Phytochrome Signaling Mechanisms Author(s) :Jigang Li, Gang Li, Haiyang Wang and Xing Wang Deng Source: The Arabidopsis Book, Number 9 2011. Published By: The American Society of Plant Biologists URL: http://www.bioone.org/doi/full/10.1199/tab.0148
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The Arabidopsis Book
© 2011 American Society of Plant Biologists
First published on August 22, 2011: e0148. doi: 10.1199/tab.0148 This chapter is an updated version of a chapter originally published on July 6, 2004, e0074.1. doi: 10.1199/tab.0074.1
Phytochrome Signaling Mechanisms Jigang Lia,b, Gang Lib, Haiyang Wangb, and Xing Wang Denga,b,1 Peking-Yale Joint Center for Plant Molecular Genetics and Agro-biotechnology, State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China b Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut, 06520-8104 1 Address correspondence to
[email protected] a
Phytochromes are red (R)/far-red (FR) light photoreceptors that play fundamental roles in photoperception of the light enYLURQPHQWDQGWKHVXEVHTXHQWDGDSWDWLRQRISODQWJURZWKDQGGHYHORSPHQW7KHUHDUH¿YHGLVWLQFWSK\WRFKURPHVLQArabidopsis thaliana, designated phytochrome A (phyA) to phyE. phyA is light-labile and is the primary photoreceptor responsible for mediating photomorphogenic responses in FR light, whereas phyB-phyE are light stable, and phyB is the predominant phytochrome regulating de-etiolation responses in R light. Phytochromes are synthesized in the cytosol in their inactive Pr form. Upon light irradiation, phytochromes are converted to the biologically active Pfr form, and translocate into the nucleus. SK\%FDQHQWHUWKHQXFOHXVE\LWVHOILQUHVSRQVHWR5OLJKWZKHUHDVSK\$QXFOHDULPSRUWGHSHQGVRQWZRVPDOOSODQWVSHFL¿F proteins FAR-RED ELONGATED HYPOCOTYL 1 (FHY1) and FHY1-LIKE (FHL). Phytochromes may function as light-regulated serine/threonine kinases, and can phosphorylate several substrates, including themselves in vitro. Phytochromes are phosphoproteins, and can be dephosphorylated by a few protein phosphatases. Photoactivated phytochromes rapidly change the expression of light-responsive genes by repressing the activity of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), an E3 ubiquitin ligase targeting several photomorphogenesis-promoting transcription factors for degradation, and by inducing rapid phosphorylation and degradation of Phytochrome-Interacting Factors (PIFs), a group of bHLH transcription factors repressing photomorphogenesis. Phytochromes are targeted by COP1 for degradation via the ubiquitin/26S proteasome pathway.
INTRODUCTION As sessile organisms, plants have acquired a high degree of developmental plasticity to optimize their growth and reproduction in response to their ambient environment, such as light, temperature, humidity, and salinity. Plants utilize a wide range of sensory V\VWHPV WR SHUFHLYH DQG WUDQVGXFH VSHFL¿F LQFRPLQJ HQYLURQmental signals. Light is one of the key environmental signals that LQÀXHQFHVSODQWJURZWKDQGGHYHORSPHQW,QDGGLWLRQWREHLQJWKH primary energy source for plants, light also controls multiple developmental processes in the plant life cycle, including seed germination, seedling de-etiolation, leaf expansion, stem elongation, phototropism, stomata and chloroplast movement, shade avoidDQFH FLUFDGLDQ UK\WKPV DQG ÀRZHULQJ WLPH 'HQJ DQG 4XDLO 1999; Wang and Deng, 2003; Jiao et al., 2007). Plants can monitor almost all facets of light, such as direction, duration, quantity, and wavelength by using at least four major FODVVHV RI SKRWRUHFHSWRUV SK\WRFKURPHV SK\V SULPDULO\ UHVSRQVLEOHIRUDEVRUELQJWKHUHG 5 DQGIDUUHG )5 ZDYHOHQJWKV QP DQGWKUHHW\SHVRISKRWRUHFHSWRUVSHUFHLYLQJWKH EOXH % XOWUDYLROHW$ 89$ UHJLRQRIWKHVSHFWUXP QP FU\SWRFKURPHV FU\V SKRWRWURSLQV SKRWV DQGWKUHHQHZO\UHFRJQL]HG/29)ER[.HOFKUHSHDWSURWHLQV=(,7/83( =7/ )/$9,1%,1',1*.(/&+5(3($7)%2; ).) DQG/29.(/&+ 5(3($7 3527(,1 /.3 ,Q DGGLWLRQ 89 5(6,67$1&( /2&86 895 ZDV UHFHQWO\ VKRZQ WR EH D 89%
QP SKRWRUHFHSWRU 5L]]LQL HW DO 7KHVH SKRWRUHFHSWRUV perceive, interpret, and transduce light signals, via distinct intracellular signaling pathways, to modulate photoresponsive nuclear gene expression, and ultimately leading to adaptive changes at the cell and whole organism levels. The past two decades have seen dramatic progress in molecular characterization and understanding of the photobiology and photochemistry of the phytochrome photoreceptors in higher plants. This chapter aims to highlight some of the most recent progress in elucidating the molecular, cellular and biochemical PHFKDQLVPVRISK\WRFKURPHVLJQDOLQJLQ$UDELGRSVLV,QWHUHVWHG readers are encouraged to read the accompanying reviews on RWKHUUHODWHGVXEMHFWVVXFKDVSKRWRPRUSKRJHQHVLV 1HPKDXVHUDQG&KRU\ FU\SWRFKURPHV
