiolated pea seedlings, especially the direction of growth of stems and roots, resulting in automorphosis. In etiolated pea seedlings grown in space, epicotyls were the most oriented toward the direction far from the cotyledons, and roots grew toward the aerial space of Plant Growth Chamber. Automorphosis observed in space were well simulated by a clinorotation on a 3-dimensional clinostat and also phenocopied by the application of auxin polar transport inhibitors of 2,3,5-triiodobenzoic acid, N-(1-naphtyl)phthalamic acid and 9-hydroxyfluorene-9-carboxylic acid. Judging from the results described above together with the fact that activities of auxin polar transport in epicotyls of etiolated pea seedlings grown in space substantially were reduced, auxin polar transport seems to be closely related to automorphosis. Strenuous efforts to learn in molecular levels how gravity contributes to the auxin polar transport in etiolated pea epicotyls resulted in successful identification of PsPIN2 and PsAUX1 genes located in plasma membrane which products are considered to be putative efflux and influx carriers of auxin, respectively. Based on the results of expression of PsPIN2 and PsAUX1 genes under various gravistimulations, a possible role of PsPIN2 and PsAUX1 genes for auxin polar transport in etiolated pea seedlings will be discussed.

PIF4 and PIF5 Transcription Factors Link Blue Light and Auxin to Regulate the Phototropic Response in Arabidopsis[C][W][OPEN

PubMed Central

Sun, Jiaqiang; Qi, Linlin; Li, Yanan; Zhai, Qingzhe; Li, Chuanyou

2013-01-01

Both blue light (BL) and auxin are essential for phototropism in Arabidopsis thaliana. However, the mechanisms by which light is molecularly linked to auxin during phototropism remain elusive. Here, we report that PHYTOCHROME INTERACTING FACTOR4 (PIF4) and PIF5 act downstream of the BL sensor PHOTOTROPIN1 (PHOT1) to negatively modulate phototropism in Arabidopsis. We also reveal that PIF4 and PIF5 negatively regulate auxin signaling. Furthermore, we demonstrate that PIF4 directly activates the expression of the AUXIN/INDOLE-3-ACETIC ACID (IAA) genes IAA19 and IAA29 by binding to the G-box (CACGTG) motifs in their promoters. Our genetic assays demonstrate that IAA19 and IAA29, which physically interact with AUXIN RESPONSE FACTOR7 (ARF7), are sufficient for PIF4 to negatively regulate auxin signaling and phototropism. This study identifies a key step of phototropic signaling in Arabidopsis by showing that PIF4 and PIF5 link light and auxin. PMID:23757399

Abscisic Acid Biosynthesis in Leaves and Roots of Xanthium strumarium.

PubMed

Creelman, R A; Gage, D A; Stults, J T; Zeevaart, J A

1987-11-01

RESEARCH ON THE BIOSYNTHESIS OF ABSCISIC ACID (ABA) HAS FOCUSED PRIMARILY ON TWO PATHWAYS: (a) the direct pathway from farnesyl pyrophosphate, and (b) the indirect pathway involving a carotenoid precursor. We have investigated which biosynthetic pathway is operating in turgid and stressed Xanthium leaves, and in stressed Xanthium roots using long-term incubations in (18)O(2). It was found that in stressed leaves three atoms of (18)O from (18)O(2) are incorporated into the ABA molecule, and that the amount of (18)O incorporated increases with time. One (18)O atom is incorporated rapidly into the carboxyl group of ABA, whereas the other two atoms are very slowly incorporated into the ring oxygens. The fourth oxygen atom in the carboxyl group of ABA is derived from water. ABA from stressed roots of Xanthium incubated in (18)O(2) shows a labeling pattern similar to that of ABA in stressed leaves, but with incorporation of more (18)O into the tertiary hydroxyl group at C-1' after 6 and 12 hours than found in ABA from stressed leaves. It is proposed that the precursors to stress-induced ABA are xanthophylls, and that a xanthophyll lacking an oxygen function at C-6 (carotenoid numbering scheme) plays a crucial role in ABA biosynthesis in Xanthium roots. In turgid Xanthium leaves, (18)O is incorporated into ABA to a much lesser extent than it is in stressed leaves, whereas exogenously applied (14)C-ABA is completely catabolized within 48 hours. This suggests that ABA in turgid leaves is either (a) made via a biosynthetic pathway which is different from the one in stressed leaves, or (b) has a half-life on the order of days as compared with a half-life of 15.5 hours in water-stressed Xanthium leaves. Phaseic acid showed a labeling pattern similar to that of ABA, but with an additional (18)O incorporated during 8'-hydroxylation of ABA to phaseic acid.

Abscisic acid negatively regulates post-penetration resistance of Arabidopsis to the biotrophic powdery mildew fungus.

PubMed

Xiao, Xiang; Cheng, Xi; Yin, Kangquan; Li, Huali; Qiu, Jin-Long

2017-08-01

Pytohormone abscisic acid (ABA) plays important roles in defense responses. Nonetheless, how ABA regulates plant resistance to biotrophic fungi remains largely unknown. Arabidopsis ABA-deficient mutants, aba2-1 and aba3-1, displayed enhanced resistance to the biotrophic powdery mildew fungus Golovinomyces cichoracearum. Moreover, exogenously administered ABA increased the susceptibility of Arabidopsis to G. cichoracearum. Arabidopsis ABA perception components mutants, abi1-1 and abi2-1, also displayed similar phenotypes to ABA-deficient mutants in resistance to G. cichoracearum. However, the resistance to G. cichoracearum is not changed in downstream ABA signaling transduction mutants, abi3-1, abi4-1, and abi5-1. Microscopic examination revealed that hyphal growth and conidiophore production of G. cichoracearum were compromised in the ABA deficient mutants, even though pre-penetration and penetration growth of the fungus were not affected. In addition, salicylic acid (SA) and MPK3 are found to be involved in ABA-regulated resistance to G. cichoracearum. Our work demonstrates that ABA negatively regulates post-penetration resistance of Arabidopsis to powdery mildew fungus G. cichoracearum, probably through antagonizing the function of SA.

The SnRK2-APC/CTE regulatory module mediates the antagonistic action of gibberellic acid and abscisic acid pathways

PubMed Central

Lin, Qibing; Wu, Fuqing; Sheng, Peike; Zhang, Zhe; Zhang, Xin; Guo, Xiuping; Wang, Jiulin; Cheng, Zhijun; Wang, Jie; Wang, Haiyang; Wan, Jianmin

2015-01-01

Abscisic acid (ABA) and gibberellic acid (GA) antagonistically regulate many developmental processes and responses to biotic or abiotic stresses in higher plants. However, the molecular mechanism underlying this antagonism is still poorly understood. Here, we show that loss-of-function mutation in rice Tiller Enhancer (TE), an activator of the APC/CTE complex, causes hypersensitivity and hyposensitivity to ABA and GA, respectively. We find that TE physically interacts with ABA receptor OsPYL/RCARs and promotes their degradation by the proteasome. Genetic analysis also shows OsPYL/RCARs act downstream of TE in mediating ABA responses. Conversely, ABA inhibits APC/CTE activity by phosphorylating TE through activating the SNF1-related protein kinases (SnRK2s), which may interrupt the interaction between TE and OsPYL/RCARs and subsequently stabilize OsPYL/RCARs. In contrast, GA can reduce the level of SnRK2s and may promote APC/CTE-mediated degradation of OsPYL/RCARs. Thus, we propose that the SnRK2-APC/CTE regulatory module represents a regulatory hub underlying the antagonistic action of GA and ABA in plants. PMID:26272249

Violaxanthin is an abscisic acid precursor in water-stressed dark-grown bean leaves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Yi; Walton, D.C.

The leaves a dark-grown bean (Phaseolus vulgaris L.) seedlings accumulate considerably lower quantities of xanthophylls and carotenes than do leaves of light-grown seedlings, but they synthesize at least comparable amounts of abscisic acid (ABA) and its metabolites when water stressed. We observed a 1:1 relationship on a molar basis between the reduction in levels of ciolaxanthin, 9{prime}-cis-neoxanthin, and 9-cis-violaxanthin and the accumulation of ABA, phaseic acid, and dihydrophaseic acid, when leaves from dark-grown plants were stressed for 7 hours. Early in the stress period, reductions in xanthophylls were greater than the accumulation of ABA and its metabolites, suggesting the accumulationmore » of an intermediate which was subsequently converted to ABA. Leaves which were detached, but no stressed, did not accumulate ABA nor were their xanthophyll levels reduced. Leaves from plants that had been sprayed with cycloheximido did not accumulate ABA when stressed, nor were their xanthophyll levels reduced significantly. Incubation of dark-grown stressed leaves in an {sup 18}O{sub 2}-containing atmosphere resulted in the synthesis of ABA with levels of {sup 18}O in the carboxyl group that were virtually identical to those observed in light-grown leaves. The results of these experiments indicate that violaxanthin is an ABA precursor in stressed dark-grown leaves, and they are used to suggest several possible pathways from violaxanthin to ABA.« less

Abscisic acid-dependent multisite phosphorylation regulates the activity of a transcription activator AREB1.

PubMed

Furihata, Takashi; Maruyama, Kyonoshin; Fujita, Yasunari; Umezawa, Taishi; Yoshida, Riichiro; Shinozaki, Kazuo; Yamaguchi-Shinozaki, Kazuko

2006-02-07

bZIP-type transcription factors AREBs/ABFs bind an abscisic acid (ABA)-responsive cis-acting element named ABRE and transactivate downstream gene expression in Arabidopsis. Because AREB1 overexpression could not induce downstream gene expression, activation of AREB1 requires ABA-dependent posttranscriptional modification. We confirmed that ABA activated 42-kDa kinase activity, which, in turn, phosphorylated Ser/Thr residues of R-X-X-S/T sites in the conserved regions of AREB1. Amino acid substitutions of R-X-X-S/T sites to Ala suppressed transactivation activity, and multiple substitution of these sites resulted in almost complete suppression of transactivation activity in transient assays. In contrast, substitution of the Ser/Thr residues to Asp resulted in high transactivation activity without exogenous ABA application. A phosphorylated, transcriptionally active form was achieved by substitution of Ser/Thr in all conserved R-X-X-S/T sites to Asp. Transgenic plants overexpressing the phosphorylated active form of AREB1 expressed many ABA-inducible genes, such as RD29B, without ABA treatment. These results indicate that the ABA-dependent multisite phosphorylation of AREB1 regulates its own activation in plants.

Rapid Quantification of Abscisic Acid by GC-MS/MS for Studies of Abiotic Stress Response.

PubMed

Verslues, Paul E

2017-01-01

Drought and low water potential induce large increases in Abscisic Acid (ABA ) content of plant tissue. This increased ABA content is essential to regulate downstream stress resistance responses; however, the mechanisms regulating ABA accumulation are incompletely known. Thus, the ability to accurately quantify ABA at high throughput and low cost is important for plant stress research. We have combined and modified several previously published protocols to establish a rapid ABA analysis protocol using gas chromatography-tandem mass spectrometry (GC-MS/MS). Derivatization of ABA is performed with (trimethylsilyl)-diazomethane rather than the harder to prepare diazomethane. Sensitivity of the analysis is sufficient that small samples of low water potential treated Arabidopsis thaliana seedlings can be routinely analyzed in reverse genetic studies of putative stress regulators as well as studies of natural variation in ABA accumulation.

Auxin asymmetry during gravitropism by tomato hypocotyls

NASA Technical Reports Server (NTRS)

Harrison, M. A.; Pickard, B. G.

1989-01-01

Gravitropic asymmetry of auxin was observed in hypocotyls of tomato (Lycopersicon esculentum Mill.) soon after horizontal placement: the ratio of apically supplied [3H]IAA collected from the lower sides to that from the upper sides was about 1.4 between 5 and 10 minutes. This was adequately early to account for the beginning of curvature. The auxin asymmetry ratio rose to about 2.5 between 20 and 25 minutes, and to 3.5 during the main phase of curvature. This compares reasonably well with the roughly 3.9 ratio for elongation on the lower side to elongation on the upper side that is the basis for the curvature. These data extend evidence that the Went-Cholodny theory for the mediation of tropisms is valid for dicot stems. Also consistent with the theory, an auxin asymmetry ratio of 2.5 was observed when wrong-way gravitropic curvature developed following application of a high level of auxin. In addition to reversing the asymmetry of elongation, the large supplement of auxin resulted in lower net elongation. Previous data established that ethylene is not involved in this decrease of growth as a function of increasing level of auxin.

An auxin responsive CLE gene regulates shoot apical meristem development in Arabidopsis

PubMed Central

Guo, Hongyan; Zhang, Wei; Tian, Hainan; Zheng, Kaijie; Dai, Xuemei; Liu, Shanda; Hu, Qingnan; Wang, Xianling; Liu, Bao; Wang, Shucai

2015-01-01

Plant hormone auxin regulates most, if not all aspects of plant growth and development, including lateral root formation, organ pattering, apical dominance, and tropisms. Peptide hormones are peptides with hormone activities. Some of the functions of peptide hormones in regulating plant growth and development are similar to that of auxin, however, the relationship between auxin and peptide hormones remains largely unknown. Here we report the identification of OsCLE48, a rice (Oryza sativa) CLE (CLAVATA3/ENDOSPERM SURROUNDING REGION) gene, as an auxin response gene, and the functional characterization of OsCLE48 in Arabidopsis and rice. OsCLE48 encodes a CLE peptide hormone that is similar to Arabidopsis CLEs. RT-PCR analysis showed that OsCLE48 was induced by exogenously application of IAA (indole-3-acetic acid), a naturally occurred auxin. Expression of integrated OsCLE48p:GUS reporter gene in transgenic Arabidopsis plants was also induced by exogenously IAA treatment. These results indicate that OsCLE48 is an auxin responsive gene. Histochemical staining showed that GUS activity was detected in all the tissue and organs of the OsCLE48p:GUS transgenic Arabidopsis plants. Expression of OsCLE48 under the control of the 35S promoter in Arabidopsis inhibited shoot apical meristem development. Expression of OsCLE48 under the control of the CLV3 native regulatory elements almost completely complemented clv3-2 mutant phenotypes, suggesting that OsCLE48 is functionally similar to CLV3. On the other hand, expression of OsCLE48 under the control of the 35S promoter in Arabidopsis has little, if any effects on root apical meristem development, and transgenic rice plants overexpressing OsCLE48 are morphologically indistinguishable from wild type plants, suggesting that the functions of some CLE peptides may not be fully conserved in Arabidopsis and rice. Taken together, our results showed that OsCLE48 is an auxin responsive peptide hormone gene, and it regulates shoot apical

The cyclophilin DIAGEOTROPICA has a conserved role in auxin signaling

PubMed Central

Lavy, Meirav; Prigge, Michael J.; Tigyi, Kristof; Estelle, Mark

2012-01-01

Auxin has a fundamental role throughout the life cycle of land plants. Previous studies showed that the tomato cyclophilin DIAGEOTROPICA (DGT) promotes auxin response, but its specific role in auxin signaling remains unknown. We sequenced candidate genes in auxin-insensitive mutants of Physcomitrella patens and identified mutations in highly conserved regions of the moss ortholog of tomato DGT. As P. patens and tomato diverged from a common ancestor more than 500 million years ago, this result suggests a conserved and central role for DGT in auxin signaling in land plants. In this study we characterize the P. patens dgt (Ppdgt) mutants and show that their response to auxin is altered, affecting the chloronema-to-caulonema transition and the development of rhizoids. To gain an understanding of PpDGT function we tested its interactions with the TIR1/AFB-dependent auxin signaling pathway. We did not observe a clear effect of the Ppdgt mutation on the degradation of Aux/IAA proteins. However, the induction of several auxin-regulated genes was reduced. Genetic analysis revealed that dgt can suppress the phenotype conferred by overexpression of an AFB auxin receptor. Our results indicate that the DGT protein affects auxin-induced transcription and has a conserved function in auxin regulation in land plants. PMID:22318226

Transcriptomic analysis reveals ethylene as stimulator and auxin as regulator of adventitious root formation in petunia cuttings.

PubMed

Druege, Uwe; Franken, Philipp; Lischewski, Sandra; Ahkami, Amir H; Zerche, Siegfried; Hause, Bettina; Hajirezaei, Mohammad R

2014-01-01

Adventitious root (AR) formation in the stem base (SB) of cuttings is the basis for propagation of many plant species and petunia is used as model to study this developmental process. Following AR formation from 2 to 192 hours post-excision (hpe) of cuttings, transcriptome analysis by microarray revealed a change of the character of the rooting zone from SB to root identity. The greatest shift in the number of differentially expressed genes was observed between 24 and 72 hpe, when the categories storage, mineral nutrient acquisition, anti-oxidative and secondary metabolism, and biotic stimuli showed a notable high number of induced genes. Analyses of phytohormone-related genes disclosed multifaceted changes of the auxin transport system, auxin conjugation and the auxin signal perception machinery indicating a reduction in auxin sensitivity and phase-specific responses of particular auxin-regulated genes. Genes involved in ethylene biosynthesis and action showed a more uniform pattern as a high number of respective genes were generally induced during the whole process of AR formation. The important role of ethylene for stimulating AR formation was demonstrated by the application of inhibitors of ethylene biosynthesis and perception as well as of the precursor aminocyclopropane-1-carboxylic acid, all changing the number and length of AR. A model is proposed showing the putative role of polar auxin transport and resulting auxin accumulation in initiation of subsequent changes in auxin homeostasis and signal perception with a particular role of Aux/IAA expression. These changes might in turn guide the entrance into the different phases of AR formation. Ethylene biosynthesis, which is stimulated by wounding and does probably also respond to other stresses and auxin, acts as important stimulator of AR formation probably via the expression of ethylene responsive transcription factor genes, whereas the timing of different phases seems to be controlled by auxin.

Transcriptomic analysis reveals ethylene as stimulator and auxin as regulator of adventitious root formation in petunia cuttings

PubMed Central

Druege, Uwe; Franken, Philipp; Lischewski, Sandra; Ahkami, Amir H.; Zerche, Siegfried; Hause, Bettina; Hajirezaei, Mohammad R.

2014-01-01

Adventitious root (AR) formation in the stem base (SB) of cuttings is the basis for propagation of many plant species and petunia is used as model to study this developmental process. Following AR formation from 2 to 192 hours post-excision (hpe) of cuttings, transcriptome analysis by microarray revealed a change of the character of the rooting zone from SB to root identity. The greatest shift in the number of differentially expressed genes was observed between 24 and 72 hpe, when the categories storage, mineral nutrient acquisition, anti-oxidative and secondary metabolism, and biotic stimuli showed a notable high number of induced genes. Analyses of phytohormone-related genes disclosed multifaceted changes of the auxin transport system, auxin conjugation and the auxin signal perception machinery indicating a reduction in auxin sensitivity and phase-specific responses of particular auxin-regulated genes. Genes involved in ethylene biosynthesis and action showed a more uniform pattern as a high number of respective genes were generally induced during the whole process of AR formation. The important role of ethylene for stimulating AR formation was demonstrated by the application of inhibitors of ethylene biosynthesis and perception as well as of the precursor aminocyclopropane-1-carboxylic acid, all changing the number and length of AR. A model is proposed showing the putative role of polar auxin transport and resulting auxin accumulation in initiation of subsequent changes in auxin homeostasis and signal perception with a particular role of Aux/IAA expression. These changes might in turn guide the entrance into the different phases of AR formation. Ethylene biosynthesis, which is stimulated by wounding and does probably also respond to other stresses and auxin, acts as important stimulator of AR formation probably via the expression of ethylene responsive transcription factor genes, whereas the timing of different phases seems to be controlled by auxin. PMID

CKB1 is involved in abscisic acid and gibberellic acid signaling to regulate stress responses in Arabidopsis thaliana.

PubMed

Yuan, Congying; Ai, Jianping; Chang, Hongping; Xiao, Wenjun; Liu, Lu; Zhang, Cheng; He, Zhuang; Huang, Ji; Li, Jinyan; Guo, Xinhong

2017-05-01

Casein kinase II (CK2), an evolutionarily well-conserved Ser/Thr kinase, plays critical roles in all higher organisms including plants. CKB1 is a regulatory subunit beta of CK2. In this study, homozygous T-DNA mutants (ckb1-1 and ckb1-2) and over-expression plants (35S:CKB1-1, 35S:CKB1-2) of Arabidopsis thaliana were studied to understand the role of CKB1 in abiotic stress and gibberellic acid (GA) signaling. Histochemical staining showed that although CKB1 was expressed in all organs, it had a relatively higher expression in conducting tissues. The ckb1 mutants showed reduced sensitivity to abscisic acid (ABA) during seed germination and seedling growth. The increased stomatal aperture, leaf water loss and proline accumulation were observed in ckb1 mutants. In contrast, the ckb1 mutant had increased sensitivity to polyaluminum chloride during seed germination and hypocotyl elongation. We obtained opposite results in over-expression plants. The expression levels of a number of genes in the ABA and GA regulatory network had changed. This study demonstrates that CKB1 is an ABA signaling-related gene, which subsequently influences GA metabolism, and may play a positive role in ABA signaling.

Auxin production by the plant trypanosomatid Phytomonas serpens and auxin homoeostasis in infected tomato fruits.

PubMed

Ienne, Susan; Freschi, Luciano; Vidotto, Vanessa F; De Souza, Tiago A; Purgatto, Eduardo; Zingales, Bianca

2014-09-01

Previously we have characterized the complete gene encoding a pyruvate decarboxylase (PDC)/indolepyruvate decarboxylase (IPDC) of Phytomonas serpens, a trypanosomatid highly abundant in tomato fruits. Phylogenetic analyses indicated that the clade that contains the trypanosomatid protein behaves as a sister group of IPDCs of γ-proteobacteria. Since IPDCs are key enzymes in the biosynthesis of the plant hormone indole-3-acetic acid (IAA), the ability for IAA production by P. serpens was investigated. Similar to many microorganisms, the production of IAA and related indolic compounds, quantified by high performance liquid chromatography, increased in P. serpens media in response to amounts of tryptophan. The auxin functionality was confirmed in the hypocotyl elongation assay. In tomato fruits inoculated with P. serpens the concentration of free IAA had no significant variation, whereas increased levels of IAA-amide and IAA-ester conjugates were observed. The data suggest that the auxin produced by the flagellate is converted to IAA conjugates, keeping unaltered the concentration of free IAA. Ethanol also accumulated in P. serpens-conditioned media, as the result of a PDC activity. In the article we discuss the hypothesis of the bifunctionality of P. serpens PDC/IPDC and provide a three-dimensional model of the enzyme.

SEPALLATA1/2-suppressed mature apples have low ethylene, high auxin and reduced transcription of ripening-related genes

PubMed Central

Schaffer, Robert J.; Ireland, Hilary S.; Ross, John J.; Ling, Toby J.; David, Karine M.

2012-01-01

Background and aims Fruit ripening is an important developmental trait in fleshy fruits, making the fruit palatable for seed dispersers. In some fruit species, there is a strong association between auxin concentrations and fruit ripening. We investigated the relationship between auxin concentrations and the onset of ethylene-related ripening in Malus × domestica (apples) at both the hormone and transcriptome levels. Methodology Transgenic apples suppressed for the SEPALLATA1/2 (SEP1/2) class of gene (MADS8/9) that showed severely reduced ripening were compared with untransformed control apples. In each apple type, free indole-3-acetic acid (IAA) concentrations were measured during early ripening. The changes observed in auxin were assessed in light of global changes in gene expression. Principal results It was found that mature MADS8/9-suppressed apples had a higher concentration of free IAA. This was associated with increased expression of the auxin biosynthetic genes in the indole-3-acetamide pathway. Additionally, in the MADS8/9-suppressed apples, there was less expression of the GH3 auxin-conjugating enzymes. A number of genes involved in the auxin-regulated transcription (AUX/IAA and ARF classes of genes) were also observed to change in expression, suggesting a mechanism for signal transduction at the start of ripening. Conclusions The delay in ripening observed in MADS8/9-suppressed apples may be partly due to high auxin concentrations. We propose that, to achieve low auxin associated with fruit maturation, the auxin homeostasis is controlled in a two-pronged manner: (i) by the reduction in biosynthesis and (ii) by an increase in auxin conjugation. This is associated with the change in expression of auxin-signalling genes and the up-regulation of ripening-related genes. PMID:23346344

Kinetic Characterisation of a Single Chain Antibody against the Hormone Abscisic Acid: Comparison with Its Parental Monoclonal

PubMed Central

Badescu, George O.; Marsh, Andrew; Smith, Timothy R.; Thompson, Andrew J.; Napier, Richard M.

2016-01-01

A single-chain Fv fragment antibody (scFv) specific for the plant hormone abscisic acid (ABA) has been expressed in the bacterium Escherichia coli as a fusion protein. The kinetics of ABA binding have been measured using surface plasmon resonance spectrometry (BIAcore 2000) using surface and solution assays. Care was taken to calculate the concentration of active protein in each sample using initial rate measurements under conditions of partial mass transport limitation. The fusion product, parental monoclonal antibody and the free scFv all have low nanomolar affinity constants, but there is a lower dissociation rate constant for the parental monoclonal resulting in a three-fold greater affinity. Analogue specificity was tested and structure-activity binding preferences measured. The biologically-active (+)-ABA enantiomer is recognised with an affinity three orders of magnitude higher than the inactive (-)-ABA. Metabolites of ABA including phaseic acid, dihydrophaseic acid and deoxy-ABA have affinities over 100-fold lower than that for (+)-ABA. These properties of the scFv make it suitable as a sensor domain in bioreporters specific for the naturally occurring form of ABA. PMID:27023768

The glutamate carboxypeptidase AMP1 mediates abscisic acid and abiotic stress responses in Arabidopsis.

PubMed

Shi, Yiting; Wang, Zheng; Meng, Pei; Tian, Siqi; Zhang, Xiaoyan; Yang, Shuhua

2013-07-01

ALTERED MERISTEM PROGRAM1 (AMP1) encodes a glutamate carboxypeptidase that plays an important role in shoot apical meristem development and phytohormone homeostasis. We isolated a new mutant allele of AMP1, amp1-20, from a screen for abscisic acid (ABA) hypersensitive mutants and characterized the function of AMP1 in plant stress responses. amp1 mutants displayed ABA hypersensitivity, while overexpression of AMP1 caused ABA insensitivity. Moreover, endogenous ABA concentration was increased in amp1-20- and decreased in AMP1-overexpressing plants under stress conditions. Application of ABA reduced the AMP1 protein level in plants. Interestingly, amp1 mutants accumulated excess superoxide and displayed hypersensitivity to oxidative stress. The hypersensitivity of amp1 to ABA and oxidative stress was partially rescued by reactive oxygen species (ROS) scavenging agent. Furthermore, amp1 was tolerant to freezing and drought stress. The ABA hypersensitivity and freezing tolerance of amp1 was dependent on ABA signaling. Moreover, amp1 had elevated soluble sugar content and showed hypersensitivity to high concentrations of sugar. By contrast, the contents of amino acids were changed in amp1 mutant compared to the wild-type. This study suggests that AMP1 modulates ABA, oxidative and abotic stress responses, and is involved in carbon and amino acid metabolism in Arabidopsis. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

GID1 modulates stomatal response and submergence tolerance involving abscisic acid and gibberellic acid signaling in rice.

PubMed

Du, Hao; Chang, Yu; Huang, Fei; Xiong, Lizhong

2015-11-01

Plant responses to abiotic stresses are coordinated by arrays of growth and developmental programs. Gibberellic acid (GA) and abscisic acid (ABA) play critical roles in the developmental programs and environmental responses, respectively, through complex signaling and metabolism networks. However, crosstalk between the two phytohormones in stress responses remains largely unknown. In this study, we report that GIBBERELLIN-INSENSITIVE DWARF 1 (GID1), a soluble receptor for GA, regulates stomatal development and patterning in rice (Oryza sativa L.). The gid1 mutant showed impaired biosynthesis of endogenous ABA under drought stress conditions, but it exhibited enhanced sensitivity to exogenous ABA. Scanning electron microscope and infrared thermal image analysis indicated an increase in the stomatal conductance in the gid1 mutant under drought conditions. Interestingly, the gid1 mutant had increased levels of chlorophyll and carbohydrates under submergence conditions, and showed enhanced reactive oxygen species (ROS)-scavenging ability and submergence tolerance compared with the wild-type. Further analyses suggested that the function of GID1 in submergence responses is partially dependent on ABA, and GA signaling by GID1 is involved in submergence tolerance by modulating carbohydrate consumption. Taken together, these findings suggest GID1 plays distinct roles in stomatal response and submergence tolerance through both the ABA and GA signaling pathways in rice. © 2014 Institute of Botany, Chinese Academy of Sciences.

Interactive effects of phosphorus deficiency and exogenous auxin on root morphological and physiological traits in white lupin (Lupinus albus L.).

PubMed

Tang, Hongliang; Shen, Jianbo; Zhang, Fusuo; Rengel, Zed

2013-04-01

White lupin (Lupinus albus) exhibits strong root morphological and physiological responses to phosphorus (P) deficiency and auxin treatments, but the interactive effects of P and auxin in regulating root morphological and physiological traits are not fully understood. This study aimed to assess white lupin root traits as influenced by P (0 or 250 μmol L(-1)) and auxin (10(-8) mol L(-1) NAA) in nutrient solution. Both P deficiency and auxin treatments significantly altered root morphological traits, as evidenced by reduced taproot length, increased number and density of first-order lateral roots, and enhanced cluster-root formation. Changes in root physiological traits were also observed, i.e., increased proton, citrate, and acid phosphatase exudation. Exogenous auxin enhanced root responses and sensitivity to P deficiency. A significant interplay exists between P and auxin in the regulation of root morphological and physiological traits. Principal component analysis showed that P availability explained 64.8% and auxin addition 21.3% of the total variation in root trait parameters, indicating that P availability is much more important than auxin in modifying root responses of white lupin. This suggests that white lupin can coordinate root morphological and physiological responses to enhance acquisition of P resources, with an optimal trade-off between root morphological and physiological traits regulated by external stimuli such as P availability and auxin.

Root-derived auxin contributes to the phosphorus-deficiency-induced cluster-root formation in white lupin (Lupinus albus).

PubMed

Meng, Zhi Bin; You, Xue Di; Suo, Dong; Chen, Yun Long; Tang, Caixian; Yang, Jian Li; Zheng, Shao Jian

2013-08-01

Formation of cluster roots is a typical morphological response to phosphorus (P) deficiency in white lupin (Lupinus albus), but its physiological and molecular mechanisms are still unclear. We investigated the role of auxin in the initiation of cluster roots by distinguishing the sources of auxin, measuring the longitudinal distribution patterns of free indole-3-acetic acid (IAA) along the root and the related gene expressions responsible for polar auxin transport (PAT) in different developmental stages of cluster roots. We found that removal of shoot apex or primary root apex and application of auxin-influx or -efflux transport inhibitors, 3-chloro-4-hydroxyphenylacetic acid, N-1-naphthylphthalamic acid and 2,3,5-triiodobenzoic acid, to the stem did not affect the number of cluster roots and the free-IAA concentration in the roots of P-deficient plants, but when these inhibitors were applied directly to the growth media, the cluster-root formation was greatly suppressed, suggesting the fundamental role of root-derived IAA in cluster-root formation. The concentration of free IAA in the roots was higher in P-deficient plants than in P-adequate ones, and the highest in the lateral-root apex and the lowest in the mature cluster roots. Meanwhile the expression patterns of LaAUX1, LaPIN1 and LaPIN3 transcripts related to PAT was consistent with concentrations of free IAA along the lateral root, indicating the contribution of IAA redistribution in the cluster-root development. We proposed that root-derived IAA plays a direct and important role in the P-deficiency-induced formation of cluster roots. Copyright © Physiologia Plantarum 2012.

Physcomitrella patens auxin conjugate synthetase (GH3) double knockout mutants are more resistant to Pythium infection than wild type.

PubMed

Mittag, Jennifer; Šola, Ivana; Rusak, Gordana; Ludwig-Müller, Jutta

2015-07-01

Auxin homeostasis is involved in many different plant developmental and stress responses. The auxin amino acid conjugate synthetases belonging to the GH3 family play major roles in the regulation of free indole-3-acetic acid (IAA) levels and the moss Physcomitrella patens has two GH3 genes in its genome. A role for IAA in several angiosperm--pathogen interactions was reported, however, in a moss--oomycete pathosystem it had not been published so far. Using GH3 double knockout lines we have investigated the role of auxin homeostasis during the infection of P. patens with the two oomycete species, Pythium debaryanum and Pythium irregulare. We show that infection with P. debaryanum caused stronger disease symptoms than with P. irregulare. Also, P. patens lines harboring fusion constructs of an auxin-inducible promoter from soybean (GmGH3) with a reporter (ß-glucuronidase) showed higher promoter induction after P. debaryanum infection than after P. irregulare, indicating a differential induction of the auxin response. Free IAA was induced upon P. debaryanum infection in wild type by 1.6-fold and in two GH3 double knockout (GH3-doKO) mutants by 4- to 5-fold. All GH3-doKO lines showed a reduced disease symptom progression compared to wild type. Since P. debaryanum can be inhibited in growth on medium containing IAA, these data might indicate that endogenous high auxin levels in P. patens GH3-doKO mutants lead to higher resistance against the oomycete. Copyright © 2015 Elsevier GmbH. All rights reserved.

Gravistimulation changes expression of genes encoding putative carrier proteins of auxin polar transport in etiolated pea epicotyls

NASA Astrophysics Data System (ADS)

Hoshino, T.; Hitotsubashi, R.; Miyamoto, K.; Tanimoto, E.; Ueda, J.

STS-95 space experiment has showed that auxin polar transport in etiolated epicotyls of pea (Pisum sativum L. cv. Alaska) seedlings is controlled by gravistimulation. In Arabidopsis thaliana auxin polar transport has considered to be regulated by efflux and influx carrier proteins in plasma membranes, AtPIN1 and AtAUX1, respectively. In order to know how gravistimuli control auxin polar transport in etiolated pea epicotyls at molecular levels, strenuous efforts have been made, resulting in successful isolation of full-length cDNAs of a putative auxin efflux and influx carriers, PsPIN2 and PsAUX1, respectively. Significantly high levels in homology were found on nucleotide and deduced amino acid sequences among PsPIN2, PsPIN1 (accession no. AY222857, Chawla and DeMason, 2003) and AtPINs, and also among PsAUX1, AtAUX1 and their related genes. Phylogenetic analyses based on the deduced amino acid sequences revealed that PsPIN2 belonged to a subclade including AtPIN3, AtPIN4 relating to lateral transport of auxin, while PsPIN1 belonged to the same clade as AtPIN1 relating to auxin polar transport. In the present study, we examined the effects of gravistimuli on the expression of PsPINs and PsAUX1 in etiolated pea seedlings by northern blot analysis. Expression of PsPIN1, PsPIN2 and PsAUX1 in hook region of 3.5-d-old etiolated pea seedlings grown under simulated microgravity conditions on a 3-D clinostat increased as compared with that of the seedlings grown under 1 g conditions. On the other hand, that of PsPIN1 and PsAUX1 in the 1st internode region under simulated microgravity conditions on a 3-D clinostat also increased, while that of PsPIN2 was affected little. These results suggest that expression of PsPIN1, PsPIN2 and PsAUX1 regulating polar/lateral transport of auxin is substantially under the control of gravity. A possible role of PsPINs and PsAUX1 of auxin polar transport in etiolated pea seedlings will also be discussed.

Transcriptional regulation of Arabidopsis MIR168a and argonaute1 homeostasis in abscisic acid and abiotic stress responses.

PubMed

Li, Wei; Cui, Xiao; Meng, Zhaolu; Huang, Xiahe; Xie, Qi; Wu, Heng; Jin, Hailing; Zhang, Dabing; Liang, Wanqi

2012-03-01

The accumulation of a number of small RNAs in plants is affected by abscisic acid (ABA) and abiotic stresses, but the underlying mechanisms are poorly understood. The miR168-mediated feedback regulatory loop regulates ARGONAUTE1 (AGO1) homeostasis, which is crucial for gene expression modulation and plant development. Here, we reveal a transcriptional regulatory mechanism by which MIR168 controls AGO1 homeostasis during ABA treatment and abiotic stress responses in Arabidopsis (Arabidopsis thaliana). Plants overexpressing MIR168a and the AGO1 loss-of-function mutant ago1-27 display ABA hypersensitivity and drought tolerance, while the mir168a-2 mutant shows ABA hyposensitivity and drought hypersensitivity. Both the precursor and mature miR168 were induced under ABA and several abiotic stress treatments, but no obvious decrease for the target of miR168, AGO1, was shown under the same conditions. However, promoter activity analysis indicated that AGO1 transcription activity was increased under ABA and drought treatments, suggesting that transcriptional elevation of MIR168a is required for maintaining a stable AGO1 transcript level during the stress response. Furthermore, we showed both in vitro and in vivo that the transcription of MIR168a is directly regulated by four abscisic acid-responsive element (ABRE) binding factors, which bind to the ABRE cis-element within the MIR168a promoter. This ABRE motif is also found in the promoter of MIR168a homologs in diverse plant species. Our findings suggest that transcriptional regulation of miR168 and posttranscriptional control of AGO1 homeostasis may play an important and conserved role in stress response and signal transduction in plants.

Inhibition of polar calcium movement and gravitropism in roots treated with auxin-transport inhibitors

NASA Technical Reports Server (NTRS)

Lee, J. S.; Mulkey, T. J.; Evans, M. L.

1984-01-01

Primary roots of maize (Zea mays L.) and pea (Pisum sativum L.) exhibit strong positive gravitropism. In both species, gravistimulation induces polar movement of calcium across the root tip from the upper side to the lower side. Roots of onion (Allium cepa L.) are not responsive to gravity and gravistimulation induces little or no polar movement of calcium across the root tip. Treatment of maize or pea roots with inhibitors of auxin transport (morphactin, naphthylphthalamic acid, 2,3,5-triiodobenzoic acid) prevents both gravitropism and gravity-induced polar movement of calcium across the root tip. The results indicate that calcium movement and auxin movement are closely linked in roots and that gravity-induced redistribution of calcium across the root cap may play an important role in the development of gravitropic curvature.

Abscisic Acid Regulation of Root Hydraulic Conductivity and Aquaporin Gene Expression Is Crucial to the Plant Shoot Growth Enhancement Caused by Rhizosphere Humic Acids1

PubMed Central

Bacaicoa, Eva; Garnica, María; Fuentes, Marta; Casanova, Esther; Etayo, David; Ederra, Iñigo; Gonzalo, Ramón

2015-01-01

The physiological and metabolic mechanisms behind the humic acid-mediated plant growth enhancement are discussed in detail. Experiments using cucumber (Cucumis sativus) plants show that the shoot growth enhancement caused by a structurally well-characterized humic acid with sedimentary origin is functionally associated with significant increases in abscisic acid (ABA) root concentration and root hydraulic conductivity. Complementary experiments involving a blocking agent of cell wall pores and water root transport (polyethylenglycol) show that increases in root hydraulic conductivity are essential in the shoot growth-promoting action of the model humic acid. Further experiments involving an inhibitor of ABA biosynthesis in root and shoot (fluridone) show that the humic acid-mediated enhancement of both root hydraulic conductivity and shoot growth depended on ABA signaling pathways. These experiments also show that a significant increase in the gene expression of the main root plasma membrane aquaporins is associated with the increase of root hydraulic conductivity caused by the model humic acid. Finally, experimental data suggest that all of these actions of model humic acid on root functionality, which are linked to its beneficial action on plant shoot growth, are likely related to the conformational structure of humic acid in solution and its interaction with the cell wall at the root surface. PMID:26450705

Specific photoaffinity labeling of two plasma membrane polypeptides with an azido auxin

NASA Technical Reports Server (NTRS)

Hicks, G. R.; Rayle, D. L.; Jones, A. M.; Lomax, T. L.

1989-01-01

Plasma membrane vesicles were isolated from zucchini (Cucurbita pepo) hypocotyl tissue by aqueous phase partitioning and assessed for homogeneity by the use of membrane-specific enzyme assays. The highly pure (ca. 95%) plasma membrane vesicles maintained a pH differential across the membrane and accumulated a tritiated azido analogue of 3-indoleacetic acid (IAA), 5-azido-[7-3H]IAA ([3H]N3IAA), in a manner similar to the accumulation of [3H]IAA. The association of the [3H]N3IAA with membrane vesicles was saturable and subject to competition by IAA and auxin analogues. Auxin-binding proteins were photoaffinity labeled by addition of [3H]N3IAA to plasma membrane vesicles prior to exposure to UV light (15 sec; 300 nm) and detected by subsequent NaDodSO4/PAGE and fluorography. When the reaction temperature was lowered to -196 degrees C, high-specific-activity labeling of a 40-kDa and a 42-kDa polypeptide was observed. Triton X-100 (0.1%) increased the specific activity of labeling and reduced the background, which suggests that the labeled polypeptides are intrinsic membrane proteins. The labeled polypeptides are of low abundance, as expected for auxin receptors. Further, the addition of IAA and auxin analogues to the photoaffinity reaction mixture resulted in reduced labeling that was qualitatively similar to their effects on the accumulation of radiolabeled IAA in membrane vesicles. Collectively, these results suggest that the radiolabeled polypeptides are auxin receptors. The covalent nature of the label should facilitate purification and further characterization of the receptors.

Specific photoaffinity labeling of two plasma membrane polypeptides with an azido auxin.

PubMed

Hicks, G R; Rayle, D L; Jones, A M; Lomax, T L

1989-07-01

Plasma membrane vesicles were isolated from zucchini (Cucurbita pepo) hypocotyl tissue by aqueous phase partitioning and assessed for homogeneity by the use of membrane-specific enzyme assays. The highly pure (ca. 95%) plasma membrane vesicles maintained a pH differential across the membrane and accumulated a tritiated azido analogue of 3-indoleacetic acid (IAA), 5-azido-[7-3H]IAA ([3H]N3IAA), in a manner similar to the accumulation of [3H]IAA. The association of the [3H]N3IAA with membrane vesicles was saturable and subject to competition by IAA and auxin analogues. Auxin-binding proteins were photoaffinity labeled by addition of [3H]N3IAA to plasma membrane vesicles prior to exposure to UV light (15 sec; 300 nm) and detected by subsequent NaDodSO4/PAGE and fluorography. When the reaction temperature was lowered to -196 degrees C, high-specific-activity labeling of a 40-kDa and a 42-kDa polypeptide was observed. Triton X-100 (0.1%) increased the specific activity of labeling and reduced the background, which suggests that the labeled polypeptides are intrinsic membrane proteins. The labeled polypeptides are of low abundance, as expected for auxin receptors. Further, the addition of IAA and auxin analogues to the photoaffinity reaction mixture resulted in reduced labeling that was qualitatively similar to their effects on the accumulation of radiolabeled IAA in membrane vesicles. Collectively, these results suggest that the radiolabeled polypeptides are auxin receptors. The covalent nature of the label should facilitate purification and further characterization of the receptors.

Auxin-Regulated Polypeptide Changes at Different Stages of Strawberry Fruit Development 1

PubMed Central

Veluthambi, K.; Poovaiah, B. W.

1984-01-01

The pattern of polypeptides at different stages of strawberry (Fragaria ananassa Duch. cv Ozark Beauty) fruit development was studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. An 81,000-dalton polypeptide appeared between 5 and 10 days after pollination. Polypeptides with molecular weights of 76,000 and 37,000 daltons were formed after 10 days. The control exerted by auxin in the stage-specific formation of polypeptides was investigated by stopping fruit growth after removing the achenes and reinitiating fruit growth by the application of a synthetic auxin, α-naphthaleneacetic acid (NAA). When the achenes were removed from the 5- and 10-day-old fruits, the fruits failed to grow, the 81,000 dalton polypeptide was not formed between 5 and 10 days, and the 76,000- and 37,000-dalton polypeptides were not formed between 10 and 20 days. Application of NAA to fruits deprived of auxin by removal of achenes resulted in the resumption of growth and also in the appearance of these polypeptides. Removal of achenes of the 5- or 10-day-old fruits and growing them without auxin resulted in the formation of 52,000- and 57,000-dalton polypeptides. These two polypeptides were not formed when NAA was applied to fruits after removal of achenes. Supply of NAA to auxin-deprived fruits 5 days after removal of achenes resulted in resumption of growth and also in the disappearance of these two polypeptides, pointing out their possible relation to the inhibition of fruit growth. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 PMID:16663624

The Effects of High Steady State Auxin Levels on Root Cell Elongation in Brachypodium[OPEN

PubMed Central

Pacheco-Villalobos, David; Tamaki, Takayuki; Gujas, Bojan; Jaspert, Nina; Oecking, Claudia; Bulone, Vincent; Hardtke, Christian S.

2016-01-01

The long-standing Acid Growth Theory of plant cell elongation posits that auxin promotes cell elongation by stimulating cell wall acidification and thus expansin action. To date, the paucity of pertinent genetic materials has precluded thorough analysis of the importance of this concept in roots. The recent isolation of mutants of the model grass species Brachypodium distachyon with dramatically enhanced root cell elongation due to increased cellular auxin levels has allowed us to address this question. We found that the primary transcriptomic effect associated with elevated steady state auxin concentration in elongating root cells is upregulation of cell wall remodeling factors, notably expansins, while plant hormone signaling pathways maintain remarkable homeostasis. These changes are specifically accompanied by reduced cell wall arabinogalactan complexity but not by increased proton excretion. On the contrary, we observed a tendency for decreased rather than increased proton extrusion from root elongation zones with higher cellular auxin levels. Moreover, similar to Brachypodium, root cell elongation is, in general, robustly buffered against external pH fluctuation in Arabidopsis thaliana. However, forced acidification through artificial proton pump activation inhibits root cell elongation. Thus, the interplay between auxin, proton pump activation, and expansin action may be more flexible in roots than in shoots. PMID:27169463

The auxin transporter, OsAUX1, is involved in primary root and root hair elongation and in Cd stress responses in rice (Oryza sativa L.).

PubMed

Yu, ChenLiang; Sun, ChenDong; Shen, Chenjia; Wang, Suikang; Liu, Fang; Liu, Yan; Chen, YunLong; Li, Chuanyou; Qian, Qian; Aryal, Bibek; Geisler, Markus; Jiang, De An; Qi, YanHua

2015-09-01

Auxin and cadmium (Cd) stress play critical roles during root development. There are only a few reports on the mechanisms by which Cd stress influences auxin homeostasis and affects primary root (PR) and lateral root (LR) development, and almost nothing is known about how auxin and Cd interfere with root hair (RH) development. Here, we characterize rice osaux1 mutants that have a longer PR and shorter RHs in hydroponic culture, and that are more sensitive to Cd stress compared to wild-type (Dongjin). OsAUX1 expression in root hair cells is different from that of its paralogous gene, AtAUX1, which is expressed in non-hair cells. However, OsAUX1, like AtAUX1, localizes at the plasma membrane and appears to function as an auxin tranporter. Decreased auxin distribution and contents in the osaux1 mutant result in reduction of OsCyCB1;1 expression and shortened PRs, LRs and RHs under Cd stress, but may be rescued by treatment with the membrane-permeable auxin 1-naphthalene acetic acid. Treatment with the auxin transport inhibitors 1-naphthoxyacetic acid and N-1-naphthylphthalamic acid increased the Cd sensitivity of WT rice. Cd contents in the osaux1 mutant were not altered, but reactive oxygen species-mediated damage was enhanced, further increasing the sensitivity of the osaux1 mutant to Cd stress. Taken together, our results indicate that OsAUX1 plays an important role in root development and in responses to Cd stress. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.