Functional roles of PIL5 in Arabidopsis seed germination = 애기장대 발아 조절에 관여하는 PIL5 기능

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The first decision made by an angiosperm seed, whether to germinate or not, is based on integration of various environmental signals such as light, moisture and temperature. The phytochromes act as red and far-red light photoreceptors to mediate various light responses including seed germination. However, the molecular mechanism by which phytochromes regulate seed germination has not been elucidated. Here, I showed that PIL5 protein, a basic helix-loop-helix transcription factor, is a key negative regulator of phytochrome-mediated seed germination by phenotypic analyses using PIL5 loss of function and gain of function mutant. PIL5 also regulated other phytochrome mediated light responses including inhibition of hypocotyls elongation and hypocotyls negative gravitropism. Like, PIF3, PIL5 also preferentially interacted with Pfr form of phytochrome. Expression analysis revealed that PIL5 repressed the expression of gibberellin (GA) biosynthetic genes ($GA3ox1$ and $GA3ox2$) and activated the expression of a GA catabolic gene ($GA2ox$). Consistent with these gene expression patterns, the amount of bioactive GA was higher in the pil5 mutant and lower in the PIL5 overexpression line. I also showed that red and far-red light signals trigger PIL5 protein degradation through the 26S proteasome, thus releasing the inhibition of bioactive GA biosynthesis by PIL5. In addition to GA metabolic genes, PIL5 also regulates the expression of GA repressor (DELLA) genes (GAI and RGA) and ABA metabolic genes and ABA metabolic genes (ABA1, NCED6 and CYP707A2). Chromatin immunoprecipitation analyses indicated that PIL5 directly binds to GAI and RGA promoters through G-box element, but not to GA and ABA metabolic gene promoters. Taken together, these results show that light signals perceived by phytochromes cause a reduction in the PIL5 protein level, which in turn regulates the transcription of two DELLA genes directly and that of GA and ABA metabolic genes indirectly. To find more P...
Advisors
Choi, Gil-tsuresearcher최길주researcher
Description
한국과학기술원 : 생명과학과,
Publisher
한국과학기술원
Issue Date
2008
Identifier
295337/325007  / 020037387
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 생명과학과, 2008.2, [ x, 190 p. ]

Keywords

PIL5; Phytochrome; Gibberellin; Germination; Arabidopsis; PIL5; 파이토크롬; 지베렐린; 발아; 애기장대; PIL5; Phytochrome; Gibberellin; Germination; Arabidopsis; PIL5; 파이토크롬; 지베렐린; 발아; 애기장대

URI
http://hdl.handle.net/10203/27642
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=295337&flag=dissertation
Appears in Collection
BS-Theses_Ph.D.(박사논문)
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