PIL5, a phytochrome-interacting basic helix-loop-helix protein, is a key negative regulator of seed germination in Arabidopsis thaliana.
The first decision made by an angiosperm seed, whether to germinate or not, is based on integration of various environmental signals such as water and light. The phytochromes (Phys) act as red and far-red light (Pfr) photoreceptors to mediate light signaling through yet uncharacterized pathways. We report here that the ... PIF3-like 5 (PIL5) protein, a basic helix-loop-helix transcription factor, is a key negative regulator of phytochrome-mediated seed germination. PIL5 preferentially interacts with the Pfr forms of Phytochrome A (PhyA) and Phytochrome B (PhyB). Analyses of a pil5 mutant in conjunction with phyA and phyB mutants, a pif3 pil5 double mutant, and PIL5 overexpression lines indicate that PIL5 is a negative factor in Phy-mediated promotion of seed germination, inhibition of hypocotyl negative gravitropism, and inhibition of hypocotyl elongation. Our data identify PIL5 as the first Phy-interacting protein that regulates seed germination.
Mesh Terms:
Arabidopsis, Arabidopsis Proteins, Basic Helix-Loop-Helix Transcription Factors, DNA-Binding Proteins, Germination, Gravitropism, Helix-Loop-Helix Motifs, Hypocotyl, Mutation, Photoreceptor Cells, Phytochrome, Phytochrome A, Phytochrome B, Seeds, Transcription Factors
Arabidopsis, Arabidopsis Proteins, Basic Helix-Loop-Helix Transcription Factors, DNA-Binding Proteins, Germination, Gravitropism, Helix-Loop-Helix Motifs, Hypocotyl, Mutation, Photoreceptor Cells, Phytochrome, Phytochrome A, Phytochrome B, Seeds, Transcription Factors
Plant Cell
Date: Nov. 01, 2004
PubMed ID: 15486102
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