High CO2 Primes Plant Biotic Stress Defences through Redox-Linked Pathways1[OPEN

PubMed Central

2016-01-01

Industrial activities have caused tropospheric CO2 concentrations to increase over the last two centuries, a trend that is predicted to continue for at least the next several decades. Here, we report that growth of plants in a CO2-enriched environment activates responses that are central to defense against pathogenic attack. Salicylic acid accumulation was triggered by high-growth CO2 in Arabidopsis (Arabidopsis thaliana) and other plants such as bean (Phaseolus vulgaris). A detailed analysis in Arabidopsis revealed that elevated CO2 primes multiple defense pathways, leading to increased resistance to bacterial and fungal challenge. Analysis of gene-specific mutants provided no evidence that activation of plant defense pathways by high CO2 was caused by stomatal closure. Rather, the activation is partly linked to metabolic effects involving redox signaling. In support of this, genetic modification of redox components (glutathione contents and NADPH-generating enzymes) prevents full priming of the salicylic acid pathway and associated resistance by high CO2. The data point to a particularly influential role for the nonphosphorylating glyceraldehyde-3-phosphate dehydrogenase, a cytosolic enzyme whose role in plants remains unclear. Our observations add new information on relationships between high CO2 and oxidative signaling and provide novel insight into plant stress responses in conditions of increased CO2. PMID:27578552

Induced Plant Defense Responses against Chewing Insects. Ethylene Signaling Reduces Resistance of Arabidopsis against Egyptian Cotton Worm But Not Diamondback Moth1

PubMed Central

Stotz, Henrik U.; Pittendrigh, Barry R.; Kroymann, Jürgen; Weniger, Kerstin; Fritsche, Jacqueline; Bauke, Antje; Mitchell-Olds, Thomas

2000-01-01

The induction of plant defenses by insect feeding is regulated via multiple signaling cascades. One of them, ethylene signaling, increases susceptibility of Arabidopsis to the generalist herbivore Egyptian cotton worm (Spodoptera littoralis; Lepidoptera: Noctuidae). The hookless1 mutation, which affects a downstream component of ethylene signaling, conferred resistance to Egyptian cotton worm as compared with wild-type plants. Likewise, ein2, a mutant in a central component of the ethylene signaling pathway, caused enhanced resistance to Egyptian cotton worm that was similar in magnitude to hookless1. Moreover, pretreatment of plants with ethephon (2-chloroethanephosphonic acid), a chemical that releases ethylene, elevated plant susceptibility to Egyptian cotton worm. By contrast, these mutations in the ethylene-signaling pathway had no detectable effects on diamondback moth (Plutella xylostella) feeding. It is surprising that this is not due to nonactivation of defense signaling, because diamondback moth does induce genes that relate to wound-response pathways. Of these wound-related genes, jasmonic acid regulates a novel β-glucosidase 1 (BGL1), whereas ethylene controls a putative calcium-binding elongation factor hand protein. These results suggest that a specialist insect herbivore triggers general wound-response pathways in Arabidopsis but, unlike a generalist herbivore, does not react to ethylene-mediated physiological changes. PMID:11080278

B1-Phytoprostanes Trigger Plant Defense and Detoxification Responses1[w

PubMed Central

Loeffler, Christiane; Berger, Susanne; Guy, Alexandre; Durand, Thierry; Bringmann, Gerhard; Dreyer, Michael; von Rad, Uta; Durner, Jörg; Mueller, Martin J.

2005-01-01

Phytoprostanes are prostaglandin/jasmonate-like products of nonenzymatic lipid peroxidation that not only occur ubiquitously in healthy plants but also increase in response to oxidative stress. In this work, we show that the two naturally occurring B1-phytoprostanes (PPB1) regioisomers I and II (each comprising two enantiomers) are short-lived stress metabolites that display a broad spectrum of biological activities. Gene expression analysis of Arabidopsis (Arabidopsis thaliana) cell cultures treated with PPB1-I or -II revealed that both regioisomers triggered a massive detoxification and defense response. Interestingly, expression of several glutathione S-transferases, glycosyl transferases, and putative ATP-binding cassette transporters was found to be increased by one or both PPB1 regioisomers, and hence, may enhance the plant's capacity to inactivate and sequester reactive products of lipid peroxidation. Moreover, pretreatment of tobacco (Nicotiana tabacum) suspension cells with PPB1 considerably prevented cell death caused by severe CuSO4 poisoning. Several Arabidopsis genes induced by PPB1, such as those coding for adenylylsulfate reductase, tryptophan synthase β-chain, and PAD3 pointed to an activation of the camalexin biosynthesis pathway that indeed led to the accumulation of camalexin in PPB1 treated leaves of Arabidopsis. Stimulation of secondary metabolism appears to be a common plant reaction in response to PPB1. In three different plant species, PPB1-II induced a concentration dependent accumulation of phytoalexins that was comparable to that induced by methyl jasmonate. PPB1-I was much weaker active or almost inactive. No differences were found between the enantiomers of each regioisomer. Thus, results suggest that PPB1 represent stress signals that improve plants capacity to cope better with a variety of stresses. PMID:15618427

Partial Activation of SA- and JA-Defensive Pathways in Strawberry upon Colletotrichum acutatum Interaction.

PubMed

Amil-Ruiz, Francisco; Garrido-Gala, José; Gadea, José; Blanco-Portales, Rosario; Muñoz-Mérida, Antonio; Trelles, Oswaldo; de Los Santos, Berta; Arroyo, Francisco T; Aguado-Puig, Ana; Romero, Fernando; Mercado, José-Ángel; Pliego-Alfaro, Fernando; Muñoz-Blanco, Juan; Caballero, José L

2016-01-01

Understanding the nature of pathogen host interaction may help improve strawberry (Fragaria × ananassa) cultivars. Plant resistance to pathogenic agents usually operates through a complex network of defense mechanisms mediated by a diverse array of signaling molecules. In strawberry, resistance to a variety of pathogens has been reported to be mostly polygenic and quantitatively inherited, making it difficult to associate molecular markers with disease resistance genes. Colletotrichum acutatum spp. is a major strawberry pathogen, and completely resistant cultivars have not been reported. Moreover, strawberry defense network components and mechanisms remain largely unknown and poorly understood. Assessment of the strawberry response to C. acutatum included a global transcript analysis, and acidic hormones SA and JA measurements were analyzed after challenge with the pathogen. Induction of transcripts corresponding to the SA and JA signaling pathways and key genes controlling major steps within these defense pathways was detected. Accordingly, SA and JA accumulated in strawberry after infection. Contrastingly, induction of several important SA, JA, and oxidative stress-responsive defense genes, including FaPR1-1, FaLOX2, FaJAR1, FaPDF1, and FaGST1, was not detected, which suggests that specific branches in these defense pathways (those leading to FaPR1-2, FaPR2-1, FaPR2-2, FaAOS, FaPR5, and FaPR10) were activated. Our results reveal that specific aspects in SA and JA dependent signaling pathways are activated in strawberry upon interaction with C. acutatum. Certain described defense-associated transcripts related to these two known signaling pathways do not increase in abundance following infection. This finding suggests new insight into a specific putative molecular strategy for defense against this pathogen.

Partial Activation of SA- and JA-Defensive Pathways in Strawberry upon Colletotrichum acutatum Interaction

PubMed Central

Amil-Ruiz, Francisco; Garrido-Gala, José; Gadea, José; Blanco-Portales, Rosario; Muñoz-Mérida, Antonio; Trelles, Oswaldo; de los Santos, Berta; Arroyo, Francisco T.; Aguado-Puig, Ana; Romero, Fernando; Mercado, José-Ángel; Pliego-Alfaro, Fernando; Muñoz-Blanco, Juan; Caballero, José L.

2016-01-01

Understanding the nature of pathogen host interaction may help improve strawberry (Fragaria × ananassa) cultivars. Plant resistance to pathogenic agents usually operates through a complex network of defense mechanisms mediated by a diverse array of signaling molecules. In strawberry, resistance to a variety of pathogens has been reported to be mostly polygenic and quantitatively inherited, making it difficult to associate molecular markers with disease resistance genes. Colletotrichum acutatum spp. is a major strawberry pathogen, and completely resistant cultivars have not been reported. Moreover, strawberry defense network components and mechanisms remain largely unknown and poorly understood. Assessment of the strawberry response to C. acutatum included a global transcript analysis, and acidic hormones SA and JA measurements were analyzed after challenge with the pathogen. Induction of transcripts corresponding to the SA and JA signaling pathways and key genes controlling major steps within these defense pathways was detected. Accordingly, SA and JA accumulated in strawberry after infection. Contrastingly, induction of several important SA, JA, and oxidative stress-responsive defense genes, including FaPR1-1, FaLOX2, FaJAR1, FaPDF1, and FaGST1, was not detected, which suggests that specific branches in these defense pathways (those leading to FaPR1-2, FaPR2-1, FaPR2-2, FaAOS, FaPR5, and FaPR10) were activated. Our results reveal that specific aspects in SA and JA dependent signaling pathways are activated in strawberry upon interaction with C. acutatum. Certain described defense-associated transcripts related to these two known signaling pathways do not increase in abundance following infection. This finding suggests new insight into a specific putative molecular strategy for defense against this pathogen. PMID:27471515

Disarming the Jasmonate-Dependent Plant Defense Makes Nonhost Arabidopsis Plants Accessible to the American Serpentine Leafminer1

PubMed Central

Abe, Hiroshi; Tateishi, Ken; Seo, Shigemi; Kugimiya, Soichi; Hirai, Masami Yokota; Sawada, Yuji; Murata, Yoshiyuki; Yara, Kaori; Shimoda, Takeshi; Kobayashi, Masatomo

2013-01-01

Here, we analyzed the interaction between Arabidopsis (Arabidopsis thaliana) and the American serpentine leafminer (Liriomyza trifolii), an important and intractable herbivore of many cultivated plants. We examined the role of the immunity-related plant hormone jasmonate (JA) in the plant response and resistance to leafminer feeding to determine whether JA affects host suitability for leafminers. The expression of marker genes for the JA-dependent plant defense was induced by leafminer feeding on Arabidopsis wild-type plants. Analyses of JA-insensitive coi1-1 mutants suggested the importance of JA in the plant response to leafminer feeding. The JA content of wild-type plants significantly increased after leafminer feeding. Moreover, coi1-1 mutants showed lower feeding resistance against leafminer attack than did wild-type plants. The number of feeding scars caused by inoculated adult leafminers in JA-insensitive coi1-1 mutants was higher than that in wild-type plants. In addition, adults of the following generation appeared only from coi1-1 mutants and not from wild-type plants, suggesting that the loss of the JA-dependent plant defense converted nonhost plants to accessible host plants. Interestingly, the glucosinolate-myrosinase defense system may play at most a minor role in this conversion, indicating that this major antiherbivore defense of Brassica species plants probably does not have a major function in plant resistance to leafminer. Application of JA to wild-type plants before leafminer feeding enhanced feeding resistance in Chinese cabbage (Brassica rapa), tomato (Solanum lycopersicum), and garland chrysanthemum (Chrysanthemum coronarium). Our results indicate that JA plays an important role in the plant response and resistance to leafminers and, in so doing, affects host plant suitability for leafminers. PMID:24022267

Biochemical Plant Responses to Ozone (IV. Cross-Induction of Defensive Pathways in Parsley (Petroselinum crispum L.) Plants).

PubMed Central

Eckey-Kaltenbach, H.; Ernst, D.; Heller, W.; Sandermann, H.

1994-01-01

Parsley (Petroselinum crispum L.) is known to respond to ultraviolet irradiation by the synthesis of flavone glycosides, whereas fungal or elicitor stress leads to the synthesis of furanocoumarin phytoalexins. We tested how these defensive pathways are affected by a single ozone treatment (200 nL L-1; 10 h). Assays were performed at the levels of transcripts, for enzyme activities, and for secondary products. The most rapid transcript accumulation was maximal at 3 h, whereas flavone glycosides and furanocoumarins were maximally induced at 12 and 24 h, respectively, after the start of ozone treatment. Ozone acted as a cross-inducer because the two distinct pathways were simultaneously induced. These results are consistent with the previously observed ozone induction of fungal and viral defense reactions in tobacco, spruce, and pine. PMID:12232062

Distinct Roles of Jasmonates and Aldehydes in Plant-Defense Responses

PubMed Central

Chehab, E. Wassim; Kaspi, Roy; Savchenko, Tatyana; Rowe, Heather; Negre-Zakharov, Florence; Kliebenstein, Dan; Dehesh, Katayoon

2008-01-01

Background Many inducible plant-defense responses are activated by jasmonates (JAs), C6-aldehydes, and their corresponding derivatives, produced by the two main competing branches of the oxylipin pathway, the allene oxide synthase (AOS) and hydroperoxide lyase (HPL) branches, respectively. In addition to competition for substrates, these branch-pathway-derived metabolites have substantial overlap in regulation of gene expression. Past experiments to define the role of C6-aldehydes in plant defense responses were biased towards the exogenous application of the synthetic metabolites or the use of genetic manipulation of HPL expression levels in plant genotypes with intact ability to produce the competing AOS-derived metabolites. To uncouple the roles of the C6-aldehydes and jasmonates in mediating direct and indirect plant-defense responses, we generated Arabidopsis genotypes lacking either one or both of these metabolites. These genotypes were subsequently challenged with a phloem-feeding insect (aphids: Myzus persicae), an insect herbivore (leafminers: Liriomyza trifolii), and two different necrotrophic fungal pathogens (Botrytis cinerea and Alternaria brassicicola). We also characterized the volatiles emitted by these plants upon aphid infestation or mechanical wounding and identified hexenyl acetate as the predominant compound in these volatile blends. Subsequently, we examined the signaling role of this compound in attracting the parasitoid wasp (Aphidius colemani), a natural enemy of aphids. Principal Findings This study conclusively establishes that jasmonates and C6-aldehydes play distinct roles in plant defense responses. The jasmonates are indispensable metabolites in mediating the activation of direct plant-defense responses, whereas the C6-aldehyes are not. On the other hand, hexenyl acetate, an acetylated C6-aldehyde, is the predominant wound-inducible volatile signal that mediates indirect defense responses by directing tritrophic (plant

Modifications of Sphingolipid Content Affect Tolerance to Hemibiotrophic and Necrotrophic Pathogens by Modulating Plant Defense Responses in Arabidopsis1[OPEN

PubMed Central

Magnin-Robert, Maryline; Le Bourse, Doriane; Markham, Jonathan; Dorey, Stéphan; Clément, Christophe; Baillieul, Fabienne; Dhondt-Cordelier, Sandrine

2015-01-01

Sphingolipids are emerging as second messengers in programmed cell death and plant defense mechanisms. However, their role in plant defense is far from being understood, especially against necrotrophic pathogens. Sphingolipidomics and plant defense responses during pathogenic infection were evaluated in the mutant of long-chain base phosphate (LCB-P) lyase, encoded by the dihydrosphingosine-1-phosphate lyase1 (AtDPL1) gene and regulating long-chain base/LCB-P homeostasis. Atdpl1 mutants exhibit tolerance to the necrotrophic fungus Botrytis cinerea but susceptibility to the hemibiotrophic bacterium Pseudomonas syringae pv tomato (Pst). Here, a direct comparison of sphingolipid profiles in Arabidopsis (Arabidopsis thaliana) during infection with pathogens differing in lifestyles is described. In contrast to long-chain bases (dihydrosphingosine [d18:0] and 4,8-sphingadienine [d18:2]), hydroxyceramide and LCB-P (phytosphingosine-1-phosphate [t18:0-P] and 4-hydroxy-8-sphingenine-1-phosphate [t18:1-P]) levels are higher in Atdpl1-1 than in wild-type plants in response to B. cinerea. Following Pst infection, t18:0-P accumulates more strongly in Atdpl1-1 than in wild-type plants. Moreover, d18:0 and t18:0-P appear as key players in Pst- and B. cinerea-induced cell death and reactive oxygen species accumulation. Salicylic acid levels are similar in both types of plants, independent of the pathogen. In addition, salicylic acid-dependent gene expression is similar in both types of B. cinerea-infected plants but is repressed in Atdpl1-1 after treatment with Pst. Infection with both pathogens triggers higher jasmonic acid, jasmonoyl-isoleucine accumulation, and jasmonic acid-dependent gene expression in Atdpl1-1 mutants. Our results demonstrate that sphingolipids play an important role in plant defense, especially toward necrotrophic pathogens, and highlight a novel connection between the jasmonate signaling pathway, cell death, and sphingolipids. PMID:26378098

Stage-Related Defense Response Induction in Tomato Plants by Nesidiocoris tenuis

PubMed Central

Naselli, Mario; Urbaneja, Alberto; Siscaro, Gaetano; Jaques, Josep A.; Zappalà, Lucia; Flors, Víctor; Pérez-Hedo, Meritxell

2016-01-01

The beneficial effects of direct predation by zoophytophagous biological control agents (BCAs), such as the mirid bug Nesidiocoris tenuis, are well-known. However, the benefits of zoophytophagous BCAs’ relation with host plants, via induction of plant defensive responses, have not been investigated until recently. To date, only the females of certain zoophytophagous BCAs have been demonstrated to induce defensive plant responses in tomato plants. The aim of this work was to determine whether nymphs, adult females, and adult males of N. tenuis are able to induce defense responses in tomato plants. Compared to undamaged tomato plants (i.e., not exposed to the mirid), plants on which young or mature nymphs, or adult males or females of N. tenuis fed and developed were less attractive to the whitefly Bemisia tabaci, but were more attractive to the parasitoid Encarsia formosa. Female-exposed plants were more repellent to B. tabaci and more attractive to E. formosa than were male-exposed plants. When comparing young- and mature-nymph-exposed plants, the same level of repellence was obtained for B. tabaci, but mature-nymph-exposed plants were more attractive to E. formosa. The repellent effect is attributed to the signaling pathway of abscisic acid, which is upregulated in N. tenuis-exposed plants, whereas the parasitoid attraction was attributed to the activation of the jasmonic acid signaling pathway. Our results demonstrate that all motile stages of N. tenuis can trigger defensive responses in tomato plants, although these responses may be slightly different depending on the stage considered. PMID:27472328

Turnabout Is Fair Play: Herbivory-Induced Plant Chitinases Excreted in Fall Armyworm Frass Suppress Herbivore Defenses in Maize1[OPEN

PubMed Central

Alves, Patrick C.M.S.; Gaffoor, Iffa; Acevedo, Flor E.; Peiffer, Michelle; Jin, Shan; Han, Yang; Shakeel, Samina; Felton, Gary W.

2016-01-01

The perception of herbivory by plants is known to be triggered by the deposition of insect-derived factors such as saliva and oral secretions, oviposition materials, and even feces. Such insect-derived materials harbor chemical cues that may elicit herbivore and/or pathogen-induced defenses in plants. Several insect-derived molecules that trigger herbivore-induced defenses in plants are known; however, insect-derived molecules suppressing them are largely unknown. In this study, we identified two plant chitinases from fall armyworm (Spodoptera frugiperda) larval frass that suppress herbivore defenses while simultaneously inducing pathogen defenses in maize (Zea mays). Fall armyworm larvae feed in enclosed whorls of maize plants, where frass accumulates over extended periods of time in close proximity to damaged leaf tissue. Our study shows that maize chitinases, Pr4 and Endochitinase A, are induced during herbivory and subsequently deposited on the host with the feces. These plant chitinases mediate the suppression of herbivore-induced defenses, thereby increasing the performance of the insect on the host. Pr4 and Endochitinase A also trigger the antagonistic pathogen defense pathway in maize and suppress fungal pathogen growth on maize leaves. Frass-induced suppression of herbivore defenses by deposition of the plant-derived chitinases Pr4 and Endochitinase A is a unique way an insect can co-opt the plant’s defense proteins for its own benefit. It is also a phenomenon unlike the induction of herbivore defenses by insect oral secretions in most host-herbivore systems. PMID:26979328

Prunus domestica Pathogenesis-Related Protein-5 Activates the Defense Response Pathway and Enhances the Resistance to Fungal Infection

PubMed Central

El-kereamy, Ashraf; El-sharkawy, Islam; Ramamoorthy, Rengasamy; Taheri, Ali; Errampalli, Deena; Kumar, Prakash; Jayasankar, Subramanian

2011-01-01

Pathogenesis-related protein-5 (PR-5) has been implicated in plant disease resistance and its antifungal activity has been demonstrated in some fruit species. However, their roles, especially their interactions with the other defense responses in plant cells, are still not fully understood. In this study, we have cloned and characterized a new PR-5 cDNA named PdPR5-1 from the European plum (Prunus domestica). Expression of PdPR5-1 was studied in different cultivars varying in resistance to the brown rot disease caused by the necrotrophic fungus Monilinia fructicola. In addition transgenic Arabidopsis, ectopically expressing PdPR5-1 was used to study its role in other plant defense responses after fungal infection. We show that the resistant cultivars exhibited much higher levels of transcripts than the susceptible cultivars during fruit ripening. However, significant rise in the transcript levels after infection with M. fructicola was observed in the susceptible cultivars too. Transgenic Arabidopsis plants exhibited more resistance to Alternaria brassicicola. Further, there was a significant increase in the transcripts of genes involved in the phenylpropanoid biosynthesis pathway such as phenylalanine ammonia-lyase (PAL) and phytoalexin (camalexin) pathway leading to an increase in camalexin content after fungal infection. Our results show that PdPR5-1 gene, in addition to its anti-fungal properties, has a possible role in activating other defense pathways, including phytoalexin production. PMID:21448276

Jasmonates induce both defense responses and communication in monocotyledonous and dicotyledonous plants.

PubMed

Okada, Kazunori; Abe, Hiroshi; Arimura, Gen-ichiro

2015-01-01

Jasmonic acid (JA) and its derivatives (jasmonates, JAs) are phytohormones with essential roles in plant defense against pathogenesis and herbivorous arthropods. Both the up- and down-regulation of defense responses are dependent on signaling pathways mediated by JAs as well as other stress hormones (e.g. salicylic acid), generally those involving the transcriptional and post-transcriptional regulation of transcription factors via protein modification and epigenetic regulation. In addition to the typical model plant Arabidopsis (a dicotyledon), advances in genetics research have made rice a model monocot in which innovative pest control traits can be introduced and whose JA signaling pathway can be studied. In this review, we introduce the dynamic functions of JAs in plant defense strategy using defensive substances (e.g. indole alkaloids and terpenoid phytoalexins) and airborne signals (e.g. green leaf volatiles and volatile terpenes) in response to biotrophic and necrotrophic pathogens as well as above-ground and below-ground herbivores. We then discuss the important issue of how the mutualism of herbivorous arthropods with viruses or bacteria can cause cross-talk between JA and other phytohormones to counter the defense systems. © The Author 2014. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Recognizing Plant Defense Priming.

PubMed

Martinez-Medina, Ainhoa; Flors, Victor; Heil, Martin; Mauch-Mani, Brigitte; Pieterse, Corné M J; Pozo, Maria J; Ton, Jurriaan; van Dam, Nicole M; Conrath, Uwe

2016-10-01

Defense priming conditions diverse plant species for the superinduction of defense, often resulting in enhanced pest and disease resistance and abiotic stress tolerance. Here, we propose a guideline that might assist the plant research community in a consistent assessment of defense priming in plants. Copyright © 2016 Elsevier Ltd. All rights reserved.

Arabidopsis Transcriptome Analysis Reveals Key Roles of Melatonin in Plant Defense Systems

PubMed Central

Weeda, Sarah; Zhang, Na; Zhao, Xiaolei; Ndip, Grace; Guo, Yangdong; Buck, Gregory A.; Fu, Conggui; Ren, Shuxin

2014-01-01

Melatonin is a ubiquitous molecule and exists across kingdoms including plant species. Studies on melatonin in plants have mainly focused on its physiological influence on growth and development, and on its biosynthesis. Much less attention has been drawn to its affect on genome-wide gene expression. To comprehensively investigate the role(s) of melatonin at the genomics level, we utilized mRNA-seq technology to analyze Arabidopsis plants subjected to a 16-hour 100 pM (low) and 1 mM (high) melatonin treatment. The expression profiles were analyzed to identify differentially expressed genes. 100 pM melatonin treatment significantly affected the expression of only 81 genes with 51 down-regulated and 30 up-regulated. However, 1 mM melatonin significantly altered 1308 genes with 566 up-regulated and 742 down-regulated. Not all genes altered by low melatonin were affected by high melatonin, indicating different roles of melatonin in regulation of plant growth and development under low and high concentrations. Furthermore, a large number of genes altered by melatonin were involved in plant stress defense. Transcript levels for many stress receptors, kinases, and stress-associated calcium signals were up-regulated. The majority of transcription factors identified were also involved in plant stress defense. Additionally, most identified genes in ABA, ET, SA and JA pathways were up-regulated, while genes pertaining to auxin responses and signaling, peroxidases, and those associated with cell wall synthesis and modifications were mostly down-regulated. Our results indicate critical roles of melatonin in plant defense against various environmental stresses, and provide a framework for functional analysis of genes in melatonin-mediated signaling pathways. PMID:24682084

Pipecolic Acid Orchestrates Plant Systemic Acquired Resistance and Defense Priming via Salicylic Acid-Dependent and -Independent Pathways.

PubMed

Bernsdorff, Friederike; Döring, Anne-Christin; Gruner, Katrin; Schuck, Stefan; Bräutigam, Andrea; Zeier, Jürgen

2016-01-01

We investigated the relationships of the two immune-regulatory plant metabolites, salicylic acid (SA) and pipecolic acid (Pip), in the establishment of plant systemic acquired resistance (SAR), SAR-associated defense priming, and basal immunity. Using SA-deficient sid2, Pip-deficient ald1, and sid2 ald1 plants deficient in both SA and Pip, we show that SA and Pip act both independently from each other and synergistically in Arabidopsis thaliana basal immunity to Pseudomonas syringae. Transcriptome analyses reveal that SAR establishment in Arabidopsis is characterized by a strong transcriptional response systemically induced in the foliage that prepares plants for future pathogen attack by preactivating multiple stages of defense signaling and that SA accumulation upon SAR activation leads to the downregulation of photosynthesis and attenuated jasmonate responses systemically within the plant. Whereas systemic Pip elevations are indispensable for SAR and necessary for virtually the whole transcriptional SAR response, a moderate but significant SA-independent component of SAR activation and SAR gene expression is revealed. During SAR, Pip orchestrates SA-dependent and SA-independent priming of pathogen responses in a FLAVIN-DEPENDENT-MONOOXYGENASE1 (FMO1)-dependent manner. We conclude that a Pip/FMO1 signaling module acts as an indispensable switch for the activation of SAR and associated defense priming events and that SA amplifies Pip-triggered responses to different degrees in the distal tissue of SAR-activated plants. © 2016 American Society of Plant Biologists. All rights reserved.

Antiviral Defenses in Plants through Genome Editing

PubMed Central

Romay, Gustavo; Bragard, Claude

2017-01-01

Plant–virus interactions based-studies have contributed to increase our understanding on plant resistance mechanisms, providing new tools for crop improvement. In the last two decades, RNA interference, a post-transcriptional gene silencing approach, has been used to induce antiviral defenses in plants with the help of genetic engineering technologies. More recently, the new genome editing systems (GES) are revolutionizing the scope of tools available to confer virus resistance in plants. The most explored GES are zinc finger nucleases, transcription activator-like effector nucleases, and clustered regularly interspaced short palindromic repeats/Cas9 endonuclease. GES are engineered to target and introduce mutations, which can be deleterious, via double-strand breaks at specific DNA sequences by the error-prone non-homologous recombination end-joining pathway. Although GES have been engineered to target DNA, recent discoveries of GES targeting ssRNA molecules, including virus genomes, pave the way for further studies programming plant defense against RNA viruses. Most of plant virus species have an RNA genome and at least 784 species have positive ssRNA. Here, we provide a summary of the latest progress in plant antiviral defenses mediated by GES. In addition, we also discuss briefly the GES perspectives in light of the rebooted debate on genetic modified organisms (GMOs) and the current regulatory frame for agricultural products involving the use of such engineering technologies. PMID:28167937

The role of NDR1 in pathogen perception and plant defense signaling.

PubMed

Knepper, Caleb; Savory, Elizabeth A; Day, Brad

2011-08-01

The biochemical and cellular function of NDR1 in plant immunity and defense signaling has long remained elusive. Herein, we describe a novel role for NDR1 in both pathogen perception and plant defense signaling, elucidated by exploring a broader, physiological role for NDR1 in general stress responses and cell wall adhesion. Based on our predictive homology modeling, coupled with a structure-function approach, we found that NDR1 shares a striking similarity to mammalian integrins, well-characterized for their role in mediating the interaction between the extracellular matrix and stress signaling. ndr1-1 mutant plants exhibit higher electrolyte leakage following pathogen infection, compared to wild type Col-0. In addition, we observed an altered plasmolysis phenotype, supporting a role for NDR1 in maintaining cell wall-plasma membrane adhesions through mediating fluid loss under stress. 

Plant Defense against Insect Herbivores

PubMed Central

Fürstenberg-Hägg, Joel; Zagrobelny, Mika; Bak, Søren

2013-01-01

Plants have been interacting with insects for several hundred million years, leading to complex defense approaches against various insect feeding strategies. Some defenses are constitutive while others are induced, although the insecticidal defense compound or protein classes are often similar. Insect herbivory induce several internal signals from the wounded tissues, including calcium ion fluxes, phosphorylation cascades and systemic- and jasmonate signaling. These are perceived in undamaged tissues, which thereafter reinforce their defense by producing different, mostly low molecular weight, defense compounds. These bioactive specialized plant defense compounds may repel or intoxicate insects, while defense proteins often interfere with their digestion. Volatiles are released upon herbivory to repel herbivores, attract predators or for communication between leaves or plants, and to induce defense responses. Plants also apply morphological features like waxes, trichomes and latices to make the feeding more difficult for the insects. Extrafloral nectar, food bodies and nesting or refuge sites are produced to accommodate and feed the predators of the herbivores. Meanwhile, herbivorous insects have adapted to resist plant defenses, and in some cases even sequester the compounds and reuse them in their own defense. Both plant defense and insect adaptation involve metabolic costs, so most plant-insect interactions reach a stand-off, where both host and herbivore survive although their development is suboptimal. PMID:23681010

Pipecolic Acid Orchestrates Plant Systemic Acquired Resistance and Defense Priming via Salicylic Acid-Dependent and -Independent Pathways

PubMed Central

Bernsdorff, Friederike; Döring, Anne-Christin; Gruner, Katrin; Schuck, Stefan; Bräutigam, Andrea; Zeier, Jürgen

2016-01-01

We investigated the relationships of the two immune-regulatory plant metabolites, salicylic acid (SA) and pipecolic acid (Pip), in the establishment of plant systemic acquired resistance (SAR), SAR-associated defense priming, and basal immunity. Using SA-deficient sid2, Pip-deficient ald1, and sid2 ald1 plants deficient in both SA and Pip, we show that SA and Pip act both independently from each other and synergistically in Arabidopsis thaliana basal immunity to Pseudomonas syringae. Transcriptome analyses reveal that SAR establishment in Arabidopsis is characterized by a strong transcriptional response systemically induced in the foliage that prepares plants for future pathogen attack by preactivating multiple stages of defense signaling and that SA accumulation upon SAR activation leads to the downregulation of photosynthesis and attenuated jasmonate responses systemically within the plant. Whereas systemic Pip elevations are indispensable for SAR and necessary for virtually the whole transcriptional SAR response, a moderate but significant SA-independent component of SAR activation and SAR gene expression is revealed. During SAR, Pip orchestrates SA-dependent and SA-independent priming of pathogen responses in a FLAVIN-DEPENDENT-MONOOXYGENASE1 (FMO1)-dependent manner. We conclude that a Pip/FMO1 signaling module acts as an indispensable switch for the activation of SAR and associated defense priming events and that SA amplifies Pip-triggered responses to different degrees in the distal tissue of SAR-activated plants. PMID:26672068

The Arabidopsis mutant cev1 has constitutively active jasmonate and ethylene signal pathways and enhanced resistance to pathogens.

PubMed

Ellis, C; Turner, J G

2001-05-01

Jasmonates (JAs) inhibit plant growth and induce plant defense responses. To define genes in the Arabidopsis JA signal pathway, we screened for mutants with constitutive expression of a luciferase reporter for the JA-responsive promoter from the vegetative storage protein gene VSP1. One mutant, named constitutive expression of VSP1 (cev1), produced plants that were smaller than wild type, had stunted roots with long root hairs, accumulated anthocyanin, had constitutive expression of the defense-related genes VSP1, VSP2, Thi2.1, PDF1.2, and CHI-B, and had enhanced resistance to powdery mildew diseases. Genetic evidence indicated that the cev1 phenotype required both COI1, an essential component of the JA signal pathway, and ETR1, which encodes the ethylene receptor. We conclude that cev1 stimulates both the JA and the ethylene signal pathways and that CEV1 regulates an early step in an Arabidopsis defense pathway.

The Arabidopsis Mutant cev1 Has Constitutively Active Jasmonate and Ethylene Signal Pathways and Enhanced Resistance to Pathogens

PubMed Central

Ellis, Christine; Turner, John G.

2001-01-01

Jasmonates (JAs) inhibit plant growth and induce plant defense responses. To define genes in the Arabidopsis JA signal pathway, we screened for mutants with constitutive expression of a luciferase reporter for the JA-responsive promoter from the vegetative storage protein gene VSP1. One mutant, named constitutive expression of VSP1 (cev1), produced plants that were smaller than wild type, had stunted roots with long root hairs, accumulated anthocyanin, had constitutive expression of the defense-related genes VSP1, VSP2, Thi2.1, PDF1.2, and CHI-B, and had enhanced resistance to powdery mildew diseases. Genetic evidence indicated that the cev1 phenotype required both COI1, an essential component of the JA signal pathway, and ETR1, which encodes the ethylene receptor. We conclude that cev1 stimulates both the JA and the ethylene signal pathways and that CEV1 regulates an early step in an Arabidopsis defense pathway. PMID:11340179

Silverleaf whitefly induces salicylic acid defenses and suppresses effectual jasmonic acid defenses.

PubMed

Zarate, Sonia I; Kempema, Louisa A; Walling, Linda L

2007-02-01

The basal defenses important in curtailing the development of the phloem-feeding silverleaf whitefly (Bemisia tabaci type B; SLWF) on Arabidopsis (Arabidopsis thaliana) were investigated. Sentinel defense gene RNAs were monitored in SLWF-infested and control plants. Salicylic acid (SA)-responsive gene transcripts accumulated locally (PR1, BGL2, PR5, SID2, EDS5, PAD4) and systemically (PR1, BGL2, PR5) during SLWF nymph feeding. In contrast, jasmonic acid (JA)- and ethylene-dependent RNAs (PDF1.2, VSP1, HEL, THI2.1, FAD3, ERS1, ERF1) were repressed or not modulated in SLWF-infested leaves. To test for a role of SA and JA pathways in basal defense, SLWF development on mutant and transgenic lines that constitutively activate or impair defense pathways was determined. By monitoring the percentage of SLWF nymphs in each instar, we show that mutants that activate SA defenses (cim10) or impair JA defenses (coi1) accelerated SLWF nymphal development. Reciprocally, mutants that activate JA defenses (cev1) or impair SA defenses (npr1, NahG) slowed SLWF nymphal development. Furthermore, when npr1 plants, which do not activate downstream SA defenses, were treated with methyl jasmonate, a dramatic delay in nymph development was observed. Collectively, these results showed that SLWF-repressed, JA-regulated defenses were associated with basal defense to the SLWF.

The MAP kinase substrate MKS1 is a regulator of plant defense responses

PubMed Central

Andreasson, Erik; Jenkins, Thomas; Brodersen, Peter; Thorgrimsen, Stephan; Petersen, Nikolaj H T; Zhu, Shijiang; Qiu, Jin-Long; Micheelsen, Pernille; Rocher, Anne; Petersen, Morten; Newman, Mari-Anne; Bjørn Nielsen, Henrik; Hirt, Heribert; Somssich, Imre; Mattsson, Ole; Mundy, John

2005-01-01

Arabidopsis MAP kinase 4 (MPK4) functions as a regulator of pathogen defense responses, because it is required for both repression of salicylic acid (SA)-dependent resistance and for activation of jasmonate (JA)-dependent defense gene expression. To understand MPK4 signaling mechanisms, we used yeast two-hybrid screening to identify the MPK4 substrate MKS1. Analyses of transgenic plants and genome-wide transcript profiling indicated that MKS1 is required for full SA-dependent resistance in mpk4 mutants, and that overexpression of MKS1 in wild-type plants is sufficient to activate SA-dependent resistance, but does not interfere with induction of a defense gene by JA. Further yeast two-hybrid screening revealed that MKS1 interacts with the WRKY transcription factors WRKY25 and WRKY33. WRKY25 and WRKY33 were shown to be in vitro substrates of MPK4, and a wrky33 knockout mutant was found to exhibit increased expression of the SA-related defense gene PR1. MKS1 may therefore contribute to MPK4-regulated defense activation by coupling the kinase to specific WRKY transcription factors. PMID:15990873

Aphid performance changes with plant defense mediated by Cucumber mosaic virus titer.

PubMed

Shi, Xiaobin; Gao, Yang; Yan, Shuo; Tang, Xin; Zhou, Xuguo; Zhang, Deyong; Liu, Yong

2016-04-22

Cucumber mosaic virus (CMV) causes appreciable losses in vegetables, ornamentals and agricultural crops. The green peach aphid, Myzus persicae Sulzer (Aphididae) is one of the most efficient vectors for CMV. The transmission ecology of aphid-vectored CMV has been well investigated. However, the detailed description of the dynamic change in the plant-CMV-aphid interaction associated with plant defense and virus epidemics is not well known. In this report, we investigated the relationship of virus titer with plant defense of salicylic acid (SA) and jasmonic acid (JA) during the different infection time and their interaction with aphids in CMV-infected tobacco plants. Our results showed that aphid performance changed with virus titer and plant defense on CMV-inoculated plants. At first, plant defense was low and aphid number increased gradually. The plant defense of SA signaling pathway was induced when virus titer was at a high level, and aphid performance was correspondingly reduced. Additionally, the winged aphids were increased. Our results showed that aphid performance was reduced due to the induced plant defense mediated by Cucumber mosaic virus titer. Additionally, some wingless aphids became to winged aphids. In this way CMV could be transmitted with the migration of winged aphids. We should take measures to prevent aphids in the early stage of their occurrence in the field to prevent virus outbreak.

Plant elicitor peptides are conserved signals regulating direct and indirect antiherbivore defense

PubMed Central

Huffaker, Alisa; Pearce, Gregory; Veyrat, Nathalie; Erb, Matthias; Turlings, Ted C. J.; Sartor, Ryan; Shen, Zhouxin; Briggs, Steven P.; Vaughan, Martha M.; Alborn, Hans T.; Teal, Peter E. A.; Schmelz, Eric A.

2013-01-01

Insect-induced defenses occur in nearly all plants and are regulated by conserved signaling pathways. As the first described plant peptide signal, systemin regulates antiherbivore defenses in the Solanaceae, but in other plant families, peptides with analogous activity have remained elusive. In the current study, we demonstrate that a member of the maize (Zea mays) plant elicitor peptide (Pep) family, ZmPep3, regulates responses against herbivores. Consistent with being a signal, expression of the ZmPROPEP3 precursor gene is rapidly induced by Spodoptera exigua oral secretions. At concentrations starting at 5 pmol per leaf, ZmPep3 stimulates production of jasmonic acid, ethylene, and increased expression of genes encoding proteins associated with herbivory defense. These include proteinase inhibitors and biosynthetic enzymes for production of volatile terpenes and benzoxazinoids. In accordance with gene expression data, plants treated with ZmPep3 emit volatiles similar to those from plants subjected to herbivory. ZmPep3-treated plants also exhibit induced accumulation of the benzoxazinoid phytoalexin 2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one glucoside. Direct and indirect defenses induced by ZmPep3 contribute to resistance against S. exigua through significant reduction of larval growth and attraction of Cotesia marginiventris parasitoids. ZmPep3 activity is specific to Poaceous species; however, peptides derived from PROPEP orthologs identified in Solanaceous and Fabaceous plants also induce herbivory-associated volatiles in their respective species. These studies demonstrate that Peps are conserved signals across diverse plant families regulating antiherbivore defenses and are likely to be the missing functional homologs of systemin outside of the Solanaceae. PMID:23509266

Key Components of Different Plant Defense Pathways Are Dispensable for Powdery Mildew Resistance of the Arabidopsis mlo2 mlo6 mlo12 Triple Mutant.

PubMed

Kuhn, Hannah; Lorek, Justine; Kwaaitaal, Mark; Consonni, Chiara; Becker, Katia; Micali, Cristina; Ver Loren van Themaat, Emiel; Bednarek, Paweł; Raaymakers, Tom M; Appiano, Michela; Bai, Yuling; Meldau, Dorothea; Baum, Stephani; Conrath, Uwe; Feussner, Ivo; Panstruga, Ralph

2017-01-01

Loss of function mutations of particular plant MILDEW RESISTANCE LOCUS O ( MLO ) genes confer durable and broad-spectrum penetration resistance against powdery mildew fungi. Here, we combined genetic, transcriptomic and metabolomic analyses to explore the defense mechanisms in the fully resistant Arabidopsis thaliana mlo2 mlo6 mlo12 triple mutant. We found that this genotype unexpectedly overcomes the requirement for indolic antimicrobials and defense-related secretion, which are critical for incomplete resistance of mlo2 single mutants. Comparative microarray-based transcriptome analysis of mlo2 mlo6 mlo12 mutants and wild type plants upon Golovinomyces orontii inoculation revealed an increased and accelerated accumulation of many defense-related transcripts. Despite the biotrophic nature of the interaction, this included the non-canonical activation of a jasmonic acid/ethylene-dependent transcriptional program. In contrast to a non-adapted powdery mildew pathogen, the adapted powdery mildew fungus is able to defeat the accumulation of defense-relevant indolic metabolites in a MLO protein-dependent manner. We suggest that a broad and fast activation of immune responses in mlo2 mlo6 mlo12 plants can compensate for the lack of single or few defense pathways. In addition, our results point to a role of Arabidopsis MLO2, MLO6, and MLO12 in enabling defense suppression during invasion by adapted powdery mildew fungi.

Key Components of Different Plant Defense Pathways Are Dispensable for Powdery Mildew Resistance of the Arabidopsis mlo2 mlo6 mlo12 Triple Mutant

PubMed Central

Kuhn, Hannah; Lorek, Justine; Kwaaitaal, Mark; Consonni, Chiara; Becker, Katia; Micali, Cristina; Ver Loren van Themaat, Emiel; Bednarek, Paweł; Raaymakers, Tom M.; Appiano, Michela; Bai, Yuling; Meldau, Dorothea; Baum, Stephani; Conrath, Uwe; Feussner, Ivo; Panstruga, Ralph

2017-01-01

Loss of function mutations of particular plant MILDEW RESISTANCE LOCUS O (MLO) genes confer durable and broad-spectrum penetration resistance against powdery mildew fungi. Here, we combined genetic, transcriptomic and metabolomic analyses to explore the defense mechanisms in the fully resistant Arabidopsis thaliana mlo2 mlo6 mlo12 triple mutant. We found that this genotype unexpectedly overcomes the requirement for indolic antimicrobials and defense-related secretion, which are critical for incomplete resistance of mlo2 single mutants. Comparative microarray-based transcriptome analysis of mlo2 mlo6 mlo12 mutants and wild type plants upon Golovinomyces orontii inoculation revealed an increased and accelerated accumulation of many defense-related transcripts. Despite the biotrophic nature of the interaction, this included the non-canonical activation of a jasmonic acid/ethylene-dependent transcriptional program. In contrast to a non-adapted powdery mildew pathogen, the adapted powdery mildew fungus is able to defeat the accumulation of defense-relevant indolic metabolites in a MLO protein-dependent manner. We suggest that a broad and fast activation of immune responses in mlo2 mlo6 mlo12 plants can compensate for the lack of single or few defense pathways. In addition, our results point to a role of Arabidopsis MLO2, MLO6, and MLO12 in enabling defense suppression during invasion by adapted powdery mildew fungi. PMID:28674541

The Defense Metabolite, Allyl Glucosinolate, Modulates Arabidopsis thaliana Biomass Dependent upon the Endogenous Glucosinolate Pathway

PubMed Central

Francisco, Marta; Joseph, Bindu; Caligagan, Hart; Li, Baohua; Corwin, Jason A.; Lin, Catherine; Kerwin, Rachel; Burow, Meike; Kliebenstein, Daniel J.

2016-01-01

Glucosinolates (GSLs) play an important role in plants as direct mediators of biotic and abiotic stress responses. Recent work is beginning to show that the GSLs can also inducing complex defense and growth networks. However, the physiological significance of these GSL-induced responses and the molecular mechanisms by which GSLs are sensed and/or modulate these responses are not understood. To identify these potential mechanisms within the plant and how they may relate to the endogenous GSLs, we tested the regulatory effect of exogenous allyl GSL application on growth and defense metabolism across sample of Arabidopsis thaliana accessions. We found that application of exogenous allyl GSL had the ability to initiate changes in plant biomass and accumulation of defense metabolites that genetically varied across accessions. This growth effect was related to the allyl GSL side-chain structure. Utilizing this natural variation and mutants in genes within the GSL pathway we could show that the link between allyl GSL and altered growth responses are dependent upon the function of known genes controlling the aliphatic GSL pathway. PMID:27313596

The Defense Metabolite, Allyl Glucosinolate, Modulates Arabidopsis thaliana Biomass Dependent upon the Endogenous Glucosinolate Pathway.

PubMed

Francisco, Marta; Joseph, Bindu; Caligagan, Hart; Li, Baohua; Corwin, Jason A; Lin, Catherine; Kerwin, Rachel; Burow, Meike; Kliebenstein, Daniel J

2016-01-01

Glucosinolates (GSLs) play an important role in plants as direct mediators of biotic and abiotic stress responses. Recent work is beginning to show that the GSLs can also inducing complex defense and growth networks. However, the physiological significance of these GSL-induced responses and the molecular mechanisms by which GSLs are sensed and/or modulate these responses are not understood. To identify these potential mechanisms within the plant and how they may relate to the endogenous GSLs, we tested the regulatory effect of exogenous allyl GSL application on growth and defense metabolism across sample of Arabidopsis thaliana accessions. We found that application of exogenous allyl GSL had the ability to initiate changes in plant biomass and accumulation of defense metabolites that genetically varied across accessions. This growth effect was related to the allyl GSL side-chain structure. Utilizing this natural variation and mutants in genes within the GSL pathway we could show that the link between allyl GSL and altered growth responses are dependent upon the function of known genes controlling the aliphatic GSL pathway.

Parasitism by Cuscuta pentagona attenuates host plant defenses against insect herbivores.

PubMed

Runyon, Justin B; Mescher, Mark C; De Moraes, Consuelo M

2008-03-01

Considerable research has examined plant responses to concurrent attack by herbivores and pathogens, but the effects of attack by parasitic plants, another important class of plant-feeding organisms, on plant defenses against other enemies has not been explored. We investigated how attack by the parasitic plant Cuscuta pentagona impacted tomato (Solanum lycopersicum) defenses against the chewing insect beet armyworm (Spodoptera exigua; BAW). In response to insect feeding, C. pentagona-infested (parasitized) tomato plants produced only one-third of the antiherbivore phytohormone jasmonic acid (JA) produced by unparasitized plants. Similarly, parasitized tomato, in contrast to unparasitized plants, failed to emit herbivore-induced volatiles after 3 d of BAW feeding. Although parasitism impaired antiherbivore defenses, BAW growth was slower on parasitized tomato leaves. Vines of C. pentagona did not translocate JA from BAW-infested plants: amounts of JA in parasite vines grown on caterpillar-fed and control plants were similar. Parasitized plants generally contained more salicylic acid (SA), which can inhibit JA in some systems. Parasitized mutant (NahG) tomato plants deficient in SA produced more JA in response to insect feeding than parasitized wild-type plants, further suggesting cross talk between the SA and JA defense signaling pathways. However, JA induction by BAW was still reduced in parasitized compared to unparasitized NahG, implying that other factors must be involved. We found that parasitized plants were capable of producing induced volatiles when experimentally treated with JA, indicating that resource depletion by the parasite does not fully explain the observed attenuation of volatile response to herbivore feeding. Collectively, these findings show that parasitic plants can have important consequences for host plant defense against herbivores.

Crosstalk between nitric oxide and glutathione is required for NONEXPRESSOR OF PATHOGENESIS-RELATED GENES 1 (NPR1)-dependent defense signaling in Arabidopsis thaliana.

PubMed

Kovacs, Izabella; Durner, Jörg; Lindermayr, Christian

2015-11-01

Nitric oxide (NO) is a ubiquitous signaling molecule involved in a wide range of physiological and pathophysiological processes in animals and plants. Although its significant influence on plant immunity is well known, information about the exact regulatory mechanisms and signaling pathways involved in the defense response to pathogens is still limited. We used genetic, biochemical, pharmacological approaches in combination with infection experiments to investigate the NO-triggered salicylic acid (SA)-dependent defense response in Arabidopsis thaliana. The NO donor S-nitrosoglutathione (GSNO) promoted the nuclear accumulation of NONEXPRESSOR OF PATHOGENESIS-RELATED GENES 1 (NPR1) protein accompanied by an elevated SA concentration and the activation of pathogenesis-related (PR) genes, leading to induced resistance of A. thaliana against Pseudomonas infection. Moreover, NO induced a rapid change in the glutathione status, resulting in increased concentrations of glutathione, which is required for SA accumulation and activation of the NPR1-dependent defense response. Our data imply crosstalk between NO and glutathione, which is integral to the NPR1-dependent defense signaling pathway, and further demonstrate that glutathione is not only an important cellular redox buffer but also a signaling molecule in the plant defense response. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

High CO2 Primes Plant Biotic Stress Defences through Redox-Linked Pathways.

PubMed

Mhamdi, Amna; Noctor, Graham

2016-10-01

Industrial activities have caused tropospheric CO 2 concentrations to increase over the last two centuries, a trend that is predicted to continue for at least the next several decades. Here, we report that growth of plants in a CO 2 -enriched environment activates responses that are central to defense against pathogenic attack. Salicylic acid accumulation was triggered by high-growth CO 2 in Arabidopsis (Arabidopsis thaliana) and other plants such as bean (Phaseolus vulgaris). A detailed analysis in Arabidopsis revealed that elevated CO 2 primes multiple defense pathways, leading to increased resistance to bacterial and fungal challenge. Analysis of gene-specific mutants provided no evidence that activation of plant defense pathways by high CO 2 was caused by stomatal closure. Rather, the activation is partly linked to metabolic effects involving redox signaling. In support of this, genetic modification of redox components (glutathione contents and NADPH-generating enzymes) prevents full priming of the salicylic acid pathway and associated resistance by high CO 2 The data point to a particularly influential role for the nonphosphorylating glyceraldehyde-3-phosphate dehydrogenase, a cytosolic enzyme whose role in plants remains unclear. Our observations add new information on relationships between high CO 2 and oxidative signaling and provide novel insight into plant stress responses in conditions of increased CO 2 . © 2016 American Society of Plant Biologists. All Rights Reserved.

Capsicum annuum homeobox 1 (CaHB1) is a nuclear factor that has roles in plant development, salt tolerance, and pathogen defense.

PubMed

Oh, Sang-Keun; Yoon, Joonseon; Choi, Gyung Ja; Jang, Hyun A; Kwon, Suk-Yoon; Choi, Doil

2013-12-06

Homeodomain-leucine zipper (HD-Zip) family proteins are unique to plants, but little is known about their role in defense responses. CaHB1 is a nuclear factor in peppers, belonging to subfamily II of HD-Zip proteins. Here, we determined the role of CaHB1 in the defense response. CaHB1 expression was induced when pepper plants were challenged with Phytophthora capsici, a plant pathogen to which peppers are susceptible, or environmental stresses such as drought and salt stimuli. CaHB1 was also highly expressed in pepper leaves following application of SA, whereas ethephon and MeJA had a moderate effect. To further investigate the function of CaHB1 in plants, we performed gain-of-function study by overexpression of CaHB1 in tomato. CaHB1-transgenic tomatoes showed significant growth enhancement including increased leaf thickness and enlarged cell size (1.8-fold larger than control plants). Microscopic analysis revealed that leaves from CaHB1-transgenic plants had thicker cell walls and cuticle layers than those from controls. Moreover, CaHB1-transgenic plants displayed enhanced resistance against Phytophthora infestans and increased tolerance to salt stress. Additionally, RT-PCR analysis of CaHB1-transgenic tomatoes revealed constitutive up-regulation of multiple genes involved in plant defense and osmotic stress. Therefore, our findings suggest roles for CaHB1 in development, salt stress, and pathogen defense. Copyright © 2013 Elsevier Inc. All rights reserved.

Downstream divergence of the ethylene signaling pathway for harpin-stimulated Arabidopsis growth and insect defense.

PubMed

Dong, Hong-Ping; Peng, Jianling; Bao, Zhilong; Meng, Xiangdong; Bonasera, Jean M; Chen, Guangyong; Beer, Steven V; Dong, Hansong

2004-11-01

Ethylene (ET) signal transduction may regulate plant growth and defense, depending on which components are recruited into the pathway in response to different stimuli. We report here that the ET pathway controls both insect resistance (IR) and plant growth enhancement (PGE) in Arabidopsis (Arabidopsis thaliana) plants responding to harpin, a protein produced by a plant pathogenic bacterium. PGE may result from spraying plant tops with harpin or by soaking seeds in harpin solution; the latter especially enhances root growth. Plants treated similarly develop resistance to the green peach aphid (Myzus persicae). The salicylic acid pathway, although activated by harpin, does not lead to PGE and IR. By contrast, PGE and IR are induced in both wild-type plants and genotypes that have defects in salicylic acid signaling. In response to harpin, levels of jasmonic acid (JA) decrease, and the COI1 gene, which is indispensable for JA signal transduction, is not expressed in wild-type plants. However, PGE and IR are stimulated in the JA-resistant mutant jar1-1. In the wild type, PGE and IR develop coincidently with increases in ET levels and the expression of several genes essential for ET signaling. The ET receptor gene ETR1 is required because both phenotypes are arrested in the etr1-1 mutant. Consistently, inhibition of ET perception nullifies the induction of both PGE and IR. The signal transducer EIN2 is required for IR, and EIN5 is required for PGE because IR and PGE are impaired correspondingly in the ein2-1 and ein5-1 mutants. Therefore, harpin activates ET signaling while conscribing EIN2 and EIN5 to confer IR and PGE, respectively.

Volatile compounds from beneficial or pathogenic bacteria differentially regulate root exudation, transcription of iron transporters, and defense signaling pathways in Sorghum bicolor.

PubMed

Hernández-Calderón, Erasto; Aviles-Garcia, Maria Elizabeth; Castulo-Rubio, Diana Yazmín; Macías-Rodríguez, Lourdes; Ramírez, Vicente Montejano; Santoyo, Gustavo; López-Bucio, José; Valencia-Cantero, Eduardo

2018-02-01

Our results show that Sorghum bicolor is able to recognize bacteria through its volatile compounds and differentially respond to beneficial or pathogens via eliciting nutritional or defense adaptive traits. Plants establish beneficial, harmful, or neutral relationships with bacteria. Plant growth promoting rhizobacteria (PGPR) emit volatile compounds (VCs), which may act as molecular cues influencing plant development, nutrition, and/or defense. In this study, we compared the effects of VCs produced by bacteria with different lifestyles, including Arthrobacter agilis UMCV2, Bacillus methylotrophicus M4-96, Sinorhizobium meliloti 1021, the plant pathogen Pseudomonas aeruginosa PAO1, and the commensal rhizobacterium Bacillus sp. L2-64, on S. bicolor. We show that VCs from all tested bacteria, except Bacillus sp. L2-64, increased biomass and chlorophyll content, and improved root architecture, but notheworthy A. agilis induced the release of attractant molecules, whereas P. aeruginosa activated the exudation of growth inhibitory compounds by roots. An analysis of the expression of iron-transporters SbIRT1, SbIRT2, SbYS1, and SbYS2 and genes related to plant defense pathways COI1 and PR-1 indicated that beneficial, pathogenic, and commensal bacteria could up-regulate iron transporters, whereas only beneficial and pathogenic species could induce a defense response. These results show how S. bicolor could recognize bacteria through their volatiles profiles and highlight that PGPR or pathogens can elicit nutritional or defensive traits in plants.

Microbial modulation of bacoside A biosynthetic pathway and systemic defense mechanism in Bacopa monnieri under Meloidogyne incognita stress.

PubMed

Gupta, Rupali; Singh, Akanksha; Srivastava, Madhumita; Singh, Vivek; Gupta, M M; Pandey, Rakesh

2017-02-03

Plant-associated beneficial microbes have been explored to fulfill the imperative function for plant health. However, their impact on the host secondary metabolite production and nematode disease management remains elusive. Our present work has shown that chitinolytic microbes viz., Chitiniphilus sp. MTN22 and Streptomyces sp. MTN14 singly as well as in combination modulated the biosynthetic pathway of bacoside A and systemic defense mechanism against Meloidogyne incognita in Bacopa monnieri. Interestingly, expression of bacoside biosynthetic pathway genes (3-Hydroxy-3-methylglutaryl coenzyme A reductase, mevalonate diphosphate decarboxylase, and squalene synthase) were upregulated in plants treated with the microbial combination in the presence as well as in absence of M. incognita stress. These microbes not only augmented bacoside A production (1.5 fold) but also strengthened host resistance via enhancement in chlorophyll a, defense enzymes and phenolic compounds like gallic acid, syringic acid, ferulic acid and cinnamic acid. Furthermore, elevated lignification and callose deposition in the microbial combination treated plants corroborate well with the above findings. Overall, the results provide novel insights into the underlying mechanisms of priming by beneficial microbes and underscore their capacity to trigger bacoside A production in B. monnieri under biotic stress.

Microbial modulation of bacoside A biosynthetic pathway and systemic defense mechanism in Bacopa monnieri under Meloidogyne incognita stress

PubMed Central

Gupta, Rupali; Singh, Akanksha; Srivastava, Madhumita; Singh, Vivek; Gupta, M. M.; Pandey, Rakesh

2017-01-01

Plant-associated beneficial microbes have been explored to fulfill the imperative function for plant health. However, their impact on the host secondary metabolite production and nematode disease management remains elusive. Our present work has shown that chitinolytic microbes viz., Chitiniphilus sp. MTN22 and Streptomyces sp. MTN14 singly as well as in combination modulated the biosynthetic pathway of bacoside A and systemic defense mechanism against Meloidogyne incognita in Bacopa monnieri. Interestingly, expression of bacoside biosynthetic pathway genes (3-Hydroxy-3-methylglutaryl coenzyme A reductase, mevalonate diphosphate decarboxylase, and squalene synthase) were upregulated in plants treated with the microbial combination in the presence as well as in absence of M. incognita stress. These microbes not only augmented bacoside A production (1.5 fold) but also strengthened host resistance via enhancement in chlorophyll a, defense enzymes and phenolic compounds like gallic acid, syringic acid, ferulic acid and cinnamic acid. Furthermore, elevated lignification and callose deposition in the microbial combination treated plants corroborate well with the above findings. Overall, the results provide novel insights into the underlying mechanisms of priming by beneficial microbes and underscore their capacity to trigger bacoside A production in B. monnieri under biotic stress. PMID:28157221

Unbalanced Activation of Glutathione Metabolic Pathways Suggests Potential Involvement in Plant Defense against the Gall Midge Mayetiola destructor in Wheat

PubMed Central

Liu, Xuming; Zhang, Shize; Whitworth, R. Jeff; Stuart, Jeffrey J.; Chen, Ming-Shun

2015-01-01

Glutathione, γ-glutamylcysteinylglycine, exists abundantly in nearly all organisms. Glutathione participates in various physiological processes involved in redox reactions by serving as an electron donor/acceptor. We found that the abundance of total glutathione increased up to 60% in resistant wheat plants within 72 hours following attack by the gall midge Mayetiola destructor, the Hessian fly. The increase in total glutathione abundance, however, is coupled with an unbalanced activation of glutathione metabolic pathways. The activity and transcript abundance of glutathione peroxidases, which convert reduced glutathione (GSH) to oxidized glutathione (GSSG), increased in infested resistant plants. However, the enzymatic activity and transcript abundance of glutathione reductases, which convert GSSG back to GSH, did not change. This unbalanced regulation of the glutathione oxidation/reduction cycle indicates the existence of an alternative pathway to regenerate GSH from GSSG to maintain a stable GSSG/GSH ratio. Our data suggest the possibility that GSSG is transported from cytosol to apoplast to serve as an oxidant for class III peroxidases to generate reactive oxygen species for plant defense against Hessian fly larvae. Our results provide a foundation for elucidating the molecular processes involved in glutathione-mediated plant resistance to Hessian fly and potentially other pests as well. PMID:25627558

Host plant species determines symbiotic bacterial community mediating suppression of plant defenses.

PubMed

Chung, Seung Ho; Scully, Erin D; Peiffer, Michelle; Geib, Scott M; Rosa, Cristina; Hoover, Kelli; Felton, Gary W

2017-01-03

Herbivore associated bacteria are vital mediators of plant and insect interactions. Host plants play an important role in shaping the gut bacterial community of insects. Colorado potato beetles (CPB; Leptinotarsa decemlineata) use several Solanum plants as hosts in their natural environment. We previously showed that symbiotic gut bacteria from CPB larvae suppressed jasmonate (JA)-induced defenses in tomato. However, little is known about how changes in the bacterial community may be involved in the manipulation of induced defenses in wild and cultivated Solanum plants of CPB. Here, we examined suppression of JA-mediated defense in wild and cultivated hosts of CPB by chemical elicitors and their symbiotic bacteria. Furthermore, we investigated associations between the gut bacterial community and suppression of plant defenses using 16 S rRNA amplicon sequencing. Symbiotic bacteria decreased plant defenses in all Solanum hosts and there were different gut bacterial communities in CPB fed on different host plants. When larvae were reared on different hosts, defense suppression differed among host plants. These results demonstrate that host plants influence herbivore gut bacterial communities and consequently affect the herbivore's ability to manipulate JA-mediated plant defenses. Thus, the presence of symbiotic bacteria that suppress plant defenses might help CPB adapt to host plants.

Host plant species determines symbiotic bacterial community mediating suppression of plant defenses

PubMed Central

Chung, Seung Ho; Scully, Erin D.; Peiffer, Michelle; Geib, Scott M.; Rosa, Cristina; Hoover, Kelli; Felton, Gary W.

2017-01-01

Herbivore associated bacteria are vital mediators of plant and insect interactions. Host plants play an important role in shaping the gut bacterial community of insects. Colorado potato beetles (CPB; Leptinotarsa decemlineata) use several Solanum plants as hosts in their natural environment. We previously showed that symbiotic gut bacteria from CPB larvae suppressed jasmonate (JA)-induced defenses in tomato. However, little is known about how changes in the bacterial community may be involved in the manipulation of induced defenses in wild and cultivated Solanum plants of CPB. Here, we examined suppression of JA-mediated defense in wild and cultivated hosts of CPB by chemical elicitors and their symbiotic bacteria. Furthermore, we investigated associations between the gut bacterial community and suppression of plant defenses using 16 S rRNA amplicon sequencing. Symbiotic bacteria decreased plant defenses in all Solanum hosts and there were different gut bacterial communities in CPB fed on different host plants. When larvae were reared on different hosts, defense suppression differed among host plants. These results demonstrate that host plants influence herbivore gut bacterial communities and consequently affect the herbivore’s ability to manipulate JA-mediated plant defenses. Thus, the presence of symbiotic bacteria that suppress plant defenses might help CPB adapt to host plants. PMID:28045052

Ligand-receptor co-evolution shaped the jasmonate pathway in land plants.

PubMed

Monte, Isabel; Ishida, Sakiko; Zamarreño, Angel M; Hamberg, Mats; Franco-Zorrilla, José M; García-Casado, Gloria; Gouhier-Darimont, Caroline; Reymond, Philippe; Takahashi, Kosaku; García-Mina, José M; Nishihama, Ryuichi; Kohchi, Takayuki; Solano, Roberto

2018-05-01

The phytohormone jasmonoyl-isoleucine (JA-Ile) regulates defense, growth and developmental responses in vascular plants. Bryophytes have conserved sequences for all JA-Ile signaling pathway components but lack JA-Ile. We show that, in spite of 450 million years of independent evolution, the JA-Ile receptor COI1 is functionally conserved between the bryophyte Marchantia polymorpha and the eudicot Arabidopsis thaliana but COI1 responds to different ligands in each species. We identified the ligand of Marchantia MpCOI1 as two isomeric forms of the JA-Ile precursor dinor-OPDA (dinor-cis-OPDA and dinor-iso-OPDA). We demonstrate that AtCOI1 functionally complements Mpcoi1 mutation and confers JA-Ile responsiveness and that a single-residue substitution in MpCOI1 is responsible for the evolutionary switch in ligand specificity. Our results identify the ancestral bioactive jasmonate and clarify its biosynthetic pathway, demonstrate the functional conservation of its signaling pathway, and show that JA-Ile and COI1 emergence in vascular plants required co-evolution of hormone biosynthetic complexity and receptor specificity.

Tricking the guard: exploiting plant defense for disease susceptibility.

PubMed

Lorang, J; Kidarsa, T; Bradford, C S; Gilbert, B; Curtis, M; Tzeng, S-C; Maier, C S; Wolpert, T J

2012-11-02

Typically, pathogens deploy virulence effectors to disable defense. Plants defeat effectors with resistance proteins that guard effector targets. We found that a pathogen exploits a resistance protein by activating it to confer susceptibility in Arabidopsis. The guard mechanism of plant defense is recapitulated by interactions among victorin (an effector produced by the necrotrophic fungus Cochliobolus victoriae), TRX-h5 (a defense-associated thioredoxin), and LOV1 (an Arabidopsis susceptibility protein). In LOV1's absence, victorin inhibits TRX-h5, resulting in compromised defense but not disease by C. victoriae. In LOV1's presence, victorin binding to TRX-h5 activates LOV1 and elicits a resistance-like response that confers disease susceptibility. We propose that victorin is, or mimics, a conventional pathogen virulence effector that was defeated by LOV1 and confers virulence to C. victoriae solely because it incites defense.

Capsicum annuum homeobox 1 (CaHB1) is a nuclear factor that has roles in plant development, salt tolerance, and pathogen defense

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

Oh, Sang-Keun; Yoon, Joonseon; Choi, Gyung Ja

Highlights: •The CaHB1 is a nuclear factor, belonging to HD-Zip proteins. •SA and ET, as signal molecules, modulate CaHB1-mediated responses. •Overexpression of CaHB1 in tomato resulted in a thicker cell wall. •CaHB1-transgenic tomato confers resistance to Phytophthora infestans. •CaHB1 enhanced tolerance to saline stress in tomato. -- Abstract: Homeodomain-leucine zipper (HD-Zip) family proteins are unique to plants, but little is known about their role in defense responses. CaHB1 is a nuclear factor in peppers, belonging to subfamily II of HD-Zip proteins. Here, we determined the role of CaHB1 in the defense response. CaHB1 expression was induced when pepper plants weremore » challenged with Phytophthora capsici, a plant pathogen to which peppers are susceptible, or environmental stresses such as drought and salt stimuli. CaHB1 was also highly expressed in pepper leaves following application of SA, whereas ethephon and MeJA had a moderate effect. To further investigate the function of CaHB1 in plants, we performed gain-of-function study by overexpression of CaHB1 in tomato. CaHB1-transgenic tomatoes showed significant growth enhancement including increased leaf thickness and enlarged cell size (1.8-fold larger than control plants). Microscopic analysis revealed that leaves from CaHB1-transgenic plants had thicker cell walls and cuticle layers than those from controls. Moreover, CaHB1-transgenic plants displayed enhanced resistance against Phytophthora infestans and increased tolerance to salt stress. Additionally, RT-PCR analysis of CaHB1-transgenic tomatoes revealed constitutive up-regulation of multiple genes involved in plant defense and osmotic stress. Therefore, our findings suggest roles for CaHB1 in development, salt stress, and pathogen defense.« less

Mechanisms and strategies of plant defense against Botrytis cinerea.

PubMed

AbuQamar, Synan; Moustafa, Khaled; Tran, Lam Son

2017-03-01

Biotic factors affect plant immune responses and plant resistance to pathogen infections. Despite the considerable progress made over the past two decades in manipulating genes, proteins and their levels from diverse sources, no complete genetic tolerance to environmental stresses has been developed so far in any crops. Plant defense response to pathogens, including Botrytis cinerea, is a complex biological process involving various changes at the biochemical, molecular (i.e. transcriptional) and physiological levels. Once a pathogen is detected, effective plant resistance activates signaling networks through the generation of small signaling molecules and the balance of hormonal signaling pathways to initiate defense mechanisms to the particular pathogen. Recently, studies using Arabidopsis thaliana and crop plants have shown that many genes are involved in plant responses to B. cinerea infection. In this article, we will review our current understanding of mechanisms regulating plant responses to B. cinerea with a particular interest on hormonal regulatory networks involving phytohormones salicylic acid (SA), jasmonic acid (JA), ethylene (ET) and abscisic acid (ABA). We will also highlight some potential gene targets that are promising for improving crop resistance to B. cinerea through genetic engineering and breeding programs. Finally, the role of biological control as a complementary and alternative disease management will be overviewed.

Indirect Plant Defense against Insect Herbivores: A Review

USDA-ARS?s Scientific Manuscript database

Plants respond to herbivore attack by launching two types of defenses: direct defense and indirect defense. Direct defense includes all plant traits that increase the resistance of host plants to attacking insect herbivores by affecting the physiology and/or behavior of the attackers. Indirect defe...

NpPDR1, a Pleiotropic Drug Resistance-Type ATP-Binding Cassette Transporter from Nicotiana plumbaginifolia, Plays a Major Role in Plant Pathogen Defense1

PubMed Central

Stukkens, Yvan; Bultreys, Alain; Grec, Sébastien; Trombik, Tomasz; Vanham, Delphine; Boutry, Marc

2005-01-01

Nicotiana plumbaginifolia NpPDR1, a plasma membrane pleiotropic drug resistance-type ATP-binding cassette transporter formerly named NpABC1, has been suggested to transport the diterpene sclareol, an antifungal compound. However, direct evidence for a role of pleiotropic drug resistance transporters in the plant defense is still lacking. In situ immunolocalization and histochemical analysis using the gusA reporter gene showed that NpPDR1 was constitutively expressed in the whole root, in the leaf glandular trichomes, and in the flower petals. However, NpPDR1 expression was induced in the whole leaf following infection with the fungus Botrytis cinerea, and the bacteria Pseudomonas syringae pv tabaci, Pseudomonas fluorescens, and Pseudomonas marginalis pv marginalis, which do not induce a hypersensitive response in N. plumbaginifolia, whereas a weaker response was observed using P. syringae pv syringae, which does induce a hypersensitive response. Induced NpPDR1 expression was more associated with the jasmonic acid than the salicylic acid signaling pathway. These data suggest that NpPDR1 is involved in both constitutive and jasmonic acid-dependent induced defense. Transgenic plants in which NpPDR1 expression was prevented by RNA interference showed increased sensitivity to sclareol and reduced resistance to B. cinerea. These data show that NpPDR1 is involved in pathogen resistance and thus demonstrate a new role for the ATP-binding cassette transporter family. PMID:16126865

Transcriptome analysis of tobacco BY-2 cells elicited by cryptogein reveals new potential actors of calcium-dependent and calcium-independent plant defense pathways.

PubMed

Amelot, Nicolas; Dorlhac de Borne, François; San Clemente, Hélène; Mazars, Christian; Grima-Pettenati, Jacqueline; Brière, Christian

2012-02-01

Cryptogein is a proteinaceous elicitor secreted by the oomycete Phytophthora cryptogea, which induces a hypersensitive response in tobacco plants. We have previously reported that in tobacco BY-2 cells treated with cryptogein, most of the genes of the phenylpropanoid pathway were upregulated and cell wall-bound phenolics accumulated. Both events were Ca(2+) dependent. In this study, we designed a microarray covering a large proportion of the tobacco genome and monitored gene expression in cryptogein-elicited BY-2 cells to get a more complete view of the transcriptome changes and to assess their Ca(2+) dependence. The predominant functional gene categories affected by cryptogein included stress- and disease-related proteins, phenylpropanoid pathway, signaling components, transcription factors and cell wall reinforcement. Among the 3819 unigenes whose expression changed more than fourfold, 90% were Ca(2+) dependent, as determined by their sensitivity to lanthanum chloride. The most Ca(2+)-dependent transcripts upregulated by cryptogein were involved in defense responses or the oxylipin pathway. This genome-wide study strongly supports the importance of Ca(2+)-dependent transcriptional regulation of regulatory and defense-related genes contributing to cryptogein responses in tobacco. Copyright © 2011 Elsevier Ltd. All rights reserved.

Elevated CO2 differentially affects tobacco and rice defense against lepidopteran larvae via the jasmonic acid signaling pathway.

PubMed

Lu, Chengkai; Qi, Jinfeng; Hettenhausen, Christian; Lei, Yunting; Zhang, Jingxiong; Zhang, Mou; Zhang, Cuiping; Song, Juan; Li, Jing; Cao, Guoyan; Malook, Saif Ul; Wu, Jianqiang

2018-05-01

Atmospheric CO 2 levels are rapidly increasing due to human activities. However, the effects of elevated CO 2 (ECO 2 ) on plant defense against insects and the underlying mechanisms remain poorly understood. Here we show that ECO 2 increased the photosynthetic rates and the biomass of tobacco and rice plants, and the chewing lepidopteran insects Spodoptera litura and Mythimna separata gained less and more mass on tobacco and rice plants, respectively. Consistently, under ECO 2 , the levels of jasmonic acid (JA), the main phytohormone controlling plant defense against these lepidopteran insects, as well as the main defense-related metabolites, were increased and decreased in insect-damaged tobacco and rice plants. Importantly, bioassays and quantification of defense-related metabolites in tobacco and rice silenced in JA biosynthesis and perception indicate that ECO 2 changes plant resistance mainly by affecting the JA pathway. We further demonstrate that the defensive metabolites, but not total N or protein, are the main factors contributing to the altered defense levels under ECO 2 . This study illustrates that ECO 2 changes the interplay between plants and insects, and we propose that crops should be studied for their resistance to the major pests under ECO 2 to predict the impact of ECO 2 on future agroecosystems. © 2018 Institute of Botany, Chinese Academy of Sciences.

BPF-1, a pathogen-induced DNA-binding protein involved in the plant defense response.

PubMed

da Costa e Silva, O; Klein, L; Schmelzer, E; Trezzini, G F; Hahlbrock, K

1993-07-01

The mechanisms by which plants restrict the growth of pathogens include transient activation of numerous defense-related genes. Box P is a putative cis-acting element of a distinct group of such genes, including those encoding the enzyme phenylalanine ammonialyase (PAL). A DNA-binding activity to Box P was identified in nuclear extracts from cultured parsley cells and a cDNA encoding the protein BPF-1 (Box P-binding Factor) partially characterized. BPF-1 binds to this element with specificity similar to that of the binding activity in nuclear extracts. BPF-1 mRNA accumulates rapidly in elicitor-treated parsley cells and around fungal infection sites on parsley leaves. This accumulation is, at least partly, due to a rapid and transient increase in the transcription rate of BPF-1. Moreover, tight correlation between the relative amounts of BPF-1 and PAL mRNAs was observed in different organs of a parsley plant. These results are consistent with the hypothesis that BPF-1 is involved in disease resistance by modulating plant defense gene expression.

Interacting signal pathways control defense gene expression in Arabidopsis in response to cell wall-degrading enzymes from Erwinia carotovora.

PubMed

Norman-Setterblad, C; Vidal, S; Palva, E T

2000-04-01

We have characterized the role of salicylic acid (SA)-independent defense signaling in Arabidopsis thaliana in response to the plant pathogen Erwinia carotovora subsp. carotovora. Use of pathway-specific target genes as well as signal mutants allowed us to elucidate the role and interactions of ethylene, jasmonic acid (JA), and SA signal pathways in this response. Gene expression studies suggest a central role for both ethylene and JA pathways in the regulation of defense gene expression triggered by the pathogen or by plant cell wall-degrading enzymes (CF) secreted by the pathogen. Our results suggest that ethylene and JA act in concert in this regulation. In addition, CF triggers another, strictly JA-mediated response inhibited by ethylene and SA. SA does not appear to have a major role in activating defense gene expression in response to CF. However, SA may have a dual role in controlling CF-induced gene expression, by enhancing the expression of genes synergistically induced by ethylene and JA and repressing genes induced by JA alone.

Soybean Homologs of MPK4 Negatively Regulate Defense Responses and Positively Regulate Growth and Development1[W][OA

PubMed Central

Liu, Jian-Zhong; Horstman, Heidi D.; Braun, Edward; Graham, Michelle A.; Zhang, Chunquan; Navarre, Duroy; Qiu, Wen-Li; Lee, Yeunsook; Nettleton, Dan; Hill, John H.; Whitham, Steven A.

2011-01-01

Mitogen-activated protein kinase (MAPK) cascades play important roles in disease resistance in model plant species such as Arabidopsis (Arabidopsis thaliana) and tobacco (Nicotiana tabacum). However, the importance of MAPK signaling pathways in the disease resistance of crops is still largely uninvestigated. To better understand the role of MAPK signaling pathways in disease resistance in soybean (Glycine max), 13, nine, and 10 genes encoding distinct MAPKs, MAPKKs, and MAPKKKs, respectively, were silenced using virus-induced gene silencing mediated by Bean pod mottle virus. Among the plants silenced for various MAPKs, MAPKKs, and MAPKKKs, those in which GmMAPK4 homologs (GmMPK4s) were silenced displayed strong phenotypes including stunted stature and spontaneous cell death on the leaves and stems, the characteristic hallmarks of activated defense responses. Microarray analysis showed that genes involved in defense responses, such as those in salicylic acid (SA) signaling pathways, were significantly up-regulated in GmMPK4-silenced plants, whereas genes involved in growth and development, such as those in auxin signaling pathways and in cell cycle and proliferation, were significantly down-regulated. As expected, SA and hydrogen peroxide accumulation was significantly increased in GmMPK4-silenced plants. Accordingly, GmMPK4-silenced plants were more resistant to downy mildew and Soybean mosaic virus compared with vector control plants. Using bimolecular fluorescence complementation analysis and in vitro kinase assays, we determined that GmMKK1 and GmMKK2 might function upstream of GmMPK4. Taken together, our results indicate that GmMPK4s negatively regulate SA accumulation and defense response but positively regulate plant growth and development, and their functions are conserved across plant species. PMID:21878550

Indirect plant defense against insect herbivores: a review.

PubMed

Aljbory, Zainab; Chen, Ming-Shun

2018-02-01

Plants respond to herbivore attack by launching 2 types of defenses: direct defense and indirect defense. Direct defense includes all plant traits that increase the resistance of host plants to insect herbivores by affecting the physiology and/or behavior of the attackers. Indirect defense includes all traits that by themselves do not have significant direct impact on the attacking herbivores, but can attract natural enemies of the herbivores and thus reduce plant loss. When plants recognize herbivore-associated elicitors, they produce and release a blend of volatiles that can attract predators, parasites, and other natural enemies. Known herbivore-associated elicitors include fatty acid-amino acid conjugates, sulfur-containing fatty acids, fragments of cell walls, peptides, esters, and enzymes. Identified plant volatiles include terpenes, nitrogenous compounds, and indoles. In addition, constitive traits including extrafloral nectars, food bodies, and domatia can be further induced to higher levels and attract natural enemies as well as provide food and shelter to carnivores. A better understanding of indirect plant defense at global and componential levels via advanced high throughput technologies may lead to utilization of indirect defense in suppression of herbivore damage to plants. © 2016 Institute of Zoology, Chinese Academy of Sciences.

Disarming the jasmonate-dependent plant defense makes nonhost Arabidopsis plants accessible to the American serpentine leafminer.

PubMed

Abe, Hiroshi; Tateishi, Ken; Seo, Shigemi; Kugimiya, Soichi; Hirai, Masami Yokota; Sawada, Yuji; Murata, Yoshiyuki; Yara, Kaori; Shimoda, Takeshi; Kobayashi, Masatomo

2013-11-01

Here, we analyzed the interaction between Arabidopsis (Arabidopsis thaliana) and the American serpentine leafminer (Liriomyza trifolii), an important and intractable herbivore of many cultivated plants. We examined the role of the immunity-related plant hormone jasmonate (JA) in the plant response and resistance to leafminer feeding to determine whether JA affects host suitability for leafminers. The expression of marker genes for the JA-dependent plant defense was induced by leafminer feeding on Arabidopsis wild-type plants. Analyses of JA-insensitive coi1-1 mutants suggested the importance of JA in the plant response to leafminer feeding. The JA content of wild-type plants significantly increased after leafminer feeding. Moreover, coi1-1 mutants showed lower feeding resistance against leafminer attack than did wild-type plants. The number of feeding scars caused by inoculated adult leafminers in JA-insensitive coi1-1 mutants was higher than that in wild-type plants. In addition, adults of the following generation appeared only from coi1-1 mutants and not from wild-type plants, suggesting that the loss of the JA-dependent plant defense converted nonhost plants to accessible host plants. Interestingly, the glucosinolate-myrosinase defense system may play at most a minor role in this conversion, indicating that this major antiherbivore defense of Brassica species plants probably does not have a major function in plant resistance to leafminer. Application of JA to wild-type plants before leafminer feeding enhanced feeding resistance in Chinese cabbage (Brassica rapa), tomato (Solanum lycopersicum), and garland chrysanthemum (Chrysanthemum coronarium). Our results indicate that JA plays an important role in the plant response and resistance to leafminers and, in so doing, affects host plant suitability for leafminers.

AtNUDT7, a Negative Regulator of Basal Immunity in Arabidopsis, Modulates Two Distinct Defense Response Pathways and Is Involved in Maintaining Redox Homeostasis1[C][OA

PubMed Central

Ge, Xiaochun; Li, Guo-Jing; Wang, Sheng-Bing; Zhu, Huifen; Zhu, Tong; Wang, Xun; Xia, Yiji

2007-01-01

Plants have evolved complicated regulatory systems to control immune responses. Both positive and negative signaling pathways interplay to coordinate development of a resistance response with the appropriate amplitude and duration. AtNUDT7, a Nudix domain-containing protein in Arabidopsis (Arabidopsis thaliana) that hydrolyzes nucleotide derivatives, was found to be a negative regulator of the basal defense response, and its loss-of-function mutation results in enhanced resistance to infection by Pseudomonas syringae. The nudt7 mutation does not cause a strong constitutive disease resistance phenotype, but it leads to a heightened defense response, including accelerated activation of defense-related genes that can be triggered by pathogenic and nonpathogenic microorganisms. The nudt7 mutation enhances two distinct defense response pathways: one independent of and the other dependent on NPR1 and salicylic acid accumulation. In vitro enzymatic assays revealed that ADP-ribose and NADH are preferred substrates of NUDT7, and the hydrolysis activity of NUDT7 is essential for its biological function and is sensitive to inhibition by Ca2+. Further analyses indicate that ADP-ribose is not likely the physiological substrate of NUDT7. However, the nudt7 mutation leads to perturbation of cellular redox homeostasis and a higher level of NADH in pathogen-challenged leaves. The study suggests that the alteration in cellular antioxidant status caused by the nudt7 mutation primes the cells for the amplified defense response and NUDT7 functions to modulate the defense response to prevent excessive stimulation. PMID:17660350

Trichodiene Production in a Trichoderma harzianum erg1-Silenced Strain Provides Evidence of the Importance of the Sterol Biosynthetic Pathway in Inducing Plant Defense-Related Gene Expression.

PubMed

Malmierca, M G; McCormick, S P; Cardoza, R E; Monte, E; Alexander, N J; Gutiérrez, S

2015-11-01

Trichoderma species are often used as biocontrol agents against plant-pathogenic fungi. A complex molecular interaction occurs among the biocontrol agent, the antagonistic fungus, and the plant. Terpenes and sterols produced by the biocontrol fungus have been found to affect gene expression in both the antagonistic fungus and the plant. The terpene trichodiene (TD) elicits the expression of genes related to tomato defense and to Botrytis virulence. We show here that TD itself is able to induce the expression of Botrytis genes involved in the synthesis of botrydial (BOT) and also induces terpene gene expression in Trichoderma spp. The terpene ergosterol, in addition to its role as a structural component of the fungal cell membranes, acts as an elicitor of defense response in plants. In the present work, using a transformant of T. harzianum, which is silenced in the erg1 gene and accumulates high levels of squalene, we show that this ergosterol precursor also acts as an important elicitor molecule of tomato defense-related genes and induces Botrytis genes involved in BOT biosynthesis, in both cases, in a concentration-dependent manner. Our data emphasize the importance of a balance of squalene and ergosterol in fungal interactions as well as in the biocontrol activity of Trichoderma spp.

Long non-coding RNAs as molecular players in plant defense against pathogens.

PubMed

Zaynab, Madiha; Fatima, Mahpara; Abbas, Safdar; Umair, Muhammad; Sharif, Yasir; Raza, Muhammad Ammar

2018-05-31

Long non-coding RNAs (lncRNAs) has significant role in of gene expression and silencing pathways for several biological processes in eukaryotes. lncRNAs has been reported as key player in remodeling chromatin and genome architecture, RNA stabilization and transcription regulation, including enhancer-associated activity. Host lncRNAs are reckoned as compulsory elements of plant defense. In response to pathogen attack, plants protect themselves with the help of lncRNAs -dependent immune systems in which lncRNAs regulate pathogen-associated molecular patterns (PAMPs) and other effectors. Role of lncRNAs in plant microbe interaction has been studied extensively but regulations of several lncRNAs still need extensive research. In this study we discussed and provide as overview the topical advancements and findings relevant to pathogen attack and plant defense mediated by lncRNAs. It is hoped that lncRNAs would be exploited as a mainstream player to achieve food security by tackling different plant diseases. Copyright © 2018. Published by Elsevier Ltd.

Seaweed Polysaccharides and Derived Oligosaccharides Stimulate Defense Responses and Protection Against Pathogens in Plants

PubMed Central

Vera, Jeannette; Castro, Jorge; Gonzalez, Alberto; Moenne, Alejandra

2011-01-01

Plants interact with the environment by sensing “non-self” molecules called elicitors derived from pathogens or other sources. These molecules bind to specific receptors located in the plasma membrane and trigger defense responses leading to protection against pathogens. In particular, it has been shown that cell wall and storage polysaccharides from green, brown and red seaweeds (marine macroalgae) corresponding to ulvans, alginates, fucans, laminarin and carrageenans can trigger defense responses in plants enhancing protection against pathogens. In addition, oligosaccharides obtained by depolymerization of seaweed polysaccharides also induce protection against viral, fungal and bacterial infections in plants. In particular, most seaweed polysaccharides and derived oligosaccharides trigger an initial oxidative burst at local level and the activation of salicylic (SA), jasmonic acid (JA) and/or ethylene signaling pathways at systemic level. The activation of these signaling pathways leads to an increased expression of genes encoding: (i) Pathogenesis-Related (PR) proteins with antifungal and antibacterial activities; (ii) defense enzymes such as pheylalanine ammonia lyase (PAL) and lipoxygenase (LOX) which determine accumulation of phenylpropanoid compounds (PPCs) and oxylipins with antiviral, antifugal and antibacterial activities and iii) enzymes involved in synthesis of terpenes, terpenoids and/or alkaloids having antimicrobial activities. Thus, seaweed polysaccharides and their derived oligosaccharides induced the accumulation of proteins and compounds with antimicrobial activities that determine, at least in part, the enhanced protection against pathogens in plants. PMID:22363237

Seaweed polysaccharides and derived oligosaccharides stimulate defense responses and protection against pathogens in plants.

PubMed

Vera, Jeannette; Castro, Jorge; Gonzalez, Alberto; Moenne, Alejandra

2011-12-01

Plants interact with the environment by sensing "non-self" molecules called elicitors derived from pathogens or other sources. These molecules bind to specific receptors located in the plasma membrane and trigger defense responses leading to protection against pathogens. In particular, it has been shown that cell wall and storage polysaccharides from green, brown and red seaweeds (marine macroalgae) corresponding to ulvans, alginates, fucans, laminarin and carrageenans can trigger defense responses in plants enhancing protection against pathogens. In addition, oligosaccharides obtained by depolymerization of seaweed polysaccharides also induce protection against viral, fungal and bacterial infections in plants. In particular, most seaweed polysaccharides and derived oligosaccharides trigger an initial oxidative burst at local level and the activation of salicylic (SA), jasmonic acid (JA) and/or ethylene signaling pathways at systemic level. The activation of these signaling pathways leads to an increased expression of genes encoding: (i) Pathogenesis-Related (PR) proteins with antifungal and antibacterial activities; (ii) defense enzymes such as pheylalanine ammonia lyase (PAL) and lipoxygenase (LOX) which determine accumulation of phenylpropanoid compounds (PPCs) and oxylipins with antiviral, antifugal and antibacterial activities and iii) enzymes involved in synthesis of terpenes, terpenoids and/or alkaloids having antimicrobial activities. Thus, seaweed polysaccharides and their derived oligosaccharides induced the accumulation of proteins and compounds with antimicrobial activities that determine, at least in part, the enhanced protection against pathogens in plants.

Control of the ethylene signaling pathway prevents plant defenses during intracellular accommodation of the rhizobia.

PubMed

Berrabah, Fathi; Balliau, Thierry; Aït-Salem, El Hosseyn; George, Jeoffrey; Zivy, Michel; Ratet, Pascal; Gourion, Benjamin

2018-04-18

Massive intracellular populations of symbiotic bacteria, referred to as rhizobia, are housed in legume root nodules. Little is known about the mechanisms preventing the development of defense in these organs although genes such as SymCRK and DNF2 of the model legume Medicago truncatula are required for this control after rhizobial internalization in host nodule cells. Here we investigated the molecular basis of the symbiotic control of immunity. Proteomic analysis was performed to compare functional (wild-type) and defending nodules (symCRK). Based on the results, the control of plant immunity during the functional step of the symbiosis was further investigated by biochemical and pharmacological approaches as well as by transcript and histology analysis. Ethylene was identified as a potential signal inducing plant defenses in symCRK nodules. Involvement of this phytohormone in symCRK and dnf2-developed defenses and in the death of intracellular rhizobia was confirmed. This negative effect of ethylene depended on the M. truncatula sickle gene and was also observed in the legume Lotus japonicus. Together, these data indicate that prevention of ethylene-triggered defenses is crucial for the persistence of endosymbiosis and that the DNF2 and SymCRK genes are required for this process. © 2018 CNRS New Phytologist © 2018 New Phytologist Trust.

Silencing and innate immunity in plant defense against viral and non-viral pathogens.

PubMed

Zvereva, Anna S; Pooggin, Mikhail M

2012-10-29

The frontline of plant defense against non-viral pathogens such as bacteria, fungi and oomycetes is provided by transmembrane pattern recognition receptors that detect conserved pathogen-associated molecular patterns (PAMPs), leading to pattern-triggered immunity (PTI). To counteract this innate defense, pathogens deploy effector proteins with a primary function to suppress PTI. In specific cases, plants have evolved intracellular resistance (R) proteins detecting isolate-specific pathogen effectors, leading to effector-triggered immunity (ETI), an amplified version of PTI, often associated with hypersensitive response (HR) and programmed cell death (PCD). In the case of plant viruses, no conserved PAMP was identified so far and the primary plant defense is thought to be based mainly on RNA silencing, an evolutionary conserved, sequence-specific mechanism that regulates gene expression and chromatin states and represses invasive nucleic acids such as transposons. Endogenous silencing pathways generate 21-24 nt small (s)RNAs, miRNAs and short interfering (si)RNAs, that repress genes post-transcriptionally and/or transcriptionally. Four distinct Dicer-like (DCL) proteins, which normally produce endogenous miRNAs and siRNAs, all contribute to the biogenesis of viral siRNAs in infected plants. Growing evidence indicates that RNA silencing also contributes to plant defense against non-viral pathogens. Conversely, PTI-based innate responses may contribute to antiviral defense. Intracellular R proteins of the same NB-LRR family are able to recognize both non-viral effectors and avirulence (Avr) proteins of RNA viruses, and, as a result, trigger HR and PCD in virus-resistant hosts. In some cases, viral Avr proteins also function as silencing suppressors. We hypothesize that RNA silencing and innate immunity (PTI and ETI) function in concert to fight plant viruses. Viruses counteract this dual defense by effectors that suppress both PTI-/ETI-based innate responses and RNA

Defensive weapons and defense signals in plants: some metabolites serve both roles.

PubMed

Maag, Daniel; Erb, Matthias; Köllner, Tobias G; Gershenzon, Jonathan

2015-02-01

The defense of plants against herbivores and pathogens involves the participation of an enormous range of different metabolites, some of which act directly as defensive weapons against enemies (toxins or deterrents) and some of which act as components of the complex internal signaling network that insures that defense is timed to enemy attack. Recent work reveals a surprising trend: The same compounds may act as both weapons and signals of defense. For example, two groups of well-studied defensive weapons, glucosinolates and benzoxazinoids, trigger the accumulation of the protective polysaccharide callose as a barrier against aphids and pathogens. In the other direction, several hormones acting in defense signaling (and their precursors and products) exhibit activity as weapons against pathogens. Knowing which compounds are defensive weapons, which are defensive signals and which are both is vital for understanding the functioning of plant defense systems. © 2015 WILEY Periodicals, Inc.

The Mediator Complex Subunit PFT1 Is a Key Regulator of Jasmonate-Dependent Defense in Arabidopsis[C][W

PubMed Central

Kidd, Brendan N.; Edgar, Cameron I.; Kumar, Krish K.; Aitken, Elizabeth A.; Schenk, Peer M.; Manners, John M.; Kazan, Kemal

2009-01-01

Jasmonate signaling plays an important role in both plant defense and development. Here, we have identified a subunit of the Mediator complex as a regulator of the jasmonate signaling pathway in Arabidopsis thaliana. The Mediator complex is a conserved multiprotein complex that acts as a universal adaptor between transcription factors and the RNA polymerase II transcriptional machinery. We report that the PHYTOCHROME AND FLOWERING TIME1 (PFT1) gene, which encodes the MEDIATOR25 subunit of Mediator, is required for jasmonate-dependent defense gene expression and resistance to leaf-infecting necrotrophic fungal pathogens. Conversely, PFT1 appears to confer susceptibility to Fusarium oxysporum, a root-infecting hemibiotrophic fungal pathogen known to hijack jasmonate responses for disease development. Consistent with this, jasmonate gene expression was suppressed in the pft1 mutant during infection with F. oxysporum. In addition, a wheat (Triticum aestivum) homolog of PFT1 complemented the defense and the developmental phenotypes of the pft1 mutant, suggesting that the jasmonate signaling functions of PFT1 may be conserved in higher plants. Overall, our results identify an important control point in the regulation of the jasmonate signaling pathway within the transcriptional machinery. PMID:19671879

Precipitation affects plant communication and defense.

PubMed

Pezzola, Enrico; Mancuso, Stefano; Karban, Richard

2017-06-01

Anti-herbivore defense shows high levels of both inter- and intraspecific variability. Defending against herbivores may be costly to the plant when it requires a tradeoff in allocation between defense and other missed opportunities, such as reproduction. Indeed, the plastic expression of defensive traits allows the plant to invest resources in defense only when the risk of being damaged actually increases, avoiding wasted resources. Plants may assess risk by responding to volatile cues emitted by neighbors that are under attack. Most plastic responses likely depend on environmental conditions. In this experiment, we investigated the effect of water availability on resistance induced by volatile cues in sagebrush. We found that plants receiving additional water over summer and/or volatile cues from neighbor donor plants showed reduced herbivore damage compared to control plants. Interestingly, we found no evidence of interactions between additional water and volatile cues. We performed an inferential analysis comparing historical records of the levels of herbivore damage during different years that had different temperature and precipitation accumulations. Results confirmed findings from the experiment, as the regression model indicated that sagebrush was better defended during wetter and hotter seasons. Reports from the literature indicated that sagebrush is extremely sensitive to water availability in the soil. We suggest that water availability may directly affect resistance of herbivory as well as sensitivity to cues of damage. Costs and benefits of allocating resources to defensive traits may vary with environmental conditions. © 2017 by the Ecological Society of America.

Good neighbors make good defenses: associational refuges reduce defense investment in African savanna plants.

PubMed

Coverdale, Tyler C; Goheen, Jacob R; Palmer, Todd M; Pringle, Robert M

2018-06-25

Intraspecific variation in plant defense phenotype is common and has wide-ranging ecological consequences. Yet prevailing theories of plant defense allocation, which primarily account for interspecific differences in defense phenotype, often fail to predict intraspecific patterns. Furthermore, although individual variation in defense phenotype is often attributed to ecological interactions, few general mechanisms have been proposed to explain the ubiquity of variable defense phenotype within species. Here, we show experimentally that associational refuges and induced resistance interact to create predictable intraspecific variation in defense phenotype in African savanna plants. Physically defended species from four families (Acanthaceae, Asparagaceae, Cactaceae, and Solanaceae) growing in close association with spinescent Acacia trees had 39-78% fewer spines and thorns than did isolated conspecifics. For a subset of these species, we used a series of manipulative experiments to show that this variability is maintained primarily by a reduction in induced responses among individuals that seldom experience mammalian herbivory, whether due to association with Acacia trees or to experimental herbivore exclusion. Unassociated plants incurred 4- to 16-fold more browsing damage than did associated individuals and increased spine density by 16-38% within one month following simulated browsing. In contrast, experimental clipping induced no net change in spine density among plants growing beneath Acacia canopies or inside long-term herbivore exclosures. Associated and unassociated individuals produced similar numbers of flowers and seeds, but seedling recruitment and survival were vastly greater in refuge habitats, suggesting a net fitness benefit of association. We conclude that plant-plant associations consistently decrease defense investment in this system by reducing both the frequency of herbivory and the intensity of induced responses, and that inducible responses

Crosstalk among Jasmonate, Salicylate and Ethylene Signaling Pathways in Plant Disease and Immune Responses.

PubMed

Yang, You-Xin; Ahammed, Golam J; Wu, Caijun; Fan, Shu-ying; Zhou, Yan-Hong

2015-01-01

Phytohormone crosstalk is crucial for plant defenses against pathogens and insects in which salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) play key roles. These low molecular mass signals critically trigger and modulate plant resistance against biotrophic as well as necrotrophic pathogens through a complex signaling network that even involves participation of other hormones. Crosstalk among SA, JA and ET is mediated by different molecular players, considered as integral part of these crosscommunicating signal transduction pathways. Recent progress has revealed that the positive versus negative interactions among those pathways ultimately enable a plant to fine-tune its defense against specific aggressors. On the other hand, pathogens have evolved strategies to manipulate the signaling network to their favour in order to intensify virulence on host plant. Here we review recent advances and current knowledge on the role of classical primary defense hormones SA, JA and ET as well as their synergistic and antagonistic interaction in plant disease and immune responses. Crosstalk with other hormones such as abscisic acid, auxin, brassinosteroids, cytokinins and melatonin is also discussed mainly in plant disease resistance. In addition to our keen focus on hormonal crosstalk, this review also highlights potential implication of positive and negative regulatory interactions for developing an efficient disease management strategy through manipulation of hormone signaling in plant.

Type III secretion system effector proteins: double agents in bacterial disease and plant defense.

PubMed

Alfano, James R; Collmer, Alan

2004-01-01

Many phytopathogenic bacteria inject virulence effector proteins into plant cells via a Hrp type III secretion system (TTSS). Without the TTSS, these pathogens cannot defeat basal defenses, grow in plants, produce disease lesions in hosts, or elicit the hypersensitive response (HR) in nonhosts. Pathogen genome projects employing bioinformatic methods to identify TTSS Hrp regulon promoters and TTSS pathway targeting signals suggest that phytopathogenic Pseudomonas, Xanthomonas, and Ralstonia spp. harbor large arsenals of effectors. The Hrp TTSS employs customized cytoplasmic chaperones, conserved export components in the bacterial envelope (also used by the TTSS of animal pathogens), and a more specialized set of TTSS-secreted proteins to deliver effectors across the plant cell wall and plasma membrane. Many effectors can act as molecular double agents that betray the pathogen to plant defenses in some interactions and suppress host defenses in others. Investigations of the functions of effectors within plant cells have demonstrated the plasma membrane and nucleus as subcellular sites for several effectors, revealed some effectors to possess cysteine protease or protein tyrosine phosphatase activity, and provided new clues to the coevolution of bacterium-plant interactions.

Involvement of nitric oxide in the jasmonate-dependent basal defense against root-knot nematode in tomato plants.

PubMed

Zhou, Jie; Jia, Feifei; Shao, Shujun; Zhang, Huan; Li, Guiping; Xia, Xiaojian; Zhou, Yanhong; Yu, Jingquan; Shi, Kai

2015-01-01

Jasmonic acid (JA) and nitric oxide (NO) are well-characterized signaling molecules in plant defense responses. However, their roles in plant defense against root-knot nematode (RKN, Meloidogyne incognita) infection are largely unknown. In this study, we found that the transcript levels of the JA- and NO-related biosynthetic and signaling component genes were induced after RKN infection. Application of exogenous JA and sodium nitroprusside (SNP; a NO donor) significantly decreased the number of egg masses in tomato roots after RKN infection and partially alleviated RKN-induced decreases in plant fresh weight and net photosynthetic rate. These molecules also alleviated RKN-induced increases in root electrolyte leakage and membrane peroxidation. Importantly, NO scavenger partially inhibited JA-induced RKN defense. The pharmacological inhibition of JA biosynthesis significantly increased the plants' susceptibility to RKNs, which was effectively alleviated by SNP application, showing that NO may be involved in the JA-dependent RKN defense pathway. Furthermore, both JA and SNP induced increases in protease inhibitor 2 (PI2) gene expression after RKN infestation. Silencing of PI2 compromised both JA- and SNP-induced RKN defense responses, suggesting that the PI2 gene mediates JA- and NO-induced defense against RKNs. This work will be important for deepening the understanding of the mechanisms involved in basal defense against RKN attack in plants.

A WRKY transcription factor from Withania somnifera regulates triterpenoid withanolide accumulation and biotic stress tolerance through modulation of phytosterol and defense pathways.

PubMed

Singh, Anup Kumar; Kumar, Sarma Rajeev; Dwivedi, Varun; Rai, Avanish; Pal, Shaifali; Shasany, Ajit K; Nagegowda, Dinesh A

2017-08-01

Withania somnifera produces pharmacologically important triterpenoid withanolides that are derived via phytosterol pathway; however, their biosynthesis and regulation remain to be elucidated. A jasmonate- and salicin-inducible WRKY transcription factor from W. somnifera (WsWRKY1) exhibiting correlation with withaferin A accumulation was functionally characterized employing virus-induced gene silencing and overexpression studies combined with transcript and metabolite analyses, and chromatin immunoprecipitation assay. WsWRKY1 silencing resulted in stunted plant growth, reduced transcripts of phytosterol pathway genes with corresponding reduction in phytosterols and withanolides in W. somnifera. Its overexpression elevated the biosynthesis of triterpenoids in W. somnifera (phytosterols and withanolides), as well as tobacco and tomato (phytosterols). Moreover, WsWRKY1 binds to W-box sequences in promoters of W. somnifera genes encoding squalene synthase and squalene epoxidase, indicating its direct regulation of triterpenoid pathway. Furthermore, while WsWRKY1 silencing in W. somnifera compromised the tolerance to bacterial growth, fungal infection, and insect feeding, its overexpression in tobacco led to improved biotic stress tolerance. Together these findings demonstrate that WsWRKY1 has a positive regulatory role on phytosterol and withanolides biosynthesis, and defense against biotic stress, highlighting its importance as a metabolic engineering tool for simultaneous improvement of triterpenoid biosynthesis and plant defense. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Resistance to Hemi-Biotrophic F. graminearum Infection Is Associated with Coordinated and Ordered Expression of Diverse Defense Signaling Pathways

PubMed Central

Yi, Hongying; Yang, Liming; Kong, Zhongxin; Zhang, Lixia; Xue, Shulin; Jia, Haiyan; Ma, Zhengqiang

2011-01-01

Fusarium species cause serious diseases in cereal staple food crops such as wheat and maize. Currently, the mechanisms underlying resistance to Fusarium-caused diseases are still largely unknown. In the present study, we employed a combined proteomic and transcriptomic approach to investigate wheat genes responding to F. graminearum infection that causes Fusarium head blight (FHB). We found a total of 163 genes and 37 proteins that were induced by infection. These genes and proteins were associated with signaling pathways mediated by salicylic acid (SA), jasmonic acid (JA), ethylene (ET), calcium ions, phosphatidic acid (PA), as well as with reactive oxygen species (ROS) production and scavenging, antimicrobial compound synthesis, detoxification, and cell wall fortification. We compared the time-course expression profiles between FHB-resistant Wangshuibai plants and susceptible Meh0106 mutant plants of a selected set of genes that are critical to the plants' resistance and defense reactions. A biphasic phenomenon was observed during the first 24 h after inoculation (hai) in the resistant plants. The SA and Ca2+ signaling pathways were activated within 6 hai followed by the JA mediated defense signaling activated around 12 hai. ET signaling was activated between these two phases. Genes for PA and ROS synthesis were induced during the SA and JA phases, respectively. The delayed activation of the SA defense pathway in the mutant was associated with its susceptibility. After F. graminearum infection, the endogenous contents of SA and JA in Wangshuibai and the mutant changed in a manner similar to the investigated genes corresponding to the individual pathways. A few genes for resistance-related cell modification and phytoalexin production were also identified. This study provided important clues for designing strategies to curb diseases caused by Fusarium. PMID:21533105

Mechanisms of plant defense against insect herbivores

PubMed Central

War, Abdul Rashid; Paulraj, Michael Gabriel; Ahmad, Tariq; Buhroo, Abdul Ahad; Hussain, Barkat; Ignacimuthu, Savarimuthu; Sharma, Hari Chand

2012-01-01

Plants respond to herbivory through various morphological, biochemicals, and molecular mechanisms to counter/offset the effects of herbivore attack. The biochemical mechanisms of defense against the herbivores are wide-ranging, highly dynamic, and are mediated both by direct and indirect defenses. The defensive compounds are either produced constitutively or in response to plant damage, and affect feeding, growth, and survival of herbivores. In addition, plants also release volatile organic compounds that attract the natural enemies of the herbivores. These strategies either act independently or in conjunction with each other. However, our understanding of these defensive mechanisms is still limited. Induced resistance could be exploited as an important tool for the pest management to minimize the amounts of insecticides used for pest control. Host plant resistance to insects, particularly, induced resistance, can also be manipulated with the use of chemical elicitors of secondary metabolites, which confer resistance to insects. By understanding the mechanisms of induced resistance, we can predict the herbivores that are likely to be affected by induced responses. The elicitors of induced responses can be sprayed on crop plants to build up the natural defense system against damage caused by herbivores. The induced responses can also be engineered genetically, so that the defensive compounds are constitutively produced in plants against are challenged by the herbivory. Induced resistance can be exploited for developing crop cultivars, which readily produce the inducible response upon mild infestation, and can act as one of components of integrated pest management for sustainable crop production. PMID:22895106

Is crypsis a common defensive strategy in plants?

PubMed Central

2010-01-01

Color is a common feature of animal defense. Herbivorous insects are often colored in shades of green similar to their preferred food plants, making them difficult for predators to locate. Other insects advertise their presence with bright colors after they sequester enough toxins from their food plants to make them unpalatable. Some insects even switch between cryptic and aposomatic coloration during development.1 Although common in animals, quantitative evidence for color-based defense in plants is rare. After all, the primary function of plant leaves is to absorb light for photosynthesis, rather than reflect light in ways that alter their appearance to herbivores. However, recent research is beginning to challenge the notion that color-based defence is restricted to animals. PMID:20592801

Resistance of Cultivated Tomato to Cell Content-Feeding Herbivores Is Regulated by the Octadecanoid-Signaling Pathway1

PubMed Central

Li, Chuanyou; Williams, Mark M.; Loh, Ying-Tsu; Lee, Gyu In; Howe, Gregg A.

2002-01-01

The octadecanoid signaling pathway has been shown to play an important role in plant defense against various chewing insects and some pathogenic fungi. Here, we examined the interaction of a cell-content feeding arachnid herbivore, the two-spotted spider mite (Tetranychus urticae Koch), with cultivated tomato (Lycopersicon esculentum) and an isogenic mutant line (defenseless-1 [def-1]) that is deficient in the biosynthesis of the octadecanoid pathway-derived signal, jasmonic acid (JA). Spider mite feeding and fecundity on def-1 plants was significantly greater than on wild-type plants. Decreased resistance of def-1 plants was correlated with reduced JA accumulation and expression of defensive proteinase inhibitor (PI) genes, which were induced in mite-damaged wild-type leaves. Treatment of def-1 plants with methyl-JA restored resistance to spider mite feeding and reduced the fecundity of female mites. Plants expressing a 35S::prosystemin transgene that constitutively activates the octadecanoid pathway in a Def-1-dependent manner were highly resistant to attack by spider mites and western flower thrips (Frankliniella occidentalis), another cell-content feeder of economic importance. These findings indicate that activation of the octadecanoid signaling pathway promotes resistance of tomato to a broad spectrum of herbivores. The techniques of amplified fragment length polymorphism (AFLP) and bulk segregant analysis were used to map the Def-1 gene to a region on the long arm of chromosome 3 that is genetically separable from the map position of known JA biosynthetic genes. Tight linkage of Def-1 to a T-DNA insertion harboring the maize (Zea mays) Dissociation transposable element suggests a strategy for directed transposon tagging of the gene. PMID:12226528

TMV-Cg Coat Protein stabilizes DELLA proteins and in turn negatively modulates salicylic acid-mediated defense pathway during Arabidopsis thaliana viral infection.

PubMed

Rodriguez, Maria Cecilia; Conti, Gabriela; Zavallo, Diego; Manacorda, Carlos Augusto; Asurmendi, Sebastian

2014-08-03

Plant viral infections disturb defense regulatory networks during tissue invasion. Emerging evidence demonstrates that a significant proportion of these alterations are mediated by hormone imbalances. Although the DELLA proteins have been reported to be central players in hormone cross-talk, their role in the modulation of hormone signaling during virus infections remains unknown. This work revealed that TMV-Cg coat protein (CgCP) suppresses the salicylic acid (SA) signaling pathway without altering defense hormone SA or jasmonic acid (JA) levels in Arabidopsis thaliana. Furthermore, it was observed that the expression of CgCP reduces plant growth and delays the timing of floral transition. Quantitative RT-qPCR analysis of DELLA target genes showed that CgCP alters relative expression of several target genes, indicating that the DELLA proteins mediate transcriptional changes produced by CgCP expression. Analyses by fluorescence confocal microscopy showed that CgCP stabilizes DELLA proteins accumulation in the presence of gibberellic acid (GA) and that the DELLA proteins are also stabilized during TMV-Cg virus infections. Moreover, DELLA proteins negatively modulated defense transcript profiles during TMV-Cg infection. As a result, TMV-Cg accumulation was significantly reduced in the quadruple-DELLA mutant Arabidopsis plants compared to wild type plants. Taken together, these results demonstrate that CgCP negatively regulates the salicylic acid-mediated defense pathway by stabilizing the DELLA proteins during Arabidopsis thaliana viral infection, suggesting that CgCP alters the stability of DELLAs as a mechanism of negative modulation of antiviral defense responses.

Differential Timing of Spider Mite-Induced Direct and Indirect Defenses in Tomato Plants1[w

PubMed Central

Kant, Merijn R.; Ament, Kai; Sabelis, Maurice W.; Haring, Michel A.; Schuurink, Robert C.

2004-01-01

Through a combined metabolomics and transcriptomics approach we analyzed the events that took place during the first 5 d of infesting intact tomato (Lycopersicon esculentum) plants with spider mites (Tetranychus urticae). Although the spider mites had caused little visible damage to the leaves after 1 d, they had already induced direct defense responses. For example, proteinase inhibitor activity had doubled and the transcription of genes involved in jasmonate-, salicylate-, and ethylene-regulated defenses had been activated. On day four, proteinase inhibitor activity and particularly transcript levels of salicylate-regulated genes were still maintained. In addition, genes involved in phospholipid metabolism were up-regulated on day one and those in the secondary metabolism on day four. Although transcriptional up-regulation of the enzymes involved in the biosynthesis of monoterpenes and diterpenes already occurred on day one, a significant increase in the emission of volatile terpenoids was delayed until day four. This increase in volatile production coincided with the increased olfactory preference of predatory mites (Phytoseiulus persimilis) for infested plants. Our results indicate that tomato activates its indirect defenses (volatile production) to complement the direct defense response against spider mites. PMID:15122016

NpPDR1, a pleiotropic drug resistance-type ATP-binding cassette transporter from Nicotiana plumbaginifolia, plays a major role in plant pathogen defense.

PubMed

Stukkens, Yvan; Bultreys, Alain; Grec, Sébastien; Trombik, Tomasz; Vanham, Delphine; Boutry, Marc

2005-09-01

Nicotiana plumbaginifolia NpPDR1, a plasma membrane pleiotropic drug resistance-type ATP-binding cassette transporter formerly named NpABC1, has been suggested to transport the diterpene sclareol, an antifungal compound. However, direct evidence for a role of pleiotropic drug resistance transporters in the plant defense is still lacking. In situ immunolocalization and histochemical analysis using the gusA reporter gene showed that NpPDR1 was constitutively expressed in the whole root, in the leaf glandular trichomes, and in the flower petals. However, NpPDR1 expression was induced in the whole leaf following infection with the fungus Botrytis cinerea, and the bacteria Pseudomonas syringae pv tabaci, Pseudomonas fluorescens, and Pseudomonas marginalis pv marginalis, which do not induce a hypersensitive response in N. plumbaginifolia, whereas a weaker response was observed using P. syringae pv syringae, which does induce a hypersensitive response. Induced NpPDR1 expression was more associated with the jasmonic acid than the salicylic acid signaling pathway. These data suggest that NpPDR1 is involved in both constitutive and jasmonic acid-dependent induced defense. Transgenic plants in which NpPDR1 expression was prevented by RNA interference showed increased sensitivity to sclareol and reduced resistance to B. cinerea. These data show that NpPDR1 is involved in pathogen resistance and thus demonstrate a new role for the ATP-binding cassette transporter family.

NAD1 Controls Defense-Like Responses in Medicago truncatula Symbiotic Nitrogen Fixing Nodules Following Rhizobial Colonization in a BacA-Independent Manner

PubMed Central

Domonkos, Ágota; Kovács, Szilárd; Gombár, Anikó; Kiss, Ernő; Horváth, Beatrix; Kováts, Gyöngyi Z.; Farkas, Attila; Tóth, Mónika T.; Ayaydin, Ferhan; Bóka, Károly; Fodor, Lili; Endre, Gabriella; Kaló, Péter

2017-01-01

Legumes form endosymbiotic interaction with host compatible rhizobia, resulting in the development of nitrogen-fixing root nodules. Within symbiotic nodules, rhizobia are intracellularly accommodated in plant-derived membrane compartments, termed symbiosomes. In mature nodule, the massively colonized cells tolerate the existence of rhizobia without manifestation of visible defense responses, indicating the suppression of plant immunity in the nodule in the favur of the symbiotic partner. Medicago truncatula DNF2 (defective in nitrogen fixation 2) and NAD1 (nodules with activated defense 1) genes are essential for the control of plant defense during the colonization of the nitrogen-fixing nodule and are required for bacteroid persistence. The previously identified nodule-specific NAD1 gene encodes a protein of unknown function. Herein, we present the analysis of novel NAD1 mutant alleles to better understand the function of NAD1 in the repression of immune responses in symbiotic nodules. By exploiting the advantage of plant double and rhizobial mutants defective in establishing nitrogen-fixing symbiotic interaction, we show that NAD1 functions following the release of rhizobia from the infection threads and colonization of nodule cells. The suppression of plant defense is self-dependent of the differentiation status of the rhizobia. The corresponding phenotype of nad1 and dnf2 mutants and the similarity in the induction of defense-associated genes in both mutants suggest that NAD1 and DNF2 operate close together in the same pathway controlling defense responses in symbiotic nodules. PMID:29240711

NAD1 Controls Defense-Like Responses in Medicago truncatula Symbiotic Nitrogen Fixing Nodules Following Rhizobial Colonization in a BacA-Independent Manner.

PubMed

Domonkos, Ágota; Kovács, Szilárd; Gombár, Anikó; Kiss, Ernő; Horváth, Beatrix; Kováts, Gyöngyi Z; Farkas, Attila; Tóth, Mónika T; Ayaydin, Ferhan; Bóka, Károly; Fodor, Lili; Ratet, Pascal; Kereszt, Attila; Endre, Gabriella; Kaló, Péter

2017-12-14

Legumes form endosymbiotic interaction with host compatible rhizobia, resulting in the development of nitrogen-fixing root nodules. Within symbiotic nodules, rhizobia are intracellularly accommodated in plant-derived membrane compartments, termed symbiosomes. In mature nodule, the massively colonized cells tolerate the existence of rhizobia without manifestation of visible defense responses, indicating the suppression of plant immunity in the nodule in the favur of the symbiotic partner. Medicago truncatula DNF2 (defective in nitrogen fixation 2) and NAD1 (nodules with activated defense 1) genes are essential for the control of plant defense during the colonization of the nitrogen-fixing nodule and are required for bacteroid persistence. The previously identified nodule-specific NAD1 gene encodes a protein of unknown function. Herein, we present the analysis of novel NAD1 mutant alleles to better understand the function of NAD1 in the repression of immune responses in symbiotic nodules. By exploiting the advantage of plant double and rhizobial mutants defective in establishing nitrogen-fixing symbiotic interaction, we show that NAD1 functions following the release of rhizobia from the infection threads and colonization of nodule cells. The suppression of plant defense is self-dependent of the differentiation status of the rhizobia. The corresponding phenotype of nad1 and dnf2 mutants and the similarity in the induction of defense-associated genes in both mutants suggest that NAD1 and DNF2 operate close together in the same pathway controlling defense responses in symbiotic nodules.

Costs of defense and a test of the carbon-nutrient balance and growth-differentiation balance hypotheses for two co-occurring classes of plant defense.

PubMed

Massad, Tara Joy; Dyer, Lee A; Vega C, Gerardo

2012-01-01

One of the goals of chemical ecology is to assess costs of plant defenses. Intraspecific trade-offs between growth and defense are traditionally viewed in the context of the carbon-nutrient balance hypothesis (CNBH) and the growth-differentiation balance hypothesis (GDBH). Broadly, these hypotheses suggest that growth is limited by deficiencies in carbon or nitrogen while rates of photosynthesis remain unchanged, and the subsequent reduced growth results in the more abundant resource being invested in increased defense (mass-balance based allocation). The GDBH further predicts trade-offs in growth and defense should only be observed when resources are abundant. Most support for these hypotheses comes from work with phenolics. We examined trade-offs related to production of two classes of defenses, saponins (triterpenoids) and flavans (phenolics), in Pentaclethra macroloba (Fabaceae), an abundant tree in Costa Rican wet forests. We quantified physiological costs of plant defenses by measuring photosynthetic parameters (which are often assumed to be stable) in addition to biomass. Pentaclethra macroloba were grown in full sunlight or shade under three levels of nitrogen alone or with conspecific neighbors that could potentially alter nutrient availability via competition or facilitation. Biomass and photosynthesis were not affected by nitrogen or competition for seedlings in full sunlight, but they responded positively to nitrogen in shade-grown plants. The trade-off predicted by the GDBH between growth and metabolite production was only present between flavans and biomass in sun-grown plants (abundant resource conditions). Support was also only partial for the CNBH as flavans declined with nitrogen but saponins increased. This suggests saponin production should be considered in terms of detailed biosynthetic pathway models while phenolic production fits mass-balance based allocation models (such as the CNBH). Contrary to expectations based on the two defense

Involvement of nitric oxide in the jasmonate-dependent basal defense against root-knot nematode in tomato plants

PubMed Central

Zhou, Jie; Jia, Feifei; Shao, Shujun; Zhang, Huan; Li, Guiping; Xia, Xiaojian; Zhou, Yanhong; Yu, Jingquan; Shi, Kai

2015-01-01

Jasmonic acid (JA) and nitric oxide (NO) are well-characterized signaling molecules in plant defense responses. However, their roles in plant defense against root-knot nematode (RKN, Meloidogyne incognita) infection are largely unknown. In this study, we found that the transcript levels of the JA- and NO-related biosynthetic and signaling component genes were induced after RKN infection. Application of exogenous JA and sodium nitroprusside (SNP; a NO donor) significantly decreased the number of egg masses in tomato roots after RKN infection and partially alleviated RKN-induced decreases in plant fresh weight and net photosynthetic rate. These molecules also alleviated RKN-induced increases in root electrolyte leakage and membrane peroxidation. Importantly, NO scavenger partially inhibited JA-induced RKN defense. The pharmacological inhibition of JA biosynthesis significantly increased the plants’ susceptibility to RKNs, which was effectively alleviated by SNP application, showing that NO may be involved in the JA-dependent RKN defense pathway. Furthermore, both JA and SNP induced increases in protease inhibitor 2 (PI2) gene expression after RKN infestation. Silencing of PI2 compromised both JA- and SNP-induced RKN defense responses, suggesting that the PI2 gene mediates JA- and NO-induced defense against RKNs. This work will be important for deepening the understanding of the mechanisms involved in basal defense against RKN attack in plants. PMID:25914698

The pepper cysteine/histidine-rich DC1 domain protein CaDC1 binds both RNA and DNA and is required for plant cell death and defense response.

PubMed

Hwang, In Sun; Choi, Du Seok; Kim, Nak Hyun; Kim, Dae Sung; Hwang, Byung Kook

2014-01-01

Plant defense against microbial pathogens is coordinated by a complex regulatory network. Cysteine/histidine-rich DC1 domain proteins mediate a variety of cellular processes involved in plant growth, development and stress responses. We identified a pepper (Capsicum annuum) cysteine/histidine-rich DC1 domain protein gene, CaDC1, which positively regulates plant defense during microbial infection, based on gene silencing and transient expression in pepper, as well as ectopic expression in Arabidopsis. Induction of CaDC1 by avirulent Xanthomonas campestris pv vesicatoria (Xcv) infection was pronounced at both transcriptional and translational levels in pepper leaves. Purified CaDC1 protein bound to both DNA and RNA in vitro, especially in the presence of Zn(2+). CaDC1 was localized to both the nucleus and the cytoplasm, which was required for plant cell death signaling. The nuclear localization of CaDC1 was dependent on the divergent C1 (DC1) domain. CaDC1 silencing in pepper conferred increased susceptibility to Xcv infection, which was accompanied by reduced salicylic acid accumulation and defense-related gene expression. Ectopic expression of CaDC1 in Arabidopsis enhanced resistance to Hyaloperonospora arabidopsidis. CaDC1 binds both RNA and DNA and functions as a positive regulator of plant cell death and SA-dependent defense responses. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Landscape Variation in Plant Defense Syndromes across a Tropical Rainforest

NASA Astrophysics Data System (ADS)

McManus, K. M.; Asner, G. P.; Martin, R.; Field, C. B.

2014-12-01

Plant defenses against herbivores shape tropical rainforest biodiversity, yet community- and landscape-scale patterns of plant defense and the phylogenetic and environmental factors that may shape them are poorly known. We measured foliar defense, growth, and longevity traits for 345 canopy trees across 84 species in a tropical rainforest and examined whether patterns of trait co-variation indicated the existence of plant defense syndromes. Using a DNA-barcode phylogeny and remote sensing and land-use data, we investigated how phylogeny and topo-edaphic properties influenced the distribution of syndromes. We found evidence for three distinct defense syndromes, characterized by rapid growth, growth compensated by defense, or limited palatability/low nutrition. Phylogenetic signal was generally lower for defense traits than traits related to growth or longevity. Individual defense syndromes were organized at different taxonomic levels and responded to different spatial-environmental gradients. The results suggest that a diverse set of tropical canopy trees converge on a limited number of strategies to secure resources and mitigate fitness losses due to herbivory, with patterns of distribution mediated by evolutionary histories and local habitat associations. Plant defense syndromes are multidimensional plant strategies, and thus are a useful means of discerning ecologically-relevant variation in highly diverse tropical rainforest communities. Scaling this approach to the landscape level, if plant defense syndromes can be distinguished in remotely-sensed data, they may yield new insights into the role of plant defense in structuring diverse tropical rainforest communities.

Expression and regulation of ATL9, an E3 ubiquitin ligase involved in plant defense

PubMed Central

Lefebvre, Mitchell; Scaglione, Steven; Antico, Christopher J.; Jing, Tao; Yang, Xin; Shan, Weixing

2017-01-01

Plants are continually exposed to a variety of pathogenic organisms, including bacteria, fungi and viruses. In response to these assaults, plants have developed various defense pathways to protect themselves from pathogen invasion. An understanding of the expression and regulation of genes involved in defense signaling is essential to controlling plant disease. ATL9, an Arabidopsis RING zinc finger protein, is an E3 ubiquitin ligase that is induced by chitin and involved in basal resistance to the biotrophic fungal pathogen, Golovinomyces cichoracearum (G. cichoracearum). To better understand the expression and regulation of ATL9, we studied its expression pattern and the functions of its different protein domains. Using pATL9:GUS transgenic Arabidopsis lines we found that ATL9 is expressed in numerous tissues at various developmental stages and that GUS activity was induced rapidly upon wounding. Using a GFP control protein, we showed that ATL9 is a short-lived protein within plant cells and it is degraded via the ubiquitin-proteasome pathway. ATL9 contains two transmembrane domains (TM), a RING zinc-finger domain, and a PEST domain. Using a series of deletion mutants, we found that the PEST domain and the RING domain have effects on ATL9 degradation. Further infection assays with G. cichoracearum showed that both the RING domain and the TM domains are important for ATL9’s resistance phenotype. Interestingly, the PEST domain was also shown to be significant for resistance to fungal pathogens. This study demonstrates that the PEST domain is directly coupled to plant defense regulation and the importance of protein degradation in plant immunity. PMID:29161311

Plant antiherbivore defenses in Fabaceae species of the Chaco.

PubMed

Lima, T E; Sartori, A L B; Rodrigues, M L M

2017-01-01

The establishment and maintenance of plant species in the Chaco, one of the widest continuous areas of forests in the South American with sharp climatic variations, are possibly related to biological features favoring plants with particular defenses. This study assesses the physical and chemical defenses mechanisms against herbivores of vegetative and reproductive organs. Its analyses of 12 species of Fabaceae (Leguminosae) collected in remnants of Brazilian Chaco shows that 75% present structural defense characters and 50% have chemical defense - defense proteins in their seeds, like protease inhibitors and lectins. Physical defenses occur mainly on branches (78% of the species), leaves (67%), and reproductive organs (56%). The most common physical characters are trichomes and thorns, whose color represents a cryptic character since it does not contrast with the other plant structures. Defense proteins occur in different concentrations and molecular weight classes in the seeds of most species. Protease inhibitors are reported for the first time in seeds of: Albizia niopoides, Anadenanthera colubrina, Mimosa glutinosa, Prosopis rubriflora, and Poincianella pluviosa. The occurrence of physical and chemical defenses in members of Fabaceae indicate no associations between defense characters in these plant species of the Chaco.

Parasitic Cuscuta factor(s) and the detection by tomato initiates plant defense.

PubMed

Fürst, Ursula; Hegenauer, Volker; Kaiser, Bettina; Körner, Max; Welz, Max; Albert, Markus

2016-01-01

Dodders ( Cuscuta spp.) are holoparasitic plants that enwind stems of host plants and penetrate those by haustoria to connect to the vascular bundles. Having a broad host plant spectrum, Cuscuta spp infect nearly all dicot plants - only cultivated tomato as one exception is mounting an active defense specifically against C. reflexa . In a recent work we identified a pattern recognition receptor of tomato, "Cuscuta Receptor 1" (CuRe1), which is critical to detect a "Cuscuta factor" (CuF) and initiate defense responses such as the production of ethylene or the generation of reactive oxygen species. CuRe1 also contributes to the tomato resistance against C. reflexa . Here we point to the fact that CuRe1 is not the only relevant component for full tomato resistance but it requires additional defense mechanisms, or receptors, respectively, to totally fend off the parasite.

Phylogenetic escalation and decline of plant defense strategies

PubMed Central

Agrawal, Anurag A.; Fishbein, Mark

2008-01-01

As the basal resource in most food webs, plants have evolved myriad strategies to battle consumption by herbivores. Over the past 50 years, plant defense theories have been formulated to explain the remarkable variation in abundance, distribution, and diversity of secondary chemistry and other defensive traits. For example, classic theories of enemy-driven evolutionary dynamics have hypothesized that defensive traits escalate through the diversification process. Despite the fact that macroevolutionary patterns are an explicit part of defense theories, phylogenetic analyses have not been previously attempted to disentangle specific predictions concerning (i) investment in resistance traits, (ii) recovery after damage, and (iii) plant growth rate. We constructed a molecular phylogeny of 38 species of milkweed and tested four major predictions of defense theory using maximum-likelihood methods. We did not find support for the growth-rate hypothesis. Our key finding was a pattern of phyletic decline in the three most potent resistance traits (cardenolides, latex, and trichomes) and an escalation of regrowth ability. Our neontological approach complements more common paleontological approaches to discover directional trends in the evolution of life and points to the importance of natural enemies in the macroevolution of species. The finding of macroevolutionary escalating regowth ability and declining resistance provides a window into the ongoing coevolutionary dynamics between plants and herbivores and suggests a revision of classic plant defense theory. Where plants are primarily consumed by specialist herbivores, regrowth (or tolerance) may be favored over resistance traits during the diversification process. PMID:18645183

Stimulation of the Salicylic Acid Pathway Aboveground Recruits Entomopathogenic Nematodes Belowground

PubMed Central

Filgueiras, Camila Cramer; Willett, Denis S.; Junior, Alcides Moino; Pareja, Martin; Borai, Fahiem El; Dickson, Donald W.; Stelinski, Lukasz L.; Duncan, Larry W.

2016-01-01

Plant defense pathways play a critical role in mediating tritrophic interactions between plants, herbivores, and natural enemies. While the impact of plant defense pathway stimulation on natural enemies has been extensively explored aboveground, belowground ramifications of plant defense pathway stimulation are equally important in regulating subterranean pests and still require more attention. Here we investigate the effect of aboveground stimulation of the salicylic acid pathway through foliar application of the elicitor methyl salicylate on belowground recruitment of the entomopathogenic nematode, Steinernema diaprepesi. Also, we implicate a specific root-derived volatile that attracts S. diaprepesi belowground following aboveground plant stimulation by an elicitor. In four-choice olfactometer assays, citrus plants treated with foliar applications of methyl salicylate recruited S. diaprepesi in the absence of weevil feeding as compared with negative controls. Additionally, analysis of root volatile profiles of citrus plants receiving foliar application of methyl salicylate revealed production of d-limonene, which was absent in negative controls. The entomopathogenic nematode S. diaprepesi was recruited to d-limonene in two-choice olfactometer trials. These results reinforce the critical role of plant defense pathways in mediating tritrophic interactions, suggest a broad role for plant defense pathway signaling belowground, and hint at sophisticated plant responses to pest complexes. PMID:27136916

The spitting image of plant defenses: effects of plant secondary chemistry on the efficiency of caterpillar regurgitant as an anti-predator defense

USDA-ARS?s Scientific Manuscript database

In the arms race between plants, herbivores, and their natural enemies, specialized herbivores may use plant defenses for their own benefit. In such cases, variation in secondary chemistry among host plants may affect the benefits that herbivores derive from these defenses. Caterpillars of Pieris br...

Plant innate immunity: an updated insight into defense mechanism.

PubMed

Muthamilarasan, Mehanathan; Prasad, Manoj

2013-06-01

Plants are invaded by an array of pathogens of which only a few succeed in causing disease. The attack by others is countered by a sophisticated immune system possessed by the plants. The plant immune system is broadly divided into two, viz. microbial-associated molecular-patterns-triggered immunity (MTI) and effector-triggered immunity (ETI). MTI confers basal resistance, while ETI confers durable resistance, often resulting in hypersensitive response. Plants also possess systemic acquired resistance (SAR), which provides long-term defense against a broad-spectrum of pathogens. Salicylic-acid-mediated systemic acquired immunity provokes the defense response throughout the plant system during pathogen infection at a particular site. Trans-generational immune priming allows the plant to heritably shield their progeny towards pathogens previously encountered. Plants circumvent the viral infection through RNA interference phenomena by utilizing small RNAs. This review summarizes the molecular mechanisms of plant immune system, and the latest breakthroughs reported in plant defense. We discuss the plant–pathogen interactions and integrated defense responses in the context of presenting an integral understanding in plant molecular immunity.

Plant neighbor identity influences plant biochemistry and physiology related to defense.

PubMed

Broz, Amanda K; Broeckling, Corey D; De-la-Peña, Clelia; Lewis, Matthew R; Greene, Erick; Callaway, Ragan M; Sumner, Lloyd W; Vivanco, Jorge M

2010-06-17

Chemical and biological processes dictate an individual organism's ability to recognize and respond to other organisms. A small but growing body of evidence suggests that plants may be capable of recognizing and responding to neighboring plants in a species specific fashion. Here we tested whether or not individuals of the invasive exotic weed, Centaurea maculosa, would modulate their defensive strategy in response to different plant neighbors. In the greenhouse, C. maculosa individuals were paired with either conspecific (C. maculosa) or heterospecific (Festuca idahoensis) plant neighbors and elicited with the plant defense signaling molecule methyl jasmonate to mimic insect herbivory. We found that elicited C. maculosa plants grown with conspecific neighbors exhibited increased levels of total phenolics, whereas those grown with heterospecific neighbors allocated more resources towards growth. To further investigate these results in the field, we conducted a metabolomics analysis to explore chemical differences between individuals of C. maculosa growing in naturally occurring conspecific and heterospecific field stands. Similar to the greenhouse results, C. maculosa individuals accumulated higher levels of defense-related secondary metabolites and lower levels of primary metabolites when growing in conspecific versus heterospecific field stands. Leaf herbivory was similar in both stand types; however, a separate field study positively correlated specialist herbivore load with higher densities of C. maculosa conspecifics. Our results suggest that an individual C. maculosa plant can change its defensive strategy based on the identity of its plant neighbors. This is likely to have important consequences for individual and community success.

Parasitic Cuscuta factor(s) and the detection by tomato initiates plant defense

PubMed Central

Fürst, Ursula; Hegenauer, Volker; Kaiser, Bettina; Körner, Max; Welz, Max; Albert, Markus

2016-01-01

ABSTRACT Dodders (Cuscuta spp.) are holoparasitic plants that enwind stems of host plants and penetrate those by haustoria to connect to the vascular bundles. Having a broad host plant spectrum, Cuscuta spp infect nearly all dicot plants – only cultivated tomato as one exception is mounting an active defense specifically against C. reflexa. In a recent work we identified a pattern recognition receptor of tomato, “Cuscuta Receptor 1“ (CuRe1), which is critical to detect a “Cuscuta factor” (CuF) and initiate defense responses such as the production of ethylene or the generation of reactive oxygen species. CuRe1 also contributes to the tomato resistance against C. reflexa. Here we point to the fact that CuRe1 is not the only relevant component for full tomato resistance but it requires additional defense mechanisms, or receptors, respectively, to totally fend off the parasite. PMID:28042379

Plant defense compounds: systems approaches to metabolic analysis.

PubMed

Kliebenstein, Daniel J

2012-01-01

Systems biology attempts to answer biological questions by integrating across diverse genomic data sets. With the increasing ability to conduct genomics experiments, this integrative approach is being rapidly applied across numerous biological research communities. One of these research communities investigates how plants utilize secondary metabolites or defense metabolites to defend against attack by pathogens and other biotic organisms. This use of systems biology to integrate across transcriptomics, metabolomics, and genomics is significantly enhancing the rate of discovery of genes, metabolites, and bioactivities for plant defense compounds as well as extending our knowledge of how these compounds are regulated. Plant defense compounds are also providing a unique proving platform to develop new approaches that enhance the ability to conduct systems biology with existing and previously unforseen genomics data sets. This review attempts to illustrate both how systems biology is helping the study of plant defense compounds and vice versa.

The AMPK-PPARGC1A pathway is required for antimicrobial host defense through activation of autophagy.

PubMed

Yang, Chul-Su; Kim, Jwa-Jin; Lee, Hye-Mi; Jin, Hyo Sun; Lee, Sang-Hee; Park, Ji-Hoon; Kim, Soung Jung; Kim, Jin-Man; Han, Yong-Mahn; Lee, Myung-Shik; Kweon, Gi Ryang; Shong, Minho; Jo, Eun-Kyeong

2014-05-01

AMP-activated protein kinase (AMPK) is a crucial energy sensor and plays a key role in integration of cellular functions to maintain homeostasis. Despite this, it is largely unknown whether targeting the AMPK pathway can be used as a therapeutic strategy for infectious diseases. Herein, we show that AMPK activation robustly induces antibacterial autophagy, which contributes to antimicrobial defense against Mycobacterium tuberculosis (Mtb). AMPK activation led to inhibition of Mtb-induced phosphorylation of the mechanistic target of rapamycin (MTOR) in macrophages. In addition, AMPK activation increased the genes involved in oxidative phosphorylation, mitochondrial ATP production, and biogenesis in Mtb-infected macrophages. Notably, peroxisome proliferator-activated receptor-gamma, coactivator 1α (PPARGC1A) was required for AMPK-mediated antimicrobial activity, as well as enhancement of mitochondrial function and biogenesis, in macrophages. Further, the AMPK-PPARGC1A pathway was involved in the upregulation of multiple autophagy-related genes via CCAAT/enhancer binding protein (C/EBP), β (CEBPB). PPARGC1A knockdown inhibited the AMPK-mediated induction of autophagy and impaired the fusion of phagosomes with MAP1LC3B (LC3B) autophagosomes in Mtb-infected macrophages. The link between autophagy, mitochondrial function, and antimicrobial activity was further demonstrated by studying LysMCre-mediated knockout of atg7, demonstrating mitochondrial ultrastructural defects and dysfunction, as well as blockade of antimicrobial activity against mycobacteria. Collectively, our results identify the AMPK-PPARGC1A axis as contributing to autophagy activation leading to an antimicrobial response, as a novel host defense mechanism.

Variation in Plant Defense Suppresses Herbivore Performance.

PubMed

Pearse, Ian S; Paul, Ryan; Ode, Paul J

2018-06-18

Defensive variability of crops and natural systems can alter herbivore communities and reduce herbivory [1, 2]. However, it is still unknown how defense variability translates into herbivore suppression. Nonlinear averaging and constraints in physiological tracking (also more generally called time-dependent effects) are the two mechanisms by which defense variability might impact herbivores [3, 4]. We conducted a set of experiments manipulating the mean and variability of a plant defense, showing that defense variability does suppress herbivore performance and that it does so through physiological tracking effects that cannot be explained by nonlinear averaging. While nonlinear averaging predicted higher or the same herbivore performance on a variable defense than on an invariable defense, we show that variability actually decreased herbivore performance and population growth rate. Defense variability reduces herbivore performance in a way that is more than the average of its parts. This is consistent with constraints in physiological matching of detoxification systems for herbivores experiencing variable toxin levels in their diet and represents a more generalizable way of understanding the impacts of variability on herbivory [5]. Increasing defense variability in croplands at a scale encountered by individual herbivores can suppress herbivory, even if that is not anticipated by nonlinear averaging. Published by Elsevier Ltd.

Role of proline and pyrroline-5-carboxylate metabolism in plant defense against invading pathogens

PubMed Central

Qamar, Aarzoo; Mysore, Kirankumar S.; Senthil-Kumar, Muthappa

2015-01-01

Pyrroline-5-carboxylate (P5C) is an intermediate product of both proline biosynthesis and catabolism. Recent evidences indicate that proline-P5C metabolism is tightly regulated in plants, especially during pathogen infection and abiotic stress. However, role of P5C and its metabolism in plants has not yet been fully understood. Studies indicate that P5C synthesized in mitochondria has a role in both resistance (R)-gene-mediated and non-host resistance against invading pathogens. Proline dehydrogenase and delta-ornithine amino transferase-encoding genes, both involved in P5C synthesis in mitochondria are implicated in defense response of Nicotiana benthamiana and Arabidopsis thaliana against bacterial pathogens. Such defense response is proposed to involve salicylic acid-dependent pathway, reactive oxygen species (ROS) and hypersensitive response (HR)-associated cell death. Recently HR, a form of programmed cell death (PCD), has been proposed to be induced by changes in mitochondrial P5C synthesis or the increase in P5C levels per se in plants inoculated with either a host pathogen carrying suitable avirulent (Avr) gene or a non-host pathogen. Consistently, A. thaliana mutant plants deficient in P5C catabolism showed HR like cell death when grown in external P5C or proline supplemented medium. Similarly, yeast and plant cells under oxidative stress were shown to increase ROS production and PCD due to increase in P5C levels. Similar mechanism has also been reported as one of the triggers for apoptosis in mammalian cells. This review critically analyzes results from various studies and enumerates the pathways for regulation of P5C levels in the plant cell, especially in mitochondria, during pathogen infection. Further, mechanisms regulating P5C- mediated defense responses, namely HR are outlined. This review also provides new insights into the differential role of proline-P5C metabolism in plants exposed to pathogen infection. PMID:26217357

Plant neighbor identity influences plant biochemistry and physiology related to defense

PubMed Central

2010-01-01

Background Chemical and biological processes dictate an individual organism's ability to recognize and respond to other organisms. A small but growing body of evidence suggests that plants may be capable of recognizing and responding to neighboring plants in a species specific fashion. Here we tested whether or not individuals of the invasive exotic weed, Centaurea maculosa, would modulate their defensive strategy in response to different plant neighbors. Results In the greenhouse, C. maculosa individuals were paired with either conspecific (C. maculosa) or heterospecific (Festuca idahoensis) plant neighbors and elicited with the plant defense signaling molecule methyl jasmonate to mimic insect herbivory. We found that elicited C. maculosa plants grown with conspecific neighbors exhibited increased levels of total phenolics, whereas those grown with heterospecific neighbors allocated more resources towards growth. To further investigate these results in the field, we conducted a metabolomics analysis to explore chemical differences between individuals of C. maculosa growing in naturally occurring conspecific and heterospecific field stands. Similar to the greenhouse results, C. maculosa individuals accumulated higher levels of defense-related secondary metabolites and lower levels of primary metabolites when growing in conspecific versus heterospecific field stands. Leaf herbivory was similar in both stand types; however, a separate field study positively correlated specialist herbivore load with higher densities of C. maculosa conspecifics. Conclusions Our results suggest that an individual C. maculosa plant can change its defensive strategy based on the identity of its plant neighbors. This is likely to have important consequences for individual and community success. PMID:20565801

Climate Change, CO2, and Defense: The Metabolic, Redox, and Signaling Perspectives.

PubMed

Noctor, Graham; Mhamdi, Amna

2017-10-01

Ongoing human-induced changes in the composition of the atmosphere continue to stimulate interest in the effects of high CO 2 on plants, but its potential impact on inducible plant defense pathways remains poorly defined. Recently, several studies have reported that growth at elevated CO 2 is sufficient to induce defenses such as the salicylic acid pathway, thereby increasing plant resistance to pathogens. These reports contrast with evidence that defense pathways can be promoted by photorespiration, which is inhibited at high CO 2 . Here, we review signaling, metabolic, and redox processes modulated by CO 2 levels and discuss issues to be resolved in elucidating the relationships between primary metabolism, inducible defense, and biotic stress resistance. Copyright © 2017 Elsevier Ltd. All rights reserved.

Involvement of Trichoderma harzianum Epl-1 Protein in the Regulation of Botrytis Virulence- and Tomato Defense-Related Genes.

PubMed

Gomes, Eriston V; Ulhoa, Cirano J; Cardoza, Rosa E; Silva, Roberto N; Gutiérrez, Santiago

2017-01-01

Several Trichoderma spp. are well known for their ability to: (i) act as important biocontrol agents against phytopathogenic fungi; (ii) function as biofertilizers; (iii) increase the tolerance of plants to biotic and abiotic stresses; and (iv) induce plant defense responses via the production and secretion of elicitor molecules. In this study, we analyzed the gene-regulation effects of Trichoderma harzianum Epl-1 protein during the interactions of mutant Δ epl-1 or wild-type T. harzianum strains with: (a) the phytopathogen Botrytis cinerea and (b) with tomato plants, on short (24 h hydroponic cultures) and long periods (4-weeks old plants) after Trichoderma inoculation. Our results indicate that T. harzianum Epl-1 protein affects the in vitro expression of B. cinerea virulence genes, especially those involved in the botrydial biosynthesis ( BcBOT genes), during the mycoparasitism interaction. The tomato defense-related genes were also affected, indicating that Epl-1 is involved in the elicitation of the salicylic acid pathway. Moreover, Epl-1 also regulates the priming effect in host tomato plants and contributes to enhance the interaction with the host tomato plant during the early stage of root colonization.

Involvement of Trichoderma harzianum Epl-1 Protein in the Regulation of Botrytis Virulence- and Tomato Defense-Related Genes

PubMed Central

Gomes, Eriston V.; Ulhoa, Cirano J.; Cardoza, Rosa E.; Silva, Roberto N.; Gutiérrez, Santiago

2017-01-01

Several Trichoderma spp. are well known for their ability to: (i) act as important biocontrol agents against phytopathogenic fungi; (ii) function as biofertilizers; (iii) increase the tolerance of plants to biotic and abiotic stresses; and (iv) induce plant defense responses via the production and secretion of elicitor molecules. In this study, we analyzed the gene-regulation effects of Trichoderma harzianum Epl-1 protein during the interactions of mutant Δepl-1 or wild-type T. harzianum strains with: (a) the phytopathogen Botrytis cinerea and (b) with tomato plants, on short (24 h hydroponic cultures) and long periods (4-weeks old plants) after Trichoderma inoculation. Our results indicate that T. harzianum Epl-1 protein affects the in vitro expression of B. cinerea virulence genes, especially those involved in the botrydial biosynthesis (BcBOT genes), during the mycoparasitism interaction. The tomato defense-related genes were also affected, indicating that Epl-1 is involved in the elicitation of the salicylic acid pathway. Moreover, Epl-1 also regulates the priming effect in host tomato plants and contributes to enhance the interaction with the host tomato plant during the early stage of root colonization. PMID:28611802

Regulated nuclear trafficking of rpL10A mediated by NIK1 represents a defense strategy of plant cells against virus.

PubMed

Carvalho, Claudine M; Santos, Anésia A; Pires, Silvana R; Rocha, Carolina S; Saraiva, Daniela I; Machado, João Paulo B; Mattos, Eliciane C; Fietto, Luciano G; Fontes, Elizabeth P B

2008-12-01

The NSP-interacting kinase (NIK) receptor-mediated defense pathway has been identified recently as a virulence target of the geminivirus nuclear shuttle protein (NSP). However, the NIK1-NSP interaction does not fit into the elicitor-receptor model of resistance, and hence the molecular mechanism that links this antiviral response to receptor activation remains obscure. Here, we identified a ribosomal protein, rpL10A, as a specific partner and substrate of NIK1 that functions as an immediate downstream effector of NIK1-mediated response. Phosphorylation of cytosolic rpL10A by NIK1 redirects the protein to the nucleus where it may act to modulate viral infection. While ectopic expression of normal NIK1 or a hyperactive NIK1 mutant promotes the accumulation of phosphorylated rpL10A within the nuclei, an inactive NIK1 mutant fails to redirect the protein to the nuclei of co-transfected cells. Likewise, a mutant rpL10A defective for NIK1 phosphorylation is not redirected to the nucleus. Furthermore, loss of rpL10A function enhances susceptibility to geminivirus infection, resembling the phenotype of nik1 null alleles. We also provide evidence that geminivirus infection directly interferes with NIK1-mediated nuclear relocalization of rpL10A as a counterdefensive measure. However, the NIK1-mediated defense signaling neither activates RNA silencing nor promotes a hypersensitive response but inhibits plant growth and development. Although the virulence function of the particular geminivirus NSP studied here overcomes this layer of defense in Arabidopsis, the NIK1-mediated signaling response may be involved in restricting the host range of other viruses.

Jasmonate response decay and defense metabolite accumulation contributes to age-regulated dynamics of plant insect resistance

PubMed Central

Mao, Ying-Bo; Liu, Yao-Qian; Chen, Dian-Yang; Chen, Fang-Yan; Fang, Xin; Hong, Gao-Jie; Wang, Ling-Jian; Wang, Jia-Wei; Chen, Xiao-Ya

2017-01-01

Immunity deteriorates with age in animals but comparatively little is known about the temporal regulation of plant resistance to herbivores. The phytohormone jasmonate (JA) is a key regulator of plant insect defense. Here, we show that the JA response decays progressively in Arabidopsis. We show that this decay is regulated by the miR156-targeted SQUAMOSA PROMOTER BINDING PROTEIN-LIKE9 (SPL9) group of proteins, which can interact with JA ZIM-domain (JAZ) proteins, including JAZ3. As SPL9 levels gradually increase, JAZ3 accumulates and the JA response is attenuated. We provide evidence that this pathway contributes to insect resistance in young plants. Interestingly however, despite the decay in JA response, older plants are still comparatively more resistant to both the lepidopteran generalist Helicoverpa armigera and the specialist Plutella xylostella, along with increased accumulation of glucosinolates. We propose a model whereby constitutive accumulation of defense compounds plays a role in compensating for age-related JA-response attenuation during plant maturation. PMID:28067238

Nitric Oxide-Mediated Maintenance of Redox Homeostasis Contributes to NPR1-Dependent Plant Innate Immunity Triggered by Lipopolysaccharides1[C][W

PubMed Central

Sun, Aizhen; Nie, Shengjun; Xing, Da

2012-01-01

The perception of lipopolysaccharides (LPS) by plant cells can lead to nitric oxide (NO) production and defense gene induction. However, the signaling cascades underlying these cellular responses have not yet been resolved. This work investigated the biosynthetic origin of NO and the role of NONEXPRESSOR OF PATHOGENESIS-RELATED GENES1 (NPR1) to gain insight into the mechanism involved in LPS-induced resistance of Arabidopsis (Arabidopsis thaliana). Analysis of inhibitors and mutants showed that LPS-induced NO synthesis was mainly mediated by an arginine-utilizing source of NO generation. Furthermore, LPS-induced NO caused transcript accumulation of alternative oxidase genes and increased antioxidant enzyme activity, which enhanced antioxidant capacity and modulated redox state. We also analyzed the subcellular localization of NPR1 to identify the mechanism for protein-modulated plant innate immunity triggered by LPS. LPS-activated defense responses, including callose deposition and defense-related gene expression, were found to be regulated through an NPR1-dependent pathway. In summary, a significant NO synthesis induced by LPS contributes to the LPS-induced defense responses by up-regulation of defense genes and modulation of cellular redox state. Moreover, NPR1 plays an important role in LPS-triggered plant innate immunity. PMID:22926319

Growth–Defense Tradeoffs in Plants: A Balancing Act to Optimize Fitness

PubMed Central

Huot, Bethany; Yao, Jian; Montgomery, Beronda L.; He, Sheng Yang

2014-01-01

Growth–defense tradeoffs are thought to occur in plants due to resource restrictions, which demand prioritization towards either growth or defense, depending on external and internal factors. These tradeoffs have profound implications in agriculture and natural ecosystems, as both processes are vital for plant survival, reproduction, and, ultimately, plant fitness. While many of the molecular mechanisms underlying growth and defense tradeoffs remain to be elucidated, hormone crosstalk has emerged as a major player in regulating tradeoffs needed to achieve a balance. In this review, we cover recent advances in understanding growth–defense tradeoffs in plants as well as what is known regarding the underlying molecular mechanisms. Specifically, we address evidence supporting the growth–defense tradeoff concept, as well as known interactions between defense signaling and growth signaling. Understanding the molecular basis of these tradeoffs in plants should provide a foundation for the development of breeding strategies that optimize the growth–defense balance to maximize crop yield to meet rising global food and biofuel demands. PMID:24777989

Plant hormone jasmonate prioritizes defense over growth by interfering with gibberellin signaling cascade.

PubMed

Yang, Dong-Lei; Yao, Jian; Mei, Chuan-Sheng; Tong, Xiao-Hong; Zeng, Long-Jun; Li, Qun; Xiao, Lang-Tao; Sun, Tai-ping; Li, Jigang; Deng, Xing-Wang; Lee, Chin Mei; Thomashow, Michael F; Yang, Yinong; He, Zuhua; He, Sheng Yang

2012-05-08

Plants must effectively defend against biotic and abiotic stresses to survive in nature. However, this defense is costly and is often accompanied by significant growth inhibition. How plants coordinate the fluctuating growth-defense dynamics is not well understood and remains a fundamental question. Jasmonate (JA) and gibberellic acid (GA) are important plant hormones that mediate defense and growth, respectively. Binding of bioactive JA or GA ligands to cognate receptors leads to proteasome-dependent degradation of specific transcriptional repressors (the JAZ or DELLA family of proteins), which, at the resting state, represses cognate transcription factors involved in defense (e.g., MYCs) or growth [e.g. phytochrome interacting factors (PIFs)]. In this study, we found that the coi1 JA receptor mutants of rice (a domesticated monocot crop) and Arabidopsis (a model dicot plant) both exhibit hallmark phenotypes of GA-hypersensitive mutants. JA delays GA-mediated DELLA protein degradation, and the della mutant is less sensitive to JA for growth inhibition. Overexpression of a selected group of JAZ repressors in Arabidopsis plants partially phenocopies GA-associated phenotypes of the coi1 mutant, and JAZ9 inhibits RGA (a DELLA protein) interaction with transcription factor PIF3. Importantly, the pif quadruple (pifq) mutant no longer responds to JA-induced growth inhibition, and overexpression of PIF3 could partially overcome JA-induced growth inhibition. Thus, a molecular cascade involving the COI1-JAZ-DELLA-PIF signaling module, by which angiosperm plants prioritize JA-mediated defense over growth, has been elucidated.

Whiteflies interfere with indirect plant defense against spider mites in Lima bean

PubMed Central

Zhang, Peng-Jun; Zheng, Si-Jun; van Loon, Joop J. A.; Boland, Wilhelm; David, Anja; Mumm, Roland; Dicke, Marcel

2009-01-01

Plants under herbivore attack are able to initiate indirect defense by synthesizing and releasing complex blends of volatiles that attract natural enemies of the herbivore. However, little is known about how plants respond to infestation by multiple herbivores, particularly if these belong to different feeding guilds. Here, we report the interference by a phloem-feeding insect, the whitefly Bemisia tabaci, with indirect plant defenses induced by spider mites (Tetranychus urticae) in Lima bean (Phaseolus lunatus) plants. Additional whitefly infestation of spider-mite infested plants resulted in a reduced attraction of predatory mites (Phytoseiulus persimilis) compared to attraction to plants infested by spider mites only. This interference is shown to result from the reduction in (E)-β-ocimene emission from plants infested by both spider mites and whiteflies. When using exogenous salicylic acid (SA) application to mimic B. tabaci infestation, we observed similar results in behavioral and chemical analyses. Phytohormone and gene-expression analyses revealed that B. tabaci infestation, as well as SA application, inhibited spider mite-induced jasmonic acid (JA) production and reduced the expression of two JA-regulated genes, one of which encodes for the P. lunatus enzyme β-ocimene synthase that catalyzes the synthesis of (E)-β-ocimene. Remarkably, B. tabaci infestation concurrently inhibited SA production induced by spider mites. We therefore conclude that in dual-infested Lima bean plants the suppression of the JA signaling pathway by whitefly feeding is not due to enhanced SA levels. PMID:19965373

Induction of plant virus defense response by brassinosteroids and brassinosteroid signaling in Arabidopsis thaliana.

PubMed

Zhang, Da-Wei; Deng, Xing-Guang; Fu, Fa-Qiong; Lin, Hong-Hui

2015-04-01

Our study demonstrated that CMV resistance was upregulated by brassinosteroids (BRs) treatment, and BR signaling was needed for this BRs-induced CMV tolerance. Plant steroid hormones, brassinosteroids (BRs), play essential roles in variety of plant developmental processes and adaptation to various biotic and abiotic stresses. BR signal through plasma membrane-localized receptor and other components to modulate several transcription factors that modulate thousands of target genes including certain stress-responsive genes. To study the effects of BRs on plant virus defense and how BRs induce plant virus stress tolerance, we manipulated the BRs levels in Arabidopsis thaliana and found that BRs levels were positively correlated with the tolerance to Cucumber mosaic virus (CMV). We also showed that BRs treatment alleviated photosystem damage, enhanced antioxidant enzymes activity and induced defense-associated genes expression under CMV stress in Arabidopsis. To see whether BR signaling is essential for the plant virus defense response, we made use of BR signaling mutants (a weak allele of the BRs receptor mutant bri1-5 and constitutive BRs response mutant bes1-D). Compared with wild-type Arabidopsis plants, bri1-5 displayed reversed tolerance to CMV, but the resistance was enhanced in bes1-D. Together our results suggest that BRs can induce plant virus defense response through BR signaling.

Plant allocation of carbon to defense as a function of herbivory, light and nutrient availability

USGS Publications Warehouse

DeAngelis, Donald L.; Ju, Shu; Liu, Rongsong; Bryant, John P.; Gourley, Stephen A.

2012-01-01

We use modeling to determine the optimal relative plant carbon allocations between foliage, fine roots, anti-herbivore defense, and reproduction to maximize reproductive output. The model treats these plant components and the herbivore compartment as variables. Herbivory is assumed to be purely folivory. Key external factors include nutrient availability, degree of shading, and intensity of herbivory. Three alternative functional responses are used for herbivory, two of which are variations on donor-dependent herbivore (models 1a and 1b) and one of which is a Lotka–Volterra type of interaction (model 2). All three were modified to include the negative effect of chemical defenses on the herbivore. Analysis showed that, for all three models, two stable equilibria could occur, which differs from most common functional responses when no plant defense component is included. Optimal strategies of carbon allocation were defined as the maximum biomass of reproductive propagules produced per unit time, and found to vary with changes in external factors. Increased intensity of herbivory always led to an increase in the fractional allocation of carbon to defense. Decreases in available limiting nutrient generally led to increasing importance of defense. Decreases in available light had little effect on defense but led to increased allocation to foliage. Decreases in limiting nutrient and available light led to decreases in allocation to reproduction in models 1a and 1b but not model 2. Increases in allocation to plant defense were usually accompanied by shifts in carbon allocation away from fine roots, possibly because higher plant defense reduced the loss of nutrients to herbivory.

Effectors from Wheat Rust Fungi Suppress Multiple Plant Defense Responses.

PubMed

Ramachandran, Sowmya R; Yin, Chuntao; Kud, Joanna; Tanaka, Kiwamu; Mahoney, Aaron K; Xiao, Fangming; Hulbert, Scot H

2017-01-01

Fungi that cause cereal rust diseases (genus Puccinia) are important pathogens of wheat globally. Upon infection, the fungus secretes a number of effector proteins. Although a large repository of putative effectors has been predicted using bioinformatic pipelines, the lack of available high-throughput effector screening systems has limited functional studies on these proteins. In this study, we mined the available transcriptomes of Puccinia graminis and P. striiformis to look for potential effectors that suppress host hypersensitive response (HR). Twenty small (<300 amino acids), secreted proteins, with no predicted functions were selected for the HR suppression assay using Nicotiana benthamiana, in which each of the proteins were transiently expressed and evaluated for their ability to suppress HR caused by four cytotoxic effector-R gene combinations (Cp/Rx, ATR13/RPP13, Rpt2/RPS-2, and GPA/RBP-1) and one mutated R gene-Pto(Y207D). Nine out of twenty proteins, designated Shr1 to Shr9 (suppressors of hypersensitive response), were found to suppress HR in N. benthamiana. These effectors varied in the effector-R gene defenses they suppressed, indicating these pathogens can interfere with a variety of host defense pathways. In addition to HR suppression, effector Shr7 also suppressed PAMP-triggered immune response triggered by flg22. Finally, delivery of Shr7 through Pseudomonas fluorescens EtHAn suppressed nonspecific HR induced by Pseudomonas syringae DC3000 in wheat, confirming its activity in a homologous system. Overall, this study provides the first evidence for the presence of effectors in Puccinia species suppressing multiple plant defense responses.

Growth-defense tradeoffs in plants: a balancing act to optimize fitness.

PubMed

Huot, Bethany; Yao, Jian; Montgomery, Beronda L; He, Sheng Yang

2014-08-01

Growth-defense tradeoffs are thought to occur in plants due to resource restrictions, which demand prioritization towards either growth or defense, depending on external and internal factors. These tradeoffs have profound implications in agriculture and natural ecosystems, as both processes are vital for plant survival, reproduction, and, ultimately, plant fitness. While many of the molecular mechanisms underlying growth and defense tradeoffs remain to be elucidated, hormone crosstalk has emerged as a major player in regulating tradeoffs needed to achieve a balance. In this review, we cover recent advances in understanding growth-defense tradeoffs in plants as well as what is known regarding the underlying molecular mechanisms. Specifically, we address evidence supporting the growth-defense tradeoff concept, as well as known interactions between defense signaling and growth signaling. Understanding the molecular basis of these tradeoffs in plants should provide a foundation for the development of breeding strategies that optimize the growth-defense balance to maximize crop yield to meet rising global food and biofuel demands. © The Author 2014. Published by the Molecular Plant Shanghai Editorial Office in association with Oxford University Press on behalf of CSPB and IPPE, SIBS, CAS.

Citrus leprosis virus C Infection Results in Hypersensitive-Like Response, Suppression of the JA/ET Plant Defense Pathway and Promotion of the Colonization of Its Mite Vector

PubMed Central

Arena, Gabriella D.; Ramos-González, Pedro L.; Nunes, Maria A.; Ribeiro-Alves, Marcelo; Camargo, Luis E. A.; Kitajima, Elliot W.; Machado, Marcos A.; Freitas-Astúa, Juliana

2016-01-01

Leprosis is a serious disease of citrus caused by Citrus leprosis virus C (CiLV-C, genus Cilevirus) whose transmission is mediated by false spider mites of the genus Brevipalpus. CiLV-C infection does not systemically spread in any of its known host plants, thus remaining restricted to local lesions around the feeding sites of viruliferous mites. To get insight into this unusual pathosystem, we evaluated the expression profiles of genes involved in defense mechanisms of Arabidopsis thaliana and Citrus sinensis upon infestation with non-viruliferous and viruliferous mites by using reverse-transcription qPCR. These results were analyzed together with the production of reactive oxygen species (ROS) and the appearance of dead cells as assessed by histochemical assays. After interaction with non-viruliferous mites, plants locally accumulated ROS and triggered the salicylic acid (SA) and jasmonate/ethylene (JA/ET) pathways. ERF branch of the JA/ET pathways was highly activated. In contrast, JA pathway genes were markedly suppressed upon the CiLV-C infection mediated by viruliferous mites. Viral infection also intensified the ROS burst and cell death, and enhanced the expression of genes involved in the RNA silencing mechanism and SA pathway. After 13 days of infestation of two sets of Arabidopsis plants with non-viruliferous and viruliferous mites, the number of mites in the CiLV-C infected Arabidopsis plants was significantly higher than in those infested with the non-viruliferous ones. Oviposition of the viruliferous mites occurred preferentially in the CiLV-C infected leaves. Based on these results, we postulated the first model of plant/Brevipalpus mite/cilevirus interaction in which cells surrounding the feeding sites of viruliferous mites typify the outcome of a hypersensitive-like response, whereas viral infection induces changes in the behavior of its vector. PMID:27933078

Mechanical defenses of plant extrafloral nectaries against herbivory

PubMed Central

Gish, Moshe; Mescher, Mark C.; De Moraes, Consuelo M.

2016-01-01

ABSTRACT Extrafloral nectaries play an important role in plant defense against herbivores by providing nectar rewards that attract ants and other carnivorous insects. However, extrafloral nectaries can themselves be targets of herbivory, in addition to being exploited by nectar-robbing insects that do not provide defensive services. We recently found that the extrafloral nectaries of Vicia faba plants, as well as immediately adjacent tissues, exhibit high concentrations of chemical toxins, apparently as a defense against herbivory. Here we report that the nectary tissues of this plant also exhibit high levels of structural stiffness compared to surrounding tissues, likely due to cell wall lignification and the concentration of calcium oxalate crystals in nectary tissues, which may provide an additional deterrent to herbivore feeding on nectary tissues. PMID:27489584

The OXI1 Kinase Pathway Mediates Piriformospora indica-Induced Growth Promotion in Arabidopsis

PubMed Central

Camehl, Iris; Drzewiecki, Corinna; Vadassery, Jyothilakshmi; Shahollari, Bationa; Sherameti, Irena; Forzani, Celine; Munnik, Teun; Hirt, Heribert; Oelmüller, Ralf

2011-01-01

Piriformospora indica is an endophytic fungus that colonizes roots of many plant species and promotes growth and resistance to certain plant pathogens. Despite its potential use in agriculture, little is known on the molecular basis of this beneficial plant-fungal interaction. In a genetic screen for plants, which do not show a P. indica- induced growth response, we isolated an Arabidopsis mutant in the OXI1 (Oxidative Signal Inducible1) gene. OXI1 has been characterized as a protein kinase which plays a role in pathogen response and is regulated by H2O2 and PDK1 (3-PHOSPHOINOSITIDE-DEPENDENT PROTEIN KINASE1). A genetic analysis showed that double mutants of the two closely related PDK1.1 and PDK1.2 genes are defective in the growth response to P. indica. While OXI1 and PDK1 gene expression is upregulated in P. indica-colonized roots, defense genes are downregulated, indicating that the fungus suppresses plant defense reactions. PDK1 is activated by phosphatidic acid (PA) and P. indica triggers PA synthesis in Arabidopsis plants. Under beneficial co-cultivation conditions, H2O2 formation is even reduced by the fungus. Importantly, phospholipase D (PLD)α1 or PLDδ mutants, which are impaired in PA synthesis do not show growth promotion in response to fungal infection. These data establish that the P. indica-stimulated growth response is mediated by a pathway consisting of the PLD-PDK1-OXI1 cascade. PMID:21625539

Next Generation Nuclear Plant Defense-in-Depth Approach

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

Edward G. Wallace; Karl N. Fleming; Edward M. Burns

2009-12-01

The purpose of this paper is to (1) document the definition of defense-in-depth and the pproach that will be used to assure that its principles are satisfied for the NGNP project and (2) identify the specific questions proposed for preapplication discussions with the NRC. Defense-in-depth is a safety philosophy in which multiple lines of defense and conservative design and evaluation methods are applied to assure the safety of the public. The philosophy is also intended to deliver a design that is tolerant to uncertainties in knowledge of plant behavior, component reliability or operator performance that might compromise safety. This papermore » includes a review of the regulatory foundation for defense-in-depth, a definition of defense-in-depth that is appropriate for advanced reactor designs based on High Temperature Gas-cooled Reactor (HTGR) technology, and an explanation of how this safety philosophy is achieved in the NGNP.« less

Hormone crosstalk in plant disease and defense: more than just jasmonate-salicylate antagonism.

PubMed

Robert-Seilaniantz, Alexandre; Grant, Murray; Jones, Jonathan D G

2011-01-01

Until recently, most studies on the role of hormones in plant-pathogen interactions focused on salicylic acid (SA), jasmonic acid (JA), and ethylene (ET). It is now clear that pathogen-induced modulation of signaling via other hormones contributes to virulence. A picture is emerging of complex crosstalk and induced hormonal changes that modulate disease and resistance, with outcomes dependent on pathogen lifestyles and the genetic constitution of the host. Recent progress has revealed intriguing similarities between hormone signaling mechanisms, with gene induction responses often achieved by derepression. Here, we report on recent advances, updating current knowledge on classical defense hormones SA, JA, and ET, and the roles of auxin, abscisic acid (ABA), cytokinins (CKs), and brassinosteroids in molding plant-pathogen interactions. We highlight an emerging theme that positive and negative regulators of these disparate hormone signaling pathways are crucial regulatory targets of hormonal crosstalk in disease and defense. Copyright © 2011 by Annual Reviews. All rights reserved.

Ca2+/Calmodulin-Dependent AtSR1/CAMTA3 Plays Critical Roles in Balancing Plant Growth and Immunity.

PubMed

Yuan, Peiguo; Du, Liqun; Poovaiah, B W

2018-06-14

During plant-pathogen interactions, plants have to relocate their resources including energy to defend invading organisms; as a result, plant growth and development are usually reduced. Arabidopsis signal responsive1 (AtSR1) has been documented as a negative regulator of plant immune responses and could serve as a positive regulator of plant growth and development. However, the mechanism by which AtSR1 balances plant growth and immunity is poorly understood. Here, we performed a global gene expression profiling using Affymetrix microarrays to study how AtSR1 regulates defense- and growth-related genes in plants with and without bacterial pathogen infection. Results revealed that AtSR1 negatively regulates most of the immune-related genes involved in molecular pattern-triggered immunity (PTI), effector-triggered immunity (ETI), and in salicylic acid (SA)- and jasmonate (JA)-mediated signaling pathways. AtSR1 may rigidly regulate several steps of the SA-mediated pathway, from the activation of SA synthesis to the perception of SA signal. Furthermore, AtSR1 may also regulate plant growth through its involvement in regulating auxin- and BRs-related pathways. Although microarray data revealed that expression levels of defense-related genes induced by pathogens are higher in wild-type (WT) plants than that in atsr1 mutant plants, WT plants are more susceptible to the infection of virulent pathogen as compared to atsr1 mutant plants. These observations indicate that the AtSR1 functions in suppressing the expression of genes induced by pathogen attack and contributes to the rapid establishment of resistance in WT background. Results of electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP)-PCR assays suggest that AtSR1 acts as transcription factor in balancing plant growth and immunity, through interaction with the “CGCG” containing CG-box in the promotors of its target genes.

Induced plant-defenses suppress herbivore reproduction but also constrain predation of their offspring.

PubMed

Ataide, Livia M S; Pappas, Maria L; Schimmel, Bernardus C J; Lopez-Orenes, Antonio; Alba, Juan M; Duarte, Marcus V A; Pallini, Angelo; Schuurink, Robert C; Kant, Merijn R

2016-11-01

Inducible anti-herbivore defenses in plants are predominantly regulated by jasmonic acid (JA). On tomato plants, most genotypes of the herbivorous generalist spider mite Tetranychus urticae induce JA defenses and perform poorly on it, whereas the Solanaceae specialist Tetranychus evansi, who suppresses JA defenses, performs well on it. We asked to which extent these spider mites and the predatory mite Phytoseiulus longipes preying on these spider mites eggs are affected by induced JA-defenses. By artificially inducing the JA-response of the tomato JA-biosynthesis mutant def-1 using exogenous JA and isoleucine (Ile), we first established the relationship between endogenous JA-Ile-levels and the reproductive performance of spider mites. For both mite species we observed that they produced more eggs when levels of JA-Ile were low. Subsequently, we allowed predatory mites to prey on spider mite-eggs derived from wild-type tomato plants, def-1 and JA-Ile-treated def-1 and observed that they preferred, and consumed more, eggs produced on tomato plants with weak JA defenses. However, predatory mite oviposition was similar across treatments. Our results show that induced JA-responses negatively affect spider mite performance, but positively affect the survival of their offspring by constraining egg-predation. Copyright © 2016 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

Transcriptome analysis reveals key roles of AtLBR-2 in LPS-induced defense responses in plants.

PubMed

Iizasa, Sayaka; Iizasa, Ei'ichi; Watanabe, Keiichi; Nagano, Yukio

2017-12-29

Lipopolysaccharide (LPS) from Gram-negative bacteria cause innate immune responses in animals and plants. The molecules involved in LPS signaling in animals are well studied, whereas those in plants are not yet as well documented. Recently, we identified Arabidopsis AtLBR-2, which binds to LPS from Pseudomonas aeruginosa (pLPS) directly and regulates pLPS-induced defense responses, such as pathogenesis-related 1 (PR1) expression and reactive oxygen species (ROS) production. In this study, we investigated the pLPS-induced transcriptomic changes in wild-type (WT) and the atlbr-2 mutant Arabidopsis plants using RNA-Seq technology. RNA-Seq data analysis revealed that pLPS treatment significantly altered the expression of 2139 genes, with 605 up-regulated and 1534 down-regulated genes in WT. Gene ontology (GO) analysis on these genes showed that GO terms, "response to bacterium", "response to salicylic acid (SA) stimulus", and "response to abscisic acid (ABA) stimulus" were enriched amongst only in up-regulated genes, as compared to the genes that were down-regulated. Comparative analysis of differentially expressed genes between WT and the atlbr-2 mutant revealed that 65 genes were up-regulated in WT but not in the atlbr-2 after pLPS treatment. Furthermore, GO analysis on these 65 genes demonstrated their importance for the enrichment of several defense-related GO terms, including "response to bacterium", "response to SA stimulus", and "response to ABA stimulus". We also found reduced levels of pLPS-induced conjugated SA glucoside (SAG) accumulation in atlbr-2 mutants, and no differences were observed in the gene expression levels in SA-treated WT and the atlbr-2 mutants. These 65 AtLBR-2-dependent up-regulated genes appear to be important for the enrichment of some defense-related GO terms. Moreover, AtLBR-2 might be a key molecule that is indispensable for the up-regulation of defense-related genes and for SA signaling pathway, which is involved in defense against

Plant peptides in defense and signaling.

PubMed

Marmiroli, Nelson; Maestri, Elena

2014-06-01

This review focuses on plant peptides involved in defense against pathogen infection and those involved in the regulation of growth and development. Defense peptides, defensins, cyclotides and anti-microbial peptides are compared and contrasted. Signaling peptides are classified according to their major sites of activity. Finally, a network approach to creating an interactomic peptide map is described. Copyright © 2014 Elsevier Inc. All rights reserved.

Conveying endogenous and exogenous signals: MAPK cascades in plant growth and defense.

PubMed

Zhang, Mengmeng; Su, Jianbin; Zhang, Yan; Xu, Juan; Zhang, Shuqun

2018-05-09

Mitogen-activated protein kinase (MAPK) cascades are key signaling modules downstream of receptors/sensors that perceive endogenous and exogenous stimuli such as hormones, peptide ligands, and pathogen-derived patterns/effectors. In this review, we summarize recent advances in the establishment of MAPK cascades as unified signaling modules downstream of receptor-like kinases (RLKs) and receptor-like proteins (RLPs) in plant growth and defense, the identification of components connecting the RLK/RLP receptor complexes to the MAPK cascades, and the interactions between MAPK and hormone signaling pathways. We also propose a set of criteria for defining the physiological substrates of plant MAPKs. With only a limited number of MAPK components, multiple functional pathways often share the same MAPK cascade. As a result, understanding the signaling specificity, which requires detailed information about the spatiotemporal expression of the components involved, their complex formation, and the consequence of substrate phosphorylation, is central to our study of MAPK functions. Copyright © 2018 Elsevier Ltd. All rights reserved.

Induction of Jasmonic Acid-Associated Defenses by Thrips Alters Host Suitability for Conspecifics and Correlates with Increased Trichome Densities in Tomato

PubMed Central

Klinkhamer, Peter G.L.; Leiss, Kirsten A.

2017-01-01

Plant defenses inducible by herbivorous arthropods can determine performance of subsequent feeding herbivores. We investigated how infestation of tomato (Solanum lycopersicum) plants with the Western flower thrips (Frankliniella occidentalis) alters host plant suitability and foraging decisions of their conspecifics. We explored the role of delayed-induced jasmonic acid (JA)-mediated plant defense responses in thrips preference by using the tomato mutant def-1, impaired in JA biosynthesis. In particular, we investigated the effect of thrips infestation on trichome-associated tomato defenses. The results showed that when offered a choice, thrips preferred non-infested plants over infested wild-type plants, while no differences were observed in def-1. Exogenous application of methyl jasmonate restored the repellency effect in def-1. Gene expression analysis showed induction of the JA defense signaling pathway in wild-type plants, while activating the ethylene signaling pathway in both genotypes. Activation of JA defenses led to increases in type-VI leaf glandular trichome densities in the wild type, augmenting the production of trichome-associated volatiles, i.e. terpenes. Our study revealed that plant-mediated intraspecific interactions between thrips are determined by JA-mediated defenses in tomato. We report that insects can alter not only trichome densities but also the allelochemicals produced therein, and that this response might depend on the magnitude and/or type of the induction. PMID:28158865

Vitamin B1 Functions as an Activator of Plant Disease Resistance1

PubMed Central

Ahn, Il-Pyung; Kim, Soonok; Lee, Yong-Hwan

2005-01-01

Vitamin B1 (thiamine) is an essential nutrient for humans. Vitamin B1 deficiency causes beriberi, which disturbs the central nervous and circulatory systems. In countries in which rice (Oryza sativa) is a major food, thiamine deficiency is prevalent because polishing of rice removes most of the thiamine in the grain. We demonstrate here that thiamine, in addition to its nutritional value, induces systemic acquired resistance (SAR) in plants. Thiamine-treated rice, Arabidopsis (Arabidopsis thaliana), and vegetable crop plants showed resistance to fungal, bacterial, and viral infections. Thiamine treatment induces the transient expression of pathogenesis-related (PR) genes in rice and other plants. In addition, thiamine treatment potentiates stronger and more rapid PR gene expression and the up-regulation of protein kinase C activity. The effects of thiamine on disease resistance and defense-related gene expression mobilize systemically throughout the plant and last for more than 15 d after treatment. Treatment of Arabidopsis ecotype Columbia-0 plants with thiamine resulted in the activation of PR-1 but not PDF1.2. Furthermore, thiamine prevented bacterial infection in Arabidopsis mutants insensitive to jasmonic acid or ethylene but not in mutants impaired in the SAR transduction pathway. These results clearly demonstrate that thiamine induces SAR in plants through the salicylic acid and Ca2+-related signaling pathways. The findings provide a novel paradigm for developing alternative strategies for the control of plant diseases. PMID:15980201

Genome-Wide Prediction of Metabolic Enzymes, Pathways, and Gene Clusters in Plants1[OPEN

PubMed Central

Zhang, Peifen; Kim, Taehyong; Banf, Michael; Chavali, Arvind K.; Nilo-Poyanco, Ricardo; Bernard, Thomas

2017-01-01

Plant metabolism underpins many traits of ecological and agronomic importance. Plants produce numerous compounds to cope with their environments but the biosynthetic pathways for most of these compounds have not yet been elucidated. To engineer and improve metabolic traits, we need comprehensive and accurate knowledge of the organization and regulation of plant metabolism at the genome scale. Here, we present a computational pipeline to identify metabolic enzymes, pathways, and gene clusters from a sequenced genome. Using this pipeline, we generated metabolic pathway databases for 22 species and identified metabolic gene clusters from 18 species. This unified resource can be used to conduct a wide array of comparative studies of plant metabolism. Using the resource, we discovered a widespread occurrence of metabolic gene clusters in plants: 11,969 clusters from 18 species. The prevalence of metabolic gene clusters offers an intriguing possibility of an untapped source for uncovering new metabolite biosynthesis pathways. For example, more than 1,700 clusters contain enzymes that could generate a specialized metabolite scaffold (signature enzymes) and enzymes that modify the scaffold (tailoring enzymes). In four species with sufficient gene expression data, we identified 43 highly coexpressed clusters that contain signature and tailoring enzymes, of which eight were characterized previously to be functional pathways. Finally, we identified patterns of genome organization that implicate local gene duplication and, to a lesser extent, single gene transposition as having played roles in the evolution of plant metabolic gene clusters. PMID:28228535

DEAR1, a transcriptional repressor of DREB protein that mediates plant defense and freezing stress responses in Arabidopsis.

PubMed

Tsutsui, Tomokazu; Kato, Wataru; Asada, Yutaka; Sako, Kaori; Sato, Takeo; Sonoda, Yutaka; Kidokoro, Satoshi; Yamaguchi-Shinozaki, Kazuko; Tamaoki, Masanori; Arakawa, Keita; Ichikawa, Takanari; Nakazawa, Miki; Seki, Motoaki; Shinozaki, Kazuo; Matsui, Minami; Ikeda, Akira; Yamaguchi, Junji

2009-11-01

Plants have evolved intricate mechanisms to respond and adapt to a wide variety of biotic and abiotic stresses in their environment. The Arabidopsis DEAR1 (DREB and EAR motif protein 1; At3g50260) gene encodes a protein containing significant homology to the DREB1/CBF (dehydration-responsive element binding protein 1/C-repeat binding factor) domain and the EAR (ethylene response factor-associated amphiphilic repression) motif. We show here that DEAR1 mRNA accumulates in response to both pathogen infection and cold treatment. Transgenic Arabidopsis overexpressing DEAR1 (DEAR1ox) showed a dwarf phenotype and lesion-like cell death, together with constitutive expression of PR genes and accumulation of salicylic acid. DEAR1ox also showed more limited P. syringae pathogen growth compared to wild-type, consistent with an activated defense phenotype. In addition, transient expression experiments revealed that the DEAR1 protein represses DRE/CRT (dehydration-responsive element/C-repeat)-dependent transcription, which is regulated by low temperature. Furthermore, the induction of DREB1/CBF family genes by cold treatment was suppressed in DEAR1ox, leading to a reduction in freezing tolerance. These results suggest that DEAR1 has an upstream regulatory role in mediating crosstalk between signaling pathways for biotic and abiotic stress responses.

Intra-plant variation in cyanogenesis and the continuum of foliar plant defense traits in the rainforest tree Ryparosa kurrangii (Achariaceae).

PubMed

Webber, Bruce L; Woodrow, Ian E

2008-06-01

At the intra-plant level, temporal and spatial variations in plant defense traits can be influenced by resource requirements, defensive priorities and storage opportunities. Across a leaf age gradient, cyanogenic glycoside concentrations in the rainforest understory tree Ryparosa kurrangii B.L. Webber were higher in young expanding leaves than in mature leaves (2.58 and 1.38 mg g(-1), respectively). Moreover, cyanogens, as an effective chemical defense against generalist herbivores, contributed to a defense continuum protecting foliar tissue during leaf development. Chemical (cyanogens and phenolic compounds) and phenological (delayed greening) defense traits protected young leaves, whereas mature leaves were largely protected by physical defense mechanisms (lamina toughness; explained primarily by leaf mass per area). Cyanogen concentration was considerably higher in floral tissue than in foliar tissue and decreased in floral tissue during development. Across contrasting tropical seasons, foliar cyanogenic concentration varied significantly, being highest in the late wet season and lowest during the pre-wet season, the latter coinciding with fruiting and leaf flushing. Cyanogens in R. kurrangii appear to be differentially allocated in a way that maximizes plant fitness but may also act as a store of reduced nitrogen that is remobilized during flowering and leaf flushing.

Evidence of salicylic acid pathway with EDS1 and PAD4 proteins by molecular dynamics simulation for grape improvement.

PubMed

Tandon, Gitanjali; Jaiswal, Sarika; Iquebal, M A; Kumar, Sunil; Kaur, Sukhdeep; Rai, Anil; Kumar, Dinesh

2015-01-01

Biotic stress is a major cause of heavy loss in grape productivity. In order to develop biotic stress-resistant grape varieties, the key defense genes along with its pathway have to be deciphered. In angiosperm plants, lipase-like protein phytoalexin deficient 4 (PAD4) is well known to be essential for systemic resistance against biotic stress. PAD4 functions together with its interacting partner protein enhanced disease susceptibility 1 (EDS1) to promote salicylic acid (SA)-dependent and SA-independent defense pathway. Existence and structure of key protein of systemic resistance EDS1 and PAD4 are not known in grapes. Before SA pathway studies are taken in grape, molecular evidence of EDS1: PAD4 complex is to be established. To establish this, EDS1 protein sequence was retrieved from NCBI and homologous PAD4 protein was generated using Arabidopsis thaliana as template and conserved domains were confirmed. In this study, computational methods were used to model EDS1 and PAD4 and simulated the interactions of EDS1 and PAD4. Since no structural details of the proteins were available, homology modeling was employed to construct three-dimensional structures. Further, molecular dynamic simulations were performed to study the dynamic behavior of the EDS1 and PAD4. The modeled proteins were validated and subjected to molecular docking analysis. Molecular evidence of stable complex of EDS1:PAD4 in grape supporting SA defense pathway in response to biotic stress is reported in this study. If SA defense pathway genes are explored, then markers of genes involved can play pivotal role in grape variety development especially against biotic stress leading to higher productivity.

Defense mutualisms enhance plant diversification

PubMed Central

Weber, Marjorie G.; Agrawal, Anurag A.

2014-01-01

The ability of plants to form mutualistic relationships with animal defenders has long been suspected to influence their evolutionary success, both by decreasing extinction risk and by increasing opportunity for speciation through an expanded realized niche. Nonetheless, the hypothesis that defense mutualisms consistently enhance plant diversification across lineages has not been well tested due to a lack of phenotypic and phylogenetic information. Using a global analysis, we show that the >100 vascular plant families in which species have evolved extrafloral nectaries (EFNs), sugar-secreting organs that recruit arthropod mutualists, have twofold higher diversification rates than families that lack species with EFNs. Zooming in on six distantly related plant clades, trait-dependent diversification models confirmed the tendency for lineages with EFNs to display increased rates of diversification. These results were consistent across methodological approaches. Inference using reversible-jump Markov chain Monte Carlo (MCMC) to model the placement and number of rate shifts revealed that high net diversification rates in EFN clades were driven by an increased number of positive rate shifts following EFN evolution compared with sister clades, suggesting that EFNs may be indirect facilitators of diversification. Our replicated analysis indicates that defense mutualisms put lineages on a path toward increased diversification rates within and between clades, and is concordant with the hypothesis that mutualistic interactions with animals can have an impact on deep macroevolutionary patterns and enhance plant diversity. PMID:25349406

Defense mutualisms enhance plant diversification.

PubMed

Weber, Marjorie G; Agrawal, Anurag A

2014-11-18

The ability of plants to form mutualistic relationships with animal defenders has long been suspected to influence their evolutionary success, both by decreasing extinction risk and by increasing opportunity for speciation through an expanded realized niche. Nonetheless, the hypothesis that defense mutualisms consistently enhance plant diversification across lineages has not been well tested due to a lack of phenotypic and phylogenetic information. Using a global analysis, we show that the >100 vascular plant families in which species have evolved extrafloral nectaries (EFNs), sugar-secreting organs that recruit arthropod mutualists, have twofold higher diversification rates than families that lack species with EFNs. Zooming in on six distantly related plant clades, trait-dependent diversification models confirmed the tendency for lineages with EFNs to display increased rates of diversification. These results were consistent across methodological approaches. Inference using reversible-jump Markov chain Monte Carlo (MCMC) to model the placement and number of rate shifts revealed that high net diversification rates in EFN clades were driven by an increased number of positive rate shifts following EFN evolution compared with sister clades, suggesting that EFNs may be indirect facilitators of diversification. Our replicated analysis indicates that defense mutualisms put lineages on a path toward increased diversification rates within and between clades, and is concordant with the hypothesis that mutualistic interactions with animals can have an impact on deep macroevolutionary patterns and enhance plant diversity.

The pepper GNA-related lectin and PAN domain protein gene, CaGLP1, is required for plant cell death and defense signaling during bacterial infection.

PubMed

Kim, Nak Hyun; Lee, Dong Hyuk; Choi, Du Seok; Hwang, Byung Kook

2015-12-01

Carbohydrate-binding proteins, commonly referred to as lectins or agglutinins, function in defense responses to microbial pathogens. Pepper (Capsicum annuum) GNA-related lectin and PAN-domain protein gene CaGLP1 was isolated and functionally characterized from pepper leaves infected with Xanthomonas campestris pv. vesicatoria (Xcv). CaGLP1 contained an amine-terminus prokaryotic membrane lipoprotein lipid attachment site, a Galanthus nivalis agglutinin (GNA)-related lectin domain responsible for the recognition of high-mannose N-glycans, and a carboxyl-terminus PAN/apple domain. RNA gel blot and immunoblot analyses determined that CaGLP1 was strongly induced in pepper by compatible and incompatible Xcv infection. CaGLP1 protein localized primarily to the plasma membrane and exhibited mannose-binding specificity. CaGLP1-silenced pepper plants were more susceptible to compatible or incompatible Xcv infection compared with that of non-silenced control plants. CaGLP1 silencing in pepper leaves did not accumulate H2O2 and induce cell death during incompatible Xcv infection. Defense-related CaDEF1 (defensin) gene expression was significantly reduced in CaGLP1-silenced pepper plants. CaGLP1-overexpression in Arabidopsis thaliana enhanced resistance to Pseudomonas syringae pv. tomato. Defense-related AtPDF1.2 expression was elevated in CaGLP1-overexpression lines. Together, these results suggest that CaGLP1 is required for plant cell death and defense responses through the reactive oxygen species burst and downstream defense-related gene expression in response to bacterial pathogen challenge. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Novel beta-1,3-, 1,6-oligoglucan elicitor from Alternaria alternata 102 for defense responses in tobacco.

PubMed

Shinya, Tomonori; Ménard, Rozenn; Kozone, Ikuko; Matsuoka, Hideaki; Shibuya, Naoto; Kauffmann, Serge; Matsuoka, Ken; Saito, Mikako

2006-06-01

A novel elicitor that induces chitinases in tobacco BY-2 cells was isolated from Alternaria alternata 102. Six other fungi, including A. alternata IFO 6587, could not induce, or weakly induce chitinase activity. The purified elicitor was soluble in 75% methanol and showed the chitinase-inducing activity when applied at concentrations of as low as 25 ng x mL(-1). Structural determination by methylation analysis, reducing-end analysis, MALDI-TOF/MS, and NMR spectroscopy indicated that the elicitor was a mixture of beta-1,3-, 1,6-oligoglucans mostly with a degree of polymerization of between 8 and 17. Periodate oxidation of the elicitor suggested that the 1,6-linked and nonreducing terminal residues are essential for the elicitor activity. Further analysis of the elicitor responses in BY-2 cells indicated that the activity of this beta-1,3-, 1,6-glucan elicitor was about 1000 times more potent than that of laminarin, which is a known elicitor of defense responses in tobacco. Analyzing the expression of defense-related genes indicated that a phenylalanine ammonia-lyase gene and a coumaroyl-CoA O-methyltransferase gene were transiently expressed by this beta-1,3-, 1,6-glucan elicitor. The elicitor induced a weak oxidative burst but did not induce cell death in the BY-2 cells. In the tissue of tobacco plants, this beta-1,3-, 1,6-glucan elicitor induced the expression of basic PR-3 genes, the phenylpropanoid pathway genes, and the sesquiterpenoid pathway genes. In comparison with laminarin and laminarin sulfate, which are reported to be potent elicitors of defense responses in tobacco, the expression pattern of genes induced by the purified beta-1,3-, 1,6-glucan elicitor was more similar to that induced by laminarin than to that induced by laminarin sulfate.

The Arabidopsis Rho of Plants GTPase AtROP6 Functions in Developmental and Pathogen Response Pathways1[C][W][OA

PubMed Central

Poraty-Gavra, Limor; Zimmermann, Philip; Haigis, Sabine; Bednarek, Paweł; Hazak, Ora; Stelmakh, Oksana Rogovoy; Sadot, Einat; Schulze-Lefert, Paul; Gruissem, Wilhelm; Yalovsky, Shaul

2013-01-01

How plants coordinate developmental processes and environmental stress responses is a pressing question. Here, we show that Arabidopsis (Arabidopsis thaliana) Rho of Plants6 (AtROP6) integrates developmental and pathogen response signaling. AtROP6 expression is induced by auxin and detected in the root meristem, lateral root initials, and leaf hydathodes. Plants expressing a dominant negative AtROP6 (rop6DN) under the regulation of its endogenous promoter are small and have multiple inflorescence stems, twisted leaves, deformed leaf epidermis pavement cells, and differentially organized cytoskeleton. Microarray analyses of rop6DN plants revealed that major changes in gene expression are associated with constitutive salicylic acid (SA)-mediated defense responses. In agreement, their free and total SA levels resembled those of wild-type plants inoculated with a virulent powdery mildew pathogen. The constitutive SA-associated response in rop6DN was suppressed in mutant backgrounds defective in SA signaling (nonexpresser of PR genes1 [npr1]) or biosynthesis (salicylic acid induction deficient2 [sid2]). However, the rop6DN npr1 and rop6DN sid2 double mutants retained the aberrant developmental phenotypes, indicating that the constitutive SA response can be uncoupled from ROP function(s) in development. rop6DN plants exhibited enhanced preinvasive defense responses to a host-adapted virulent powdery mildew fungus but were impaired in preinvasive defenses upon inoculation with a nonadapted powdery mildew. The host-adapted powdery mildew had a reduced reproductive fitness on rop6DN plants, which was retained in mutant backgrounds defective in SA biosynthesis or signaling. Our findings indicate that both the morphological aberrations and altered sensitivity to powdery mildews of rop6DN plants result from perturbations that are independent from the SA-associated response. These perturbations uncouple SA-dependent defense signaling from disease resistance execution. PMID

Creation of a Genome-Wide Metabolic Pathway Database for Populus trichocarpa Using a New Approach for Reconstruction and Curation of Metabolic Pathways for Plants1[W][OA

PubMed Central

Zhang, Peifen; Dreher, Kate; Karthikeyan, A.; Chi, Anjo; Pujar, Anuradha; Caspi, Ron; Karp, Peter; Kirkup, Vanessa; Latendresse, Mario; Lee, Cynthia; Mueller, Lukas A.; Muller, Robert; Rhee, Seung Yon

2010-01-01

Metabolic networks reconstructed from sequenced genomes or transcriptomes can help visualize and analyze large-scale experimental data, predict metabolic phenotypes, discover enzymes, engineer metabolic pathways, and study metabolic pathway evolution. We developed a general approach for reconstructing metabolic pathway complements of plant genomes. Two new reference databases were created and added to the core of the infrastructure: a comprehensive, all-plant reference pathway database, PlantCyc, and a reference enzyme sequence database, RESD, for annotating metabolic functions of protein sequences. PlantCyc (version 3.0) includes 714 metabolic pathways and 2,619 reactions from over 300 species. RESD (version 1.0) contains 14,187 literature-supported enzyme sequences from across all kingdoms. We used RESD, PlantCyc, and MetaCyc (an all-species reference metabolic pathway database), in conjunction with the pathway prediction software Pathway Tools, to reconstruct a metabolic pathway database, PoplarCyc, from the recently sequenced genome of Populus trichocarpa. PoplarCyc (version 1.0) contains 321 pathways with 1,807 assigned enzymes. Comparing PoplarCyc (version 1.0) with AraCyc (version 6.0, Arabidopsis [Arabidopsis thaliana]) showed comparable numbers of pathways distributed across all domains of metabolism in both databases, except for a higher number of AraCyc pathways in secondary metabolism and a 1.5-fold increase in carbohydrate metabolic enzymes in PoplarCyc. Here, we introduce these new resources and demonstrate the feasibility of using them to identify candidate enzymes for specific pathways and to analyze metabolite profiling data through concrete examples. These resources can be searched by text or BLAST, browsed, and downloaded from our project Web site (http://plantcyc.org). PMID:20522724

Root symbionts: Powerful drivers of plant above- and belowground indirect defenses.

PubMed

Rasmann, Sergio; Bennett, Alison; Biere, Arjen; Karley, Alison; Guerrieri, Emilio

2017-12-01

Soil microbial mutualists of plants, including mycorrhizal fungi, non-mycorrhizal fungi and plant growth promoting rhizobacteria, have been typically characterized for increasing nutrient acquisition and plant growth. More recently, soil microbes have also been shown to increase direct plant defense against above- and belowground herbivores. Plants, however, do not only rely on direct defenses when attacked, but they can also recruit pest antagonists such as predators and parasitoids, both above and belowground, mainly via the release of volatile organic compounds (i.e., indirect defenses). In this review, we illustrate the main features and effects of soil microbial mutualists of plants on plant indirect defenses and discuss possible applications within the framework of sustainable crop protection against root- and shoot-feeding arthropod pests. We indicate the main knowledge gaps and the future challenges to be addressed in the study and application of these multifaceted interactions. © 2017 Institute of Zoology, Chinese Academy of Sciences.

Plant lectins: the ties that bind in root symbiosis and plant defense.

PubMed

De Hoff, Peter L; Brill, Laurence M; Hirsch, Ann M

2009-07-01

Lectins are a diverse group of carbohydrate-binding proteins that are found within and associated with organisms from all kingdoms of life. Several different classes of plant lectins serve a diverse array of functions. The most prominent of these include participation in plant defense against predators and pathogens and involvement in symbiotic interactions between host plants and symbiotic microbes, including mycorrhizal fungi and nitrogen-fixing rhizobia. Extensive biological, biochemical, and molecular studies have shed light on the functions of plant lectins, and a plethora of uncharacterized lectin genes are being revealed at the genomic scale, suggesting unexplored and novel diversity in plant lectin structure and function. Integration of the results from these different types of research is beginning to yield a more detailed understanding of the function of lectins in symbiosis, defense, and plant biology in general.

Jasmonate is essential for insect defense in Arabidopsis.

PubMed

McConn, M; Creelman, R A; Bell, E; Mullet, J E; Browse, J

1997-05-13

The signaling pathways that allow plants to mount defenses against chewing insects are known to be complex. To investigate the role of jasmonate in wound signaling in Arabidopsis and to test whether parallel or redundant pathways exist for insect defense, we have studied a mutant (fad3-2 fad7-2 fad8) that is deficient in the jasmonate precursor linolenic acid. Mutant plants contained negligible levels of jasmonate and showed extremely high mortality ( approximately 80%) from attack by larvae of a common saprophagous fungal gnat, Bradysia impatiens (Diptera: Sciaridae), even though neighboring wild-type plants were largely unaffected. Application of exogenous methyl jasmonate substantially protected the mutant plants and reduced mortality to approximately 12%. These experiments precisely define the role of jasmonate as being essential for the induction of biologically effective defense in this plant-insect interaction. The transcripts of three wound-responsive genes were shown not to be induced by wounding of mutant plants but the same transcripts could be induced by application of methyl jasmonate. By contrast, measurements of transcript levels for a gene encoding glutathione S-transferase demonstrated that wound induction of this gene is independent of jasmonate synthesis. These results indicate that the mutant will be a good genetic model for testing the practical effectiveness of candidate defense genes.

Plant defense response against Fusarium oxysporum and strategies to develop tolerant genotypes in banana.

PubMed

Swarupa, V; Ravishankar, K V; Rekha, A

2014-04-01

Soil-borne fungal pathogen, Fusarium oxysporum causes major economic losses by inducing necrosis and wilting symptoms in many crop plants. Management of fusarium wilt is achieved mainly by the use of chemical fungicides which affect the soil health and their efficiency is often limited by pathogenic variability. Hence understanding the nature of interaction between pathogen and host may help to select and improve better cultivars. Current research evidences highlight the role of oxidative burst and antioxidant enzymes indicating that ROS act as an important signaling molecule in banana defense response against Fusarium oxysporum f.sp. cubense. The role of jasmonic acid signaling in plant defense against necrotrophic pathogens is well recognized. But recent studies show that the role of salicylic acid is complex and ambiguous against necrotrophic pathogens like Fusarium oxysporum, leading to many intriguing questions about its relationship between other signaling compounds. In case of banana, a major challenge is to identify specific receptors for effector proteins like SIX proteins and also the components of various signal transduction pathways. Significant progress has been made to uncover the role of defense genes but is limited to only model plants such as Arabidopsis and tomato. Keeping this in view, we review the host response, pathogen diversity, current understanding of biochemical and molecular changes that occur during host and pathogen interaction. Developing resistant cultivars through mutation, breeding, transgenic and cisgenic approaches have been discussed. This would help us to understand host defenses against Fusarium oxysporum and to formulate strategies to develop tolerant cultivars.

Behavioral Sabotage of Plant Defenses by Insect Folivores.

PubMed

Dussourd, David E

2017-01-31

Plant susceptibility to herbivore attack is determined not just by the suite of defenses present in different tissues of the plant, but also by the capabilities of the herbivore for tolerating, circumventing, or disarming the defenses. This article reviews the elaborate behaviors exhibited by leaf-chewing insects that appear to function specifically to deactivate hostplant defenses. Shortcomings in our understanding and promising areas for future research are highlighted. Behaviors covered include vein cutting, trenching, girdling, leaf clipping, and application of fluids from exocrine glands. Many of these behaviors have a widespread distribution, having evolved independently in multiple insect lineages. Insects utilizing the behaviors include significant agricultural, horticultural, and forestry pests, as well as numerous species important in natural ecosystems. Behavioral, ecological, and phylogenetic studies have documented the importance of the behaviors and their ancient history, but the molecular analysis of how the behaviors affect plant physiology has scarcely begun.

Deficiencies in Jasmonate-Mediated Plant Defense Reveal Quantitative Variation in Botrytis cinerea Pathogenesis

PubMed Central

Rowe, Heather C.; Walley, Justin W.; Corwin, Jason; Chan, Eva K.-F.; Dehesh, Katayoon; Kliebenstein, Daniel J.

2010-01-01

Despite the described central role of jasmonate signaling in plant defense against necrotrophic pathogens, the existence of intraspecific variation in pathogen capacity to activate or evade plant jasmonate-mediated defenses is rarely considered. Experimental infection of jasmonate-deficient and jasmonate-insensitive Arabidopsis thaliana with diverse isolates of the necrotrophic fungal pathogen Botrytis cinerea revealed pathogen variation for virulence inhibition by jasmonate-mediated plant defenses and induction of plant defense metabolites. Comparison of the transcriptional effects of infection by two distinct B. cinerea isolates showed only minor differences in transcriptional responses of wild-type plants, but notable isolate-specific transcript differences in jasmonate-insensitive plants. These transcriptional differences suggest B. cinerea activation of plant defenses that require plant jasmonate signaling for activity in response to only one of the two B. cinerea isolates tested. Thus, similar infection phenotypes observed in wild-type plants result from different signaling interactions with the plant that are likely integrated by jasmonate signaling. PMID:20419157

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

Regulation of plant immunity through ubiquitin-mediated modulation of Ca(2+) -calmodulin-AtSR1/CAMTA3 signaling.

PubMed

Zhang, Lei; Du, Liqun; Shen, Chenjia; Yang, Yanjun; Poovaiah, B W

2014-04-01

Transient changes in intracellular Ca(2+) concentration are essential signals for activation of plant immunity. It has also been reported that Ca(2+) signals suppress salicylic acid-mediated plant defense through AtSR1/CAMTA3, a member of the Ca(2+) /calmodulin-regulated transcription factor family that is conserved in multicellular eukaryotes. How plants overcome this negative regulation to mount an effective defense response during a stage of intracellular Ca(2+) surge is unclear. Here we report the identification and functional characterization of an important component of ubiquitin ligase, and the associated AtSR1 turnover. The AtSR1 interaction protein 1 (SR1IP1) was identified by CytoTrap two-hybrid screening. The loss-of-function mutant of SR1IP1 is more susceptible to bacterial pathogens, and over-expression of SR1IP1 confers enhanced resistance, indicating that SR1IP1 acts as a positive regulator of plant defense. SR1IP1 and AtSR1 act in the same signaling pathway to regulate plant immunity. SR1IP1 contains the structural features of a substrate adaptor in cullin 3-based E3 ubiquitin ligase, and was shown to serve as a substrate adaptor that recruits AtSR1 for ubiquitination and degradation when plants are challenged with pathogens. Hence, SR1IP1 positively regulates plant immunity by removing the defense suppressor AtSR1. These findings provide a mechanistic insight into how Ca(2+) -mediated actions are coordinated to achieve effective plant immunity. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

Plants, plant pathogens, and microgravity--a deadly trio.

PubMed

Leach, J E; Ryba-White, M; Sun, Q; Wu, C J; Hilaire, E; Gartner, C; Nedukha, O; Kordyum, E; Keck, M; Leung, H; Guikema, J A

2001-06-01

Plants grown in spaceflight conditions are more susceptible to colonization by plant pathogens. The underlying causes for this enhanced susceptibility are not known. Possibly the formation of structural barriers and the activation of plant defense response components are impaired in spaceflight conditions. Either condition would result from altered gene expression of the plant. Because of the tools available, past studies focused on a few physiological responses or biochemical pathways. With recent advances in genomics research, new tools, including microarray technologies, are available to examine the global impact of growth in the spacecraft on the plant's gene expression profile. In ground-based studies, we have developed cDNA subtraction libraries of rice that are enriched for genes induced during pathogen infection and the defense response. Arrays of these genes are being used to dissect plant defense response pathways in a model system involving wild-type rice plants and lesion mimic mutants. The lesion mimic mutants are ideal experimental tools because they erratically develop defense response-like lesions in the absence of pathogens. The gene expression profiles from these ground-based studies will provide the molecular basis for understanding the biochemical and physiological impacts of spaceflight on plant growth, development and disease defense responses. This, in turn, will allow the development of strategies to manage plant disease for life in the space environment.

Plants, plant pathogens, and microgravity--a deadly trio

NASA Technical Reports Server (NTRS)

Leach, J. E.; Ryba-White, M.; Sun, Q.; Wu, C. J.; Hilaire, E.; Gartner, C.; Nedukha, O.; Kordyum, E.; Keck, M.; Leung, H.;

The Pepper Extracellular Xyloglucan-Specific Endo-β-1,4-Glucanase Inhibitor Protein Gene, CaXEGIP1, Is Required for Plant Cell Death and Defense Responses1[C][W][OA

PubMed Central

Choi, Hyong Woo; Kim, Nak Hyun; Lee, Yeon Kyeong; Hwang, Byung Kook

2013-01-01

Plants produce various proteinaceous inhibitors to protect themselves against microbial pathogen attack. A xyloglucan-specific endo-β-1,4-glucanase inhibitor1 gene, CaXEGIP1, was isolated and functionally characterized in pepper (Capsicum annuum) plants. CaXEGIP1 was rapidly and strongly induced in pepper leaves infected with avirulent Xanthomonas campestris pv vesicatoria, and purified CaXEGIP1 protein significantly inhibited the hydrolytic activity of the glycoside hydrolase74 family xyloglucan-specific endo-β-1,4-glucanase from Clostridium thermocellum. Soluble-modified green fluorescent protein-tagged CaXEGIP1 proteins were mainly localized to the apoplast of onion (Allium cepa) epidermal cells. Agrobacterium tumefaciens-mediated overexpression of CaXEGIP1 triggered pathogen-independent, spontaneous cell death in pepper and Nicotiana benthamiana leaves. CaXEGIP1 silencing in pepper conferred enhanced susceptibility to virulent and avirulent X. campestris pv vesicatoria, accompanied by a compromised hypersensitive response and lowered expression of defense-related genes. Overexpression of dexamethasone:CaXEGIP1 in Arabidopsis (Arabidopsis thaliana) enhanced resistance to Hyaloperonospora arabidopsidis infection. Comparative histochemical and proteomic analyses revealed that CaXEGIP1 overexpression induced a spontaneous cell death response and also increased the expression of some defense-related proteins in transgenic Arabidopsis leaves. This response was also accompanied by cell wall thickening and darkening. Together, these results suggest that pathogen-inducible CaXEGIP1 positively regulates cell death-mediated defense responses in plants. PMID:23093361

Insect response to plant defensive protease inhibitors.

PubMed

Zhu-Salzman, Keyan; Zeng, Rensen

2015-01-07

Plant protease inhibitors (PIs) are natural plant defense proteins that inhibit proteases of invading insect herbivores. However, their anti-insect efficacy is determined not only by their potency toward a vulnerable insect system but also by the response of the insect to such a challenge. Through the long history of coevolution with their host plants, insects have developed sophisticated mechanisms to circumvent antinutritional effects of dietary challenges. Their response takes the form of changes in gene expression and the protein repertoire in cells lining the alimentary tract, the first line of defense. Research in insect digestive proteases has revealed the crucial roles they play in insect adaptation to plant PIs and has brought about a new appreciation of how phytophagous insects employ this group of molecules in both protein digestion and counterdefense. This review provides researchers in related fields an up-to-date summary of recent advances.

Evolutionary potential of root chemical defense: genetic correlations with shoot chemistry and plant growth.

PubMed

Parker, J D; Salminen, J-P; Agrawal, Anurag A

2012-08-01

Root herbivores can affect plant fitness, and roots often contain the same secondary metabolites that act as defenses in shoots, but the ecology and evolution of root chemical defense have been little investigated. Here, we investigated genetic variance, heritability, and correlations among defensive phenolic compounds in shoot vs. root tissues of common evening primrose, Oenothera biennis. Across 20 genotypes, there were roughly similar concentrations of total phenolics in shoots vs. roots, but the allocation of particular phenolics to shoots vs. roots varied along a continuum of genotype growth rate. Slow-growing genotypes allocated 2-fold more of the potential pro-oxidant oenothein B to shoots than roots, whereas fast-growing genotypes had roughly equivalent above and belowground concentrations. Phenolic concentrations in both roots and shoots were strongly heritable, with mostly positive patterns of genetic covariation. Nonetheless, there was genotype-specific variation in the presence/absence of two major ellagitannins (oenothein A and its precursor oenothein B), indicating two different chemotypes based on alterations in this chemical pathway. Overall, the presence of strong genetic variation in root defenses suggests ample scope for the evolution of these compounds as defenses against root herbivores.

Synchronization of developmental processes and defense signaling by growth regulating transcription factors.

PubMed

Liu, Jinyi; Rice, J Hollis; Chen, Nana; Baum, Thomas J; Hewezi, Tarek

2014-01-01

Growth regulating factors (GRFs) are a conserved class of transcription factor in seed plants. GRFs are involved in various aspects of tissue differentiation and organ development. The implication of GRFs in biotic stress response has also been recently reported, suggesting a role of these transcription factors in coordinating the interaction between developmental processes and defense dynamics. However, the molecular mechanisms by which GRFs mediate the overlaps between defense signaling and developmental pathways are elusive. Here, we report large scale identification of putative target candidates of Arabidopsis GRF1 and GRF3 by comparing mRNA profiles of the grf1/grf2/grf3 triple mutant and those of the transgenic plants overexpressing miR396-resistant version of GRF1 or GRF3. We identified 1,098 and 600 genes as putative targets of GRF1 and GRF3, respectively. Functional classification of the potential target candidates revealed that GRF1 and GRF3 contribute to the regulation of various biological processes associated with defense response and disease resistance. GRF1 and GRF3 participate specifically in the regulation of defense-related transcription factors, cell-wall modifications, cytokinin biosynthesis and signaling, and secondary metabolites accumulation. GRF1 and GRF3 seem to fine-tune the crosstalk between miRNA signaling networks by regulating the expression of several miRNA target genes. In addition, our data suggest that GRF1 and GRF3 may function as negative regulators of gene expression through their association with other transcription factors. Collectively, our data provide new insights into how GRF1 and GRF3 might coordinate the interactions between defense signaling and plant growth and developmental pathways.

Variation in plant defense suppresses herbivore performance

USGS Publications Warehouse

Pearse, Ian; Paul, Ryan; Ode, Paul J.

2018-01-01

Defensive variability of crops and natural systems can alter herbivore communities and reduce herbivory. However, it is still unknown how defense variability translates into herbivore suppression. Nonlinear averaging and constraints in physiological tracking (also more generally called time-dependent effects) are the two mechanisms by which defense variability might impact herbivores. We conducted a set of experiments manipulating the mean and variability of a plant defense, showing that defense variability does suppress herbivore performance and that it does so through physiological tracking effects that cannot be explained by nonlinear averaging. While nonlinear averaging predicted higher or the same herbivore performance on a variable defense than on an invariable defense, we show that variability actually decreased herbivore performance and population growth rate. Defense variability reduces herbivore performance in a way that is more than the average of its parts. This is consistent with constraints in physiological matching of detoxification systems for herbivores experiencing variable toxin levels in their diet and represents a more generalizable way of understanding the impacts of variability on herbivory. Increasing defense variability in croplands at a scale encountered by individual herbivores can suppress herbivory, even if that is not anticipated by nonlinear averaging.

Coevolutionary arms race versus host defense chase in a tropical herbivore-plant system.

PubMed

Endara, María-José; Coley, Phyllis D; Ghabash, Gabrielle; Nicholls, James A; Dexter, Kyle G; Donoso, David A; Stone, Graham N; Pennington, R Toby; Kursar, Thomas A

2017-09-05

Coevolutionary models suggest that herbivores drive diversification and community composition in plants. For herbivores, many questions remain regarding how plant defenses shape host choice and community structure. We addressed these questions using the tree genus Inga and its lepidopteran herbivores in the Amazon. We constructed phylogenies for both plants and insects and quantified host associations and plant defenses. We found that similarity in herbivore assemblages between Inga species was correlated with similarity in defenses. There was no correlation with phylogeny, a result consistent with our observations that the expression of defenses in Inga is independent of phylogeny. Furthermore, host defensive traits explained 40% of herbivore community similarity. Analyses at finer taxonomic scales showed that different lepidopteran clades select hosts based on different defenses, suggesting taxon-specific histories of herbivore-host plant interactions. Finally, we compared the phylogeny and defenses of Inga to phylogenies for the major lepidopteran clades. We found that closely related herbivores fed on Inga with similar defenses rather than on closely related plants. Together, these results suggest that plant defenses might be more evolutionarily labile than the herbivore traits related to host association. Hence, there is an apparent asymmetry in the evolutionary interactions between Inga and its herbivores. Although plants may evolve under selection by herbivores, we hypothesize that herbivores may not show coevolutionary adaptations, but instead "chase" hosts based on the herbivore's own traits at the time that they encounter a new host, a pattern more consistent with resource tracking than with the arms race model of coevolution.

Coevolutionary arms race versus host defense chase in a tropical herbivore–plant system

PubMed Central

Coley, Phyllis D.; Ghabash, Gabrielle; Nicholls, James A.; Donoso, David A.; Stone, Graham N.; Pennington, R. Toby; Kursar, Thomas A.

2017-01-01

Coevolutionary models suggest that herbivores drive diversification and community composition in plants. For herbivores, many questions remain regarding how plant defenses shape host choice and community structure. We addressed these questions using the tree genus Inga and its lepidopteran herbivores in the Amazon. We constructed phylogenies for both plants and insects and quantified host associations and plant defenses. We found that similarity in herbivore assemblages between Inga species was correlated with similarity in defenses. There was no correlation with phylogeny, a result consistent with our observations that the expression of defenses in Inga is independent of phylogeny. Furthermore, host defensive traits explained 40% of herbivore community similarity. Analyses at finer taxonomic scales showed that different lepidopteran clades select hosts based on different defenses, suggesting taxon-specific histories of herbivore–host plant interactions. Finally, we compared the phylogeny and defenses of Inga to phylogenies for the major lepidopteran clades. We found that closely related herbivores fed on Inga with similar defenses rather than on closely related plants. Together, these results suggest that plant defenses might be more evolutionarily labile than the herbivore traits related to host association. Hence, there is an apparent asymmetry in the evolutionary interactions between Inga and its herbivores. Although plants may evolve under selection by herbivores, we hypothesize that herbivores may not show coevolutionary adaptations, but instead “chase” hosts based on the herbivore’s own traits at the time that they encounter a new host, a pattern more consistent with resource tracking than with the arms race model of coevolution. PMID:28827317

The FA pathway counteracts oxidative stress through selective protection of antioxidant defense gene promoters.

PubMed

Du, Wei; Rani, Reena; Sipple, Jared; Schick, Jonathan; Myers, Kasiani C; Mehta, Parinda; Andreassen, Paul R; Davies, Stella M; Pang, Qishen

2012-05-03

Oxidative stress has been implicated in the pathogenesis of many human diseases including Fanconi anemia (FA), a genetic disorder associated with BM failure and cancer. Here we show that major antioxidant defense genes are down-regulated in FA patients, and that gene down-regulation is selectively associated with increased oxidative DNA damage in the promoters of the antioxidant defense genes. Assessment of promoter activity and DNA damage repair kinetics shows that increased initial damage, rather than a reduced repair rate, contributes to the augmented oxidative DNA damage. Mechanistically, FA proteins act in concert with the chromatin-remodeling factor BRG1 to protect the promoters of antioxidant defense genes from oxidative damage. Specifically, BRG1 binds to the promoters of the antioxidant defense genes at steady state. On challenge with oxidative stress, FA proteins are recruited to promoter DNA, which correlates with significant increase in the binding of BRG1 within promoter regions. In addition, oxidative stress-induced FANCD2 ubiquitination is required for the formation of a FA-BRG1-promoter complex. Taken together, these data identify a role for the FA pathway in cellular antioxidant defense.

A translational study on looming-evoked defensive response and the underlying subcortical pathway in autism.

PubMed

Hu, Yu; Chen, Zhuoming; Huang, Lu; Xi, Yue; Li, Bingxiao; Wang, Hong; Yan, Jiajian; Lee, Tatia M C; Tao, Qian; So, Kwok-Fai; Ren, Chaoran

2017-11-07

Rapidly approaching objects indicating threats can induce defensive response through activating a subcortical pathway comprising superior colliculus (SC), lateral posterior nucleus (LP), and basolateral amygdala (BLA). Abnormal defensive response has been reported in autism, and impaired synaptic connections could be the underlying mechanism. Whether the SC-LP-BLA pathway processes looming stimuli abnormally in autism is not clear. Here, we found that looming-evoked defensive response is impaired in a subgroup of the valproic acid (VPA) mouse model of autism. By combining the conventional neurotracer and transneuronal rabies virus tracing techniques, we demonstrated that synaptic connections in the SC-LP-BLA pathway were abnormal in VPA mice whose looming-evoked defensive responses were absent. Importantly, we further translated the finding to children with autism and observed that they did not present looming-evoked defensive response. Furthermore, the findings of the DTI with the probabilistic tractography showed that the structural connections of SC-pulvinar-amygdala in autism children were weak. The pulvinar is parallel to the LP in a mouse. Because looming-evoked defensive response is innate in humans and emerges much earlier than do social and language functions, the absence of defensive response could be an earlier sign of autism in children.

Salicylic acid is required for Mi-1-mediated resistance of tomato to whitefly Bemisia tabaci, but not for basal defense to this insect pest.

PubMed

Rodríguez-Álvarez, C I; López-Climent, M F; Gómez-Cadenas, A; Kaloshian, I; Nombela, G

2015-10-01

Plant defense to pests or pathogens involves global changes in gene expression mediated by multiple signaling pathways. A role for the salicylic acid (SA) signaling pathway in Mi-1-mediated resistance of tomato (Solanum lycopersicum) to aphids was previously identified and its implication in the resistance to root-knot nematodes is controversial, but the importance of SA in basal and Mi-1-mediated resistance of tomato to whitefly Bemisia tabaci had not been determined. SA levels were measured before and after B. tabaci infestation in susceptible and resistant Mi-1-containing tomatoes, and in plants with the NahG bacterial transgene. Tomato plants of the same genotypes were also screened with B. tabaci (MEAM1 and MED species, before known as B and Q biotypes, respectively). The SA content in all tomato genotypes transiently increased after infestation with B. tabaci albeit at variable levels. Whitefly fecundity or infestation rates on susceptible Moneymaker were not significantly affected by the expression of NahG gene, but the Mi-1-mediated resistance to B. tabaci was lost in VFN NahG plants. Results indicated that whiteflies induce both SA and jasmonic acid accumulation in tomato. However, SA has no role in basal defense of tomato against B. tabaci. In contrast, SA is an important component of the Mi-1-mediated resistance to B. tabaci in tomato.

The glabra1 Mutation Affects Cuticle Formation and Plant Responses to Microbes1[C][W][OA

PubMed Central

Xia, Ye; Yu, Keshun; Navarre, Duroy; Seebold, Kenneth; Kachroo, Aardra; Kachroo, Pradeep

2010-01-01

Systemic acquired resistance (SAR) is a form of defense that provides resistance against a broad spectrum of pathogens in plants. Previous work indicates a role for plastidial glycerolipid biosynthesis in SAR. Specifically, mutations in FATTY ACID DESATURASE7 (FAD7), which lead to reduced trienoic fatty acid levels and compromised plastidial lipid biosynthesis, have been associated with defective SAR. We show that the defective SAR in Arabidopsis (Arabidopsis thaliana) fad7-1 plants is not associated with a mutation in FAD7 but rather with a second-site mutation in GLABRA1 (GL1), a gene well known for its role in trichome formation. The compromised SAR in gl1 plants is associated with impairment in their cuticles. Furthermore, mutations in two other components of trichome development, GL3 and TRANSPARENT TESTA GLABRA1, also impaired cuticle development and SAR. This suggests an overlap in the biochemical pathways leading to cuticle and trichome development. Interestingly, exogenous application of gibberellic acid (GA) not only enhanced SAR in wild-type plants but also restored SAR in gl1 plants. In contrast to GA, the defense phytohoromes salicylic acid and jasmonic acid were unable to restore SAR in gl1 plants. GA application increased levels of cuticular components but not trichome formation on gl1 plants, thus implicating cuticle, but not trichomes, as an important component of SAR. Our findings question the prudence of using mutant backgrounds for genetic screens and underscore a need to reevaluate phenotypes previously studied in the gl1 background. PMID:20699396

Regulation of SOBIR1 accumulation and activation of defense responses in bir1-1 by specific components of ER quality control.

PubMed

Sun, Tongjun; Zhang, Qian; Gao, Minghui; Zhang, Yuelin

2014-03-01

Receptor-like kinases play diverse roles in plant biology. Arabidopsis BAK1-INTERACTING RECEPTOR-LIKE KINASE 1 (BIR1) functions as a negative regulator of plant immunity. bir1-1 mutant plants display spontaneous cell death and constitutive defense responses that are dependent on SUPPRESSOR OF BIR1,1 (SOBIR1) and PHYTOALEXIN DEFICIENT4 (PAD4). Here we report that mutations in three components of ER quality control, CALRETICULIN3 (CRT3), ER-LOCALIZED DnaJ-LIKE PROTEIN 3b (ERdj3b) and STROMAL-DERIVED FACTOR-2 (SDF2), also suppress the spontaneous cell death and constitutive defense responses in bir1-1. Further analysis revealed that accumulation of the SOBIR1 protein is reduced in crt3-1 and erdj3b-1 mutant plants. These data suggest that ER quality control plays important roles in the biogenesis of SOBIR1, and is required for cell death and defense responses in bir1-1. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

Pipecolic acid, an endogenous mediator of defense amplification and priming, is a critical regulator of inducible plant immunity.

PubMed

Návarová, Hana; Bernsdorff, Friederike; Döring, Anne-Christin; Zeier, Jürgen

2012-12-01

Metabolic signals orchestrate plant defenses against microbial pathogen invasion. Here, we report the identification of the non-protein amino acid pipecolic acid (Pip), a common Lys catabolite in plants and animals, as a critical regulator of inducible plant immunity. Following pathogen recognition, Pip accumulates in inoculated Arabidopsis thaliana leaves, in leaves distal from the site of inoculation, and, most specifically, in petiole exudates from inoculated leaves. Defects of mutants in AGD2-LIKE DEFENSE RESPONSE PROTEIN1 (ALD1) in systemic acquired resistance (SAR) and in basal, specific, and β-aminobutyric acid-induced resistance to bacterial infection are associated with a lack of Pip production. Exogenous Pip complements these resistance defects and increases pathogen resistance of wild-type plants. We conclude that Pip accumulation is critical for SAR and local resistance to bacterial pathogens. Our data indicate that biologically induced SAR conditions plants to more effectively synthesize the phytoalexin camalexin, Pip, and salicylic acid and primes plants for early defense gene expression. Biological priming is absent in the pipecolate-deficient ald1 mutants. Exogenous pipecolate induces SAR-related defense priming and partly restores priming responses in ald1. We conclude that Pip orchestrates defense amplification, positive regulation of salicylic acid biosynthesis, and priming to guarantee effective local resistance induction and the establishment of SAR.

Molecular Steps in the Immune Signaling Pathway Evoked by Plant Elicitor Peptides: Ca2+-Dependent Protein Kinases, Nitric Oxide, and Reactive Oxygen Species Are Downstream from the Early Ca2+ Signal1[OPEN

PubMed Central

Ma, Yi; Zhao, Yichen; Walker, Robin K.; Berkowitz, Gerald A.

2013-01-01

Endogenous plant elicitor peptides (Peps) can act to facilitate immune signaling and pathogen defense responses. Binding of these peptides to the Arabidopsis (Arabidopsis thaliana) plasma membrane-localized Pep receptors (PEPRs) leads to cytosolic Ca2+ elevation, an early event in a signaling cascade that activates immune responses. This immune response includes the amplification of signaling evoked by direct perception of pathogen-associated molecular patterns by plant cells under assault. Work included in this report further characterizes the Pep immune response and identifies new molecular steps in the signal transduction cascade. The PEPR coreceptor BRASSINOSTEROID-INSENSITIVE1 Associated Kinase1 contributes to generation of the Pep-activated Ca2+ signal and leads to increased defense gene expression and resistance to a virulent bacterial pathogen. Ca2+-dependent protein kinases (CPKs) decode the Ca2+ signal, also facilitating defense gene expression and enhanced resistance to the pathogen. Nitric oxide and reduced nicotinamide adenine dinucleotide phosphate oxidase-dependent reactive oxygen species generation (due to the function of Respiratory Burst Oxidase Homolog proteins D and F) are also involved downstream from the Ca2+ signal in the Pep immune defense signal transduction cascade, as is the case with BRASSINOSTEROID-INSENSITIVE1 Associated Kinase1 and CPK5, CPK6, and CPK11. These steps of the pathogen defense response are required for maximal Pep immune activation that limits growth of a virulent bacterial pathogen in the plant. We find a synergism between function of the PEPR and Flagellin Sensing2 receptors in terms of both nitric oxide and reactive oxygen species generation. Presented results are also consistent with the involvement of the secondary messenger cyclic GMP and a cyclic GMP-activated Ca2+-conducting channel in the Pep immune signaling pathway. PMID:24019427

Control of Citrus Huanglongbing via Trunk Injection of Plant Defense Activators and Antibiotics.

PubMed

Hu, J; Jiang, J; Wang, N

2018-02-01

Citrus huanglongbing (HLB) or greening is a devastating disease of citrus worldwide and no effective control measure is currently available. Plant defense activators environmentally friendly compounds capable of inducing resistance against many plant pathogens. Earlier studies showed that foliar spray of plant defense inducers could slow down HLB disease progress. In this study, eight plant defense activators and three antibiotics were evaluated in three field trials for their effect to control HLB by trunk injection of young and mature sweet orange trees. Results showed that four trunk injections of several activators, including salicylic acid, oxalic acid, acibenzolar-S-methyl, and potassium phosphate, provided significant control of HLB by suppressing 'Candidatus Liberibacter asiaticus' titer and disease progress. Trunk injection of penicillin, streptomycin, and oxytetracycline hydrochloride resulted in excellent control of HLB. In general, antibiotics were more effective in reduction of 'Ca. L. asiaticus' titer and HLB symptom expressions than plant defense activators. These treatments also resulted in increased yield and better fruit quality. Injection of both salicylic acid and acibenzolar-S-methyl led to significant induction of pathogenesis-related (PR) genes PR-1 and PR-2 genes. Meanwhile, injection of either potassium phosphate or oxalic acid resulted in significant induction of PR-2 or PR-15 gene expression, respectively. These results suggested that HLB diseased trees remained inducible for systemic acquired resistance under field conditions. In summary, this study presents information regarding controlling HLB via trunk injection of plant defense activators and antibiotics, which helps citrus growers in decision making regarding developing an effective HLB management program.

Changes in plant defense chemistry (pyrrolizidine alkaloids) revealed through high-resolution spectroscopy

NASA Astrophysics Data System (ADS)

Carvalho, Sabrina; Macel, Mirka; Schlerf, Martin; Moghaddam, Fatemeh Eghbali; Mulder, Patrick P. J.; Skidmore, Andrew K.; van der Putten, Wim H.

2013-06-01

Plant toxic biochemicals play an important role in defense against natural enemies and often are toxic to humans and livestock. Hyperspectral reflectance is an established method for primary chemical detection and could be further used to determine plant toxicity in the field. In order to make a first step for pyrrolizidine alkaloids detection (toxic defense compound against mammals and many insects) we studied how such spectral data can estimate plant defense chemistry under controlled conditions. In a greenhouse, we grew three related plant species that defend against generalist herbivores through pyrrolizidine alkaloids: Jacobaea vulgaris, Jacobaea erucifolia and Senecio inaequidens, and analyzed the relation between spectral measurements and chemical concentrations using multivariate statistics. Nutrient addition enhanced tertiary-amine pyrrolizidine alkaloids contents of J. vulgaris and J. erucifolia and decreased N-oxide contents in S. inaequidens and J. vulgaris. Pyrrolizidine alkaloids could be predicted with a moderate accuracy. Pyrrolizidine alkaloid forms tertiary-amines and epoxides were predicted with 63% and 56% of the variation explained, respectively. The most relevant spectral regions selected for prediction were associated with electron transitions and Csbnd H, Osbnd H, and Nsbnd H bonds in the 1530 and 2100 nm regions. Given the relatively low concentration in pyrrolizidine alkaloids concentration (in the order of mg g-1) and resultant predictions, it is promising that pyrrolizidine alkaloids interact with incident light. Further studies should be considered to determine if such a non-destructive method may predict changes in PA concentration in relation to plant natural enemies. Spectroscopy may be used to study plant defenses in intact plant tissues, and may provide managers of toxic plants, food industry and multitrophic-interaction researchers with faster and larger monitoring possibilities.

Herbivore Diet Breadth and Host Plant Defense Mediate the Tri-Trophic Effects of Plant Toxins on Multiple Coccinellid Predators.

PubMed

Katsanis, Angelos; Rasmann, Sergio; Mooney, Kailen A

2016-01-01

Host plant defenses are known to cascade up food chains to influence herbivores and their natural enemies, but how herbivore and predator traits and identity mediate such tri-trophic dynamics is largely unknown. We assessed the influence of plant defense on aphid and coccinellid performance in laboratory trials with low- vs. high-glucosinolate varieties of Brassica napus, a dietary specialist (Brevicoryne brassicae) and generalist (Myzus persicae) aphid, and five species of aphidophagous coccinellids. The performance of the specialist and generalist aphids was similar and unaffected by variation in plant defense. Aphid glucosinolate concentration and resistance to predators differed by aphid species and host plant defense, and these effects acted independently. With respect to aphid species, the dietary generalist aphid (vs. specialist) had 14% lower glucosinolate concentration and coccinellid predators ate three-fold more aphids. With respect to host plant variety, the high-glucosinolate plants (vs. low) increased aphid glucosinolate concentration by 21%, but had relatively weak effects on predation by coccinellids and these effects varied among coccinellid species. In turn, coccinellid performance was influenced by the interactive effects of plant defense and aphid species, as the cascading, indirect effect of plant defense was greater when feeding upon the specialist than generalist aphid. When feeding upon specialist aphids, low- (vs. high-) glucosinolate plants increased coccinellid mass gain by 78% and accelerated development by 14%. In contrast, when feeding upon generalist aphids, low- (vs. high-) glucosinolate plants increased coccinellid mass gain by only 11% and had no detectable effect on development time. These interactive effects of plant defense and aphid diet breadth on predator performance also varied among coccinellid species; the indirect negative effects of plant defenses on predator performance was consistent among the five predators when

A Bacterial Pathogen Targets a Host Rab-Family GTPase Defense Pathway with a GAP.

PubMed

Spanò, Stefania; Gao, Xiang; Hannemann, Sebastian; Lara-Tejero, María; Galán, Jorge E

2016-02-10

Cell-autonomous defense mechanisms are potent strategies that protect individual cells against intracellular pathogens. The Rab-family GTPase Rab32 was previously shown to restrict the intracellular human pathogen Salmonella Typhi, but its potential broader role in antimicrobial defense remains unknown. We show that Rab32 represents a general cell-autonomous, antimicrobial defense that is counteracted by two Salmonella effectors. Mice lacking Rab-32 or its nucleotide exchange factor BLOC-3 are permissive to S. Typhi infection and exhibit increased susceptibility to S. Typhimurium. S. Typhimurium counters this defense pathway by delivering two type III secretion effectors, SopD2, a Rab32 GAP, and GtgE, a specific Rab32 protease. An S. Typhimurium mutant strain lacking these two effectors exhibits markedly reduced virulence, which is fully restored in BLOC-3-deficient mice. These results demonstrate that a cell-autonomous, Rab32-dependent host defense pathway plays a central role in the defense against vacuolar pathogens and describe a mechanism evolved by a bacterial pathogen to counter it. Copyright © 2016 Elsevier Inc. All rights reserved.

Plants versus Fungi and Oomycetes: Pathogenesis, Defense and Counter-Defense in the Proteomics Era

PubMed Central

El Hadrami, Abdelbasset; El-Bebany, Ahmed F.; Yao, Zhen; Adam, Lorne R.; El Hadrami, Ismailx; Daayf, Fouad

2012-01-01

Plant-fungi and plant-oomycete interactions have been studied at the proteomic level for many decades. However, it is only in the last few years, with the development of new approaches, combined with bioinformatics data mining tools, gel staining, and analytical instruments, such as 2D-PAGE/nanoflow-LC-MS/MS, that proteomic approaches thrived. They allow screening and analysis, at the sub-cellular level, of peptides and proteins resulting from plants, pathogens, and their interactions. They also highlight post-translational modifications to proteins, e.g., glycosylation, phosphorylation or cleavage. However, many challenges are encountered during in planta studies aimed at stressing details of host defenses and fungal and oomycete pathogenicity determinants during interactions. Dissecting the mechanisms of such host-pathogen systems, including pathogen counter-defenses, will ensure a step ahead towards understanding current outcomes of interactions from a co-evolutionary point of view, and eventually move a step forward in building more durable strategies for management of diseases caused by fungi and oomycetes. Unraveling intricacies of more complex proteomic interactions that involve additional microbes, i.e., PGPRs and symbiotic fungi, which strengthen plant defenses will generate valuable information on how pathosystems actually function in nature, and thereby provide clues to solving disease problems that engender major losses in crops every year. PMID:22837691

Plants versus fungi and oomycetes: pathogenesis, defense and counter-defense in the proteomics era.

PubMed

El Hadrami, Abdelbasset; El-Bebany, Ahmed F; Yao, Zhen; Adam, Lorne R; El Hadrami, Ismailx; Daayf, Fouad

2012-01-01

Plant-fungi and plant-oomycete interactions have been studied at the proteomic level for many decades. However, it is only in the last few years, with the development of new approaches, combined with bioinformatics data mining tools, gel staining, and analytical instruments, such as 2D-PAGE/nanoflow-LC-MS/MS, that proteomic approaches thrived. They allow screening and analysis, at the sub-cellular level, of peptides and proteins resulting from plants, pathogens, and their interactions. They also highlight post-translational modifications to proteins, e.g., glycosylation, phosphorylation or cleavage. However, many challenges are encountered during in planta studies aimed at stressing details of host defenses and fungal and oomycete pathogenicity determinants during interactions. Dissecting the mechanisms of such host-pathogen systems, including pathogen counter-defenses, will ensure a step ahead towards understanding current outcomes of interactions from a co-evolutionary point of view, and eventually move a step forward in building more durable strategies for management of diseases caused by fungi and oomycetes. Unraveling intricacies of more complex proteomic interactions that involve additional microbes, i.e., PGPRs and symbiotic fungi, which strengthen plant defenses will generate valuable information on how pathosystems actually function in nature, and thereby provide clues to solving disease problems that engender major losses in crops every year.

Exploring plant defense theory in tall goldenrod, Solidago altissima.

PubMed

Heath, Jeremy J; Kessler, André; Woebbe, Eric; Cipollini, Don; Stireman, John O

2014-06-01

Understanding the evolutionary reasons for patterns of chemical defense in plants is an ongoing theoretical and empirical challenge. The goal is to develop a model that can reliably predict how defenses are distributed within the plant over space and time. This is difficult given that evolutionary, ecological, and physiological processes and tradeoffs can operate over different spatial and temporal scales. We evaluated the major predictions of two leading defense theories, the growth-differentiation balance hypothesis (GDBH) and optimal defense theory (ODT). To achieve this, enemies, fitness components, terpenoids, and protease inhibitors were measured in Solidago altissima and used to construct conventional univariate and structural equation models (SEMs). Leaf-tissue value indices extracted from an SEM revealed a strong correlation between tissue value and terpenoid defense that supports ODT. A tradeoff between serine protease inhibition and growth as well as an indirect tradeoff between growth and terpenoids manifested through galling insects supported the GDBH. Interestingly, there was a strong direct effect of terpenoids on rhizome mass, suggesting service to both storage and defense. The results support established theories but unknown genotypic traits explained much of the variation in defense, confirming the need to integrate emerging theories such as pollination constraints, defense syndromes, tolerance, mutualisms, and facilitation. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Importance of Mediator complex in the regulation and integration of diverse signaling pathways in plants.

PubMed

Samanta, Subhasis; Thakur, Jitendra K

2015-01-01

Basic transcriptional machinery in eukaryotes is assisted by a number of cofactors, which either increase or decrease the rate of transcription. Mediator complex is one such cofactor, and recently has drawn a lot of interest because of its integrative power to converge different signaling pathways before channeling the transcription instructions to the RNA polymerase II machinery. Like yeast and metazoans, plants do possess the Mediator complex across the kingdom, and its isolation and subunit analyses have been reported from the model plant, Arabidopsis. Genetic, and molecular analyses have unraveled important regulatory roles of Mediator subunits at every stage of plant life cycle starting from flowering to embryo and organ development, to even size determination. It also contributes immensely to the survival of plants against different environmental vagaries by the timely activation of its resistance mechanisms. Here, we have provided an overview of plant Mediator complex starting from its discovery to regulation of stoichiometry of its subunits. We have also reviewed involvement of different Mediator subunits in different processes and pathways including defense response pathways evoked by diverse biotic cues. Wherever possible, attempts have been made to provide mechanistic insight of Mediator's involvement in these processes.

Importance of Mediator complex in the regulation and integration of diverse signaling pathways in plants

PubMed Central

Samanta, Subhasis; Thakur, Jitendra K.

2015-01-01

Basic transcriptional machinery in eukaryotes is assisted by a number of cofactors, which either increase or decrease the rate of transcription. Mediator complex is one such cofactor, and recently has drawn a lot of interest because of its integrative power to converge different signaling pathways before channeling the transcription instructions to the RNA polymerase II machinery. Like yeast and metazoans, plants do possess the Mediator complex across the kingdom, and its isolation and subunit analyses have been reported from the model plant, Arabidopsis. Genetic, and molecular analyses have unraveled important regulatory roles of Mediator subunits at every stage of plant life cycle starting from flowering to embryo and organ development, to even size determination. It also contributes immensely to the survival of plants against different environmental vagaries by the timely activation of its resistance mechanisms. Here, we have provided an overview of plant Mediator complex starting from its discovery to regulation of stoichiometry of its subunits. We have also reviewed involvement of different Mediator subunits in different processes and pathways including defense response pathways evoked by diverse biotic cues. Wherever possible, attempts have been made to provide mechanistic insight of Mediator's involvement in these processes. PMID:26442070

Evolutionary routes to biochemical innovation revealed by integrative analysis of a plant-defense related specialized metabolic pathway

PubMed Central

Moghe, Gaurav D; Leong, Bryan J; Hurney, Steven M; Daniel Jones, A

2017-01-01

The diversity of life on Earth is a result of continual innovations in molecular networks influencing morphology and physiology. Plant specialized metabolism produces hundreds of thousands of compounds, offering striking examples of these innovations. To understand how this novelty is generated, we investigated the evolution of the Solanaceae family-specific, trichome-localized acylsugar biosynthetic pathway using a combination of mass spectrometry, RNA-seq, enzyme assays, RNAi and phylogenomics in different non-model species. Our results reveal hundreds of acylsugars produced across the Solanaceae family and even within a single plant, built on simple sugar cores. The relatively short biosynthetic pathway experienced repeated cycles of innovation over the last 100 million years that include gene duplication and divergence, gene loss, evolution of substrate preference and promiscuity. This study provides mechanistic insights into the emergence of plant chemical novelty, and offers a template for investigating the ~300,000 non-model plant species that remain underexplored. PMID:28853706

Evolutionary routes to biochemical innovation revealed by integrative analysis of a plant-defense related specialized metabolic pathway.

PubMed

Moghe, Gaurav D; Leong, Bryan J; Hurney, Steven M; Daniel Jones, A; Last, Robert L

2017-08-30

The diversity of life on Earth is a result of continual innovations in molecular networks influencing morphology and physiology. Plant specialized metabolism produces hundreds of thousands of compounds, offering striking examples of these innovations. To understand how this novelty is generated, we investigated the evolution of the Solanaceae family-specific, trichome-localized acylsugar biosynthetic pathway using a combination of mass spectrometry, RNA-seq, enzyme assays, RNAi and phylogenomics in different non-model species. Our results reveal hundreds of acylsugars produced across the Solanaceae family and even within a single plant, built on simple sugar cores. The relatively short biosynthetic pathway experienced repeated cycles of innovation over the last 100 million years that include gene duplication and divergence, gene loss, evolution of substrate preference and promiscuity. This study provides mechanistic insights into the emergence of plant chemical novelty, and offers a template for investigating the ~300,000 non-model plant species that remain underexplored.

Plant defenses against parasitic plants show similarities to those induced by herbivores and pathogens

PubMed Central

Runyon, Justin B; Mescher, Mark C

2010-01-01

Herbivores and pathogens come quickly to mind when one thinks of the biotic challenges faced by plants. Important but less appreciated enemies are parasitic plants, which can have important consequences for the fitness and survival of their hosts. Our knowledge of plant perception, signaling and response to herbivores and pathogens has expanded rapidly in recent years, but information is generally lacking for parasitic species. In a recent paper we reported that some of the same defense responses induced by herbivores and pathogens—notably increases in jasmonic acid (JA), salicylic acid (SA), and a hypersensitive-like response (HLR)—also occur in tomato plants upon attack by the parasitic plant Cuscuta pentagona (field dodder). Parasitism induced a distinct pattern of JA and SA accumulation, and growth trials using genetically-altered tomato hosts suggested that both JA and SA govern effective defenses against the parasite, though the extent of the response varied with host plant age. Here we discuss similarities between the induced responses we observed in response to Cuscuta parasitism to those previously described for herbivores and pathogens and present new data showing that trichomes should be added to the list of plant defenses that act against multiple enemies and across kingdoms. PMID:20495380

Plant defenses against parasitic plants show similarities to those induced by herbivores and pathogens.

PubMed

Runyon, Justin B; Mescher, Mark C; De Moraes, Consuelo M

2010-08-01

Herbivores and pathogens come quickly to mind when one thinks of the biotic challenges faced by plants. Important but less appreciated enemies are parasitic plants, which can have important consequences for the fitness and survival of their hosts. Our knowledge of plant perception, signaling, and response to herbivores and pathogens has expanded rapidly in recent years, but information is generally lacking for parasitic species. In a recent paper we reported that some of the same defense responses induced by herbivores and pathogens--notably increases in jasmonic acid (JA), salicylic acid (SA), and a hypersensitive-like response (HLR)--also occur in tomato plants upon attack by the parasitic plant Cuscuta pentagona (field dodder). Parasitism induced a distinct pattern of JA and SA accumulation, and growth trials using genetically-altered tomato hosts suggested that both JA and SA govern effective defenses against the parasite, though the extent of the response varied with host plant age. Here we discuss similarities between the induced responses we observed in response to Cuscuta parasitism to those previously described for herbivores and pathogens and present new data showing that trichomes should be added to the list of plant defenses that act against multiple enemies and across Kingdoms.

Transgenerational Effects Alter Plant Defense and Resistance in Nature

PubMed Central

Colicchio, Jack

2017-01-01

Trichomes, or leaf hairs, are epidermal extensions that take a variety of forms and perform many functions in plants, including herbivore defense. In this study, I document genetically determined variation, within-generation plasticity, and a direct role of trichomes in herbivore defense for Mimulus guttatus. After establishing the relationship between trichomes and herbivory, I test for transgenerational effects of wounding on trichome density and herbivore resistance. Patterns of inter-annual variation in herbivore density and the high cost of plant defense makes plant-herbivore interactions a system in which transgenerational phenotypic plasticity (TPP) is apt to evolve. Here, I demonstrate that parental damage alters offspring trichome density and herbivore resistance in nature. Moreover, this response varies between populations. This is among the first studies to demonstrate that TPP contributes to variation in nature, and also suggests that selection can modify TPP in response to local conditions. PMID:28102915

Elicitors and defense gene induction in plants with altered lignin compositions.

PubMed

Gallego-Giraldo, Lina; Posé, Sara; Pattathil, Sivakumar; Peralta, Angelo Gabriel; Hahn, Michael G; Ayre, Brian G; Sunuwar, Janak; Hernandez, Jonathan; Patel, Monika; Shah, Jyoti; Rao, Xiaolan; Knox, J Paul; Dixon, Richard A

2018-06-27

A reduction in the lignin content in transgenic plants induces the ectopic expression of defense genes, but the importance of altered lignin composition in such phenomena remains unclear. Two Arabidopsis lines with similar lignin contents, but strikingly different lignin compositions, exhibited different quantitative and qualitative transcriptional responses. Plants with lignin composed primarily of guaiacyl units overexpressed genes responsive to oomycete and bacterial pathogen attack, whereas plants with lignin composed primarily of syringyl units expressed a far greater number of defense genes, including some associated with cis-jasmone-mediated responses to aphids; these plants exhibited altered responsiveness to bacterial and aphid inoculation. Several of the defense genes were differentially induced by water-soluble extracts from cell walls of plants of the two lines. Glycome profiling, fractionation and enzymatic digestion studies indicated that the different lignin compositions led to differential extractability of a range of heterogeneous oligosaccharide epitopes, with elicitor activity originating from different cell wall polymers. Alteration of lignin composition affects interactions with plant cell wall matrix polysaccharides to alter the sequestration of multiple latent defense signal molecules with an impact on biotic stress responses. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

Cell death-inducing stresses are required for defense activation in DS1-phosphatidic acid phosphatase-silenced Nicotiana benthamiana.

PubMed

Nakano, Masahito; Yoshioka, Hirofumi; Ohnishi, Kouhei; Hikichi, Yasufumi; Kiba, Akinori

2015-07-20

We previously identified DS1 plants that showed resistance to compatible Ralstonia solanacearum with accelerated defense responses. Here, we describe activation mechanisms of defense responses in DS1 plants. After inoculation with incompatible R. solanacearum 8107, DS1 plants showed hyperinduction of hypersensitive response (HR) and reactive oxygen species (ROS) generation. Transient expression of PopP1 and AvrA induced hyperinduction of HR and ROS generation. Furthermore, Pseudomonas cichorii (Pc) and a type III secretion system (TTSS)-deficient mutant of P. cichorii showed accelerated induction of HR and ROS generation. Chitin and flg22 did not induce either HR or ROS hyperaccumulation; however, INF1 accelerated HR and ROS in DS1 plants. Activation of these defense responses was closely associated with increased phosphatidic acid (PA) content. Our results show that DS1 plants exhibit PA-mediated sensitization of plant defenses and that cell death-inducing stress is required to achieve full activation of defense responses. Copyright © 2015 Elsevier GmbH. All rights reserved.

ALD1 Regulates Basal Immune Components and Early Inducible Defense Responses in Arabidopsis.

PubMed

Cecchini, Nicolás M; Jung, Ho Won; Engle, Nancy L; Tschaplinski, Timothy J; Greenberg, Jean T

2015-04-01

Robust immunity requires basal defense machinery to mediate timely responses and feedback cycles to amplify defenses against potentially spreading infections. AGD2-LIKE DEFENSE RESPONSE PROTEIN 1 (ALD1) is needed for the accumulation of the plant defense signal salicylic acid (SA) during the first hours after infection with the pathogen Pseudomonas syringae and is also upregulated by infection and SA. ALD1 is an aminotransferase with multiple substrates and products in vitro. Pipecolic acid (Pip) is an ALD1-dependent bioactive product induced by P. syringae. Here, we addressed roles of ALD1 in mediating defense amplification as well as the levels and responses of basal defense machinery. ALD1 needs immune components PAD4 and ICS1 (an SA synthesis enzyme) to confer disease resistance, possibly through a transcriptional amplification loop between them. Furthermore, ALD1 affects basal defense by controlling microbial-associated molecular pattern (MAMP) receptor levels and responsiveness. Vascular exudates from uninfected ALD1-overexpressing plants confer local immunity to the wild type and ald1 mutants yet are not enriched for Pip. We infer that, in addition to affecting Pip accumulation, ALD1 produces non-Pip metabolites that play roles in immunity. Thus, distinct metabolite signals controlled by the same enzyme affect basal and early defenses versus later defense responses, respectively.

Molecular functions of Xanthomonas type III effector AvrBsT and its plant interactors in cell death and defense signaling.

PubMed

Han, Sang Wook; Hwang, Byung Kook

2017-02-01

Xanthomonas effector AvrBsT interacts with plant defense proteins and triggers cell death and defense response. This review highlights our current understanding of the molecular functions of AvrBsT and its host interactor proteins. The AvrBsT protein is a member of a growing family of effector proteins in both plant and animal pathogens. Xanthomonas type III effector AvrBsT, a member of the YopJ/AvrRxv family, suppresses plant defense responses in susceptible hosts, but triggers cell death signaling leading to hypersensitive response (HR) and defense responses in resistant plants. AvrBsT interacts with host defense-related proteins to trigger the HR cell death and defense responses in plants. Here, we review and discuss recent progress in understanding the molecular functions of AvrBsT and its host interactor proteins in pepper (Capsicum annuum). Pepper arginine decarboxylase1 (CaADC1), pepper aldehyde dehydrogenase1 (CaALDH1), pepper heat shock protein 70a (CaHSP70a), pepper suppressor of the G2 allele of skp1 (CaSGT1), pepper SNF1-related kinase1 (SnRK1), and Arabidopsis acetylated interacting protein1 (ACIP1) have been identified as AvrBsT interactors in pepper and Arabidopsis. Gene expression profiling, virus-induced gene silencing, and transient transgenic overexpression approaches have advanced the functional characterization of AvrBsT-interacting proteins in plants. AvrBsT is localized in the cytoplasm and forms protein-protein complexes with host interactors. All identified AvrBsT interactors regulate HR cell death and defense responses in plants. Notably, CaSGT1 physically binds to both AvrBsT and pepper receptor-like cytoplasmic kinase1 (CaPIK1) in the cytoplasm. During infection with Xanthomonas campestris pv. vesicatoria strain Ds1 (avrBsT), AvrBsT is phosphorylated by CaPIK1 and forms the active AvrBsT-CaSGT1-CaPIK1 complex, which ultimately triggers HR cell death and defense responses. Collectively, the AvrBsT interactor proteins are involved in plant

Large-scale transcriptome analysis reveals arabidopsis metabolic pathways are frequently influenced by different pathogens.

PubMed

Jiang, Zhenhong; He, Fei; Zhang, Ziding

2017-07-01

Through large-scale transcriptional data analyses, we highlighted the importance of plant metabolism in plant immunity and identified 26 metabolic pathways that were frequently influenced by the infection of 14 different pathogens. Reprogramming of plant metabolism is a common phenomenon in plant defense responses. Currently, a large number of transcriptional profiles of infected tissues in Arabidopsis (Arabidopsis thaliana) have been deposited in public databases, which provides a great opportunity to understand the expression patterns of metabolic pathways during plant defense responses at the systems level. Here, we performed a large-scale transcriptome analysis based on 135 previously published expression samples, including 14 different pathogens, to explore the expression pattern of Arabidopsis metabolic pathways. Overall, metabolic genes are significantly changed in expression during plant defense responses. Upregulated metabolic genes are enriched on defense responses, and downregulated genes are enriched on photosynthesis, fatty acid and lipid metabolic processes. Gene set enrichment analysis (GSEA) identifies 26 frequently differentially expressed metabolic pathways (FreDE_Paths) that are differentially expressed in more than 60% of infected samples. These pathways are involved in the generation of energy, fatty acid and lipid metabolism as well as secondary metabolite biosynthesis. Clustering analysis based on the expression levels of these 26 metabolic pathways clearly distinguishes infected and control samples, further suggesting the importance of these metabolic pathways in plant defense responses. By comparing with FreDE_Paths from abiotic stresses, we find that the expression patterns of 26 FreDE_Paths from biotic stresses are more consistent across different infected samples. By investigating the expression correlation between transcriptional factors (TFs) and FreDE_Paths, we identify several notable relationships. Collectively, the current study

Spatial and phylogenetic variation in plant defense in a tropical moist forest canopy community

NASA Astrophysics Data System (ADS)

McManus, K. M.; Asner, G. P.; Martin, R.

2013-12-01

Plants employ physical and chemical defenses to mitigate damage caused by herbivory. Spatial patterns of plant defense may provide insight into the role of plant-herbivore interactions in the assembly of plant communities. Within plant communities, the spatial overdispersion of anti-herbivore defenses by individuals may reflect a strategy to avoid host shifts from herbivore assemblages of neighboring plants. However, variation in plant defense may also result from trade-offs between foliar investment into defense and growth, mediated by variations in abiotic nutrient availability, or constrained by phylogeny. We measured four defensive traits (leaf toughness, total phenols, condensed tannins, and hydrolysable tannins) and three growth traits (LMA, C:N, total protein) of outer canopy foliage for 345 canopy trees representing 78 species, 65 genera, and 34 families in a moist tropical rainforest on Barro Colorado Island, Panama. The outer canopy provides an important, but rarely evaluated, cross-sectional image of the tropical forest ecosystem, and observations at this scale may provide an important link between field and remote sensing based studies. We used existing data on edaphic and geological properties to investigate the relationships of abiotic nutrient variation on variation in defense. Using regression and nested random-effects variance modeling, we found strong phylogenetic association with defensive traits at the family and species level, and little evidence for a trade-off between defensive traits. Greater understanding of phylogenetic structure in trait variation may yield improved characterizations of tropical biodiversity, from functional traits to risk assessments.

A whole-plant perspective reveals unexpected impacts of above- and belowground herbivores on plant growth and defense

USDA-ARS?s Scientific Manuscript database

Tradeoffs between plant growth and defense are central to theoretical frameworks used to study the ecology and evolution of plant defense against herbivores. However, these frameworks, as well as the experiments designed to test them, rarely include the remarkable diversity of belowground herbivores...

Defense Commissary Agency Financial Reporting of Property, Plant, and Equipment.

DTIC Science & Technology

1998-03-27

ort DEFENSE COMMISSARY AGENCY FINANCIAL REPORTING OF PROPERTY, PLANT, AND EQUIPMENT Report Number 98-097 March 27, 1998 Office of the Inspector...UNDER SECRETARY OF DEFENSE (COMPTROLLER) DIRECTOR, DEFENSE COMMISSARY AGENCY SUBJECT: Audit Report on Defense Commissary Agency Financial Reporting of...the costs of the capital assets used to p erform the DeCA mission were in accordance with DoD financial reporting policy, and whether the FY 1996 DeCA

Defense Logistics Agency FY 1998 Property, Plant, and Equipment Financial Reporting

DTIC Science & Technology

1999-04-26

0it ort DEFENSE LOGISTICS AGENCY FY 1998 PROPERTY, PLANT, AND EQUIPMENT FINANCIAL REPORTING Report No. 99-142 April 26, 1999 Office of the Inspector...LOGISTICS AGENCY SUBJECT: Audit Report on Defense Logistics Agency FY 1998 Property, Plant, and Equipment Financial Reporting (Report No. 99-142) We...Property, Plant, and Equipment Financial Reporting Executive Summary Introduction. The audit was performed in support of our work to meet the requirements of

Plant defense activators: applications and prospects in cereal crops

USDA-ARS?s Scientific Manuscript database

This review addresses the current understanding of the plant immune response and the molecular mechanisms responsible for systemic acquired resistance as well as the phenomenon of "priming" in plant defense. A detailed discussion of the role of salicylic acid in activating the plant transcription c...

Self/nonself perception in plants in innate immunity and defense

PubMed Central

Sanabria, Natasha M; Huang, Ju-Chi

2010-01-01

The ability to distinguish ‘self’ from ‘nonself’ is the most fundamental aspect of any immune system. The evolutionary solution in plants to the problems of perceiving and responding to pathogens involves surveillance of nonself, damaged-self and altered-self as danger signals. This is reflected in basal resistance or non-host resistance, which is the innate immune response that protects plants against the majority of pathogens. In the case of surveillance of nonself, plants utilize receptor-like proteins or -kinases (RLP/Ks) as pattern recognition receptors (PRRs), which can detect conserved pathogen/microbe-associated molecular pattern (P/MAMP) molecules. P/MAMP detection serves as an early warning system for the presence of a wide range of potential pathogens and the timely activation of plant defense mechanisms. However, adapted microbes express a suite of effector proteins that often interfere or act as suppressors of these defenses. In response, plants have evolved a second line of defense that includes intracellular nucleotide binding leucine-rich repeat (NB-LRR)-containing resistance proteins, which recognize isolate-specific pathogen effectors once the cell wall has been compromised. This host-immunity acts within the species level and is controlled by polymorphic host genes, where resistance protein-mediated activation of defense is based on an ‘altered-self’ recognition mechanism. PMID:21559176

Plant Reactome: a resource for plant pathways and comparative analysis

PubMed Central

Naithani, Sushma; Preece, Justin; D'Eustachio, Peter; Gupta, Parul; Amarasinghe, Vindhya; Dharmawardhana, Palitha D.; Wu, Guanming; Fabregat, Antonio; Elser, Justin L.; Weiser, Joel; Keays, Maria; Fuentes, Alfonso Munoz-Pomer; Petryszak, Robert; Stein, Lincoln D.; Ware, Doreen; Jaiswal, Pankaj

2017-01-01

Plant Reactome (http://plantreactome.gramene.org/) is a free, open-source, curated plant pathway database portal, provided as part of the Gramene project. The database provides intuitive bioinformatics tools for the visualization, analysis and interpretation of pathway knowledge to support genome annotation, genome analysis, modeling, systems biology, basic research and education. Plant Reactome employs the structural framework of a plant cell to show metabolic, transport, genetic, developmental and signaling pathways. We manually curate molecular details of pathways in these domains for reference species Oryza sativa (rice) supported by published literature and annotation of well-characterized genes. Two hundred twenty-two rice pathways, 1025 reactions associated with 1173 proteins, 907 small molecules and 256 literature references have been curated to date. These reference annotations were used to project pathways for 62 model, crop and evolutionarily significant plant species based on gene homology. Database users can search and browse various components of the database, visualize curated baseline expression of pathway-associated genes provided by the Expression Atlas and upload and analyze their Omics datasets. The database also offers data access via Application Programming Interfaces (APIs) and in various standardized pathway formats, such as SBML and BioPAX. PMID:27799469

Blufensin1 Negatively Impacts Basal Defense in Response to Barley Powdery Mildew

USDA-ARS?s Scientific Manuscript database

Plants have evolved complex regulatory mechanisms to control the defense response against microbial attack. Both temporal and spatial gene expression are tightly regulated in response to pathogen ingress, modulating both positive and negative control of defense. BLUFENSIN1 (BLN1), a small peptide ...

Rutin-Mediated Priming of Plant Resistance to Three Bacterial Pathogens Initiating the Early SA Signal Pathway

PubMed Central

Li, Yang; Wang, Yingzi; Li, Ming; Wang, Yong; Ding, Xinhua; Chu, Zhaohui

2016-01-01

Flavonoids are ubiquitous in the plant kingdom and have many diverse functions, including UV protection, auxin transport inhibition, allelopathy, flower coloring and insect resistance. Here we show that rutin, a proud member of the flavonoid family, could be functional as an activator to improve plant disease resistances. Three plant species pretreated with 2 mM rutin were found to enhance resistance to Xanthomonas oryzae pv. oryzae, Ralstonia solanacearum, and Pseudomonas syringae pv. tomato strain DC3000 in rice, tobacco and Arabidopsis thaliana respectively. While they were normally propagated on the cultural medium supplemented with 2 mM rutin for those pathogenic bacteria. The enhanced resistance was associated with primed expression of several pathogenesis-related genes. We also demonstrated that the rutin-mediated priming resistance was attenuated in npr1, eds1, eds5, pad4-1, ndr1 mutants, and NahG transgenic Arabidopsis plant, while not in either snc1-11, ein2-5 or jar1 mutants. We concluded that the rutin-priming defense signal was modulated by the salicylic acid (SA)-dependent pathway from an early stage upstream of NDR1 and EDS1. PMID:26751786

Modeling the plant uptake of organic chemicals, including the soil-air-plant pathway.

PubMed

Collins, Chris D; Finnegan, Eilis

2010-02-01

The soil-air-plant pathway is potentially important in the vegetative accumulation of organic pollutants from contaminated soils. While a number of qualitative frameworks exist for the prediction of plant accumulation of organic chemicals by this pathway, there are few quantitative models that incorporate this pathway. The aim of the present study was to produce a model that included this pathway and could quantify its contribution to the total plant contamination for a range of organic pollutants. A new model was developed from three submodels for the processes controlling plant contamination via this pathway: aerial deposition, soil volatilization, and systemic translocation. Using the combined model, the soil-air-plant pathway was predicted to account for a significant proportion of the total shoot contamination for those compounds with log K(OA) > 9 and log K(AW) < -3. For those pollutants with log K(OA) < 9 and log K(AW) > -3 there was a higher deposition of pollutant via the soil-air-plant pathway than for those chemicals with log K(OA) > 9 and log K(AW) < -3, but this was an insignificant proportion of the total shoot contamination because of the higher mobility of these compounds via the soil-root-shoot pathway. The incorporation of the soil-air-plant pathway into the plant uptake model did not significantly improve the prediction of the contamination of vegetation from polluted soils when compared across a range of studies. This was a result of the high variability between the experimental studies where the bioconcentration factors varied by 2 orders of magnitude at an equivalent log K(OA). One potential reason for this is the background air concentration of the pollutants under study. It was found background air concentrations would dominate those from soil volatilization in many situations unless there was a soil hot spot of contamination, i.e., >100 mg kg(-1).

Cyclic Lipopeptides of Bacillus amyloliquefaciens subsp. plantarum Colonizing the Lettuce Rhizosphere Enhance Plant Defense Responses Toward the Bottom Rot Pathogen Rhizoctonia solani.

PubMed

Chowdhury, Soumitra Paul; Uhl, Jenny; Grosch, Rita; Alquéres, Sylvia; Pittroff, Sabrina; Dietel, Kristin; Schmitt-Kopplin, Philippe; Borriss, Rainer; Hartmann, Anton

2015-09-01

The commercially available inoculant Bacillus amyloliquefaciens FZB42 is able to considerably reduce lettuce bottom rot caused by Rhizoctonia solani. To understand the interaction between FZB42 and R. solani in the rhizosphere of lettuce, we used an axenic system with lettuce bacterized with FZB42 and inoculated with R. solani. Confocal laser scanning microscopy showed that FZB42 could delay the initial establishment of R. solani on the plants. To show which secondary metabolites of FZB42 are produced under these in-situ conditions, we developed an ultra-high performance liquid chromatography coupled to time of flight mass spectrometry-based method and identified surfactin, fengycin, and bacillomycin D in the lettuce rhizosphere. We hypothesized that lipopeptides and polyketides play a role in enhancing the plant defense responses in addition to the direct antagonistic effect toward R. solani and used a quantitative real-time polymerase chain reaction-based assay for marker genes involved in defense signaling pathways in lettuce. A significant higher expression of PDF 1.2 observed in the bacterized plants in response to subsequent pathogen challenge showed that FZB42 could enhance the lettuce defense response toward the fungal pathogen. To identify if surfactin or other nonribosomally synthesized secondary metabolites could elicit the observed enhanced defense gene expression, we examined two mutants of FZB42 deficient in production of surfactin and the lipopetides and polyketides, by expression analysis and pot experiments. In the absence of surfactin and other nonribosomally synthesized secondary metabolites, there was no enhanced PDF 1.2-mediated response to the pathogen challenge. Pot experiment results showed that the mutants failed to reduce disease incidence in lettuce as compared with the FZB42 wild type, indicating, that surfactin as well as other nonribosomally synthesized secondary metabolites play a role in the actual disease suppression and on lettuce

Mechanisms to Mitigate the Trade-Off between Growth and Defense.

PubMed

Karasov, Talia L; Chae, Eunyoung; Herman, Jacob J; Bergelson, Joy

2017-04-01

Plants have evolved an array of defenses against pathogens. However, mounting a defense response frequently comes with the cost of a reduction in growth and reproduction, carrying critical implications for natural and agricultural populations. This review focuses on how costs are generated and whether and how they can be mitigated. Most well-characterized growth-defense trade-offs stem from antagonistic crosstalk among hormones rather than an identified metabolic expenditure. A primary way plants mitigate such costs is through restricted expression of resistance; this can be achieved through inducible expression of defense genes or by the concentration of defense to particular times or tissues. Defense pathways can be primed for more effective induction, and primed states can be transmitted to offspring. We examine the resistance ( R ) genes as a case study of how the toll of defense can be generated and ameliorated. The fine-scale regulation of R genes is critical to alleviate the burden of their expression, and the genomic organization of R genes into coregulatory modules reduces costs. Plants can also recruit protection from other species. Exciting new evidence indicates that a plant's genotype influences the microbiome composition, lending credence to the hypothesis that plants shape their microbiome to enhance defense. © 2017 American Society of Plant Biologists. All rights reserved.

Which Plant Proteins Are Involved in Antiviral Defense? Review on In Vivo and In Vitro Activities of Selected Plant Proteins against Viruses.

PubMed

Musidlak, Oskar; Nawrot, Robert; Goździcka-Józefiak, Anna

2017-11-01

Plants have evolved a variety of defense mechanisms to tackle virus attack. Endogenous plant proteins can function as virus suppressors. Different types of proteins mediate defense responses against plant viruses. Pathogenesis-related (PR) proteins are activated upon pathogen infections or in different stress situations and their production is one of many components in plant defense. Ribosome-inactivating proteins (RIPs) suppress translation by enzymatically damaging ribosomes and they have been found to have antiviral activity. RNA-binding proteins (RBPs) bind to target RNAs via specialized RNA-binding domain and can directly or indirectly function in plant defense system against RNA viruses. Proteins involved in silencing machinery, namely Dicer-like (DCL) proteins, Argonaute (AGO) proteins, and RNA-dependent RNA polymerases (RDRs) confer innate antiviral defense in plants as they are able to degrade foreign RNA of viral origin. This review aims to provide a comprehensive and up-to-date picture of plant proteins participating in antiviral defense. As a result we discuss proteins conferring plant antiviral resistance and their potential future applications in different fields of life including agriculture and medicine.

Which Plant Proteins Are Involved in Antiviral Defense? Review on In Vivo and In Vitro Activities of Selected Plant Proteins against Viruses

PubMed Central

Goździcka-Józefiak, Anna

2017-01-01

Plants have evolved a variety of defense mechanisms to tackle virus attack. Endogenous plant proteins can function as virus suppressors. Different types of proteins mediate defense responses against plant viruses. Pathogenesis-related (PR) proteins are activated upon pathogen infections or in different stress situations and their production is one of many components in plant defense. Ribosome-inactivating proteins (RIPs) suppress translation by enzymatically damaging ribosomes and they have been found to have antiviral activity. RNA-binding proteins (RBPs) bind to target RNAs via specialized RNA-binding domain and can directly or indirectly function in plant defense system against RNA viruses. Proteins involved in silencing machinery, namely Dicer-like (DCL) proteins, Argonaute (AGO) proteins, and RNA-dependent RNA polymerases (RDRs) confer innate antiviral defense in plants as they are able to degrade foreign RNA of viral origin. This review aims to provide a comprehensive and up-to-date picture of plant proteins participating in antiviral defense. As a result we discuss proteins conferring plant antiviral resistance and their potential future applications in different fields of life including agriculture and medicine. PMID:29104238

Pipecolic Acid, an Endogenous Mediator of Defense Amplification and Priming, Is a Critical Regulator of Inducible Plant Immunity[W

PubMed Central

Návarová, Hana; Bernsdorff, Friederike; Döring, Anne-Christin; Zeier, Jürgen

2012-01-01

Metabolic signals orchestrate plant defenses against microbial pathogen invasion. Here, we report the identification of the non-protein amino acid pipecolic acid (Pip), a common Lys catabolite in plants and animals, as a critical regulator of inducible plant immunity. Following pathogen recognition, Pip accumulates in inoculated Arabidopsis thaliana leaves, in leaves distal from the site of inoculation, and, most specifically, in petiole exudates from inoculated leaves. Defects of mutants in AGD2-LIKE DEFENSE RESPONSE PROTEIN1 (ALD1) in systemic acquired resistance (SAR) and in basal, specific, and β-aminobutyric acid–induced resistance to bacterial infection are associated with a lack of Pip production. Exogenous Pip complements these resistance defects and increases pathogen resistance of wild-type plants. We conclude that Pip accumulation is critical for SAR and local resistance to bacterial pathogens. Our data indicate that biologically induced SAR conditions plants to more effectively synthesize the phytoalexin camalexin, Pip, and salicylic acid and primes plants for early defense gene expression. Biological priming is absent in the pipecolate-deficient ald1 mutants. Exogenous pipecolate induces SAR-related defense priming and partly restores priming responses in ald1. We conclude that Pip orchestrates defense amplification, positive regulation of salicylic acid biosynthesis, and priming to guarantee effective local resistance induction and the establishment of SAR. PMID:23221596

Ethylene Contributes to maize insect resistance1-Mediated Maize Defense against the Phloem Sap-Sucking Corn Leaf Aphid1[OPEN

PubMed Central

Louis, Joe; Basu, Saumik; Varsani, Suresh; Castano-Duque, Lina; Jiang, Victoria; Williams, W. Paul; Felton, Gary W.; Luthe, Dawn S.

2015-01-01

Signaling networks among multiple phytohormones fine-tune plant defense responses to insect herbivore attack. Previously, it was reported that the synergistic combination of ethylene (ET) and jasmonic acid (JA) was required for accumulation of the maize insect resistance1 (mir1) gene product, a cysteine (Cys) proteinase that is a key defensive protein against chewing insect pests in maize (Zea mays). However, this study suggests that mir1-mediated resistance to corn leaf aphid (CLA; Rhopalosiphum maidis), a phloem sap-sucking insect pest, is independent of JA but regulated by the ET-signaling pathway. Feeding by CLA triggers the rapid accumulation of mir1 transcripts in the resistant maize genotype, Mp708. Furthermore, Mp708 provided elevated levels of antibiosis (limits aphid population)- and antixenosis (deters aphid settling)-mediated resistance to CLA compared with B73 and Tx601 maize susceptible inbred lines. Synthetic diet aphid feeding trial bioassays with recombinant Mir1-Cys Protease demonstrates that Mir1-Cys Protease provides direct toxicity to CLA. Furthermore, foliar feeding by CLA rapidly sends defensive signal(s) to the roots that trigger belowground accumulation of the mir1, signifying a potential role of long-distance signaling in maize defense against the phloem-feeding insects. Collectively, our data indicate that ET-regulated mir1 transcript accumulation, uncoupled from JA, contributed to heightened resistance to CLA in maize. In addition, our results underscore the significance of ET acting as a central node in regulating mir1 expression to different feeding guilds of insect herbivores. PMID:26253737

Plant Reactome: a resource for plant pathways and comparative analysis.

PubMed

Naithani, Sushma; Preece, Justin; D'Eustachio, Peter; Gupta, Parul; Amarasinghe, Vindhya; Dharmawardhana, Palitha D; Wu, Guanming; Fabregat, Antonio; Elser, Justin L; Weiser, Joel; Keays, Maria; Fuentes, Alfonso Munoz-Pomer; Petryszak, Robert; Stein, Lincoln D; Ware, Doreen; Jaiswal, Pankaj

2017-01-04

Plant Reactome (http://plantreactome.gramene.org/) is a free, open-source, curated plant pathway database portal, provided as part of the Gramene project. The database provides intuitive bioinformatics tools for the visualization, analysis and interpretation of pathway knowledge to support genome annotation, genome analysis, modeling, systems biology, basic research and education. Plant Reactome employs the structural framework of a plant cell to show metabolic, transport, genetic, developmental and signaling pathways. We manually curate molecular details of pathways in these domains for reference species Oryza sativa (rice) supported by published literature and annotation of well-characterized genes. Two hundred twenty-two rice pathways, 1025 reactions associated with 1173 proteins, 907 small molecules and 256 literature references have been curated to date. These reference annotations were used to project pathways for 62 model, crop and evolutionarily significant plant species based on gene homology. Database users can search and browse various components of the database, visualize curated baseline expression of pathway-associated genes provided by the Expression Atlas and upload and analyze their Omics datasets. The database also offers data access via Application Programming Interfaces (APIs) and in various standardized pathway formats, such as SBML and BioPAX. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

Plant virus differentially alters the plant's defense response to its closely related vectors.

PubMed

Shi, Xiaobin; Pan, Huipeng; Xie, Wen; Wu, Qingjun; Wang, Shaoli; Liu, Yang; Fang, Yong; Chen, Gong; Gao, Xiwu; Zhang, Youjun

2013-01-01

The whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae), is one of the most widely distributed agricultural pests. In recent years, B. tabaci Q has invaded China, and Q has displaced B in many areas now. In a number of regions of the world, invasion by B and/or Q has been followed by outbreaks of tomato yellow leaf curl virus (TYLCV). Our previous study showed TYLCV directly and indirectly modified the feeding behavior of B. tabaci in favor of Q rather than B. In this study, we quantified the salicylic acid (SA) titers and relative gene expression of SA in tomato leaves that were infested with viruliferous or non-viruliferous B and Q. We also measured the impacts of exogenous SA on the performance of B and Q, including the effects on ovary development. SA titer was always higher in leaves that were infested with viruliferous B than with viruliferous Q, whereas the SA titer did not differ between leaves infested with non-viruliferous B and Q. The relative gene expression of SA signaling was increased by feeding of viruliferous B but was not increased by feeding of viruliferous Q. The life history traits of B and Q were adversely affected on SA-treated plants. On SA-treated plants, both B and Q had lower fecundity, shorter longevity, longer developmental time and lower survival rate than on untreated plants. Compared with whiteflies feeding on control plants, those feeding on SA-treated plants had fewer oocytes and slower ovary development. On SA-treated plants, viruliferous B had fewer oocytes than viruliferous Q. These results indicate that TYLCV tends to induce SA-regulated plant defense against B but SA-regulated plant defense against Q was reduced. In other words, Q may have a mutualistic relationship with TYLCV that results in the reduction of the plant's defense response.

Host plant invests in growth rather than chemical defense when attacked by a specialist herbivore.

PubMed

Arab, Alberto; Trigo, José Roberto

2011-05-01

Plant defensive compounds may be a cost rather than a benefit when plants are attacked by specialist insects that may overcome chemical barriers by strategies such as sequestering plant compounds. Plants may respond to specialist herbivores by compensatory growth rather than chemical defense. To explore the use of defensive chemistry vs. compensatory growth we studied Brugmansia suaveolens (Solanaceae) and the specialist larvae of the ithomiine butterfly Placidina euryanassa, which sequester defensive tropane alkaloids (TAs) from this host plant. We investigated whether the concentration of TAs in B. suaveolens was changed by P. euryanassa damage, and whether plants invest in growth, when damaged by the specialist. Larvae feeding during 24 hr significantly decreased TAs in damaged plants, but they returned to control levels after 15 days without damage. Damaged and undamaged plants did not differ significantly in leaf area after 15 days, indicating compensatory growth. Our results suggest that B. suaveolens responds to herbivory by the specialist P. euryanassa by investing in growth rather than chemical defense.

Plant Bio-Wars: Maize Protein Networks Reveal Tissue-Specific Defense Strategies in Response to a Root Herbivore.

PubMed

Castano-Duque, Lina; Helms, Anjel; Ali, Jared Gregory; Luthe, Dawn S

2018-06-21

In this study we examined global changes in protein expression in both roots and leaves of maize plants attacked by the root herbivore, Western corn rootworm (WCR, Diabrotica virgifera virgifera). The changes in protein expression Are indicative of metabolic changes during WCR feeding that enable the plant to defend itself. This is one of the first studies to look above- and below-ground at global protein expression patterns of maize plants grown in soil and infested with a root herbivore. We used advanced proteomic and network analyses to identify metabolic pathways that contribute to global defenses deployed by the insect resistant maize genotype, Mp708, infested with WCR. Using proteomic analysis, 4878 proteins in roots and leaves were detected and of these 863 showed significant changes of abundance during WCR infestation. Protein abundance patterns were analyzed using hierarchical clustering, protein correlation and protein-protein interaction networks. All three data analysis pipelines showed that proteins such as jasmonic acid biosynthetic enzymes, serine proteases, protease inhibitors, proteins involved in biosynthesis and signaling of ethylene, and enzymes producing reactive oxygen species and isopentenyl pyrophosphate, a precursor for volatile production, were upregulated in roots during WCR infestation. In leaves, highly abundant proteins were involved in signal perception suggesting activation of systemic signaling. We conclude that these protein networks contribute to the overall herbivore defense mechanisms in Mp708. Because the plants were grown in potting mix and not sterilized sand, we found that both microbial and insect defense-related proteins were present in the roots. The presence of the high constitutive levels of reduced ascorbate in roots and benzothiazole in the root volatile profiles suggest a tight tri-trophic interaction among the plant, soil microbiomes and WCR-infested roots suggesting that defenses against insects coexist with

Angiosperms Are Unique among Land Plant Lineages in the Occurrence of Key Genes in the RNA-Directed DNA Methylation (RdDM) Pathway

PubMed Central

Ma, Lu; Hatlen, Andrea; Kelly, Laura J.; Becher, Hannes; Wang, Wencai; Kovarik, Ales; Leitch, Ilia J.; Leitch, Andrew R.

2015-01-01

The RNA-directed DNA methylation (RdDM) pathway can be divided into three phases: 1) small interfering RNA biogenesis, 2) de novo methylation, and 3) chromatin modification. To determine the degree of conservation of this pathway we searched for key genes among land plants. We used OrthoMCL and the OrthoMCL Viridiplantae database to analyze proteomes of species in bryophytes, lycophytes, monilophytes, gymnosperms, and angiosperms. We also analyzed small RNA size categories and, in two gymnosperms, cytosine methylation in ribosomal DNA. Six proteins were restricted to angiosperms, these being NRPD4/NRPE4, RDM1, DMS3 (defective in meristem silencing 3), SHH1 (SAWADEE homeodomain homolog 1), KTF1, and SUVR2, although we failed to find the latter three proteins in Fritillaria persica, a species with a giant genome. Small RNAs of 24 nt in length were abundant only in angiosperms. Phylogenetic analyses of Dicer-like (DCL) proteins showed that DCL2 was restricted to seed plants, although it was absent in Gnetum gnemon and Welwitschia mirabilis. The data suggest that phases (1) and (2) of the RdDM pathway, described for model angiosperms, evolved with angiosperms. The absence of some features of RdDM in F. persica may be associated with its large genome. Phase (3) is probably the most conserved part of the pathway across land plants. DCL2, involved in virus defense and interaction with the canonical RdDM pathway to facilitate methylation of CHH, is absent outside seed plants. Its absence in G. gnemon, and W. mirabilis coupled with distinctive patterns of CHH methylation, suggest a secondary loss of DCL2 following the divergence of Gnetales. PMID:26338185

Evolution in an Ancient Detoxification Pathway Is Coupled with a Transition to Herbivory in the Drosophilidae

PubMed Central

Gloss, Andrew D.; Vassão, Daniel G.; Hailey, Alexander L.; Nelson Dittrich, Anna C.; Schramm, Katharina; Reichelt, Michael; Rast, Timothy J.; Weichsel, Andrzej; Cravens, Matthew G.; Gershenzon, Jonathan; Montfort, William R.; Whiteman, Noah K.

2014-01-01

Chemically defended plant tissues present formidable barriers to herbivores. Although mechanisms to resist plant defenses have been identified in ancient herbivorous lineages, adaptations to overcome plant defenses during transitions to herbivory remain relatively unexplored. The fly genus Scaptomyza is nested within the genus Drosophila and includes species that feed on the living tissue of mustard plants (Brassicaceae), yet this lineage is derived from microbe-feeding ancestors. We found that mustard-feeding Scaptomyza species and microbe-feeding Drosophila melanogaster detoxify mustard oils, the primary chemical defenses in the Brassicaceae, using the widely conserved mercapturic acid pathway. This detoxification strategy differs from other specialist herbivores of mustard plants, which possess derived mechanisms to obviate mustard oil formation. To investigate whether mustard feeding is coupled with evolution in the mercapturic acid pathway, we profiled functional and molecular evolutionary changes in the enzyme glutathione S-transferase D1 (GSTD1), which catalyzes the first step of the mercapturic acid pathway and is induced by mustard defense products in Scaptomyza. GSTD1 acquired elevated activity against mustard oils in one mustard-feeding Scaptomyza species in which GstD1 was duplicated. Structural analysis and mutagenesis revealed that substitutions at conserved residues within and near the substrate-binding cleft account for most of this increase in activity against mustard oils. Functional evolution of GSTD1 was coupled with signatures of episodic positive selection in GstD1 after the evolution of herbivory. Overall, we found that preexisting functions of generalized detoxification systems, and their refinement by natural selection, could play a central role in the evolution of herbivory. PMID:24974374

Trade-Offs Between Plant Growth and Defense Against Insect Herbivory: An Emerging Mechanistic Synthesis.

PubMed

Züst, Tobias; Agrawal, Anurag A

2017-04-28

Costs of defense are central to our understanding of interactions between organisms and their environment, and defensive phenotypes of plants have long been considered to be constrained by trade-offs that reflect the allocation of limiting resources. Recent advances in uncovering signal transduction networks have revealed that defense trade-offs are often the result of regulatory "decisions" by the plant, enabling it to fine-tune its phenotype in response to diverse environmental challenges. We place these results in the context of classic studies in ecology and evolutionary biology, and propose a unifying framework for growth-defense trade-offs as a means to study the plant's allocation of limiting resources. Pervasive physiological costs constrain the upper limit to growth and defense traits, but the diversity of selective pressures on plants often favors negative correlations at intermediate trait levels. Despite the ubiquity of underlying costs of defense, the current challenge is using physiological and molecular approaches to predict the conditions where they manifest as detectable trade-offs.

The Genetics of Leaf Flecking in Maize and Its Relationship to Plant Defense and Disease Resistance1[OPEN

PubMed Central

Bian, Yang; De Vries, Brian; Tracy, William F.

2016-01-01

Physiological leaf spotting, or flecking, is a mild-lesion phenotype observed on the leaves of several commonly used maize (Zea mays) inbred lines and has been anecdotally linked to enhanced broad-spectrum disease resistance. Flecking was assessed in the maize nested association mapping (NAM) population, comprising 4,998 recombinant inbred lines from 25 biparental families, and in an association population, comprising 279 diverse maize inbreds. Joint family linkage analysis was conducted with 7,386 markers in the NAM population. Genome-wide association tests were performed with 26.5 million single-nucleotide polymorphisms (SNPs) in the NAM population and with 246,497 SNPs in the association population, resulting in the identification of 18 and three loci associated with variation in flecking, respectively. Many of the candidate genes colocalizing with associated SNPs are similar to genes that function in plant defense response via cell wall modification, salicylic acid- and jasmonic acid-dependent pathways, redox homeostasis, stress response, and vesicle trafficking/remodeling. Significant positive correlations were found between increased flecking, stronger defense response, increased disease resistance, and increased pest resistance. A nonlinear relationship with total kernel weight also was observed whereby lines with relatively high levels of flecking had, on average, lower total kernel weight. We present evidence suggesting that mild flecking could be used as a selection criterion for breeding programs trying to incorporate broad-spectrum disease resistance. PMID:27670817

Overcompensation of herbivore reproduction through hyper-suppression of plant defenses in response to competition.

PubMed

Schimmel, Bernardus C J; Ataide, Livia M S; Chafi, Rachid; Villarroel, Carlos A; Alba, Juan M; Schuurink, Robert C; Kant, Merijn R

2017-06-01

Spider mites are destructive arthropod pests on many crops. The generalist herbivorous mite Tetranychus urticae induces defenses in tomato (Solanum lycopersicum) and this constrains its fitness. By contrast, the Solanaceae-specialist Tetranychus evansi maintains a high reproductive performance by suppressing tomato defenses. Tetranychus evansi outcompetes T. urticae when infesting the same plant, but it is unknown whether this is facilitated by the defenses of the plant. We assessed the extent to which a secondary infestation by a competitor affects local plant defense responses (phytohormones and defense genes), mite gene expression and mite performance. We observed that T. evansi switches to hyper-suppression of defenses after its tomato host is also invaded by its natural competitor T. urticae. Jasmonate (JA) and salicylate (SA) defenses were suppressed more strongly, albeit only locally at the feeding site of T. evansi, upon introduction of T. urticae to the infested leaflet. The hyper-suppression of defenses coincided with increased expression of T. evansi genes coding for salivary defense-suppressing effector proteins and was paralleled by an increased reproductive performance. Together, these observations suggest that T. evansi overcompensates its reproduction through hyper-suppression of plant defenses in response to nearby competitors. We hypothesize that the competitor-induced overcompensation promotes competitive population growth of T. evansi on tomato. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Silicon: Potential to Promote Direct and Indirect Effects on Plant Defense Against Arthropod Pests in Agriculture.

PubMed

Reynolds, Olivia L; Padula, Matthew P; Zeng, Rensen; Gurr, Geoff M

2016-01-01

Silicon has generally not been considered essential for plant growth, although it is well recognized that many plants, particularly Poaceae, have substantial plant tissue concentrations of this element. Recently, however, the International Plant Nutrition Institute [IPNI] (2015), Georgia, USA has listed it as a "beneficial substance". This reflects that numerous studies have now established that silicon may alleviate both biotic and abiotic stress. This paper explores the existing knowledge and recent advances in elucidating the role of silicon in plant defense against biotic stress, particularly against arthropod pests in agriculture and attraction of beneficial insects. Silicon confers resistance to herbivores via two described mechanisms: physical and biochemical/molecular. Until recently, studies have mainly centered on two trophic levels; the herbivore and plant. However, several studies now describe tri-trophic effects involving silicon that operate by attracting predators or parasitoids to plants under herbivore attack. Indeed, it has been demonstrated that silicon-treated, arthropod-attacked plants display increased attractiveness to natural enemies, an effect that was reflected in elevated biological control in the field. The reported relationships between soluble silicon and the jasmonic acid (JA) defense pathway, and JA and herbivore-induced plant volatiles (HIPVs) suggest that soluble silicon may enhance the production of HIPVs. Further, it is feasible that silicon uptake may affect protein expression (or modify proteins structurally) so that they can produce additional, or modify, the HIPV profile of plants. Ultimately, understanding silicon under plant ecological, physiological, biochemical, and molecular contexts will assist in fully elucidating the mechanisms behind silicon and plant response to biotic stress at both the bi- and tri-trophic levels.

Silicon: Potential to Promote Direct and Indirect Effects on Plant Defense Against Arthropod Pests in Agriculture

PubMed Central

Reynolds, Olivia L.; Padula, Matthew P.; Zeng, Rensen; Gurr, Geoff M.

2016-01-01

Silicon has generally not been considered essential for plant growth, although it is well recognized that many plants, particularly Poaceae, have substantial plant tissue concentrations of this element. Recently, however, the International Plant Nutrition Institute [IPNI] (2015), Georgia, USA has listed it as a “beneficial substance”. This reflects that numerous studies have now established that silicon may alleviate both biotic and abiotic stress. This paper explores the existing knowledge and recent advances in elucidating the role of silicon in plant defense against biotic stress, particularly against arthropod pests in agriculture and attraction of beneficial insects. Silicon confers resistance to herbivores via two described mechanisms: physical and biochemical/molecular. Until recently, studies have mainly centered on two trophic levels; the herbivore and plant. However, several studies now describe tri-trophic effects involving silicon that operate by attracting predators or parasitoids to plants under herbivore attack. Indeed, it has been demonstrated that silicon-treated, arthropod-attacked plants display increased attractiveness to natural enemies, an effect that was reflected in elevated biological control in the field. The reported relationships between soluble silicon and the jasmonic acid (JA) defense pathway, and JA and herbivore-induced plant volatiles (HIPVs) suggest that soluble silicon may enhance the production of HIPVs. Further, it is feasible that silicon uptake may affect protein expression (or modify proteins structurally) so that they can produce additional, or modify, the HIPV profile of plants. Ultimately, understanding silicon under plant ecological, physiological, biochemical, and molecular contexts will assist in fully elucidating the mechanisms behind silicon and plant response to biotic stress at both the bi- and tri-trophic levels. PMID:27379104

Transcriptomes That Confer to Plant Defense against Powdery Mildew Disease in Lagerstroemia indica

PubMed Central

Shi, Weibing; Rinehart, Timothy

2015-01-01

Transcriptome analysis was conducted in two popular Lagerstroemia cultivars: “Natchez” (NAT), a white flower and powdery mildew resistant interspecific hybrid and “Carolina Beauty” (CAB), a red flower and powdery mildew susceptible L. indica cultivar. RNA-seq reads were generated from Erysiphe australiana infected leaves and de novo assembled. A total of 37,035 unigenes from 224,443 assembled contigs in both genotypes were identified. Approximately 85% of these unigenes have known function. Of them, 475 KEGG genes were found significantly different between the two genotypes. Five of the top ten differentially expressed genes (DEGs) involved in the biosynthesis of secondary metabolites (plant defense) and four in flavonoid biosynthesis pathway (antioxidant activities or flower coloration). Furthermore, 5 of the 12 assembled unigenes in benzoxazinoid biosynthesis and 7 of 11 in flavonoid biosynthesis showed higher transcript abundance in NAT. The relative abundance of transcripts for 16 candidate DEGs (9 from CAB and 7 from NAT) detected by qRT-PCR showed general agreement with the abundances of the assembled transcripts in NAT. This study provided the first transcriptome analyses in L. indica. The differential transcript abundance between two genotypes indicates that it is possible to identify candidate genes that are associated with the plant defenses or flower coloration. PMID:26247009

Regulatory Subunit B′γ of Protein Phosphatase 2A Prevents Unnecessary Defense Reactions under Low Light in Arabidopsis1[W][OA

PubMed Central

Trotta, Andrea; Wrzaczek, Michael; Scharte, Judith; Tikkanen, Mikko; Konert, Grzegorz; Rahikainen, Moona; Holmström, Maija; Hiltunen, Hanna-Maija; Rips, Stephan; Sipari, Nina; Mulo, Paula; Weis, Engelbert; von Schaewen, Antje; Aro, Eva-Mari; Kangasjärvi, Saijaliisa

2011-01-01

Light is an important environmental factor that modulates acclimation strategies and defense responses in plants. We explored the functional role of the regulatory subunit B′γ (B′γ) of protein phosphatase 2A (PP2A) in light-dependent stress responses of Arabidopsis (Arabidopsis thaliana). The predominant form of PP2A consists of catalytic subunit C, scaffold subunit A, and highly variable regulatory subunit B, which determines the substrate specificity of PP2A holoenzymes. Mutant leaves of knockdown pp2a-b′γ plants show disintegration of chloroplasts and premature yellowing conditionally under moderate light intensity. The cell-death phenotype is accompanied by the accumulation of hydrogen peroxide through a pathway that requires CONSTITUTIVE EXPRESSION OF PR GENES5 (CPR5). Moreover, the pp2a-b′γ cpr5 double mutant additionally displays growth suppression and malformed trichomes. Similar to cpr5, the pp2a-b′γ mutant shows constitutive activation of both salicylic acid- and jasmonic acid-dependent defense pathways. In contrast to cpr5, however, pp2a-b′γ leaves do not contain increased levels of salicylic acid or jasmonic acid. Rather, the constitutive defense response associates with hypomethylation of DNA and increased levels of methionine-salvage pathway components in pp2a-b′γ leaves. We suggest that the specific B′γ subunit of PP2A is functionally connected to CPR5 and operates in the basal repression of defense responses under low irradiance. PMID:21571669

Tyramine Pathways in Citrus Plant Defense: Glycoconjugates of Tyramine and Its N-Methylated Derivatives.

PubMed

Servillo, Luigi; Castaldo, Domenico; Giovane, Alfonso; Casale, Rosario; D'Onofrio, Nunzia; Cautela, Domenico; Balestrieri, Maria Luisa

2017-02-01

Glucosylated forms of tyramine and some of its N-methylated derivatives are here reported for the first time to occur in Citrus genus plants. The compounds tyramine-O-β-d-glucoside, N-methyltyramine-O-β-d-glucoside, and N,N-dimethyltyramine-O-β-d-glucoside were detected in juice and leaves of sweet orange, bitter orange, bergamot, citron, lemon, mandarin, and pomelo. The compounds were identified by mass spectrometric analysis, enzymatic synthesis, and comparison with extracts of Stapelia hirsuta L., a plant belonging to the Apocynaceae family in which N,N-dimethyltyramine-O-β-d-glucoside was identified by others. Interestingly, in Stapelia hirsuta we discovered also tyramine-O-β-d-glucoside, N-methyltyramine-O-β-d-glucoside, and the tyramine metabolite, N,N,N-trimethyltyramine-O-β-glucoside. However, the latter tyramine metabolite, never described before, was not detected in any of the Citrus plants included in this study. The presence of N-methylated tyramine derivatives and their glucosylated forms in Citrus plants, together with octopamine and synephrine, also deriving from tyramine, supports the hypothesis of specific biosynthetic pathways of adrenergic compounds aimed to defend against biotic stress.

Jasmonic acid-mediated defense suppresses brassinosteroid-mediated susceptibility to Rice black streaked dwarf virus infection in rice.

PubMed

He, Yuqing; Zhang, Hehong; Sun, Zongtao; Li, Junmin; Hong, Gaojie; Zhu, Qisong; Zhou, Xuebiao; MacFarlane, Stuart; Yan, Fei; Chen, Jianping

2017-04-01

Plant hormones play a vital role in plant immune responses. However, in contrast to the relative wealth of information on hormone-mediated immunity in dicot plants, little information is available on monocot-virus defense systems. We used a high-throughput-sequencing approach to compare the global gene expression of Rice black-streaked dwarf virus (RBSDV)-infected rice plants with that of healthy plants. Exogenous hormone applications and transgenic rice were used to test RBSDV infectivity and pathogenicity. Our results revealed that the jasmonic acid (JA) pathway was induced while the brassinosteroid (BR) pathway was suppressed in infected plants. Foliar application of methyl jasmonate (MeJA) or brassinazole (BRZ) resulted in a significant reduction in RBSDV incidence, while epibrassinolide (BL) treatment increased RBSDV infection. Infection studies using coi1-13 and Go mutants demonstrated JA-mediated resistance and BR-mediated susceptibility to RBSDV infection. A mixture of MeJA and BL treatment resulted in a significant reduction in RBSDV infection compared with a single BL treatment. MeJA application efficiently suppressed the expression of BR pathway genes, and this inhibition depended on the JA coreceptor OsCOI1. Collectively, our results reveal that JA-mediated defense can suppress the BR-mediated susceptibility to RBSDV infection. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

How to induce defense responses in wild plant populations? Using bilberry (Vaccinium myrtillus) as example.

PubMed

Seldal, Tarald; Hegland, Stein Joar; Rydgren, Knut; Rodriguez-Saona, Cesar; Töpper, Joachim Paul

2017-03-01

Inducible plant defense is a beneficial strategy for plants, which imply that plants should allocate resources from growth and reproduction to defense when herbivores attack. Plant ecologist has often studied defense responses in wild populations by biomass clipping experiments, whereas laboratory and greenhouse experiments in addition apply chemical elicitors to induce defense responses. To investigate whether field ecologists could benefit from methods used in laboratory and greenhouse studies, we established a randomized block-design in a pine-bilberry forest in Western Norway. We tested whether we could activate defense responses in bilberry ( Vaccinium myrtillus ) by nine different treatments using clipping (leaf tissue or branch removal) with or without chemical treatment by methyljasmonate (MeJA). We subsequently measured consequences of induced defenses through vegetative growth and insect herbivory during one growing season. Our results showed that only MeJA-treated plants showed consistent defense responses through suppressed vegetative growth and reduced herbivory by leaf-chewing insects, suggesting an allocation of resources from growth to defense. Leaf tissue removal reduced insect herbivory equal to the effect of the MeJa treatments, but had no negative impact on growth. Branch removal did not reduce insect herbivory or vegetative growth. MeJa treatment and clipping combined did not give an additional defense response. In this study, we investigated how to induce defense responses in wild plant populations under natural field conditions. Our results show that using the chemical elicitor MeJA, with or without biomass clipping, may be a better method to induce defense response in field experiments than clipping of leaves or branches that often has been used in ecological field studies.

Role of defense/stress-related marker genes, proteins and secondary metabolites in defining rice self-defense mechanisms.

PubMed

Jwa, Nam-Soo; Agrawal, Ganesh Kumar; Tamogami, Shigeru; Yonekura, Masami; Han, Oksoo; Iwahashi, Hitoshi; Rakwal, Randeep

2006-01-01

Rice, a first cereal crop whose draft genome sequence from two subspecies (japonica-type cv. Nipponbare and indica-type 93-11) was available in 2002, along with its almost complete genome sequence in 2005, has drawn the attention of researchers worldwide because of its immense impact on human existence. One of the most critical research areas in rice is to discern the self-defense mechanism(s), an innate property of all living organisms. The last few decades have seen scattered research into rice responses to diverse environmental stimuli and stress factors. Our understanding on rice self-defense mechanism has increased considerably with accelerated research during recent years mainly due to identification and characterization of several defense/stress-related components, genes, proteins and secondary metabolites. As these identified components have been used to study the defense/stress pathways, their compilation in this review will undoubtedly help rice (and others) researchers to effectively use them as a potential marker for better understanding, and ultimately, in defining rice (and plant) self-defense response pathways.

Target of rapamycin signaling orchestrates growth-defense trade-offs in plants.

PubMed

De Vleesschauwer, David; Filipe, Osvaldo; Hoffman, Gena; Seifi, Hamed Soren; Haeck, Ashley; Canlas, Patrick; Van Bockhaven, Jonas; De Waele, Evelien; Demeestere, Kristof; Ronald, Pamela; Hofte, Monica

2018-01-01

Plant defense to microbial pathogens is often accompanied by significant growth inhibition. How plants merge immune system function with normal growth and development is still poorly understood. Here, we investigated the role of target of rapamycin (TOR), an evolutionary conserved serine/threonine kinase, in the plant defense response. We used rice as a model system and applied a combination of chemical, genetic, genomic and cell-based analyses. We demonstrate that ectopic expression of TOR and Raptor (regulatory-associated protein of mTOR), a protein previously demonstrated to interact with TOR in Arabidopsis, positively regulates growth and development in rice. Transcriptome analysis of rice cells treated with the TOR-specific inhibitor rapamycin revealed that TOR not only dictates transcriptional reprogramming of extensive gene sets involved in central and secondary metabolism, cell cycle and transcription, but also suppresses many defense-related genes. TOR overexpression lines displayed increased susceptibility to both bacterial and fungal pathogens, whereas plants with reduced TOR signaling displayed enhanced resistance. Finally, we found that TOR antagonizes the action of the classic defense hormones salicylic acid and jasmonic acid. Together, these results indicate that TOR acts as a molecular switch for the activation of cell proliferation and plant growth at the expense of cellular immunity. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Field Evaluation of Plant Defense Inducers for the Control of Citrus Huanglongbing.

PubMed

Li, Jinyun; Trivedi, Pankaj; Wang, Nian

2016-01-01

Huanglongbing (HLB) is currently the most economically devastating disease of citrus worldwide and no established cure is available. Defense inducing compounds are able to induce plant resistance effective against various pathogens. In this study the effects of various chemical inducers on HLB diseased citrus were evaluated in four groves (three with sweet orange and one with mandarin) in Florida (United States) for two to four consecutive growing seasons. Results have demonstrated that plant defense inducers including β-aminobutyric acid (BABA), 2,1,3-benzothiadiazole (BTH), and 2,6-dichloroisonicotinic acid (INA), individually or in combination, were effective in suppressing progress of HLB disease. Ascorbic acid (AA) and the nonmetabolizable glucose analog 2-deoxy-D-glucose (2-DDG) also exhibited positive control effects on HLB. After three or four applications for each season, the treatments AA (60 to 600 µM), BABA (0.2 to 1.0 mM), BTH (1.0 mM), INA (0.1 mM), 2-DDG (100 µM), BABA (1.0 mM) plus BTH (1.0 mM), BTH (1.0 mM) plus AA (600 µM), and BTH (1.0 mM) plus 2-DDG (100 µM) slowed down the population growth in planta of 'Candidatus Liberibacter asiaticus', the putative pathogen of HLB and reduced HLB disease severity by approximately 15 to 30% compared with the nontreated control, depending on the age and initial HLB severity of infected trees. These treatments also conferred positive effect on fruit yield and quality. Altogether, these findings indicate that plant defense inducers may be a useful strategy for the management of citrus HLB.

Suppressors of systemin signaling identify genes in the tomato wound response pathway.

PubMed Central

Howe, G A; Ryan, C A

1999-01-01

In tomato plants, systemic induction of defense genes in response to herbivory or mechanical wounding is regulated by an 18-amino-acid peptide signal called systemin. Transgenic plants that overexpress prosystemin, the systemin precursor, from a 35S::prosystemin (35S::prosys) transgene exhibit constitutive expression of wound-inducible defense proteins including proteinase inhibitors and polyphenol oxidase. To study further the role of (pro)systemin in the wound response pathway, we isolated and characterized mutations that suppress 35S::prosys-mediated phenotypes. Ten recessive, extragenic suppressors were identified. Two of these define new alleles of def-1, a previously identified mutation that blocks both wound- and systemin-induced gene expression and renders plants susceptible to herbivory. The remaining mutants defined four loci designated Spr-1, Spr-2, Spr-3, and Spr-4 (for Suppressed in 35S::prosystemin-mediated responses). spr-3 and spr-4 mutants were not significantly affected in their response to either systemin or mechanical wounding. In contrast, spr-1 and spr-2 plants lacked systemic wound responses and were insensitive to systemin. These results confirm the function of (pro)systemin in the transduction of systemic wound signals and further establish that wounding, systemin, and 35S::prosys induce defensive gene expression through a common signaling pathway defined by at least three genes (Def-1, Spr-1, and Spr-2). PMID:10545469

Apoplastic effectors secreted by two unrelated eukaryotic plant pathogens target the tomato defense protease Rcr3.

PubMed

Song, Jing; Win, Joe; Tian, Miaoying; Schornack, Sebastian; Kaschani, Farnusch; Ilyas, Muhammad; van der Hoorn, Renier A L; Kamoun, Sophien

2009-02-03

Current models of plant-pathogen interactions stipulate that pathogens secrete effector proteins that disable plant defense components known as virulence targets. Occasionally, the perturbations caused by these effectors trigger innate immunity via plant disease resistance proteins as described by the "guard hypothesis." This model is nicely illustrated by the interaction between the fungal plant pathogen Cladosporium fulvum and tomato. C. fulvum secretes a protease inhibitor Avr2 that targets the tomato cysteine protease Rcr3(pim). In plants that carry the resistance protein Cf2, Rcr3(pim) is required for resistance to C. fulvum strains expressing Avr2, thus fulfilling one of the predictions of the guard hypothesis. Another prediction of the guard hypothesis has not yet been tested. Considering that virulence targets are important components of defense, different effectors from unrelated pathogens are expected to evolve to disable the same host target. In this study we confirm this prediction using a different pathogen of tomato, the oomycete Phytophthora infestans that is distantly related to fungi such as C. fulvum. This pathogen secretes an array of protease inhibitors including EPIC1 and EPIC2B that inhibit tomato cysteine proteases. Here we show that, similar to Avr2, EPIC1 and EPIC2B bind and inhibit Rcr3(pim). However, unlike Avr2, EPIC1 and EPIC2B do not trigger hypersensitive cell death or defenses on Cf-2/Rcr3(pim) tomato. We also found that the rcr3-3 mutant of tomato that carries a premature stop codon in the Rcr3 gene exhibits enhanced susceptibility to P. infestans, suggesting a role for Rcr3(pim) in defense. In conclusion, our findings fulfill a key prediction of the guard hypothesis and suggest that the effectors Avr2, EPIC1, and EPIC2B secreted by two unrelated pathogens of tomato target the same defense protease Rcr3(pim). In contrast to C. fulvum, P. infestans appears to have evolved stealthy effectors that carry inhibitory activity without

Macroevolution of plant defenses against herbivores in the evening primroses.

PubMed

Johnson, Marc T J; Ives, Anthony R; Ahern, Jeffrey; Salminen, Juha-Pekka

2014-07-01

Plant species vary greatly in defenses against herbivores, but existing theory has struggled to explain this variation. Here, we test how phylogenetic relatedness, tradeoffs, trait syndromes, and sexual reproduction affect the macroevolution of defense. To examine the macroevolution of defenses, we studied 26 Oenothera (Onagraceae) species, combining chemistry, comparative phylogenetics and experimental assays of resistance against generalist and specialist herbivores. We detected dozens of phenolic metabolites within leaves, including ellagitannins (ETs), flavonoids, and caffeic acid derivatives (CAs). The concentration and composition of phenolics exhibited low to moderate phylogenetic signal. There were clear negative correlations between multiple traits, supporting the prediction of allocation tradeoffs. There were also positively covarying suites of traits, but these suites did not strongly predict resistance to herbivores and thus did not act as defensive syndromes. By contrast, specific metabolites did correlate with the performance of generalist and specialist herbivores. Finally, that repeated losses of sex in Oenothera was associated with the evolution of increased flavonoid diversity and altered phenolic composition. These results show that secondary chemistry has evolved rapidly during the diversification of Oenothera. This evolution has been marked by allocation tradeoffs between traits, some of which are related to herbivore performance. The repeated loss of sex appears also to have constrained the evolution of plant secondary chemistry, which may help to explain variation in defense among plants. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Sucrose and invertases, a part of the plant defense response to the biotic stresses

PubMed Central

Tauzin, Alexandra S.; Giardina, Thierry

2014-01-01

Sucrose is the main form of assimilated carbon which is produced during photosynthesis and then transported from source to sink tissues via the phloem. This disaccharide is known to have important roles as signaling molecule and it is involved in many metabolic processes in plants. Essential for plant growth and development, sucrose is engaged in plant defense by activating plant immune responses against pathogens. During infection, pathogens reallocate the plant sugars for their own needs forcing the plants to modify their sugar content and triggering their defense responses. Among enzymes that hydrolyze sucrose and alter carbohydrate partitioning, invertases have been reported to be affected during plant-pathogen interactions. Recent highlights on the role of invertases in the establishment of plant defense responses suggest a more complex regulation of sugar signaling in plant-pathogen interaction. PMID:25002866

Angiosperms Are Unique among Land Plant Lineages in the Occurrence of Key Genes in the RNA-Directed DNA Methylation (RdDM) Pathway.

PubMed

Ma, Lu; Hatlen, Andrea; Kelly, Laura J; Becher, Hannes; Wang, Wencai; Kovarik, Ales; Leitch, Ilia J; Leitch, Andrew R

2015-09-02

The RNA-directed DNA methylation (RdDM) pathway can be divided into three phases: 1) small interfering RNA biogenesis, 2) de novo methylation, and 3) chromatin modification. To determine the degree of conservation of this pathway we searched for key genes among land plants. We used OrthoMCL and the OrthoMCL Viridiplantae database to analyze proteomes of species in bryophytes, lycophytes, monilophytes, gymnosperms, and angiosperms. We also analyzed small RNA size categories and, in two gymnosperms, cytosine methylation in ribosomal DNA. Six proteins were restricted to angiosperms, these being NRPD4/NRPE4, RDM1, DMS3 (defective in meristem silencing 3), SHH1 (SAWADEE homeodomain homolog 1), KTF1, and SUVR2, although we failed to find the latter three proteins in Fritillaria persica, a species with a giant genome. Small RNAs of 24 nt in length were abundant only in angiosperms. Phylogenetic analyses of Dicer-like (DCL) proteins showed that DCL2 was restricted to seed plants, although it was absent in Gnetum gnemon and Welwitschia mirabilis. The data suggest that phases (1) and (2) of the RdDM pathway, described for model angiosperms, evolved with angiosperms. The absence of some features of RdDM in F. persica may be associated with its large genome. Phase (3) is probably the most conserved part of the pathway across land plants. DCL2, involved in virus defense and interaction with the canonical RdDM pathway to facilitate methylation of CHH, is absent outside seed plants. Its absence in G. gnemon, and W. mirabilis coupled with distinctive patterns of CHH methylation, suggest a secondary loss of DCL2 following the divergence of Gnetales. © The Author(s) 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Noncanonical Function of a Small-Molecular Virulence Factor Coronatine against Plant Immunity: An In Vivo Raman Imaging Approach

PubMed Central

2017-01-01

Coronatine (1), a small-molecular virulence factor produced by plant-pathogenic bacteria, promotes bacterial infection by inducing the opening of stomatal pores, the major route of bacterial entry into the plant, via the jasmonate-mediated COI1-JAZ signaling pathway. However, this pathway is also important for multiple plant functions, including defense against wounding by herbivorous insects. Thus, suppression of the COI1-JAZ signaling pathway to block bacterial infection would concomitantly impair plant defense against herbivorous wounding. Here, we report additional, COI1-JAZ-independent, action of 1 in Arabidopsis thaliana guard cells. First, we found that a stereoisomer of 1 regulates the movement of Arabidopsis guard cells without affecting COI1-JAZ signaling. Second, we found using alkyne-tagged Raman imaging (ATRI) that 1 is localized to the endoplasmic reticulum (ER) of living guard cells of Arabidopsis. The use of arc6 mutant lacking chloroplast formation was pivotal to circumvent the issue of autofluorescence during ATRI. These findings indicate that 1 has an ER-related action on Arabidopsis stomata that bypasses the COI1-JAZ signaling module. It may be possible to suppress the action of 1 on stomata without impairing plant defense responses against herbivores. PMID:28573209

Evolution in an ancient detoxification pathway is coupled with a transition to herbivory in the drosophilidae.

PubMed

Gloss, Andrew D; Vassão, Daniel G; Hailey, Alexander L; Nelson Dittrich, Anna C; Schramm, Katharina; Reichelt, Michael; Rast, Timothy J; Weichsel, Andrzej; Cravens, Matthew G; Gershenzon, Jonathan; Montfort, William R; Whiteman, Noah K

2014-09-01

Chemically defended plant tissues present formidable barriers to herbivores. Although mechanisms to resist plant defenses have been identified in ancient herbivorous lineages, adaptations to overcome plant defenses during transitions to herbivory remain relatively unexplored. The fly genus Scaptomyza is nested within the genus Drosophila and includes species that feed on the living tissue of mustard plants (Brassicaceae), yet this lineage is derived from microbe-feeding ancestors. We found that mustard-feeding Scaptomyza species and microbe-feeding Drosophila melanogaster detoxify mustard oils, the primary chemical defenses in the Brassicaceae, using the widely conserved mercapturic acid pathway. This detoxification strategy differs from other specialist herbivores of mustard plants, which possess derived mechanisms to obviate mustard oil formation. To investigate whether mustard feeding is coupled with evolution in the mercapturic acid pathway, we profiled functional and molecular evolutionary changes in the enzyme glutathione S-transferase D1 (GSTD1), which catalyzes the first step of the mercapturic acid pathway and is induced by mustard defense products in Scaptomyza. GSTD1 acquired elevated activity against mustard oils in one mustard-feeding Scaptomyza species in which GstD1 was duplicated. Structural analysis and mutagenesis revealed that substitutions at conserved residues within and near the substrate-binding cleft account for most of this increase in activity against mustard oils. Functional evolution of GSTD1 was coupled with signatures of episodic positive selection in GstD1 after the evolution of herbivory. Overall, we found that preexisting functions of generalized detoxification systems, and their refinement by natural selection, could play a central role in the evolution of herbivory. © The Author 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e

Genetic and Functional Diversification of Small RNA Pathways in Plants

PubMed Central

Gustafson, Adam M; Kasschau, Kristin D; Lellis, Andrew D; Zilberman, Daniel; Jacobsen, Steven E

2004-01-01

Multicellular eukaryotes produce small RNA molecules (approximately 21–24 nucleotides) of two general types, microRNA (miRNA) and short interfering RNA (siRNA). They collectively function as sequence-specific guides to silence or regulate genes, transposons, and viruses and to modify chromatin and genome structure. Formation or activity of small RNAs requires factors belonging to gene families that encode DICER (or DICER-LIKE [DCL]) and ARGONAUTE proteins and, in the case of some siRNAs, RNA-dependent RNA polymerase (RDR) proteins. Unlike many animals, plants encode multiple DCL and RDR proteins. Using a series of insertion mutants of Arabidopsis thaliana, unique functions for three DCL proteins in miRNA (DCL1), endogenous siRNA (DCL3), and viral siRNA (DCL2) biogenesis were identified. One RDR protein (RDR2) was required for all endogenous siRNAs analyzed. The loss of endogenous siRNA in dcl3 and rdr2 mutants was associated with loss of heterochromatic marks and increased transcript accumulation at some loci. Defects in siRNA-generation activity in response to turnip crinkle virus in dcl2 mutant plants correlated with increased virus susceptibility. We conclude that proliferation and diversification of DCL and RDR genes during evolution of plants contributed to specialization of small RNA-directed pathways for development, chromatin structure, and defense. PMID:15024409

Rewiring of jasmonate and phytochrome B signalling uncouples plant growth-defense tradeoffs

PubMed Central

Campos, Marcelo L.; Yoshida, Yuki; Major, Ian T.; de Oliveira Ferreira, Dalton; Weraduwage, Sarathi M.; Froehlich, John E.; Johnson, Brendan F.; Kramer, David M.; Jander, Georg; Sharkey, Thomas D.; Howe, Gregg A.

2016-01-01

Plants resist infection and herbivory with innate immune responses that are often associated with reduced growth. Despite the importance of growth-defense tradeoffs in shaping plant productivity in natural and agricultural ecosystems, the molecular mechanisms that link growth and immunity are poorly understood. Here, we demonstrate that growth-defense tradeoffs mediated by the hormone jasmonate are uncoupled in an Arabidopsis mutant (jazQ phyB) lacking a quintet of Jasmonate ZIM-domain transcriptional repressors and the photoreceptor phyB. Analysis of epistatic interactions between jazQ and phyB reveal that growth inhibition associated with enhanced anti-insect resistance is likely not caused by diversion of photoassimilates from growth to defense but rather by a conserved transcriptional network that is hardwired to attenuate growth upon activation of jasmonate signalling. The ability to unlock growth-defense tradeoffs through relief of transcription repression provides an approach to assemble functional plant traits in new and potentially useful ways. PMID:27573094

Rewiring of jasmonate and phytochrome B signalling uncouples plant growth-defense tradeoffs

DOE PAGES

Campos, Marcelo L.; Yoshida, Yuki; Major, Ian T.; ...

2016-08-30

Plants resist infection and herbivory with innate immune responses that are often associated with reduced growth. Despite the importance of growth-defense tradeoffs in shaping plant productivity in natural and agricultural ecosystems, the molecular mechanisms that link growth and immunity are poorly understood. Here, we demonstrate that growth-defense tradeoffs mediated by the hormone jasmonate are uncoupled in an Arabidopsis mutant ( jazQ phyB) lacking a quintet of Jasmonate ZIM-domain transcriptional repressors and the photoreceptor phyB. Analysis of epistatic interactions between jazQ and phyB reveal that growth inhibition associated with enhanced anti-insect resistance is likely not caused by diversion of photoassimilates frommore » growth to defense but rather by a conserved transcriptional network that is hardwired to attenuate growth upon activation of jasmonate signalling. Furthermore, the ability to unlock growth-defense tradeoffs through relief of transcription repression provides an approach to assemble functional plant traits in new and potentially useful ways.« less

Rewiring of jasmonate and phytochrome B signalling uncouples plant growth-defense tradeoffs

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

Campos, Marcelo L.; Yoshida, Yuki; Major, Ian T.

Plants resist infection and herbivory with innate immune responses that are often associated with reduced growth. Despite the importance of growth-defense tradeoffs in shaping plant productivity in natural and agricultural ecosystems, the molecular mechanisms that link growth and immunity are poorly understood. Here, we demonstrate that growth-defense tradeoffs mediated by the hormone jasmonate are uncoupled in an Arabidopsis mutant ( jazQ phyB) lacking a quintet of Jasmonate ZIM-domain transcriptional repressors and the photoreceptor phyB. Analysis of epistatic interactions between jazQ and phyB reveal that growth inhibition associated with enhanced anti-insect resistance is likely not caused by diversion of photoassimilates frommore » growth to defense but rather by a conserved transcriptional network that is hardwired to attenuate growth upon activation of jasmonate signalling. Furthermore, the ability to unlock growth-defense tradeoffs through relief of transcription repression provides an approach to assemble functional plant traits in new and potentially useful ways.« less

Mechanisms to Mitigate the Trade-Off between Growth and Defense

PubMed Central

2017-01-01

Plants have evolved an array of defenses against pathogens. However, mounting a defense response frequently comes with the cost of a reduction in growth and reproduction, carrying critical implications for natural and agricultural populations. This review focuses on how costs are generated and whether and how they can be mitigated. Most well-characterized growth-defense trade-offs stem from antagonistic crosstalk among hormones rather than an identified metabolic expenditure. A primary way plants mitigate such costs is through restricted expression of resistance; this can be achieved through inducible expression of defense genes or by the concentration of defense to particular times or tissues. Defense pathways can be primed for more effective induction, and primed states can be transmitted to offspring. We examine the resistance (R) genes as a case study of how the toll of defense can be generated and ameliorated. The fine-scale regulation of R genes is critical to alleviate the burden of their expression, and the genomic organization of R genes into coregulatory modules reduces costs. Plants can also recruit protection from other species. Exciting new evidence indicates that a plant’s genotype influences the microbiome composition, lending credence to the hypothesis that plants shape their microbiome to enhance defense. PMID:28320784

Parasitism by Cuscuta pentagona attenuates host plant defenses against insect herbivores

Treesearch

Justin B. Runyon; Mark C. Mescher; Consuelo M. De Moraes

2008-01-01

Considerable research has examined plant responses to concurrent attack by herbivores and pathogens, but the effects of attack by parasitic plants, another important class of plant-feeding organisms, on plant defenses against other enemies has not been explored. We investigated how attack by the parasitic plant Cuscuta pentagona impacted tomato (

Nuclear jasmonate and salicylate signaling and crosstalk in defense against pathogens.

PubMed

Gimenez-Ibanez, Selena; Solano, Roberto

2013-01-01

An extraordinary progress has been made over the last two decades on understanding the components and mechanisms governing plant innate immunity. After detection of a pathogen, effective plant resistance depends on the activation of a complex signaling network integrated by small signaling molecules and hormonal pathways, and the balance of these hormone systems determines resistance to particular pathogens. The discovery of new components of hormonal signaling pathways, including plant nuclear hormone receptors, is providing a picture of complex crosstalk and induced hormonal changes that modulate disease and resistance through several protein families that perceive hormones within the nucleus and lead to massive gene induction responses often achieved by de-repression. This review highlights recent advances in our understanding of positive and negative regulators of these hormones signaling pathways that are crucial regulatory targets of hormonal crosstalk in disease and defense. We focus on the most recent discoveries on the jasmonate and salicylate pathway components that explain their crosstalk with other hormonal pathways in the nucleus. We discuss how these components fine-tune defense responses to build a robust plant immune system against a great number of different microbes and, finally, we summarize recent discoveries on specific nuclear hormonal manipulation by microbes which exemplify the ingenious ways by which pathogens can take control over the plant's hormone signaling network to promote disease.

The Chloroplast-Localized Phospholipases D α4 and α5 Regulate Herbivore-Induced Direct and Indirect Defenses in Rice1[C][W

PubMed Central

Qi, Jinfeng; Zhou, Guoxin; Yang, Lijuan; Erb, Matthias; Lu, Yanhua; Sun, Xiaoling; Cheng, Jiaan; Lou, Yonggen

2011-01-01

The oxylipin pathway is of central importance for plant defensive responses. Yet, the first step of the pathway, the liberation of linolenic acid following induction, is poorly understood. Phospholipases D (PLDs) have been hypothesized to mediate this process, but data from Arabidopsis (Arabidopsis thaliana) regarding the role of PLDs in plant resistance have remained controversial. Here, we cloned two chloroplast-localized PLD genes from rice (Oryza sativa), OsPLDα4 and OsPLDα5, both of which were up-regulated in response to feeding by the rice striped stem borer (SSB) Chilo suppressalis, mechanical wounding, and treatment with jasmonic acid (JA). Antisense expression of OsPLDα4 and -α5 (as-pld), which resulted in a 50% reduction of the expression of the two genes, reduced elicited levels of linolenic acid, JA, green leaf volatiles, and ethylene and attenuated the SSB-induced expression of a mitogen-activated protein kinase (OsMPK3), a lipoxygenase (OsHI-LOX), a hydroperoxide lyase (OsHPL3), as well as a 1-aminocyclopropane-1-carboxylic acid synthase (OsACS2). The impaired oxylipin and ethylene signaling in as-pld plants decreased the levels of herbivore-induced trypsin protease inhibitors and volatiles, improved the performance of SSB and the rice brown planthopper Nilaparvata lugens, and reduced the attractiveness of plants to a larval parasitoid of SSB, Apanteles chilonis. The production of trypsin protease inhibitors in as-pld plants could be partially restored by JA, while the resistance to rice brown planthopper and SSB was restored by green leaf volatile application. Our results show that phospholipases function as important components of herbivore-induced direct and indirect defenses in rice. PMID:21984727

Salicylic acid, a plant defense hormone, is specifically secreted by a molluscan herbivore.

PubMed

Kästner, Julia; von Knorre, Dietrich; Himanshu, Himanshu; Erb, Matthias; Baldwin, Ian T; Meldau, Stefan

2014-01-01

Slugs and snails are important herbivores in many ecosystems. They differ from other herbivores by their characteristic mucus trail. As the mucus is secreted at the interface between the plants and the herbivores, its chemical composition may play an essential role in plant responses to slug and snail attack. Based on our current knowledge about host-manipulation strategies employed by pathogens and insects, we hypothesized that mollusks may excrete phytohormone-like substances into their mucus. We therefore screened locomotion mucus from thirteen molluscan herbivores for the presence of the plant defense hormones jasmonic acid (JA), salicylic acid (SA) and abscisic acid (ABA). We found that the locomotion mucus of one slug, Deroceras reticulatum, contained significant amounts of SA, a plant hormone that is known to induce resistance to pathogens and to suppress plant immunity against herbivores. None of the other slugs and snails contained SA or any other hormone in their locomotion mucus. When the mucus of D. reticulatum was applied to wounded leaves of A. thaliana, the promotor of the SA-responsive gene pathogenesis related 1 (PR1) was activated, demonstrating the potential of the mucus to regulate plant defenses. We discuss the potential ecological, agricultural and medical implications of this finding.

Salicylic Acid, a Plant Defense Hormone, Is Specifically Secreted by a Molluscan Herbivore

PubMed Central

Kästner, Julia; von Knorre, Dietrich; Himanshu, Himanshu; Erb, Matthias; Baldwin, Ian T.; Meldau, Stefan

2014-01-01

Slugs and snails are important herbivores in many ecosystems. They differ from other herbivores by their characteristic mucus trail. As the mucus is secreted at the interface between the plants and the herbivores, its chemical composition may play an essential role in plant responses to slug and snail attack. Based on our current knowledge about host-manipulation strategies employed by pathogens and insects, we hypothesized that mollusks may excrete phytohormone-like substances into their mucus. We therefore screened locomotion mucus from thirteen molluscan herbivores for the presence of the plant defense hormones jasmonic acid (JA), salicylic acid (SA) and abscisic acid (ABA). We found that the locomotion mucus of one slug, Deroceras reticulatum, contained significant amounts of SA, a plant hormone that is known to induce resistance to pathogens and to suppress plant immunity against herbivores. None of the other slugs and snails contained SA or any other hormone in their locomotion mucus. When the mucus of D. reticulatum was applied to wounded leaves of A. thaliana, the promotor of the SA-responsive gene pathogenesis related 1 (PR1) was activated, demonstrating the potential of the mucus to regulate plant defenses. We discuss the potential ecological, agricultural and medical implications of this finding. PMID:24466122

A novel protein elicitor (SsCut) from Sclerotinia sclerotiorum induces multiple defense responses in plants.

PubMed

Zhang, Huajian; Wu, Qun; Cao, Shun; Zhao, Tongyao; Chen, Ling; Zhuang, Peitong; Zhou, Xiuhong; Gao, Zhimou

2014-11-01

In this study, we report the cloning of the SsCut gene encoding cutinase from Sclerotinia sclerotiorum. We isolated a 609-bp cDNA encoding a polypeptide of 202 amino acids with a molecular weight of 20.4 kDa. Heterologous expression of SsCut in Escherichia coli (His-SsCut) caused the formation of lesions in tobacco that closely resembled hypersensitive response lesions. Mutational analysis identified the C-terminal-half peptide and the same amino acids indispensable for both enzyme and elicitor activity. His-SsCut was caused cell death in Arabidopsis, soybean (Glycine max), oilseed rape (Brassica napus), rice (Oryza sativa), maize (Zea mays), and wheat (Triticum aestivum), indicating that both dicot and monocot species are responsive to the elicitor. Furthermore, the elicitation of tobacco was effective in the induction of the activities of hydrogen peroxide, phenylalanine ammonia-lyase, peroxides, and polyphenol oxidase. His-SsCut-treated plants exhibited enhanced resistance as indicated by a significant reduction in the number and size of S. sclerotiorum, Phytophthora sojae, and P. nicotianae lesions on leaves relative to controls. Real-time PCR results indicated that the expression of defense-related genes and genes involved in signal transduction were induced by His-SsCut. Our results demonstrate that SsCut is an elicitor that triggers defense responses in plants and will help to clarify its relationship to downstream signaling pathways that induce defense responses.

Functional analysis of MeCIPK23 and MeCBL1/9 in cassava defense response against Xanthomonas axonopodis pv. manihotis.

PubMed

Yan, Yu; He, Xinyi; Hu, Wei; Liu, Guoyin; Wang, Peng; He, Chaozu; Shi, Haitao

2018-06-01

MeCIPK23 interacts with MeCBL1/9, and they confer improved defense response, providing potential genes for further genetic breeding in cassava. Cassava (Manihot esculenta) is an important food crop in tropical area, but its production is largely affected by cassava bacterial blight. However, the information of defense-related genes in cassava is very limited. Calcium ions play essential roles in plant development and stress signaling pathways. Calcineurin B-like proteins (CBLs) and CBL-interacting protein kinases (CIPKs) are crucial components of calcium signals. In this study, systematic expression profile of 25MeCIPKs in response to Xanthomonas axonopodis pv. manihotis (Xam) infection was examined, by which seven candidate MeCIPKs were chosen for functional investigation. Through transient expression in Nicotiana benthamiana leaves, we found that six MeCIPKs (MeCIPK5, MeCIPK8, MeCIPK12, MeCIPK22, MeCIPK23 and MeCIPK24) conferred improved defense response, via regulating the transcripts of several defense-related genes. Notably, we found that MeCIPK23 interacted with MeCBL1 and MeCBL9, and overexpression of these genes conferred improved defense response. On the contrary, virus-induced gene silencing of either MeCIPK23 or MeCBL1/9 or both genes resulted in disease sensitive in cassava. To our knowledge, this is the first study identifying MeCIPK23 as well as MeCBL1 and MeCBL9 that confer enhanced defense response against Xam.

Remote sensing of future competitors: Impacts on plant defenses

PubMed Central

Izaguirre, Miriam M.; Mazza, Carlos A.; Biondini, Mariela; Baldwin, Ian T.; Ballaré, Carlos L.

2006-01-01

Far-red radiation (FR) reflected by green tissues is a key signal that plants use to detect the proximity of future competitors. Perception of increased levels of FR elicits a suite of responses collectively known as the shade-avoidance syndrome, which includes increased stem elongation, production of erect leaves, and reduced lateral branching. These responses improve the access to light for plants that occur in crowded populations. Responses to the proximity of competitors are known to affect the susceptibility to disease and predation in several organisms, including social animals. However, the impacts of warning signals of competition on the expression of defenses have not been explicitly investigated in plants. In the experiments reported here, we show that reflected FR induced a dramatic down-regulation of chemical defenses in wild tobacco (Nicotiana longiflora). FR altered the expression of several defense-related genes, inhibited the accumulation of herbivore-induced phenolic compounds, and augmented the performance of the specialist herbivore Manduca sexta. Complementary studies with tomato suggested that the effects of FR on defenses are mediated by the photoreceptor phytochrome B. The central implication of these results is that shade-intolerant species such as wild tobacco and tomato activate functional changes that affect their ability to cope with herbivore attack in response to phytochrome signals of future competition, even in the absence of real competition for resources. These findings suggest that competition overshadowed herbivory during the evolution of this group of species and add a new axis to the definition of the shade-avoidance syndrome. PMID:16632610

Arabidopsis double-stranded RNA binding protein DRB3 participates in methylation-mediated defense against geminiviruses.

PubMed

Raja, Priya; Jackel, Jamie N; Li, Sizhun; Heard, Isaac M; Bisaro, David M

2014-03-01

Arabidopsis encodes five double-stranded RNA binding (DRB) proteins. DRB1 and DRB2 are involved in microRNA (miRNA) biogenesis, while DRB4 functions in cytoplasmic posttranscriptional small interfering RNA (siRNA) pathways. DRB3 and DRB5 are not involved in double-stranded RNA (dsRNA) processing but assist in silencing transcripts targeted by DRB2-associated miRNAs. The goal of this study was to determine which, if any, of the DRB proteins might also participate in a nuclear siRNA pathway that leads to geminivirus genome methylation. Here, we demonstrate that DRB3 functions with Dicer-like 3 (DCL3) and Argonaute 4 (AGO4) in methylation-mediated antiviral defense. Plants employ repressive viral genome methylation as an epigenetic defense against geminiviruses, using an RNA-directed DNA methylation (RdDM) pathway similar to that used to suppress endogenous invasive DNAs such as transposons. Chromatin methylation inhibits virus replication and transcription, and methylation-deficient host plants are hypersusceptible to geminivirus infection. Using a panel of drb mutants, we found that drb3 plants uniquely exhibit a similar hypersensitivity and that viral genome methylation is substantially reduced in drb3 compared to wild-type plants. In addition, like dcl3 and ago4 mutants, drb3 plants fail to recover from infection and cannot accomplish the viral genome hypermethylation that is invariably observed in asymptomatic, recovered tissues. Small RNA analysis, bimolecular fluorescence complementation, and coimmunoprecipitation experiments show that DRB3 acts downstream of siRNA biogenesis and suggest that it associates with DCL3 and AGO4 in distinct subnuclear compartments. These studies reveal that in addition to its previously established role in the miRNA pathway, DRB3 also functions in antiviral RdDM. Plants use RNA-directed DNA methylation (RdDM) as an epigenetic defense against geminiviruses. RNA silencing pathways in Arabidopsis include five double-stranded RNA

Gaseous 3-pentanol primes plant immunity against a bacterial speck pathogen, Pseudomonas syringae pv. tomato via salicylic acid and jasmonic acid-dependent signaling pathways in Arabidopsis.

PubMed

Song, Geun C; Choi, Hye K; Ryu, Choong-Min

2015-01-01

3-Pentanol is an active organic compound produced by plants and is a component of emitted insect sex pheromones. A previous study reported that drench application of 3-pentanol elicited plant immunity against microbial pathogens and an insect pest in crop plants. Here, we evaluated whether 3-pentanol and the derivatives 1-pentanol and 2-pentanol induced plant systemic resistance using the in vitro I-plate system. Exposure of Arabidopsis seedlings to 10 μM and 100 nM 3-pentanol evaporate elicited an immune response to Pseudomonas syringae pv. tomato DC3000. We performed quantitative real-time PCR to investigate the 3-pentanol-mediated Arabidopsis immune responses by determining Pathogenesis-Related (PR) gene expression levels associated with defense signaling through salicylic acid (SA), jasmonic acid (JA), and ethylene signaling pathways. The results show that exposure to 3-pentanol and subsequent pathogen challenge upregulated PDF1.2 and PR1 expression. Selected Arabidopsis mutants confirmed that the 3-pentanol-mediated immune response involved SA and JA signaling pathways and the NPR1 gene. Taken together, this study indicates that gaseous 3-pentanol triggers induced resistance in Arabidopsis by priming SA and JA signaling pathways. To our knowledge, this is the first report that a volatile compound of an insect sex pheromone triggers plant systemic resistance against a bacterial pathogen.

L-Arginine supplementation improves antioxidant defenses through L-arginine/nitric oxide pathways in exercised rats.

PubMed

Shan, Lingling; Wang, Bin; Gao, Guizhen; Cao, Wengen; Zhang, Yunkun

2013-10-15

l-Arginine (l-Arg) supplementation has been shown to enhance physical exercise capacity and delay onset of fatigue. This work investigated the potential beneficial mechanism(s) of l-Arg supplementation by examining its effect on the cellular oxidative and nitrosative stress pathways in the exercised rats. Forty-eight rats were randomly divided into six groups: sedentary control; sedentary control with l-Arg treatment; endurance training (daily swimming training for 8 wk) control; endurance training with l-Arg treatment; an exhaustive exercise (one time swimming to fatigue) control; and an exhaustive exercise with l-Arg treatment. l-Arg (500 mg/kg body wt) or saline was given to rats by intragastric administration 1 h before the endurance training and the exhaustive swimming test. Expression levels and activities of the l-Arg/nitric oxide (NO) pathway components and parameters of the oxidative stress and antioxidant defense capacity were investigated in l-Arg-treated and control rats. The result show that the l-Arg supplementation completely reversed the exercise-induced activation of NO synthase and superoxide dismutase, increased l-Arg transport capacity, and increased NO and anti-superoxide anion levels. These data demonstrate that l-Arg supplementation effectively reduces the exercise-induced imbalance between oxidative stress and antioxidant defense capacity, and this modulation is likely mediated through the l-Arg/NO pathways. The findings of this study improved our understanding of how l-Arg supplementation prevents elevations of reactive oxygen species and favorably enhances the antioxidant defense capacity during physical exercise.

Lignin metabolism involves Botrytis cinerea BcGs1- induced defense response in tomato.

PubMed

Yang, Chenyu; Liang, Yingbo; Qiu, Dewen; Zeng, Hongmei; Yuan, Jingjing; Yang, Xiufen

2018-06-04

BcGs1, a cell wall-degrading enzyme (CWDE), was originally derived from Botrytis cinerea. Our previous study revealed that BcGs1 could trigger defense responses and protect plants against various pathogens. We researched the defense response mechanism underlying this BcGs1 elicitation in tomato. We revealed that the two domains were required for BcGs1's full necrosis activity. According to analysis and quantitative real-time PCR of the up-regulated proteins and genes filtered by iTRAQ-based quantitative proteome approach, oxidative metabolism and phenylpropanoid metabolism were speculated to be involved in BcGs1-triggered defense response in tomato. Furthermore, experimental evidence showed that BcGs1 triggered reactive oxygen species (ROS) burst and increased the level of phenylalanine-ammonia lyase (PAL) and peroxidase (POD) enzyme activity, as well as lignin accumulation. Moreover, histochemical analysis revealed that infiltration of BcGs1 in tomato leaves exhibited cell wall thickening compared with untreated plants. The results suggested that BcGs1 activated the basal defense response included lignin metabolism contributed to BcGs1-induced resistance to Botrytis. cinerea infection in tomato.

The RNA Silencing Enzyme RNA Polymerase V Is Required for Plant Immunity

PubMed Central

López, Ana; Ramírez, Vicente; García-Andrade, Javier; Flors, Victor; Vera, Pablo

2011-01-01

RNA–directed DNA methylation (RdDM) is an epigenetic control mechanism driven by small interfering RNAs (siRNAs) that influence gene function. In plants, little is known of the involvement of the RdDM pathway in regulating traits related to immune responses. In a genetic screen designed to reveal factors regulating immunity in Arabidopsis thaliana, we identified NRPD2 as the OVEREXPRESSOR OF CATIONIC PEROXIDASE 1 (OCP1). NRPD2 encodes the second largest subunit of the plant-specific RNA Polymerases IV and V (Pol IV and Pol V), which are crucial for the RdDM pathway. The ocp1 and nrpd2 mutants showed increases in disease susceptibility when confronted with the necrotrophic fungal pathogens Botrytis cinerea and Plectosphaerella cucumerina. Studies were extended to other mutants affected in different steps of the RdDM pathway, such as nrpd1, nrpe1, ago4, drd1, rdr2, and drm1drm2 mutants. Our results indicate that all the mutants studied, with the exception of nrpd1, phenocopy the nrpd2 mutants; and they suggest that, while Pol V complex is required for plant immunity, Pol IV appears dispensable. Moreover, Pol V defective mutants, but not Pol IV mutants, show enhanced disease resistance towards the bacterial pathogen Pseudomonas syringae DC3000. Interestingly, salicylic acid (SA)–mediated defenses effective against PsDC3000 are enhanced in Pol V defective mutants, whereas jasmonic acid (JA)–mediated defenses that protect against fungi are reduced. Chromatin immunoprecipitation analysis revealed that, through differential histone modifications, SA–related defense genes are poised for enhanced activation in Pol V defective mutants and provide clues for understanding the regulation of gene priming during defense. Our results highlight the importance of epigenetic control as an additional layer of complexity in the regulation of plant immunity and point towards multiple components of the RdDM pathway being involved in plant immunity based on genetic evidence, but

The RNA silencing enzyme RNA polymerase v is required for plant immunity.

PubMed

López, Ana; Ramírez, Vicente; García-Andrade, Javier; Flors, Victor; Vera, Pablo

2011-12-01

RNA-directed DNA methylation (RdDM) is an epigenetic control mechanism driven by small interfering RNAs (siRNAs) that influence gene function. In plants, little is known of the involvement of the RdDM pathway in regulating traits related to immune responses. In a genetic screen designed to reveal factors regulating immunity in Arabidopsis thaliana, we identified NRPD2 as the OVEREXPRESSOR OF CATIONIC PEROXIDASE 1 (OCP1). NRPD2 encodes the second largest subunit of the plant-specific RNA Polymerases IV and V (Pol IV and Pol V), which are crucial for the RdDM pathway. The ocp1 and nrpd2 mutants showed increases in disease susceptibility when confronted with the necrotrophic fungal pathogens Botrytis cinerea and Plectosphaerella cucumerina. Studies were extended to other mutants affected in different steps of the RdDM pathway, such as nrpd1, nrpe1, ago4, drd1, rdr2, and drm1drm2 mutants. Our results indicate that all the mutants studied, with the exception of nrpd1, phenocopy the nrpd2 mutants; and they suggest that, while Pol V complex is required for plant immunity, Pol IV appears dispensable. Moreover, Pol V defective mutants, but not Pol IV mutants, show enhanced disease resistance towards the bacterial pathogen Pseudomonas syringae DC3000. Interestingly, salicylic acid (SA)-mediated defenses effective against PsDC3000 are enhanced in Pol V defective mutants, whereas jasmonic acid (JA)-mediated defenses that protect against fungi are reduced. Chromatin immunoprecipitation analysis revealed that, through differential histone modifications, SA-related defense genes are poised for enhanced activation in Pol V defective mutants and provide clues for understanding the regulation of gene priming during defense. Our results highlight the importance of epigenetic control as an additional layer of complexity in the regulation of plant immunity and point towards multiple components of the RdDM pathway being involved in plant immunity based on genetic evidence, but whether

OsWRKY53, a versatile switch in regulating herbivore-induced defense responses in rice

PubMed Central

Hu, Lingfei; Ye, Meng; Li, Ran; Lou, Yonggen

2016-01-01

ABSTRACT WRKY proteins, which belong to a large family of plant-specific transcription factors, play important roles in plant defenses against pathogens and herbivores by regulating defense-related signaling pathways. Recently, a rice WRKY transcription factor OsWRKY53 has been reported to function as a negative feedback modulator of OsMPK3/OsMPK6 and thereby to control the size of the investment a rice plant makes to defend against a chewing herbivore, the striped stem borer Chilo suppressalis. We investigated the performance of a piecing-sucking herbivore, the brown planthopper (BPH) Nilaparvata lugens, on transgenic plants that silence or overexpress OsWRKY53, and found that OsWRKY53 activates rice defenses against BPH by activating an H2O2 burst and suppressing ethylene biosynthesis. These findings suggest that OsWRKY53 functions not only as a regulator of plants' investment in specific defenses, but also as a switch to initiate new defenses against other stresses, highlighting the versatility and importance of OsWRKY53 in herbivore-induced plant defenses. PMID:27031005

Mst1 shuts off cytosolic antiviral defense through IRF3 phosphorylation

PubMed Central

Meng, Fansen; Zhou, Ruyuan; Wu, Shiying; Zhang, Qian; Jin, Qiuheng; Zhou, Yao; Plouffe, Steven W.; Liu, Shengduo; Song, Hai; Xia, Zongping; Zhao, Bin; Ye, Sheng; Feng, Xin-Hua; Guan, Kun-Liang; Zou, Jian

2016-01-01

Cytosolic RNA/DNA sensing elicits primary defense against viral pathogens. Interferon regulatory factor 3 (IRF3), a key signal mediator/transcriptional factor of the antiviral-sensing pathway, is indispensible for interferon production and antiviral defense. However, how the status of IRF3 activation is controlled remains elusive. Through a functional screen of the human kinome, we found that mammalian sterile 20-like kinase 1 (Mst1), but not Mst2, profoundly inhibited cytosolic nucleic acid sensing. Mst1 associated with IRF3 and directly phosphorylated IRF3 at Thr75 and Thr253. This Mst1-mediated phosphorylation abolished activated IRF3 homodimerization, its occupancy on chromatin, and subsequent IRF3-mediated transcriptional responses. In addition, Mst1 also impeded virus-induced activation of TANK-binding kinase 1 (TBK1), further attenuating IRF3 activation. As a result, Mst1 depletion or ablation enabled an enhanced antiviral response and defense in cells and mice. Therefore, the identification of Mst1 as a novel physiological negative regulator of IRF3 activation provides mechanistic insights into innate antiviral defense and potential antiviral prevention strategies. PMID:27125670

The growth-defense trade-off and habitat specialization by plants in Amazonian forests.

PubMed

Fine, Paul V A; Miller, Zachariah J; Mesones, Italo; Irazuzta, Sebastian; Appel, Heidi M; Stevens, M Henry H; Sääksjärvi, Ilari; Schultz, Jack C; Coley, Phyllis D

2006-07-01

Tropical forests include a diversity of habitats, which has led to specialization in plants. Near Iquitos, in the Peruvian Amazon, nutrient-rich clay forests surround nutrient-poor white-sand forests, each harboring a unique composition of habitat specialist trees. We tested the hypothesis that the combination of impoverished soils and herbivory creates strong natural selection for plant defenses in white-sand forest, while rapid growth is favored in clay forests. Recently, we reported evidence from a reciprocal-transplant experiment that manipulated the presence of herbivores and involved 20 species from six genera, including phylogenetically independent pairs of closely related white-sand and clay specialists. When protected from herbivores, clay specialists exhibited faster growth rates than white-sand specialists in both habitats. But, when unprotected, white-sand specialists outperformed clay specialists in white-sand habitat, and clay specialists outperformed white-sand specialists in clay habitat. Here we test further the hypothesis that the growth defense trade-off contributes to habitat specialization by comparing patterns of growth, herbivory, and defensive traits in these same six genera of white-sand and clay specialists. While the probability of herbivore attack did not differ between the two habitats, an artificial defoliation experiment showed that the impact of herbivory on plant mortality was significantly greater in white-sand forests. We quantified the amount of terpenes, phenolics, leaf toughness, and available foliar protein for the plants in the experiment. Different genera invested in different defensive strategies, and we found strong evidence for phylogenetic constraint in defense type. Overall, however, we found significantly higher total defense investment for white-sand specialists, relative to their clay specialist congeners. Furthermore, herbivore resistance consistently exhibited a significant trade-off against growth rate in each of

Costs of induced defenses for the invasive plant houndstongue (Cynoglossum officinale L.) and the potential importance for weed biocontrol

Treesearch

Justin B. Runyon; Jennifer L. Birdsall

2016-01-01

Inducible plant defenses - those produced in response to herbivore feeding - are thought to have evolved as a cost-saving tactic that allows plants to enact defenses only when needed. The costs of defense can be significant, and loss of plant fitness due to commitment of resources to induced defenses could affect plant populations and play a role in...

The importance of ecological costs for the evolution of plant defense against herbivory.

PubMed

van Velzen, Ellen; Etienne, Rampal S

2015-05-07

Plant defense against herbivory comes at a cost, which can be either direct (reducing resources available for growth and reproduction) or indirect (through reducing ecological performance, for example intraspecific competitiveness). While direct costs have been well studied in theoretical models, ecological costs have received almost no attention. In this study we compare models with a direct trade-off (reduced growth rate) to models with an ecological trade-off (reduced competitive ability), using a combination of adaptive dynamics and simulations. In addition, we study the dependence of the level of defense that can evolve on the type of defense (directly by reducing consumption, or indirectly by inducing herbivore mortality (toxicity)), and on the type of herbivore against which the plant is defending itself (generalists or specialists). We find three major results: First, for both direct and ecological costs, defense only evolves if the benefit to the plant is direct (through reducing consumption). Second, the type of cost has a major effect on the evolutionary dynamics: direct costs always lead to a single optimal strategy against herbivores, but ecological costs can lead to branching and the coexistence of non-defending and defending plants; however, coexistence is only possible when defending against generalist herbivores. Finally, we find that fast-growing plants invest less than slow-growing plants when defending against generalist herbivores, as predicted by the Resource Availability Hypothesis, but invest more than slow-growing plants when defending against specialists. Our results clearly show that assumptions about ecological interactions are crucial for understanding the evolution of defense against herbivores. Copyright © 2015 Elsevier Ltd. All rights reserved.

Plant Lectins: Wheat Defense Strategy Against Hessian Fly

USDA-ARS?s Scientific Manuscript database

Plants produce a variety of defense proteins, including lectins in response to attack by phytophagous insects. Ultrastructural studies reveal that binding to insect gut structures and resistance to proteolytic degradation by insect digestive enzymes are the two main prerequisites for the lectins to...

The SAL-PAP Chloroplast Retrograde Pathway Contributes to Plant Immunity by Regulating Glucosinolate Pathway and Phytohormone Signaling.

PubMed

Ishiga, Yasuhiro; Watanabe, Mutsumi; Ishiga, Takako; Tohge, Takayuki; Matsuura, Takakazu; Ikeda, Yoko; Hoefgen, Rainer; Fernie, Alisdair R; Mysore, Kirankumar S

2017-10-01

Chloroplasts have a crucial role in plant immunity against pathogens. Increasing evidence suggests that phytopathogens target chloroplast homeostasis as a pathogenicity mechanism. In order to regulate the performance of chloroplasts under stress conditions, chloroplasts produce retrograde signals to alter nuclear gene expression. Many signals for the chloroplast retrograde pathway have been identified, including chlorophyll intermediates, reactive oxygen species, and metabolic retrograde signals. Although there is a reasonably good understanding of chloroplast retrograde signaling in plant immunity, some signals are not well-understood. In order to understand the role of chloroplast retrograde signaling in plant immunity, we investigated Arabidopsis chloroplast retrograde signaling mutants in response to pathogen inoculation. sal1 mutants (fry1-2 and alx8) responsible for the SAL1-PAP retrograde signaling pathway showed enhanced disease symptoms not only to the hemibiotrophic pathogen Pseudomonas syringae pv. tomato DC3000 but, also, to the necrotrophic pathogen Pectobacterium carotovorum subsp. carotovorum EC1. Glucosinolate profiles demonstrated the reduced accumulation of aliphatic glucosinolates in the fry1-2 and alx8 mutants compared with the wild-type Col-0 in response to DC3000 infection. In addition, quantification of multiple phytohormones and analyses of their gene expression profiles revealed that both the salicylic acid (SA)- and jasmonic acid (JA)-mediated signaling pathways were down-regulated in the fry1-2 and alx8 mutants. These results suggest that the SAL1-PAP chloroplast retrograde pathway is involved in plant immunity by regulating the SA- and JA-mediated signaling pathways.

Large-Scale Evolutionary Analysis of Genes and Supergene Clusters from Terpenoid Modular Pathways Provides Insights into Metabolic Diversification in Flowering Plants

PubMed Central

Hofberger, Johannes A.; Ramirez, Aldana M.; van den Bergh, Erik; Zhu, Xinguang; Bouwmeester, Harro J.; Schuurink, Robert C.; Schranz, M. Eric

2015-01-01

An important component of plant evolution is the plethora of pathways producing more than 200,000 biochemically diverse specialized metabolites with pharmacological, nutritional and ecological significance. To unravel dynamics underlying metabolic diversification, it is critical to determine lineage-specific gene family expansion in a phylogenomics framework. However, robust functional annotation is often only available for core enzymes catalyzing committed reaction steps within few model systems. In a genome informatics approach, we extracted information from early-draft gene-space assemblies and non-redundant transcriptomes to identify protein families involved in isoprenoid biosynthesis. Isoprenoids comprise terpenoids with various roles in plant-environment interaction, such as pollinator attraction or pathogen defense. Combining lines of evidence provided by synteny, sequence homology and Hidden-Markov-Modelling, we screened 17 genomes including 12 major crops and found evidence for 1,904 proteins associated with terpenoid biosynthesis. Our terpenoid genes set contains evidence for 840 core terpene-synthases and 338 triterpene-specific synthases. We further identified 190 prenyltransferases, 39 isopentenyl-diphosphate isomerases as well as 278 and 219 proteins involved in mevalonate and methylerithrol pathways, respectively. Assessing the impact of gene and genome duplication to lineage-specific terpenoid pathway expansion, we illustrated key events underlying terpenoid metabolic diversification within 250 million years of flowering plant radiation. By quantifying Angiosperm-wide versatility and phylogenetic relationships of pleiotropic gene families in terpenoid modular pathways, our analysis offers significant insight into evolutionary dynamics underlying diversification of plant secondary metabolism. Furthermore, our data provide a blueprint for future efforts to identify and more rapidly clone terpenoid biosynthetic genes from any plant species. PMID

Nuclear jasmonate and salicylate signaling and crosstalk in defense against pathogens

PubMed Central

Gimenez-Ibanez, Selena; Solano, Roberto

2013-01-01

An extraordinary progress has been made over the last two decades on understanding the components and mechanisms governing plant innate immunity. After detection of a pathogen, effective plant resistance depends on the activation of a complex signaling network integrated by small signaling molecules and hormonal pathways, and the balance of these hormone systems determines resistance to particular pathogens. The discovery of new components of hormonal signaling pathways, including plant nuclear hormone receptors, is providing a picture of complex crosstalk and induced hormonal changes that modulate disease and resistance through several protein families that perceive hormones within the nucleus and lead to massive gene induction responses often achieved by de-repression. This review highlights recent advances in our understanding of positive and negative regulators of these hormones signaling pathways that are crucial regulatory targets of hormonal crosstalk in disease and defense. We focus on the most recent discoveries on the jasmonate and salicylate pathway components that explain their crosstalk with other hormonal pathways in the nucleus. We discuss how these components fine-tune defense responses to build a robust plant immune system against a great number of different microbes and, finally, we summarize recent discoveries on specific nuclear hormonal manipulation by microbes which exemplify the ingenious ways by which pathogens can take control over the plant’s hormone signaling network to promote disease. PMID:23577014

Adaptation Mechanisms in the Evolution of Moss Defenses to Microbes

PubMed Central

Ponce de León, Inés; Montesano, Marcos

2017-01-01

Bryophytes, including mosses, liverworts and hornworts are early land plants that have evolved key adaptation mechanisms to cope with abiotic stresses and microorganisms. Microbial symbioses facilitated plant colonization of land by enhancing nutrient uptake leading to improved plant growth and fitness. In addition, early land plants acquired novel defense mechanisms to protect plant tissues from pre-existing microbial pathogens. Due to its evolutionary stage linking unicellular green algae to vascular plants, the non-vascular moss Physcomitrella patens is an interesting organism to explore the adaptation mechanisms developed in the evolution of plant defenses to microbes. Cellular and biochemical approaches, gene expression profiles, and functional analysis of genes by targeted gene disruption have revealed that several defense mechanisms against microbial pathogens are conserved between mosses and flowering plants. P. patens perceives pathogen associated molecular patterns by plasma membrane receptor(s) and transduces the signal through a MAP kinase (MAPK) cascade leading to the activation of cell wall associated defenses and expression of genes that encode proteins with different roles in plant resistance. After pathogen assault, P. patens also activates the production of ROS, induces a HR-like reaction and increases levels of some hormones. Furthermore, alternative metabolic pathways are present in P. patens leading to the production of a distinct metabolic scenario than flowering plants that could contribute to defense. P. patens has acquired genes by horizontal transfer from prokaryotes and fungi, and some of them could represent adaptive benefits for resistance to biotic stress. In this review, the current knowledge related to the evolution of plant defense responses against pathogens will be discussed, focusing on the latest advances made in the model plant P. patens. PMID:28360923

Trichoderma harzianum enhances tomato indirect defense against aphids.

PubMed

Coppola, Mariangela; Cascone, Pasquale; Chiusano, Maria Luisa; Colantuono, Chiara; Lorito, Matteo; Pennacchio, Francesco; Rao, Rosa; Woo, Sheridan Lois; Guerrieri, Emilio; Digilio, Maria Cristina

2017-12-01

Many fungal root symbionts of the genus Trichoderma are well-known for their beneficial effects on agronomic performance and protection against plant pathogens; moreover, they may enhance protection from insect pests, by triggering plant resistance mechanisms. Defense barriers against insects are induced by the activation of metabolic pathways involved in the production of defense-related plant compounds, either directly active against herbivore insects, or exerting an indirect effect, by increasing the attraction of herbivore natural enemies. In a model system composed of the tomato plant, the aphid Macrosiphum euphorbiae and the parasitoid Aphidius ervi, plant metabolic changes induced by Trichoderma harzianum and their effects on higher trophic levels have been assessed. T. harzianum T22 treatments induce a primed state that upon aphid attacks leads to an increased attraction of aphid parasitoids, mediated by the enhanced production of volatile organic compounds (VOCs) that are known to induce Aphidius ervi flight. Transcriptome sequencing of T22-treated plants infested by aphids showed a remarkable upregulation of genes involved in terpenoids biosynthesis and salicylic acid pathway, which are consistent with the observed flight response of A. ervi and the VOC bouquet profile underlying this behavioral response. © 2017 Institute of Zoology, Chinese Academy of Sciences.

Arabidopsis thaliana defense response to the ochratoxin A-producing strain (Aspergillus ochraceus 3.4412).

PubMed

Hao, Junran; Wu, Weihong; Wang, Yan; Yang, Zhuojun; Liu, Yang; Lv, Yangjun; Zhai, Yanan; Yang, Jing; Liang, Zhihong; Huang, Kunlun; Xu, Wentao

2015-05-01

OTA-producing strain Aspergillus ochraceus induced necrotic lesions, ROS accumulation and defense responses in Arabidopsis . Primary metabolic and defense-related proteins changed in proteomics. Ascorbate-glutathione cycle and voltage-dependent anion-selective channel proteins fluctuated. Mycotoxigenic fungi, as widespread contaminants by synthesizing mycotoxins in pre-/post-harvest infected plants and even stored commercial cereals, could usually induce plant-fungi defense responses. Notably, ochratoxin A (OTA) is a nephrotoxic, hepatotoxic, teratogenic, immunotoxic and phytotoxic mycotoxin. Herein, defense responses of model system Arabidopsis thaliana detached leaves to infection of Aspergillus ochraceus 3.4412, an OTA high-producing strain, were studied from physiological, proteomic and transcriptional perspectives. During the first 72 h after inoculation (hai), the newly formed hypersensitive responses-like lesions, decreased chlorophyll content, accumulated reactive oxygen species and upregulated defense genes expressions indicated the defense response was induced in the leaves with the possible earlier motivated jasmonic acid/ethylene signaling pathways and the later salicylic acid-related pathway. Moreover, proteomics using two-dimensional gel electrophoresis 72 hai showed 16 spots with significantly changed abundance and 13 spots corresponding to 12 unique proteins were successfully identified by MALDI-TOF/TOF MS/MS. Of these, six proteins were involved in basic metabolism and four in defense-related processes, which included glutathione-S-transferase F7, voltage-dependent anion-selective channel protein 3 (VDAC-3), osmotin-like protein OSM34 and blue copper-binding protein. Verified from proteomic and/or transcriptional perspectives, it is concluded that the primary metabolic pathways were suppressed with the ascorbate-glutathione cycle fluctuated in response to A. ochraceus and the modulation of VDACs suggested the possibility of structural damage and

Gramene 2016: comparative plant genomics and pathway resources

PubMed Central

Tello-Ruiz, Marcela K.; Stein, Joshua; Wei, Sharon; Preece, Justin; Olson, Andrew; Naithani, Sushma; Amarasinghe, Vindhya; Dharmawardhana, Palitha; Jiao, Yinping; Mulvaney, Joseph; Kumari, Sunita; Chougule, Kapeel; Elser, Justin; Wang, Bo; Thomason, James; Bolser, Daniel M.; Kerhornou, Arnaud; Walts, Brandon; Fonseca, Nuno A.; Huerta, Laura; Keays, Maria; Tang, Y. Amy; Parkinson, Helen; Fabregat, Antonio; McKay, Sheldon; Weiser, Joel; D'Eustachio, Peter; Stein, Lincoln; Petryszak, Robert; Kersey, Paul J.; Jaiswal, Pankaj; Ware, Doreen

2016-01-01

Gramene (http://www.gramene.org) is an online resource for comparative functional genomics in crops and model plant species. Its two main frameworks are genomes (collaboration with Ensembl Plants) and pathways (The Plant Reactome and archival BioCyc databases). Since our last NAR update, the database website adopted a new Drupal management platform. The genomes section features 39 fully assembled reference genomes that are integrated using ontology-based annotation and comparative analyses, and accessed through both visual and programmatic interfaces. Additional community data, such as genetic variation, expression and methylation, are also mapped for a subset of genomes. The Plant Reactome pathway portal (http://plantreactome.gramene.org) provides a reference resource for analyzing plant metabolic and regulatory pathways. In addition to ∼200 curated rice reference pathways, the portal hosts gene homology-based pathway projections for 33 plant species. Both the genome and pathway browsers interface with the EMBL-EBI's Expression Atlas to enable the projection of baseline and differential expression data from curated expression studies in plants. Gramene's archive website (http://archive.gramene.org) continues to provide previously reported resources on comparative maps, markers and QTL. To further aid our users, we have also introduced a live monthly educational webinar series and a Gramene YouTube channel carrying video tutorials. PMID:26553803

Carnivore Attractant or Plant Elicitor? Multifunctional Roles of Methyl Salicylate Lures in Tomato Defense.

PubMed

Rowen, Elizabeth; Gutensohn, Michael; Dudareva, Natalia; Kaplan, Ian

2017-06-01

Synthetic plant volatile lures attract natural enemies, but may have non-target effects due to the multifunctional nature of volatile signals. For example, methyl salicylate (MeSA) is used to attract predators, yet also serves as a signaling hormone involved in plant pathogen defense. We investigated the consequences of deploying MeSA lures to attract predators for tomato (Solanum lycopersicum) defense against herbivores. To understand the spatial distribution of the lure's effect, we exposed tomatoes in the field to MeSA along a linear distance gradient and induced defenses by simulating feeding by hornworm caterpillars in a fully crossed factorial design (+/- MeSA, +/- herbivory). Subsequently, we analyzed activity of several defensive proteins (protease inhibitors, polyphenol oxidase, peroxidase), development of hornworm larvae (Manduca sexta), growth of fungal pathogens (Cladosporium and Alternaria), and attractiveness to herbivores and predators. Overall, MeSA-exposed plants were more resistant to both insects and pathogens. Secondary pathogen infection was reduced by 25% in MeSA exposed plants, possibly due to elevated polyphenol oxidase activity. Interestingly, we found that lures affected plant pathogen defenses equivalently across all distances (up to 4 m away) indicating that horizontal diffusion of a synthetic volatile may be greater than previously assumed. While thrips avoided colonizing hornworm- damaged tomato plants, this induced resistance was not observed upon pre-exposure to MeSA, suggesting that MeSA suppresses the repellant effect induced by herbivory. Thus, using MeSA lures in biological control may inadvertently protect crops from pathogens, but has mixed effects on plant resistance to insect herbivores.

Coordinated Actions of Glyoxalase and Antioxidant Defense Systems in Conferring Abiotic Stress Tolerance in Plants

PubMed Central

Hasanuzzaman, Mirza; Nahar, Kamrun; Hossain, Md. Shahadat; Mahmud, Jubayer Al; Rahman, Anisur; Inafuku, Masashi; Oku, Hirosuke; Fujita, Masayuki

2017-01-01

Being sessile organisms, plants are frequently exposed to various environmental stresses that cause several physiological disorders and even death. Oxidative stress is one of the common consequences of abiotic stress in plants, which is caused by excess generation of reactive oxygen species (ROS). Sometimes ROS production exceeds the capacity of antioxidant defense systems, which leads to oxidative stress. In line with ROS, plants also produce a high amount of methylglyoxal (MG), which is an α-oxoaldehyde compound, highly reactive, cytotoxic, and produced via different enzymatic and non-enzymatic reactions. This MG can impair cells or cell components and can even destroy DNA or cause mutation. Under stress conditions, MG concentration in plants can be increased 2- to 6-fold compared with normal conditions depending on the plant species. However, plants have a system developed to detoxify this MG consisting of two major enzymes: glyoxalase I (Gly I) and glyoxalase II (Gly II), and hence known as the glyoxalase system. Recently, a novel glyoxalase enzyme, named glyoxalase III (Gly III), has been detected in plants, providing a shorter pathway for MG detoxification, which is also a signpost in the research of abiotic stress tolerance. Glutathione (GSH) acts as a co-factor for this system. Therefore, this system not only detoxifies MG but also plays a role in maintaining GSH homeostasis and subsequent ROS detoxification. Upregulation of both Gly I and Gly II as well as their overexpression in plant species showed enhanced tolerance to various abiotic stresses including salinity, drought, metal toxicity, and extreme temperature. In the past few decades, a considerable amount of reports have indicated that both antioxidant defense and glyoxalase systems have strong interactions in conferring abiotic stress tolerance in plants through the detoxification of ROS and MG. In this review, we will focus on the mechanisms of these interactions and the coordinated action of

Leaf-mining by Phyllonorycter blancardella reprograms the host-leaf transcriptome to modulate phytohormones associated with nutrient mobilization and plant defense.

PubMed

Zhang, Hui; Dugé de Bernonville, Thomas; Body, Mélanie; Glevarec, Gaëlle; Reichelt, Michael; Unsicker, Sybille; Bruneau, Maryline; Renou, Jean-Pierre; Huguet, Elisabeth; Dubreuil, Géraldine; Giron, David

2016-01-01

Phytohormones have long been hypothesized to play a key role in the interactions between plant-manipulating organisms and their host-plants such as insect-plant interactions that lead to gall or 'green-islands' induction. However, mechanistic understanding of how phytohormones operate in these plant reconfigurations is lacking due to limited information on the molecular and biochemical phytohormonal modulation following attack by plant-manipulating insects. In an attempt to fill this gap, the present study provides an extensive characterization of how the leaf-miner Phyllonorycter blancardella modulates the major phytohormones and the transcriptional activity of plant cells in leaves of Malus domestica. We show here, that cytokinins strongly accumulate in mined tissues despite a weak expression of plant cytokinin-related genes. Leaf-mining is also associated with enhanced biosynthesis of jasmonic acid precursors but not the active form, a weak alteration of the salicylic acid pathway and a clear inhibition of the abscisic acid pathway. Our study consolidates previous results suggesting that insects may produce and deliver cytokinins to the plant as a strategy to manipulate the physiology of the leaf to create a favorable nutritional environment. We also demonstrate that leaf-mining by P. blancardella leads to a strong reprogramming of the plant phytohormonal balance associated with increased nutrient mobilization, inhibition of leaf senescence and mitigation of plant direct and indirect defense. Copyright © 2015 Elsevier Ltd. All rights reserved.

Microbial pathogens trigger host DNA double-strand breaks whose abundance is reduced by plant defense responses.

PubMed

Song, Junqi; Bent, Andrew F

2014-04-01

Immune responses and DNA damage repair are two fundamental processes that have been characterized extensively, but the links between them remain largely unknown. We report that multiple bacterial, fungal and oomycete plant pathogen species induce double-strand breaks (DSBs) in host plant DNA. DNA damage detected by histone γ-H2AX abundance or DNA comet assays arose hours before the disease-associated necrosis caused by virulent Pseudomonas syringae pv. tomato. Necrosis-inducing paraquat did not cause detectable DSBs at similar stages after application. Non-pathogenic E. coli and Pseudomonas fluorescens bacteria also did not induce DSBs. Elevation of reactive oxygen species (ROS) is common during plant immune responses, ROS are known DNA damaging agents, and the infection-induced host ROS burst has been implicated as a cause of host DNA damage in animal studies. However, we found that DSB formation in Arabidopsis in response to P. syringae infection still occurs in the absence of the infection-associated oxidative burst mediated by AtrbohD and AtrbohF. Plant MAMP receptor stimulation or application of defense-activating salicylic acid or jasmonic acid failed to induce a detectable level of DSBs in the absence of introduced pathogens, further suggesting that pathogen activities beyond host defense activation cause infection-induced DNA damage. The abundance of infection-induced DSBs was reduced by salicylic acid and NPR1-mediated defenses, and by certain R gene-mediated defenses. Infection-induced formation of γ-H2AX still occurred in Arabidopsis atr/atm double mutants, suggesting the presence of an alternative mediator of pathogen-induced H2AX phosphorylation. In summary, pathogenic microorganisms can induce plant DNA damage. Plant defense mechanisms help to suppress rather than promote this damage, thereby contributing to the maintenance of genome integrity in somatic tissues.

Cry1Ac production is costly for native plants attacked by non-Cry1Ac-targeted herbivores in the field.

PubMed

McGale, Erica; Diezel, Celia; Schuman, Meredith C; Baldwin, Ian T

2018-05-13

Plants are the primary producers in most terrestrial ecosystems and have complex defense systems to protect their produce. Defense-deficient, high-yielding agricultural monocultures attract abundant nonhuman consumers, but are alternatively defended through pesticide application and genetic engineering to produce insecticidal proteins such as Cry1Ac (Bacillus thuringiensis). These approaches alter the balance between yield protection and maximization but have been poorly contextualized to known yield-defense trade-offs in wild plants. The native plant Nicotiana attenuata was used to compare yield benefits of plants transformed to be defenseless to those with a full suite of naturally evolved defenses, or additionally transformed to ectopically produce Cry1Ac. An insecticide treatment allowed us to examine yield under different herbivore loads in N. attenuata's native habitat. Cry1Ac, herbivore damage, and growth parameters were monitored throughout the season. Biomass and reproductive correlates were measured at season end. Non-Cry1Ac-targeted herbivores dominated on noninsecticide-treated plants, and increased the yield drag of Cry1Ac-producing plants in comparison with endogenously defended or undefended plants. Insecticide-sprayed Cry1Ac-producing plants lagged less in stalk height, shoot biomass, and flower production. In direct comparison with the endogenous defenses of a native plant, Cry1Ac production did not provide yield benefits for plants under observed herbivore loads in a field study. © 2018 The Authors New Phytologist © 2018 New Phytologist Trust.

Multitasking antimicrobial peptides, plant development, and host defense against biotic/abiotic stress

USDA-ARS?s Scientific Manuscript database

Crop losses due to pathogens are a major threat to global food security. Plants employ a multilayer defense system against pathogens including use of physical barriers (cell wall), induction of hypersensitive defense response (HR), resistance (R) proteins, and synthesis of antimicrobial peptides (AM...

Biosynthetic Pathway and Metabolic Engineering of Plant Dihydrochalcones.

PubMed

Ibdah, Mwafaq; Martens, Stefan; Gang, David R

2018-03-14

Dihydrochalcones are plant natural products containing the phenylpropanoid backbone and derived from the plant-specific phenylpropanoid pathway. Dihydrochalcone compounds are important in plant growth and response to stresses and, thus, can have large impacts on agricultural activity. In recent years, these compounds have also received increased attention from the biomedical community for their potential as anticancer treatments and other benefits for human health. However, they are typically produced at relatively low levels in plants. Therefore, an attractive alternative is to express the plant biosynthetic pathway genes in microbial hosts and to engineer the metabolic pathway/host to improve the production of these metabolites. In the present review, we discuss in detail the functions of genes and enzymes involved in the biosynthetic pathway of the dihydrochalcones and the recent strategies and achievements used in the reconstruction of multi-enzyme pathways in microorganisms in efforts to be able to attain higher amounts of desired dihydrochalcones.

Antiviral Defense Mechanisms in Honey Bees

PubMed Central

Brutscher, Laura M.; Daughenbaugh, Katie F.; Flenniken, Michelle L.

2015-01-01

Honey bees are significant pollinators of agricultural crops and other important plant species. High annual losses of honey bee colonies in North America and in some parts of Europe have profound ecological and economic implications. Colony losses have been attributed to multiple factors including RNA viruses, thus understanding bee antiviral defense mechanisms may result in the development of strategies that mitigate colony losses. Honey bee antiviral defense mechanisms include RNA-interference, pathogen-associated molecular pattern (PAMP) triggered signal transduction cascades, and reactive oxygen species generation. However, the relative importance of these and other pathways is largely uncharacterized. Herein we review the current understanding of honey bee antiviral defense mechanisms and suggest important avenues for future investigation. PMID:26273564

Keeping Control: The Role of Senescence and Development in Plant Pathogenesis and Defense

PubMed Central

Häffner, Eva; Konietzki, Sandra; Diederichsen, Elke

2015-01-01

Many plant pathogens show interactions with host development. Pathogens may modify plant development according to their nutritional demands. Conversely, plant development influences pathogen growth. Biotrophic pathogens often delay senescence to keep host cells alive, and resistance is achieved by senescence-like processes in the host. Necrotrophic pathogens promote senescence in the host, and preventing early senescence is a resistance strategy of plants. For hemibiotrophic pathogens both patterns may apply. Most signaling pathways are involved in both developmental and defense reactions. Increasing knowledge about the molecular components allows to distinguish signaling branches, cross-talk and regulatory nodes that may influence the outcome of an infection. In this review, recent reports on major molecular players and their role in senescence and in pathogen response are reviewed. Examples of pathosystems with strong developmental implications illustrate the molecular basis of selected control strategies. A study of gene expression in the interaction between the hemibiotrophic vascular pathogen Verticillium longisporum and its cruciferous hosts shows processes that are fine-tuned to counteract early senescence and to achieve resistance. The complexity of the processes involved reflects the complex genetic control of quantitative disease resistance, and understanding the relationship between disease, development and resistance will support resistance breeding. PMID:27135337

Plant training for induced defense against insect pests: a promising tool for integrated pest management in cotton.

PubMed

Llandres, Ana L; Almohamad, Raki; Brévault, Thierry; Renou, Alain; Téréta, Idrissa; Jean, Janine; Goebel, François-Regis

2018-04-17

Enhancing cotton pest management using plant natural defenses has been described as a promising way to improve the management of crop pests. We here reviewed different studies on cotton growing systems to illustrate how an ancient technique called plant training, which includes plant topping and pruning, may contribute to this goal. Based on examples from cotton crops, we show how trained plants could be promoted to a state of enhanced defense that causes faster and more robust activation of their defense responses. We revisit agricultural benefits associated to this technique in cotton crops, with a focus on its potential as a supplementary tool for Integrated Pest Management (IPM). Particularly, we examine its role in mediating plant interactions with conspecific neighboring plants, pests and associated natural enemies. We propose a new IPM tool, plant training for induced defense, which involves inducing plant defense by artificial injuries. Experimental evidence from various studies shows that cotton training is a promising technique, particularly for smallholders, which can be used as part of an IPM program to significantly reduce insecticide use and to improve productivity in cotton farming. This article is protected by copyright. All rights reserved.

Nicotiana benthamiana Matrix Metalloprotease 1 (NMMP1) gene confers disease resistance to Phytophthora infestans in tobacco and potato plants.

PubMed

Ha, Jang Ho; Jang, Hyun A; Moon, Ki-Beom; Baek, Kwang Hyun; Choi, Gyung Ja; Choi, Doil; Cho, Hye Sun; Kwon, Suk Yun; Jeon, Jae-Heung; Oh, Sang-Keun; Kim, Hyun-Soon

2017-11-01

We previously isolated Nicotiana benthamiana matrix metalloprotease 1 (NMMP1) from tobacco leaves. The NMMP1 gene encodes a highly conserved, Zn-containing catalytic protease domain that functions as a factor in the plant's defense against bacterial pathogens. Expression of NMMP1 was strongly induced during interactions between tobacco and one of its pathogens, Phytophthora infestans. To elucidate the role of the NMMP1 in defense of N. benthamiana against fungal pathogens, we performed gain-of-function and loss-of-function studies. NMMP1-overexpressing plants had stronger resistance responses against P. infestans infections than control plants, while silencing of NMMP1 resulted in greater susceptibility of the plants to the pathogen. This greater susceptibility correlated with fewer NMMP1 transcripts than the non-silenced control. We also examined cell death as a measure of disease. The amount of cell death induced by the necrosis-inducing P. infestans protein 1, PiNPP1, was dependent on NMMP1 in N. benthamiana. Potato plants overexpressing NMMP1 also had enhanced disease resistance against P. infestans. RT-PCR analysis of these transgenic potato plants revealed constitutive up-regulation of the potato defense gene NbPR5. NMMP1-overexpressing potato plants were taller and produced heavier tubers than control plants. We suggest a role for NMMP1in pathogen defense and development. Copyright © 2017 Elsevier GmbH. All rights reserved.

Regulation and function of the pepper pectin methylesterase inhibitor (CaPMEI1) gene promoter in defense and ethylene and methyl jasmonate signaling in plants.

PubMed

An, Soo Hyun; Choi, Hyong Woo; Hong, Jeum Kyu; Hwang, Byung Kook

2009-11-01

Analysis of the promoters of defense-related genes is valuable for determining stress signaling and transcriptional activation during pathogen infection. Here, we have isolated and functionally characterized the promoter region of the pepper (Capsicum annuum) pectin methylesterase inhibitor 1 (CaPMEI1) gene in transiently transformed tobacco plants and stably transformed Arabidopsis plants. Among four 5' deletion constructs analyzed, the -958-bp CaPMEI1 promoter induced a high level of GUS reporter activity in tobacco leaf tissue, driven by pathogen infection as well as by ethylene and methyl jasmonate (MeJA) treatment. The 204-bp region from -958 bp to -754 bp of the CaPMEI1 promoter is responsible for the stress-responsive expression. In addition, the pepper transcription factor CARAV1 activated the CaPMEI1 promoter in tobacco leaves, whereas the transcription factor CAbZIP1 did not. In the transgenic Arabidopsis plants, the -958 bp CaPMEI1 promoter was functionally regulated by developmental cues, bacterial and oomycete pathogen infections, and treatment with ethylene and MeJA. Histochemical GUS staining analyses of Arabidopsis tissues revealed that the CaPMEI1 promoter was mainly activated in leaf veins in response to various biotic and abiotic stimuli. Together, these results suggest that CaPMEI1 promoter activation may be a critical molecular event for host defense response and ethylene- and MeJA-mediated CaPMEI1 gene expression.

ER quality control components UGGT and STT3a are required for activation of defense responses in bir1-1.

PubMed

Zhang, Qian; Sun, Tongjun; Zhang, Yuelin

2015-01-01

The receptor-like kinase SUPPRESSOR OF BIR1, 1 (SOBIR1) functions as a critical regulator in plant immunity. It is required for activation of cell death and defense responses in Arabidopsis bak1-interacting receptor-like kinase 1,1 (bir1-1) mutant plants. Here we report that the ER quality control component UDP-glucose:glycoprotein glucosyltransferase (UGGT) is required for the biogenesis of SOBIR1 and mutations in UGGT suppress the spontaneous cell death and constitutive defense responses in bir1-1. Loss of function of STT3a, which encodes a subunit of the oligosaccharyltransferase complex, also suppresses the autoimmune phenotype in bir1-1. However, it has no effect on the accumulation of SOBIR1, suggesting that additional signaling components other than SOBIR1 may be regulated by ER quality control. Our study provides clear evidence that ER quality control play critical roles in regulating defense activation in bir1-1.

The Plant Ribosome-Inactivating Proteins Play Important Roles in Defense against Pathogens and Insect Pest Attacks

PubMed Central

Zhu, Feng; Zhou, Yang-Kai; Ji, Zhao-Lin; Chen, Xiao-Ren

2018-01-01

Ribosome-inactivating proteins (RIPs) are toxic N-glycosidases that depurinate eukaryotic and prokaryotic rRNAs, thereby arresting protein synthesis during translation. RIPs are widely found in various plant species and within different tissues. It is demonstrated in vitro and in transgenic plants that RIPs have been connected to defense by antifungal, antibacterial, antiviral, and insecticidal activities. However, the mechanism of these effects is still not completely clear. There are a number of reviews of RIPs. However, there are no reviews on the biological functions of RIPs in defense against pathogens and insect pests. Therefore, in this report, we focused on the effect of RIPs from plants in defense against pathogens and insect pest attacks. First, we summarize the three different types of RIPs based on their physical properties. RIPs are generally distributed in plants. Then, we discuss the distribution of RIPs that are found in various plant species and in fungi, bacteria, algae, and animals. Various RIPs have shown unique bioactive properties including antibacterial, antifungal, antiviral, and insecticidal activity. Finally, we divided the discussion into the biological roles of RIPs in defense against bacteria, fungi, viruses, and insects. This review is focused on the role of plant RIPs in defense against bacteria, fungi, viruses, and insect attacks. The role of plant RIPs in defense against pathogens and insects is being comprehended currently. Future study utilizing transgenic technology approaches to study the mechanisms of RIPs will undoubtedly generate a better comprehending of the role of plant RIPs in defense against pathogens and insects. Discovering additional crosstalk mechanisms between RIPs and phytohormones or reactive oxygen species (ROS) against pathogen and insect infections will be a significant subject in the field of biotic stress study. These studies are helpful in revealing significance of genetic control that can be beneficial to

Regulations and roles for alternative pathways of hexose metabolism in plants

Treesearch

Clanton C. Black; Laszlo Mustardy; S.S. Sung; P.P. Kormanik; D.-P. Xu; Nachman Paz

1987-01-01

Plants have two cytoplasmic pathways of glycolysis and gluconeogenesis for the reversible interconversion of fructose 6-phosphate (F-6-P) and fructose 1,6-bisphosphate (F-1,6,-P2). One pathway is described as a maintenance pathway that is catalyzed by a nucleotide triphosphate-dependent phosphofructokinase (EC 2.7.1.11; ATP-PFK) glycolytically and a F-1,6...

Herbivore Oral Secreted Bacteria Trigger Distinct Defense Responses in Preferred and Non-Preferred Host Plants.

PubMed

Wang, Jie; Chung, Seung Ho; Peiffer, Michelle; Rosa, Cristina; Hoover, Kelli; Zeng, Rensen; Felton, Gary W

2016-06-01

Insect symbiotic bacteria affect host physiology and mediate plant-insect interactions, yet there are few clear examples of symbiotic bacteria regulating defense responses in different host plants. We hypothesized that plants would induce distinct defense responses to herbivore- associated bacteria. We evaluated whether preferred hosts (horsenettle) or non-preferred hosts (tomato) respond similarly to oral secretions (OS) from the false potato beetle (FPB, Leptinotarsa juncta), and whether the induced defense triggered by OS was due to the presence of symbiotic bacteria in OS. Both horsenettle and tomato damaged by antibiotic (AB) treated larvae showed higher polyphenol oxidase (PPO) activity than those damaged by non-AB treated larvae. In addition, application of OS from AB treated larvae induced higher PPO activity compared with OS from non-AB treated larvae or water treatment. False potato beetles harbor bacteria that may provide abundant cues that can be recognized by plants and thus mediate corresponding defense responses. Among all tested bacterial isolates, the genera Pantoea, Acinetobacter, Enterobacter, and Serratia were found to suppress PPO activity in tomato, while only Pantoea sp. among these four isolates was observed to suppress PPO activity in horsenettle. The distinct PPO suppression caused by symbiotic bacteria in different plants was similar to the pattern of induced defense-related gene expression. Pantoea inoculated FPB suppressed JA-responsive genes and triggered a SA-responsive gene in both tomato and horsenettle. However, Enterobacter inoculated FPB eliminated JA-regulated gene expression and elevated SA-regulated gene expression in tomato, but did not show evident effects on the expression levels of horsenettle defense-related genes. These results indicate that suppression of plant defenses by the bacteria found in the oral secretions of herbivores may be a more widespread phenomenon than previously indicated.

Evolution of plant growth and defense in a continental introduction.

PubMed

Agrawal, Anurag A; Hastings, Amy P; Bradburd, Gideon S; Woods, Ellen C; Züst, Tobias; Harvey, Jeffrey A; Bukovinszky, Tibor

2015-07-01

Substantial research has addressed adaptation of nonnative biota to novel environments, yet surprisingly little work has integrated population genetic structure and the mechanisms underlying phenotypic differentiation in ecologically important traits. We report on studies of the common milkweed Asclepias syriaca, which was introduced from North America to Europe over the past 400 years and which lacks most of its specialized herbivores in the introduced range. Using 10 populations from each continent grown in a common environment, we identified several growth and defense traits that have diverged, despite low neutral genetic differentiation between continents. We next developed a Bayesian modeling approach to account for relationships between molecular and phenotypic differences, confirming that continental trait differentiation was greater than expected from neutral genetic differentiation. We found evidence that growth-related traits adaptively diverged within and between continents. Inducible defenses triggered by monarch butterfly herbivory were substantially reduced in European populations, and this reduction in inducibility was concordant with altered phytohormonal dynamics, reduced plant growth, and a trade-off with constitutive investment. Freedom from the community of native and specialized herbivores may have favored constitutive over induced defense. Our replicated analysis of plant growth and defense, including phenotypically plastic traits, suggests adaptive evolution following a continental introduction.

Silicon Supplementation Alters the Composition of Herbivore Induced Plant Volatiles and Enhances Attraction of Parasitoids to Infested Rice Plants.

PubMed

Liu, Jian; Zhu, Jiwei; Zhang, Pengjun; Han, Liwei; Reynolds, Olivia L; Zeng, Rensen; Wu, Jinhong; Shao, Yue; You, Minsheng; Gurr, Geoff M

2017-01-01

Silicon (Si) is important in plant defenses that operate in a direct manner against herbivores, and work in rice ( Oryza sativa ) has established that this is mediated by the jasmonate signaling pathway. Plant defenses also operate indirectly, by the production of herbivore induced plant volatiles (HIPVs) that attract predators and parasitoids of herbivores. These indirect defenses too are mediated by the jasmonate pathway but no earlier work has demonstrated an effect of Si on HIPVs. In this study, we tested the effect of Si supplementation versus Si deprivation to rice plants on subsequent HIPV production following feeding by the important pest, rice leaffolder ( Cnaphalocrocis medinalis ). Gas chromatography-mass spectrometry analyses showed lower production of α-bergamotene, β-sesquiohellandrene, hexanal 2-ethyl, and cedrol from +Si herbivore-infested plants compared with -Si infested plants. These changes in plant chemistry were ecologically significant in altering the extent to which parasitoids were attracted to infested plants. Adult females of Trathala flavo-orbitalis and Microplitis mediator both exhibited greater attraction to the HIPV blend of +Si plants infested with their respective insect hosts compared to -Si infested plants. In equivalent studies using RNAi rice plants in which jasmonate perception was silenced there was no equivalent change to the HIPV blend associated with Si treatment; indicating that the effects of Si on HIPVs are modulated by the jasmonate pathway. Further, this work demonstrates that silicon alters the HIPV blend of herbivore-infested rice plants. The significance of this finding is that there are no earlier-published studies of this phenomenon in rice or any other plant species. Si treatment to crops offers scope for enhancing induced, indirect defenses and associated biological control of pests because parasitoids are more strongly attracted by the HIPVs produced by +Si plants.

The cGAS-STING Defense Pathway and Its Counteraction by Viruses.

PubMed

Ma, Zhe; Damania, Blossom

2016-02-10

Upon virus infection, host cells mount a concerted innate immune response involving type I interferon and pro-inflammatory cytokines to enable elimination of the pathogen. Recently, cGAS and STING have been identified as intracellular sensors that activate the interferon pathway in response to virus infection and thus mediate host defense against a range of DNA and RNA viruses. Here we review how viruses are sensed by the cGAS-STING signaling pathway as well as how viruses modulate this pathway. Mechanisms utilized by viral proteins to inhibit cGAS and/or STING are also discussed. On the flip side, host cells have also evolved strategies to thwart viral immune escape. The balance between host immune control and viral immune evasion is pivotal to viral pathogenesis, and we discuss this virus-host stand-off in the context of the cGAS-STING innate immune pathway. Copyright © 2016 Elsevier Inc. All rights reserved.

Emerging roles in plant defense for cis-jasmone-induced cytochrome P450 CYP81D11.

PubMed

Matthes, Michaela; Bruce, Toby; Chamberlain, Keith; Pickett, John; Napier, Johnathan

2011-04-01

cis-Jasmone is a volatile organic compound emitted constitutively by flowers or leaves of several plant species where it acts as an attractant for pollinators and as a chemical cue for host localisation (or avoidance) for insects. ( 1-3) It is also released by some plant species after feeding damage inflicted by herbivorous insects and in this case might serve as a chemical cue for parasitoids to guide them to their prey (so called "indirect defense"). ( 4,5) Moreover, we have recently shown that plants can perceive cis-jasmone and that it acts as a signaling molecule in A. thaliana, inducing a discrete and distinctive suite of genes, of which a large subset is putatively involved in metabolism and defense responses. ( 6) Cytochrome P450s feature prominently in these functional subsets and of these the highest fold change upon cis-jasmone treatment occurred with the cytochrome CYP81D11 (At3g28740). ( 6) Hence this gene was chosen for a more thorough analysis of the potential biological relevance of the cis-jasmone induced defense response. Although the precise function of CYP81D11 remains to be determined, we could previously demonstrate its involvement in the indirect defense response in Arabidopsis, as plants exposed to cis-jasmone ceased to be attractive to the aphid parasitoid Aphidius ervi when this P450 was inactivated by T-DNA insertion mutagenesis. ( 6) Here we report additional experiments which give further support to a role of CYP81D11 in the direct or indirect defense response of A. thaliana.

Identification of an insect-produced olfactory cue that primes plant defenses

USDA-ARS?s Scientific Manuscript database

It is increasingly clear that plants can perceive and respond to olfactory cues. Yet, knowledge about the specificity and sensitivity of such perception remains limited. We previously documented priming of anti-herbivore defenses in tall goldenrod plants (Solidago altissima) by volatile emissions fr...

Isolation, characterization, and expression analyses of plant elicitor peptides (Pep) genes in maize

USDA-ARS?s Scientific Manuscript database

Insect-induced defenses occur in nearly all plants and are regulated by conserved signaling pathways. In plant families, peptides with analogous activity have remained elusive. Peps are conserved signals across diverse plant families regulating antiherbivore defenses and are likely to be the missing...

Signaling pathways that regulate life and cell death: evolution of apoptosis in the context of self-defense.

PubMed

Muñoz-Pinedo, Cristina

2012-01-01

Programmed Cell Death is essential for the life cycle of many organisms. Cell death in multicellular organisms can occur as a consequence of massive damage (necrosis) or in a controlled form, through engagement of diverse biochemical programs. The best well known form of programmed cell death is apoptosis. Apoptosis occurs in animals as a consequence of a variety of stimuli including stress and social signals and it plays essential roles in morphogenesis and immune defense. The machinery of apoptosis is well conserved among animals and it is composed of caspases (the proteases which execute cell death), adapter proteins (caspase activators), Bcl-2 family proteins and Inhibitor of Apoptosis Proteins (IAPs). We will describe in this chapter the main apoptotic pathways in animals: the extrinsic (death receptor-mediated), the intrinsic/mitochondrial and the Granzyme B pathway. Other forms of non-apoptotic Programmed Cell Death which occur in animals will also be discussed. We will summarize the current knowledge about apoptotic-like and other forms of cell death in other organisms such as plants and protists.Additionally, we will discuss the hypothesis that apoptosis originated as part of a host defense mechanism. We will explore the similarities between the protein complexes which mediate apoptosis (apoptosomes) and complexes involved in immunity: inflammasomes. Additional functions of apoptotic proteins related to immune function will be summarized, in an effort to explore the evolutionary origins of cell death.

Linkage of cold acclimation and disease resistance through plant-pathogen interaction pathway in Vitis amurensis grapevine.

PubMed

Wu, Jiao; Zhang, Yali; Yin, Ling; Qu, Junjie; Lu, Jiang

2014-12-01

Low temperatures cause severe damage to none cold hardy grapevines. A preliminary survey with Solexa sequencing technology was used to analyze gene expression profiles of cold hardy Vitis amurensis 'Zuoshan-1' after cold acclimation at 4 °C for 48 h. A total of 16,750 and 18,068 putative genes were annotated for 4 °C-treated and control library, respectively. Among them, 393 genes were upregulated for at least 20-fold, while 69 genes were downregulated for at least 20-fold under the 4 °C treatment for 48 h. A subset of 101 genes from this survey was investigated further using reverse transcription polymerase chain reaction (RT-PCR). Genes associated with signaling events in pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI), including generation of calcium signals (CNGC, CMLs), jasmonic acid signal (JAZ1), oxidative burst (Rboh), and phosphorylation (FLS2, BAK, MEKK1, MKKs) cascades, were upregulated after cold acclimation. Disease resistance genes (RPM1, RPS5, RIN4, PBS1) in the process of effector-triggered immunity (ETI) were also upregulated in the current condition. Defense-related genes (WRKYs, PR1, MIN7) involved in both PTI and ETI processes were abundantly expressed after cold acclimation. Our results indicated that plant-pathogen interaction pathways were linked to the cold acclimation in V. amurensis grapevine. Other biotic- and abiotic-related genes, such as defense (protein phosphatase 2C, U-box domain proteins, NCED1, stilbene synthase), transcription (DREBs, MYBs, ERFs, ZFPs), signal transduction (kinase, calcium, and auxin signaling), transport (ATP-binding cassette (ABC) transporters, auxin:hydrogen symporter), and various metabolism, were also abundantly expressed in the cold acclimation of V. Amurensis 'Zuoshan-1' grapevine. This study revealed a series of critical genes and pathways to delineate important biological processes affected by low temperature in 'Zuoshan-1'.

Jasmonic acid and salicylic acid activate a common defense system in rice.

PubMed

Tamaoki, Daisuke; Seo, Shigemi; Yamada, Shoko; Kano, Akihito; Miyamoto, Ayumi; Shishido, Hodaka; Miyoshi, Seika; Taniguchi, Shiduku; Akimitsu, Kazuya; Gomi, Kenji

2013-06-01

Jasmonic acid (JA) and salicylic acid (SA) play important roles in plant defense systems. JA and SA signaling pathways interact antagonistically in dicotyledonous plants, but, the status of crosstalk between JA and SA signaling is unknown in monocots. Our rice microarray analysis showed that more than half of the genes upregulated by the SA analog BTH are also upregulated by JA, suggesting that a major portion of the SA-upregulated genes are regulated by JA-dependent signaling in rice. A common defense system that is activated by both JA and SA is thus proposed which plays an important role in pathogen defense responses in rice.

Overexpression of an Isoprenyl Diphosphate Synthase in Spruce Leads to Unexpected Terpene Diversion Products That Function in Plant Defense1[W][OPEN

PubMed Central

Nagel, Raimund; Berasategui, Aileen; Paetz, Christian; Gershenzon, Jonathan; Schmidt, Axel

2014-01-01

Spruce (Picea spp.) and other conifers employ terpenoid-based oleoresin as part of their defense against herbivores and pathogens. The short-chain isoprenyl diphosphate synthases (IDS) are situated at critical branch points in terpene biosynthesis, producing the precursors of the different terpenoid classes. To determine the role of IDS and to create altered terpene phenotypes for assessing the defensive role of terpenoids, we overexpressed a bifunctional spruce IDS, a geranyl diphosphate and geranylgeranyl diphosphate synthase in white spruce (Picea glauca) saplings. While transcript level (350-fold), enzyme activity level (7-fold), and in planta geranyl diphosphate and geranylgeranyl diphosphate levels (4- to 8-fold) were significantly increased in the needles of transgenic plants, there was no increase in the major monoterpenes and diterpene acids of the resin and no change in primary isoprenoids, such as sterols, chlorophylls, and carotenoids. Instead, large amounts of geranylgeranyl fatty acid esters, known from various gymnosperm and angiosperm plant species, accumulated in needles and were shown to act defensively in reducing the performance of larvae of the nun moth (Lymantria monacha), a conifer pest in Eurasia. These results show the impact of overexpression of an IDS and the defensive role of an unexpected accumulation product of terpenoid biosynthesis with the potential for a broader function in plant protection. PMID:24346420

Heavy Metal Stress and Some Mechanisms of Plant Defense Response

PubMed Central

Emamverdian, Abolghassem; Ding, Yulong; Mokhberdoran, Farzad; Xie, Yinfeng

2015-01-01

Unprecedented bioaccumulation and biomagnification of heavy metals (HMs) in the environment have become a dilemma for all living organisms including plants. HMs at toxic levels have the capability to interact with several vital cellular biomolecules such as nuclear proteins and DNA, leading to excessive augmentation of reactive oxygen species (ROS). This would inflict serious morphological, metabolic, and physiological anomalies in plants ranging from chlorosis of shoot to lipid peroxidation and protein degradation. In response, plants are equipped with a repertoire of mechanisms to counteract heavy metal (HM) toxicity. The key elements of these are chelating metals by forming phytochelatins (PCs) or metallothioneins (MTs) metal complex at the intra- and intercellular level, which is followed by the removal of HM ions from sensitive sites or vacuolar sequestration of ligand-metal complex. Nonenzymatically synthesized compounds such as proline (Pro) are able to strengthen metal-detoxification capacity of intracellular antioxidant enzymes. Another important additive component of plant defense system is symbiotic association with arbuscular mycorrhizal (AM) fungi. AM can effectively immobilize HMs and reduce their uptake by host plants via binding metal ions to hyphal cell wall and excreting several extracellular biomolecules. Additionally, AM fungi can enhance activities of antioxidant defense machinery of plants. PMID:25688377

Gramene 2016: comparative plant genomics and pathway resources.

PubMed

Tello-Ruiz, Marcela K; Stein, Joshua; Wei, Sharon; Preece, Justin; Olson, Andrew; Naithani, Sushma; Amarasinghe, Vindhya; Dharmawardhana, Palitha; Jiao, Yinping; Mulvaney, Joseph; Kumari, Sunita; Chougule, Kapeel; Elser, Justin; Wang, Bo; Thomason, James; Bolser, Daniel M; Kerhornou, Arnaud; Walts, Brandon; Fonseca, Nuno A; Huerta, Laura; Keays, Maria; Tang, Y Amy; Parkinson, Helen; Fabregat, Antonio; McKay, Sheldon; Weiser, Joel; D'Eustachio, Peter; Stein, Lincoln; Petryszak, Robert; Kersey, Paul J; Jaiswal, Pankaj; Ware, Doreen

2016-01-04

Gramene (http://www.gramene.org) is an online resource for comparative functional genomics in crops and model plant species. Its two main frameworks are genomes (collaboration with Ensembl Plants) and pathways (The Plant Reactome and archival BioCyc databases). Since our last NAR update, the database website adopted a new Drupal management platform. The genomes section features 39 fully assembled reference genomes that are integrated using ontology-based annotation and comparative analyses, and accessed through both visual and programmatic interfaces. Additional community data, such as genetic variation, expression and methylation, are also mapped for a subset of genomes. The Plant Reactome pathway portal (http://plantreactome.gramene.org) provides a reference resource for analyzing plant metabolic and regulatory pathways. In addition to ∼ 200 curated rice reference pathways, the portal hosts gene homology-based pathway projections for 33 plant species. Both the genome and pathway browsers interface with the EMBL-EBI's Expression Atlas to enable the projection of baseline and differential expression data from curated expression studies in plants. Gramene's archive website (http://archive.gramene.org) continues to provide previously reported resources on comparative maps, markers and QTL. To further aid our users, we have also introduced a live monthly educational webinar series and a Gramene YouTube channel carrying video tutorials. Published by Oxford University Press on behalf of Nucleic Acids Research 2015. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Novel mode of action of plant defense peptides: hevein-like antimicrobial peptides from wheat inhibit fungal metalloproteases

USDA-ARS?s Scientific Manuscript database

The multilayered plant immune system relies on rapid recognition of pathogen-associated molecular patterns followed by activation of defense-related genes that results in the reinforcement of plant cell walls and production of antimicrobial compounds. To suppress plant defense, fungi secrete effecto...

The evolution of plant virus transmission pathways

Treesearch

Frédéric M. Hamelin; Linda J.S. Allen; Holly R. Prendeville; M. Reza Hajimorad; Michael J. Jeger

2016-01-01

The evolution of plant virus transmission pathways is studied through transmission via seed, pollen, oravector. We address the questions: under what circumstances does vector transmission make pollen transmission redundant? Can evolution lead to the coexistence of multiple virus transmission pathways? We restrict the analysis to an annual plant population in which...

A Specialist Herbivore Uses Chemical Camouflage to Overcome the Defenses of an Ant-Plant Mutualism

PubMed Central

Whitehead, Susan R.; Reid, Ellen; Sapp, Joseph; Poveda, Katja; Royer, Anne M.; Posto, Amanda L.; Kessler, André

2014-01-01

Many plants and ants engage in mutualisms where plants provide food and shelter to the ants in exchange for protection against herbivores and competitors. Although several species of herbivores thwart ant defenses and extract resources from the plants, the mechanisms that allow these herbivores to avoid attack are poorly understood. The specialist insect herbivore, Piezogaster reclusus (Hemiptera: Coreidae), feeds on Neotropical bull-horn acacias (Vachellia collinsii) despite the presence of Pseudomyrmex spinicola ants that nest in and aggressively defend the trees. We tested three hypotheses for how P. reclusus feeds on V. collinsii while avoiding ant attack: (1) chemical camouflage via cuticular surface compounds, (2) chemical deterrence via metathoracic defense glands, and (3) behavioral traits that reduce ant detection or attack. Our results showed that compounds from both P. reclusus cuticles and metathoracic glands reduce the number of ant attacks, but only cuticular compounds appear to be essential in allowing P. reclusus to feed on bull-horn acacia trees undisturbed. In addition, we found that ant attack rates to P. reclusus increased significantly when individuals were transferred between P. spinicola ant colonies. These results are consistent with the hypothesis that chemical mimicry of colony-specific ant or host plant odors plays a key role in allowing P. reclusus to circumvent ant defenses and gain access to important resources, including food and possibly enemy-free space. This interaction between ants, acacias, and their herbivores provides an excellent example of the ability of herbivores to adapt to ant defenses of plants and suggests that herbivores may play an important role in the evolution and maintenance of mutualisms. PMID:25047551

A specialist herbivore uses chemical camouflage to overcome the defenses of an ant-plant mutualism.

PubMed

Whitehead, Susan R; Reid, Ellen; Sapp, Joseph; Poveda, Katja; Royer, Anne M; Posto, Amanda L; Kessler, André

2014-01-01

Many plants and ants engage in mutualisms where plants provide food and shelter to the ants in exchange for protection against herbivores and competitors. Although several species of herbivores thwart ant defenses and extract resources from the plants, the mechanisms that allow these herbivores to avoid attack are poorly understood. The specialist insect herbivore, Piezogaster reclusus (Hemiptera: Coreidae), feeds on Neotropical bull-horn acacias (Vachellia collinsii) despite the presence of Pseudomyrmex spinicola ants that nest in and aggressively defend the trees. We tested three hypotheses for how P. reclusus feeds on V. collinsii while avoiding ant attack: (1) chemical camouflage via cuticular surface compounds, (2) chemical deterrence via metathoracic defense glands, and (3) behavioral traits that reduce ant detection or attack. Our results showed that compounds from both P. reclusus cuticles and metathoracic glands reduce the number of ant attacks, but only cuticular compounds appear to be essential in allowing P. reclusus to feed on bull-horn acacia trees undisturbed. In addition, we found that ant attack rates to P. reclusus increased significantly when individuals were transferred between P. spinicola ant colonies. These results are consistent with the hypothesis that chemical mimicry of colony-specific ant or host plant odors plays a key role in allowing P. reclusus to circumvent ant defenses and gain access to important resources, including food and possibly enemy-free space. This interaction between ants, acacias, and their herbivores provides an excellent example of the ability of herbivores to adapt to ant defenses of plants and suggests that herbivores may play an important role in the evolution and maintenance of mutualisms.

Ethylene contributes to mir1-mediated maize defense against the phloem-sap sucking insect Rhopalosiphum maidis.

USDA-ARS?s Scientific Manuscript database

Signaling networks among multiple phytohormones fine-tune plant defense responses to insect herbivore attack. Previously, it was reported that the synergistic combination of ethylene (ET) and jasmonic acid (JA) was required for providing maize insect resistance1 (mir1), a key endogenous defense sign...

The Role of Hydrogen Peroxide and Nitric Oxide in the Induction of Plant-Encoded RNA-Dependent RNA Polymerase 1 in the Basal Defense against Tobacco Mosaic Virus

PubMed Central

Shi, Kai; Li, Xin; Zhang, Guan-Qun; Xia, Xiao-Jian; Chen, Zhi-Xiang; Yu, Jing-Quan

2013-01-01

Plant RNA-dependent RNA Polymerase 1 (RDR1) is an important element of the RNA silencing pathway in the plant defense against viruses. RDR1 expression can be elicited by viral infection and salicylic acid (SA), but the mechanisms of signaling during this process remains undefined. The involvement of hydrogen peroxide (H2O2) and nitric oxide (NO) in RDR1 induction in the compatible interactions between Tobacco mosaic tobamovirus (TMV) and Nicotiana tabacum, Nicotiana benthamiana, and Arabidopsis thaliana was examined. TMV inoculation onto the lower leaves of N. tabacum induced the rapid accumulation of H2O2 and NO followed by the increased accumulation of RDR1 transcripts in the non-inoculated upper leaves. Pretreatment with exogenous H2O2 and NO on upper leaf led to increased RDR1 expression and systemic TMV resistance. Conversely, dimethylthiourea (an H2O2 scavenger) and 2-(4-carboxyphenyl)- 4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (an NO scavenger) partly blocked TMV- and SA-induced RDR1 expression and increased TMV susceptibility, whereas pretreatment with exogenous H2O2 and NO failed to diminish TMV infection in N. benthamiana plants with naturally occurring RDR1 loss-of-function. Furthermore, in N. tabacum and A. thaliana, TMV-induced H2O2 accumulation was NO-dependent, whereas NO generation was not affected by H2O2. These results suggest that, in response to TMV infection, H2O2 acts downstream of NO to mediate induction of RDR1, which plays a critical role in strengthening RNA silencing to restrict systemic viral infection. PMID:24098767

Ectopic Terpene Synthase Expression Enhances Sesquiterpene Emission in Nicotiana attenuata without Altering Defense or Development of Transgenic Plants or Neighbors1[W

PubMed Central

Schuman, Meredith C.; Palmer-Young, Evan C.; Schmidt, Axel; Gershenzon, Jonathan; Baldwin, Ian T.

2014-01-01

Sesquiterpenoids, with approximately 5,000 structures, are the most diverse class of plant volatiles with manifold hypothesized functions in defense, stress tolerance, and signaling between and within plants. These hypotheses have often been tested by transforming plants with sesquiterpene synthases expressed behind the constitutively active 35S promoter, which may have physiological costs measured as inhibited growth and reduced reproduction or may require augmentation of substrate pools to achieve enhanced emission, complicating the interpretation of data from affected transgenic lines. Here, we expressed maize (Zea mays) terpene synthase10 (ZmTPS10), which produces (E)-α-bergamotene and (E)-β-farnesene, or a point mutant ZmTPS10M, which produces primarily (E)-β-farnesene, under control of the 35S promoter in the ecological model plant Nicotiana attenuata. Transgenic N. attenuata plants had specifically enhanced emission of target sesquiterpene(s) with no changes detected in their emission of any other volatiles. Treatment with herbivore or jasmonate elicitors induces emission of (E)-α-bergamotene in wild-type plants and also tended to increase emission of (E)-α-bergamotene and (E)-β-farnesene in transgenics. However, transgenics did not differ from the wild type in defense signaling or chemistry and did not alter defense chemistry in neighboring wild-type plants. These data are inconsistent with within-plant and between-plant signaling functions of (E)-β-farnesene and (E)-α-bergamotene in N. attenuata. Ectopic sesquiterpene emission was apparently not costly for transgenics, which were similar to wild-type plants in their growth and reproduction, even when forced to compete for common resources. These transgenics would be well suited for field experiments to investigate indirect ecological effects of sesquiterpenes for a wild plant in its native habitat. PMID:25187528

Sequence/structural analysis of xylem proteome emphasizes pathogenesis-related proteins, chitinases and β-1, 3-glucanases as key players in grapevine defense against Xylella fastidiosa.

PubMed

Chakraborty, Sandeep; Nascimento, Rafael; Zaini, Paulo A; Gouran, Hossein; Rao, Basuthkar J; Goulart, Luiz R; Dandekar, Abhaya M

2016-01-01

Background. Xylella fastidiosa, the causative agent of various plant diseases including Pierce's disease in the US, and Citrus Variegated Chlorosis in Brazil, remains a continual source of concern and economic losses, especially since almost all commercial varieties are sensitive to this Gammaproteobacteria. Differential expression of proteins in infected tissue is an established methodology to identify key elements involved in plant defense pathways. Methods. In the current work, we developed a methodology named CHURNER that emphasizes relevant protein functions from proteomic data, based on identification of proteins with similar structures that do not necessarily have sequence homology. Such clustering emphasizes protein functions which have multiple copies that are up/down-regulated, and highlights similar proteins which are differentially regulated. As a working example we present proteomic data enumerating differentially expressed proteins in xylem sap from grapevines that were infected with X. fastidiosa. Results. Analysis of this data by CHURNER highlighted pathogenesis related PR-1 proteins, reinforcing this as the foremost protein function in xylem sap involved in the grapevine defense response to X. fastidiosa. β-1, 3-glucanase, which has both anti-microbial and anti-fungal activities, is also up-regulated. Simultaneously, chitinases are found to be both up and down-regulated by CHURNER, and thus the net gain of this protein function loses its significance in the defense response. Discussion. We demonstrate how structural data can be incorporated in the pipeline of proteomic data analysis prior to making inferences on the importance of individual proteins to plant defense mechanisms. We expect CHURNER to be applicable to any proteomic data set.

Molecular Dynamics Simulation and Statistics Analysis Reveals the Defense Response Mechanism in Plants

NASA Astrophysics Data System (ADS)

Liu, Zhichao; Zhao, Yunjie; Zeng, Chen; Computational Biophysics Lab Team

As the main protein of the bacterial flagella, flagellin plays an important role in perception and defense response. The newly discovered locus, FLS2, is ubiquitously expressed. FLS2 encodes a putative receptor kinase and shares many homologies with some plant resistance genes and even with some components of immune system of mammals and insects. In Arabidopsis, FLS2 perception is achieved by the recognition of epitope flg22, which induces FLS2 heteromerization with BAK1 and finally the plant immunity. Here we use both analytical methods such as Direct Coupling Analysis (DCA) and Molecular Dynamics (MD) Simulations to get a better understanding of the defense mechanism of FLS2. This may facilitate a redesign of flg22 or de-novo design for desired specificity and potency to extend the immune properties of FLS2 to other important crops and vegetables.

The receptor-like cytoplasmic kinase BSR1 mediates chitin-induced defense signaling in rice cells.