Abstract
The red and far-red light-absorbing phytochromes and UV-A/blue light-absorbing cryptochromes regulate seedling de-etiolation and flowering responses. The signaling steps that mediate the photoreceptor regulation on key flowering genes remain largely unknown. We report that a previously identified photomorphogenic mutant, hypersensitive to red and blue 1 (hrb1), flowered late and showed attenuated expression of FLOWERING LOCUS T (FT) over both long days and short days. Transgenic plants that overexpress the full-length HRB1, or its C-terminal half, flowered early and accumulated more FT messages under short-day conditions. The transgenic plants also displayed hyposensitive de-etiolation phenotypes, and the expression of these phenotypes requires the action of PIF4. The double mutant of hrb1/cry2 showed a flowering phenotype and an FT expression pattern similar to hrb1 under long-day conditions, suggesting that HRB1 may function downstream of cry2 under long-day conditions. In contrast, hrb1/phyB-9 showed a flowering phenotype and an FT expression pattern similar to phyB-9 over both long days and short days, indicating a modulatory role of HRB1 in the flowering pathway mediated by phyB. Overexpression of HRB1 did not affect the expression of the central clock oscillators, TOC1 and CCA1. HRB1 therefore represents a signaling step that regulates FT expression downstream of red and blue light perception.
Publication types
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Acyltransferases / genetics
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Acyltransferases / metabolism
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Arabidopsis / genetics
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Arabidopsis / metabolism
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Arabidopsis / radiation effects
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Arabidopsis Proteins / chemistry
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Arabidopsis Proteins / genetics*
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Arabidopsis Proteins / metabolism
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Arabidopsis Proteins / physiology*
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Basic Helix-Loop-Helix Transcription Factors / metabolism
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Basic Helix-Loop-Helix Transcription Factors / physiology
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Carrier Proteins / chemistry
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Carrier Proteins / genetics
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Carrier Proteins / physiology*
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Cell Nucleus / metabolism
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Cotyledon / growth & development
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Cotyledon / metabolism
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Cryptochromes
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Flowers / genetics
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Flowers / growth & development
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Flowers / metabolism
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Gene Expression Regulation, Plant*
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Hypocotyl / growth & development
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Hypocotyl / metabolism
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Light
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Mutation
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Phenotype
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Phytochrome B / metabolism
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Plants, Genetically Modified / metabolism
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Plants, Genetically Modified / radiation effects
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Protein Structure, Tertiary
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Signal Transduction
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Transcription Factors / genetics
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Transcription Factors / metabolism
Substances
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Arabidopsis Proteins
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Basic Helix-Loop-Helix Transcription Factors
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CCA1 protein, Arabidopsis
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CRY2 protein, Arabidopsis
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Carrier Proteins
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Cryptochromes
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FT protein, Arabidopsis
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HRB1 protein, Arabidopsis
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PHYB protein, Arabidopsis
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PIF4 protein, Arabidopsis
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TOC1 protein, Arabidopsis
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Transcription Factors
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Phytochrome B
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Acyltransferases
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AT5G13930 protein, Arabidopsis