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HYPERSENSITIVE TO RED AND BLUE 1 and its C‐terminal regulatory function control FLOWERING LOCUS T expression
Author(s) -
Kang Xiaojun,
Zhou Yun,
Sun Xiaodong,
Ni Min
Publication year - 2007
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2007.03295.x
Subject(s) - phytochrome , biology , phenotype , mutant , genetics , locus (genetics) , cryptochrome , flowering locus c , far red , gene , etiolation , seedling , microbiology and biotechnology , transgene , botany , arabidopsis , red light , circadian clock , biochemistry , enzyme
Summary 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.