In:
Plant Physiology, Oxford University Press (OUP), Vol. 133, No. 4 ( 2003-12-01), p. 1630-1642
Abstract:
The HFR1, a basic helix-loop-helix protein, is required for a subset of phytochrome A-mediated photoresponses in Arabidopsis. Here, we show that overexpression of the HFR1-ΔN105 mutant, which lacks the N-terminal 105 amino acids, confers exaggerated photoresponses even in darkness. Physiological analysis implied that overexpression of HFR1-ΔN105 activated constitutively a branch pathway of light signaling that mediates a subset of photomorphogenic responses, including germination, de-etiolation, gravitropic hypocotyl growth, blocking of greening, and expression of some light-regulated genes such as CAB, DRT112, PSAE, PSBL, PORA, and XTR7, without affecting the light-responsiveness of anthocyanin accumulation and expression of other light-regulated genes such as CHS and PSBS. Although the end-of-day far-red light response and petiole elongation were suppressed in the HFR1-ΔN105-overexpressing plants, flowering time was not affected by HFR1-ΔN105. In addition, the HFR1-ΔN105-overexpressing plants showed hypersensitive photoresponses in the inhibition of hypocotyl elongation, dependently on phytochrome A, FHY1, and FHY3 under FR light or phyB under R light, respectively. Moreover, our double mutant analysis suggested that the hypersensitive photoresponse is due to functional cooperation between HFR1-ΔN105 and other light-signaling components including HY5, a basic leucine zipper protein. Taken together, our results of gain-of-function approach with HFR1-ΔN105 suggest the existence of a complex and important basic helix-loop-helix protein-mediated transcriptional network controlling a branch pathway of light signaling and provide a useful framework for further genetic dissection of light-signaling network in Arabidopsis.
Type of Medium:
Online Resource
ISSN:
1532-2548
,
0032-0889
DOI:
10.1104/pp.103.029751
Language:
English
Publisher:
Oxford University Press (OUP)
Publication Date:
2003
detail.hit.zdb_id:
2004346-6
detail.hit.zdb_id:
208914-2
SSG:
12
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