Ullah, Hemayet , Uvetta, Dozier , McLauchlin, April , Kundu, Nabanita , Fennel, Herman .
Arabidopsis Receptor for Activated C Kinase 1 (RACK1) scaffold proteins regulate diverse environmental stress signaling pathways.
Plants encounter a combination of environmental stress conditions and to response, they often utilize overlapping signaling pathways. In this regard, scaffold proteins are uniquely poised to integrate signals from multiple pathways by bringing interacting signaling components to proximity. Scaffold protein RACK1 in metazoan mediates diverse signaling pathways and is reported to interact with more than 70 diverse proteins. Loss-of-function alleles of three rack1 genes in Arabidopsis implicate the proteins in diverse environmental stress signaling pathways. The proteins can potentially dimerize and higher levels of homo/hetrodimerization were observed under water stress conditions. Site-directed mutagenesis in the potential sumoylation site abolished dimerization. Split-ubiquitin cDNA library screen identified two RACK1 interacting clones in photorespiration and UV-B stress response pathways. The interactions are confirmed by one-to-one bait-prey split-ubiquitin assay and by co-immunoprecipitation. The rack1a mutants withstand diverse environmental conditions like drought, elevated temperature, high intensity light, and oxidative stresses significantly better than the WT plants as measured by the chlorophyll fluorescence in dark and light adapted leaves (Fv/Fm). Especially the lower non-photochemical quenching of chlorophyll fluorescence (Fm-Fm’)/Fm’ in the mutants under oxidative stress imply that the mutants can prevent over-reduction of photosynthetic electron transfer chain possibly by activating the photorespiration pathway as a sink for the electrons. It is proposed that by Homo/ heterodimerization and/or interacting with proteins in diverse stress response pathways, RACK1 proteins in Arabidopsis regulate diverse environmental stress signaling pathways.
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Ullah's lab at Howard University
1 - Howard University, Biology, 415 College St., NW, Washington, DC, 20059, USA
2 - Howard University, Biology
3 - Howard University, Genetics
Presentation Type: ASPB Minisymposium
Location: Continental A/Hilton
Date: Monday, July 9th, 2007
Time: 11:30 AM