Abstract
Chloroplast-localized sigma factor (SIG) proteins promote specificity of the plastid-encoded RNA polymerase. SIG2 function appears to be necessary for light-grown Arabidopsis thaliana plants. Specific photoreceptors or light-dependent factors that impact the light-induced accumulation of SIG2 have not been reported. A molecular link between phytochromes and nuclear-encoded SIG2, which impacts photomorphogenesis specifically under red (R) and far-red (FR) light, is described here. Both phyA and phyB promote SIG2 transcript accumulation. Disruption of SIG2 results in R- and FR-specific defects in the inhibition of hypocotyl elongation and cotyledon expansion, although no impairments in these responses are detected for sig2 mutants under blue (B) or white (W) light. SIG2 also impacts root elongation under W and R, and the R-dependent expression of PIF4, encoding a phytochrome-interacting factor, and HY2, which encodes a phytochrome chromophore biosynthetic enzyme. Whereas SIG2 apparently impacts the accumulation of the phytochromobilin (PΦB) phytochrome chromophore, sig2 mutants differ significantly from PΦB mutants, primarily due to wavelength-specific defects in photomorphogenesis and disruption of a distinct subset of phytochrome-dependent responses. The molecular link between phytochromes and SIG2 is likely to be an important part of the co-ordination of gene expression to maintain stoichiometry between the nuclear-encoded phytochrome apoprotein and plastid-derived PΦB, which combine to form photoactive phytochromes, and/or light-dependent SIG2 accumulation is involved in an inductive light signalling pathway co-ordinating components between nucleus and plastids.
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Claims 9
Claim · model-written summary
PhyA and phyB promote SIG2 transcript accumulation.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae1 - Gene
- SIG2e0
- Outcome
- SIG2 transcript accumulatione0
- Qualifier
- phyA and phyBe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both phyA and phyB promote SIG2 transcript accumulation.”
e1“Arabidopsis thaliana”
Claim · model-written summary
Disrupting SIG2 caused red- and far-red-specific defects in hypocotyl elongation inhibition and cotyledon expansion.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- Disruption of SIG2e0
- Gene
- SIG2e0
- Outcome
- inhibition of hypocotyl elongation and cotyledon expansione0
- Direction
- defectse0
- Qualifier
- R- and FR-specifice0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Disruption of SIG2 results in R- and FR-specific defects in the inhibition of hypocotyl elongation and cotyledon expansion”
e1“Arabidopsis thaliana”
Claim · model-written summary
SIG2 mutants had no detected impairment of those photomorphogenic responses under blue or white light.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Material
- sig2 mutantse0
- Outcome
- impairments in these responsese0
- Direction
- no impairmentse0
- Qualifier
- under blue (B) or white (W) lighte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“no impairments in these responses are detected for sig2 mutants under blue (B) or white (W) light”
e1“Arabidopsis thaliana”
Claim · model-written summary
SIG2 affects root elongation under white and red light.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Gene
- SIG2e0
- Outcome
- root elongatione0
- Qualifier
- under W and Re0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SIG2 also impacts root elongation under W and R”
e1“Arabidopsis thaliana”
Claim · model-written summary
SIG2 affects red-light-dependent PIF4 expression.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Gene
- PIF4e0
- Outcome
- R-dependent expression of PIF4e0
- Qualifier
- SIG2e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SIG2 also impacts root elongation under W and R, and the R-dependent expression of PIF4, encoding a phytochrome-interacting factor, and HY2, which encodes a phytochrome chromophore biosynthetic enzyme.”
e1“Arabidopsis thaliana”
Claim · model-written summary
SIG2 affects red-light-dependent HY2 expression.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Gene
- HY2e0
- Outcome
- HY2e0
- Qualifier
- SIG2e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SIG2 also impacts root elongation under W and R, and the R-dependent expression of PIF4, encoding a phytochrome-interacting factor, and HY2, which encodes a phytochrome chromophore biosynthetic enzyme.”
e1“Arabidopsis thaliana”
Claim · model-written summary
SIG2 apparently affects accumulation of the phytochromobilin chromophore.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Gene
- SIG2e0
- Outcome
- accumulation of the phytochromobilin (PΦB) phytochrome chromophoree0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SIG2 apparently impacts the accumulation of the phytochromobilin (PΦB) phytochrome chromophore”
e1“Arabidopsis thaliana”
Claim · model-written summary
SIG2 mutants differed significantly from phytochromobilin mutants in wavelength-specific photomorphogenesis and a subset of phytochrome responses.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Material
- sig2 mutantse0
- Outcome
- wavelength-specific defects in photomorphogenesis and disruption of a distinct subset of phytochrome-dependent responsese0
- Comparator
- PΦB mutantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“sig2 mutants differ significantly from PΦB mutants, primarily due to wavelength-specific defects in photomorphogenesis and disruption of a distinct subset of phytochrome-dependent responses”
e1“Arabidopsis thaliana”
Claim · model-written summary
The authors suggest a phytochrome–SIG2 link coordinates nuclear and plastid gene expression, or SIG2 participates in an inductive light-signalling pathway.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Gene
- SIG2e0
- Outcome
- co-ordination of gene expressione0
- Qualifier
- likelye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The molecular link between phytochromes and SIG2 is likely to be an important part of the co-ordination of gene expression to maintain stoichiometry between the nuclear-encoded phytochrome apoprotein and plastid-derived PΦB, which combine to form photoactive phytochromes, and/or light-dependent SIG2 accumulation is involved in an inductive light signalling pathway co-ordinating components between nucleus and plastids.”
e1“Arabidopsis thaliana”
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