Transcriptome and phenotyping analyses support a role for chloroplast sigma factor 2 in red‐light‐dependent regulation of growth, stress, and photosynthesis

Journal Article · 19 February 2018 · Plant Direct

DOI: https://doi.org/10.1002/pld3.43 · OSTI ID:1423167

Oh, Sookyung ^[1]; Strand, Deserah D. ^[1]; Kramer, David M. ^[2]; Chen, Jin ^[3]; Montgomery, Beronda L. ^[4]

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1. Department of Energy – Plant Research Laboratory Michigan State University East Lansing MI USA
2. Department of Energy – Plant Research Laboratory Michigan State University East Lansing MI USA, Department of Biochemistry and Molecular Biology Michigan State University East Lansing MI USA
3. UK Medical Center MN 150 University of Kentucky College of Medicine Lexington KY USA
4. Department of Energy – Plant Research Laboratory Michigan State University East Lansing MI USA, Department of Biochemistry and Molecular Biology Michigan State University East Lansing MI USA, Department of Microbiology &, Molecular Genetics Michigan State University East Lansing MI USA

Abstract 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, SIG 1– SIG 6, are nuclear‐encoded proteins targeted to chloroplasts. Sigma factor 2 ( SIG 2) 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, SIG 2 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 SIG 2 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 SIG 2 is necessary for phytochrome‐mediated photomorphogenesis specifically under red (R) and far‐red light, thereby suggesting a link between phytochromes and nuclear‐encoded SIG 2 in light signaling. To explore transcriptional roles of SIG 2 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 SIG 2 regulates a broader range of physiological responses at the molecular level than previously reported, with specific roles in red‐light‐mediated photomorphogenesis.

• Sponsoring Organization: USDOE
• OSTI ID: 1423167
• Journal Information: Plant Direct, Journal Name: Plant Direct Journal Issue: 2 Vol. 2; ISSN 2475-4455
• Publisher: Wiley Blackwell (John Wiley & Sons)Copyright Statement
• Country of Publication: United Kingdom
• Language: English