Phytochrome Signaling in Green Arabidopsis Seedlings： Impact Assessment of a Mutually Negative phyB-PIF Feedback Loop

作     者：Pablo Leivar Elena Monte Megan M. Cohn Peter H. Quail 

作者机构：Department of Plant and Microbial Biology University of California Berkeley CA 94720 USA United States Department of Agriculture Plant Gene Expression Center Albany CA 94710 USA Department of Molecular Genetics Center for Research in Agricultural Genomics （CRAG） CSIC-IRTA-UAB-UB Campus UAB Bellaterra （Cerdanyola del Valles） 08193 Barcelona Spain 

出 版 物：《Molecular Plant》 (分子植物（英文版）)

年 卷 期：2012年第5卷第3期

页      面：734-749页

核心收录：

学科分类：0710[理学-生物学] 07[理学] 071009[理学-细胞生物学] 09[农学] 0901[农学-作物学] 090102[农学-作物遗传育种] 

基　　金：Marie Curie International Reintegration Grant By grants Marie Curie Spanish "Ministerio de Ciencia e Innovacion" Generalitat de Catalunya By National Institutes of Health Grant Department of Energy Grant USDA Agricultural Research Service Current Research Information System Grant 

主　　题：Light regulation light signaling genetics molecular biology transcriptional control and transcription fac- tors photomorphogenesis 

摘      要：The reversibly red （R）/far-red （FR）-Iight-responsive phytochrome （phy） photosensory system initiates both the deetiolation process in dark-germinated seedlings upon first exposure to light, and the shade-avoidance process in fully deetiolated seedlings upon exposure to vegetational shade. The intracellular signaling pathway from the light-activated photoreceptor conformer （Pfr） to the transcriptional network that drives these responses involves direct, physical inter- action of Pfr with a small subfamily of bHLH transcription factors, termed Phy-lnteracting Factors （PIFs）, which induces rapid PIF proteolytic degradation. In addition, there is evidence of further complexity in light-grown seedlings, whereby phyB-PIF interaction reciprocally induces phyB degradation, in a mutually-negative, feedback-loop configuration. Here, to assess the relative contributions of these antagonistic activities to the net phenotypic readout in light-grown seedlings, we have examined the magnitude of the light- and simulated-shade-induced responses of a pentuple phyBpiflpif3pif4pif5 （phyBpifq） mutant and various multiple pif-mutant combinations. The data （1） reaffirm that phyB is the predominant, if not exclusive, photoreceptor imposing the inhibition of hypocotyl elongation in deetiolating seedlings in response to pro- longed continuous R irradiation and （2） show that the PIF quartet （PIF1, PIF3, PIF4, and PIF5） retain and exert a dual capacity to modulate hypocotyl elongation under these conditions, by concomitantly promoting cell elongation through intrinsic transcriptional-regulatory activity, and reducing phyB-inhibitory capacity through feedback-loop-induced phyB degrada- tion. In shade-exposed seedlings, immunoblot analysis shows that the shade-imposed reduction in Pfr levels induces increases in the abundance of PIF3, and mutant analysis indicates that PIF3 acts, in conjunction with PIF4 and PIF5, to promote the known shade-induced acceleration of hypocotyl elongation. Conversel