TY - JOUR ID - 1643 TI - The Arabidopsis tandem zinc finger 9 protein binds RNA and mediates pathogen-associated molecular pattern-triggered immune responses JO - Plant Cell Physiol. PY - 2014 SP - 412-425 AU - Maldonado-Bonilla, L.D. AU - Eschen-Lippold, L. AU - Gago-Zachert, S. AU - Tabassum, N. AU - Bauer, N. AU - Scheel, D. AU - Lee, J. VL - 55 UR - http://pcp.oxfordjournals.org/content/55/2/412.full.pdf+html DO - 10.1093/pcp/pct175 AB - Recognition of pathogen-associated molecular patterns (PAMPs) induces multiple defense mechanisms to limit pathogen growth. Here, we show that the Arabidopsis thaliana tandem zinc finger protein 9 (TZF9) is phosphorylated by PAMP-responsive mitogen-activated protein kinases (MAPKs) and is required to trigger a full PAMP-triggered immune response. Analysis of a tzf9 mutant revealed attenuation in specific PAMP-triggered reactions such as reactive oxygen species accumulation, MAPK activation and, partially, the expression of several PAMP-responsive genes. In accordance with these weaker PAMP-triggered responses, tzf9 mutant plants exhibit enhanced susceptibility to virulent Pseudomonas syringae pv. tomato DC3000. Visualization of TZF9 localization by fusion to green fluorescent protein revealed cytoplasmic foci that co-localize with marker proteins of processing bodies (P-bodies). This localization pattern is affected by inhibitor treatments that limit mRNA availability (such as cycloheximide or actinomycin D) or block nuclear export (leptomycin B). Coupled with its ability to bind the ribohomopolymers poly(rU) and poly(rG), these results suggest involvement of TZF9 in post-transcriptional regulation, such as mRNA processing or storage pathways, to regulate plant innate immunity. A2 - C1 - Molecular Signal Processing; Stress and Developmental Biology ER - TY - JOUR ID - 1675 TI - Agrobacterium-derived cytokinin influences plastid morphology and starch accumulation inNicotiana benthamiana during transient assays JO - BMC Plant Biol. PY - 2014 SP - 127 AU - Erickson, J. l. AU - Ziegler, J. AU - Guevara, D. AU - Abel, S. AU - Klösgen, R. B. AU - Mathur, J. AU - Rothstein, S. J. AU - Schattat, M.H. VL - 14 UR - http://www.biomedcentral.com/1471-2229/14/127 DO - 10.1186/1471-2229-14-127 AB - Background: Agrobacterium tumefaciens-based transient assays have become a common tool for answering questions related to protein localization and gene expression in a cellular context. The use of these assays assumes that the transiently transformed cells are observed under relatively authentic physiological conditions and maintain ‘normal’ sub-cellular behaviour. Although this premise is widely accepted, the question of whether cellular organization andorganelle morphology is altered in Agrobacterium-infiltrated cells has not been examined in detail. The first indications of an altered sub-cellular environment came from our observation that a common laboratory strain, GV3101(pMP90), caused a drastic increase in stromule frequency. Stromules, or ‘stroma-filled-tubules’ emanate fromthe surface of plastids and are sensitive to a variety of biotic and abiotic stresses. Starting from this observation, the goal of our experiments was to further characterize the changes to the cell resulting from short-term bacterial infestation, and to identify the factor responsible for eliciting these changes.Results: Using a protocol typical of transient assays we evaluated the impact of GV3101(pMP90) infiltration on chloroplast behaviour and morphology in Nicotiana benthamiana. Our experiments confirmed that GV3101(pMP90) consistently induces stromules and alters plastid position relative to the nucleus. These effects were found to be the result of strain-dependant secretion of cytokinin and its accumulation in the plant tissue. Bacterial production of the hormone was found to be dependant on the presence of a trans-zeatin synthase gene (tzs) located on the Ti plasmidof GV3101(pMP90). Bacteria-derived cytokinins were also correlated with changes to both soluble sugar level and starch accumulation.Conclusion: Although we have chosen to focus on how transient Agrobacterium infestation alters plastid based parameters, these changes to the morphology and position of a single organelle, combined with the measured increases in sugar and starch content, suggest global changes to cell physiology. This indicates that cells visualized during transient assays may not be as ‘normal’ as was previously assumed. Our results suggest that the impact of the bacteria can be minimized by choosing Agrobacterium strains devoid of the tzs gene, but that the alterations to sub-cellular organization and cell carbohydrate status cannot be completely avoided using this strategy.Keywords: Agrobacterium tumefaciens, Nicotiana benthamiana, Transient assays, GV3101(pMP90), LBA4404, Plastid,Stromules, Bacteria-derived, Cytokinin, Trans-zeatin synthase A2 - C1 - Molecular Signal Processing ER -