Jekat, Stephan B.; Ernst, Antonia M.; von Bohl, Andreas; Zielonka, Sascia; Twyman, Richard M.; Noll, Gundula A.; Prüfer, Dirk
Structural phloem proteins (P-proteins) are characteristic components of the sieve elements in all dicotyledonous and many monocotyledonous angiosperms. Tobacco P-proteins were recently confirmed to be encoded by the widespread sieve element occlusion (SEO) gene family, and tobacco SEO proteins were shown to be directly involved in sieve tube sealing thus preventing the loss of photosynthate. Analysis of the two Arabidopsis SEO proteins (AtSEOa and AtSEOb) indicated that the corresponding P-protein subunits do not act in a redundant manner. However, there are still pending questions regarding the interaction properties and specific functions of AtSEOa and AtSEOb as well as the general function of structural P-proteins in Arabidopsis. In this study, we characterized the Arabidopsis P-proteins in more detail. We used in planta bimolecular fluorescence complementation assays to confirm the predicted heteromeric interactions between AtSEOa and AtSEOb. Arabidopsis mutants depleted for one or both AtSEO proteins lacked the typical P-protein structures normally found in sieve elements, underlining the identity of AtSEO proteins as P-proteins and furthermore providing the means to determine the role of Arabidopsis P-proteins in sieve tube sealing. We therefore developed an assay based on phloem exudation. Mutants with reduced AtSEO expression levels lost twice as much photosynthate following injury as comparable wild-type plants, confirming that Arabidopsis P-proteins are indeed involved in sieve tube sealing. PMID:23840197
Henry, Christopher S; Bernstein, Hans C; Weisenhorn, Pamela; Taylor, Ronald C; Lee, Joon-Yong; Zucker, Jeremy; Song, Hyun-Seob
The cover image, by Hyun-Seob Song et al., is based on the Article Microbial Community Metabolic Modeling: A Community Data-Driven Network Reconstruction, DOI: 10.1002/jcp.25428. Confocal micrograph depicting a metabolically coupled microbial consortium composed of cyanobacterium Thermosynechococcus elongatus (red) supporting heterotrophic bacterium, Meiothermus ruber (green). Scientists at PNNL and ANL proposed a new approach for microbial community metabolic modeling using this phototroph-heterotroph co-culture as a model system to study how microorganisms living in communities coordinate their metabolisms in response to partnership. Imaged by PNNL scientist, William B. Chrisler. PMID:27420803
Hong, Jong Wook
. Acknowledgement: All this work has been done by Sachin Jambovane, Kirn Cramer, Woon Seob Lee, and Hoon Suk Rho. The presenter would like to thank them.