Sigma factor (SIG) proteins contribute to promoter specificity of the plastid-encoded RNA polymerase during chloroplast genome transcription. All six members of the SIG family, that is, SIG1–SIG6, are nuclear-encoded proteins targeted to chloroplasts. Sigma factor 2 (SIG2) is a phytochrome-regulated protein important for stoichiometric control of the expression of plastid- and nuclear-encoded genes that impact plastid development and plant growth and development. Among SIG factors, SIG2 is required not only for transcription of chloroplast genes (i.e., anterograde signaling), but also impacts nuclear-encoded, photosynthesis-related, and light signaling-related genes (i.e., retrograde signaling) in response to plastid functional status. Although SIG2 is involved in photomorphogenesis in Arabidopsis, the molecular bases for its role in light signaling that impacts photomorphogenesis and aspects of photosynthesis have only recently begun to be investigated. Previously, we reported that SIG2 is necessary for phytochrome-mediated photomorphogenesis specifically under red (R) and far-red light, thereby suggesting a link between phytochromes and nuclear-encoded SIG2 in light signaling. To explore transcriptional roles of SIG2 in R-dependent growth and development, we performed RNA sequencing analysis to compare gene expression in sig2-2 mutant and Col-0 wild-type seedlings at two developmental stages (1- and 7-day). We identified a subset of misregulated genes involved in growth, hormonal cross talk, stress responses, and photosynthesis. To investigate the functional relevance of these gene expression analyses, we performed several comparative phenotyping tests. In these analyses, strong sig2 mutants showed insensitivity to bioactive GA 3 , high intracellular levels of hydrogen peroxide (H 2 O 2 ) indicative of a stress response, and specific defects in photosynthesis, including elevated levels of cyclic electron flow (CEF) and nonphotochemical quenching (NPQ). We demonstrated that SIG2 regulates a broader range of physiological responses at the molecular level than previously reported, with specific roles in red-light-mediated photomorphogenesis.
|State||Published - Feb 1 2018|
Bibliographical noteFunding Information:
National Science Foundation, Grant/Award Number: MCB-1515002; Office of Science of the US Department of Energy, Grant/ Award Number: DE-FG02-91ER2002; MSU AgBioResearch; MSU Center for Advanced Algal and Plant Phenotyping (CAAPP)
This research was supported by the National Science Foundation (grant no. MCB-1515002 to B.L.M.), by infrastructure support from the Office of Science of the US Department of Energy (grant no. DE-FG02-91ER2002 to D.M.K. and B.L.M.), and MSU AgBioRe-search support for the MSU Center for Advanced Algal and Plant Phenotyping (CAAPP).
This research was supported by the National Science Foundation (grant no. MCB-1515002 to B.L.M.), by infrastructure support from the Office of Science of the US Department of Energy (grant no. DE-FG02-91ER2002 to D.M.K. and B.L.M.), and MSU AgBioResearch support for the MSU Center for Advanced Algal and Plant Phenotyping (CAAPP).
© 2018 The Authors. Plant Direct published by American Society of Plant Biologists, Society for Experimental Biology and John Wiley & Sons Ltd.
- light signaling
- plastid development
- sigma factors
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Biochemistry, Genetics and Molecular Biology (miscellaneous)
- Plant Science