Hypersensitive to red and blue 1 and its C-terminal regulatory function control FLOWERING LOCUS T expression

Xiaojun Kang, Yun Zhou, Xiaodong Sun, Min Ni

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)937-948
Number of pages12
JournalPlant Journal
Volume52
Issue number5
DOIs
StatePublished - Dec 2007

Keywords

  • Cryptochrome
  • De-etiolation
  • Flowering
  • HRB1
  • Phytochrome
  • ZZ-type zinc-finger

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