Sigma factor (
Light is critical in the ability of plants to accumulate chlorophyll. When exposed to far‐red (
We examined
Among six
Regulation of
- NSF-PAR ID:
- 10458234
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- American Journal of Botany
- Volume:
- 107
- Issue:
- 2
- ISSN:
- 0002-9122
- Page Range / eLocation ID:
- p. 329-338
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract SIG ) proteins contribute to promoter specificity of the plastid‐encodedRNA polymerase during chloroplast genome transcription. All six members of theSIG 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. AmongSIG 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. AlthoughSIG 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 thatSIG 2 is necessary for phytochrome‐mediated photomorphogenesis specifically under red (R) and far‐red light, thereby suggesting a link between phytochromes and nuclear‐encodedSIG 2 in light signaling. To explore transcriptional roles ofSIG 2 in R‐dependent growth and development, we performedRNA sequencing analysis to compare gene expression insig2‐2 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, strongsig2 mutants showed insensitivity to bioactiveGA 3, high intracellular levels of hydrogen peroxide (H2O2) indicative of a stress response, and specific defects in photosynthesis, including elevated levels of cyclic electron flow (CEF ) and nonphotochemical quenching (NPQ ). We demonstrated thatSIG 2 regulates a broader range of physiological responses at the molecular level than previously reported, with specific roles in red‐light‐mediated photomorphogenesis. -
Summary Understanding the unique features of algal metabolism may be necessary to realize the full potential of algae as feedstock for the production of biofuels and biomaterials. Under nitrogen deprivation, the green alga
C .reinhardtii showed substantial triacylglycerol (TAG ) accumulation and up‐regulation of a gene, , encoding a multidomain enzyme with a putative phosphoserine phosphatase (GPD 2PSP ) motif fused to glycerol‐3‐phosphate dehydrogenase (GPD ) domains. CanonicalGPD enzymes catalyze the synthesis of glycerol‐3‐phosphate (G3P) by reduction of dihydroxyacetone phosphate (DHAP ). G3P forms the backbone ofTAG s and membrane glycerolipids and it can be dephosphorylated to yield glycerol, an osmotic stabilizer and compatible solute under hypertonic stress. RecombinantChlamydomonas GPD 2 showed both reductase and phosphatase activitiesin vitro and it can work as a bifunctional enzyme capable of synthesizing glycerol directly fromDHAP . In addition, and a gene encoding glycerol kinase were up‐regulated inGPD 2Chlamydomonas cells exposed to high salinity.RNA ‐mediated silencing of revealed that the multidomain enzyme was required forGPD 2TAG accumulation under nitrogen deprivation and for glycerol synthesis under high salinity. Moreover, aGPD 2‐mC herry fusion protein was found to localize to the chloroplast, supporting the existence of aGPD 2‐dependent plastid pathway for the rapid synthesis of glycerol in response to hyperosmotic stress. We hypothesize that the reductase and phosphatase activities ofPSP –GPD multidomain enzymes may be modulated by post‐translational modifications/mechanisms, allowing them to synthesize primarily G3P or glycerol depending on environmental conditions and/or metabolic demands in algal species of the core Chlorophytes. -
Summary Light signal provides the spatial and temporal information for plants to adapt to the prevailing environmental conditions. Alterations in light quality and quantity can trigger robust changes in global gene expression. In
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