Light is critical in the ability of plants to accumulate chlorophyll. When exposed to far‐red (
We examined
Among six
Regulation of
Plant development requires communication on many levels, including between cells and between organelles within a cell. For example, mitochondria and plastids have been proposed to be sensors of environmental stress and to coordinate their responses. Here we present evidence for communication between mitochondria and chloroplasts during leaf and root development, based on genetic and physical interactions between three
- NSF-PAR ID:
- 10089343
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Plant Direct
- Volume:
- 3
- Issue:
- 3
- ISSN:
- 2475-4455
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Premise FR ) light and then grown in white light in the absence of sucrose, wild‐type seedlings fail to green in a response known as theFR block of greening (BOG ). This response is controlled by phytochrome A through repression of protochlorophyllide reductase‐encoding (POR ) genes byFR light coupled with irreversible plastid damage. Sigma (SIG ) factors are nuclear‐encoded proteins that contribute to plant greening and plastid development through regulating gene transcription in chloroplasts and impacting retrograde signaling from the plastid to nucleus.SIG s are regulated by phytochromes, and the expression of someSIG factors is reduced in phytochrome mutant lines, includingphyA . Given the association of phyA with theFR BOG and its regulation ofSIG factors, we investigated the potential regulatory role ofSIG factors in theFR BOG response.Methods FR BOG responses insig mutants, phytochrome‐deficient lines, and mutant lines for several phy‐associated factors. We quantified chlorophyll levels and examined expression of keyBOG ‐associated genes.Results sig mutants, only thesig6 mutant significantly accumulated chlorophyll afterFR BOG treatment, similar to thephyA mutant.SIG 6 appears to control protochlorophyllide accumulation by contributing to the regulation of tetrapyrrole biosynthesis associated with glutamyl‐tRNA reductase (HEMA 1) function, select phytochrome‐interacting factor genes (PIF4 andPIF6 ), andPENTA1 , which regulatesPORA mRNA translation afterFR exposure.Conclusions SIG6 plays a significant role in plant responses toFR exposure during theBOG response. -
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Abstract Sigma factor (
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. -
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