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.
Department of Biological Sciences, KAIST, Daejeon 305-701, Korea.
Eunkyoo
E
Oh
Jonghyun
J
Kim
Eunae
E
Park
Jeong-Il
JI
Kim
Changwon
C
Kang
Giltsu
G
Choi
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D018525:Germination / Q000235:genetics*; D018522:Gravitropism / Q000502:physiology; D018257:Helix-Loop-Helix Motifs / Q000502:physiology*; D018546:Hypocotyl / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D009154:Mutation / Q000502:physiology; D010786:Photoreceptor Cells / Q000378:metabolism; D010834:Phytochrome / Q000378:metabolism*; D051942:Phytochrome A; D051939:Phytochrome B; D012639:Seeds / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D010834:Phytochrome; D051942:Phytochrome A; D051939:Phytochrome B; D014157:Transcription Factors; C497973:PHYA protein, Arabidopsis; C497952:PHYB protein, Arabidopsis; C508068:At2g20180 protein, Arabidopsis