HY5-COP1: the central module of light signaling pathway
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REVIEW ARTICLE
HY5-COP1: the central module of light signaling pathway Akanksha Bhatnagar1
•
Shipra Singh1
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Jitendra P. Khurana1
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Naini Burman1,2
Received: 24 September 2020 / Accepted: 6 October 2020 Ó Society for Plant Biochemistry and Biotechnology 2020
Abstract Light acts catalytically to initiate a cascade of events to eventually regulate different aspects of plant development. The cascade of light signal transduction involves several components that can be broadly grouped as photoreceptors, early signaling factors, central integrators and downstream effectors. ELONGATED HYPOCOTYL 5 (HY5), a bZIP transcription factor, is the most well characterized downstream effector in Arabidopsis, which acts as a positive regulator of photomorphogenesis. HY5 acts as a master regulator and binds to promoters of close to 4000 genes, thereby, regulating wide diversity of photomorphogenic responses. It physically interacts with CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), a negative regulator of photomorphogenesis. HY5-COP1 interaction mediates cross-talk among multiple pathways, thereby, enhancing the phenotypic plasticity of plants. This interaction regulates not only the upstream components of light signaling pathway like photoreceptors but also regulates a number of downstream effectors and early signaling factors, which help to regulate a number of developmental processes in plants. This review highlights the key interaction between HY5 and COP1 and how it regulates seedling photomorphogenesis, shade avoidance, circadian clock, root architecture, flowering, thermomorphogenesis, hormone signaling and stress responses, in conjunction with other signaling components and transcription factors. Keywords Light signaling Phytochromes Cryptochromes UVR8 HY5 COP1 Photomorphogenesis Skotomorphogenesis Thermomorphogenesis Abbreviations CRY Cryptochrome PHY Phytochrome PIF Phytochrome interacting factor(s) HY5 ELONGATED HYOCOTYL 5 COP1 Constitutive photomorphogenic 1 SPA1 Suppressor of PHYA 1
& Naini Burman [email protected] 1
Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi 110021, India
2
Regional Centre for Biotechnology, 3rd Milestone, Faridabad-Gurgaon Expressway, Faridabad, Haryana 121001, India
Introduction Plant growth and development is influenced by environmental factors as well as endogenous cues. The sessile nature of plants has led to the development of phenotypic plasticity in response to various environmental stimuli like light, temperature and oxygen. Photomorphogenesis is one such example of phenotypic plasticity exhibited by plants. Depending upon whether grown in light or dark, seedlings of angiosperms can follow two developmental pathways— photomorphogenesis and skotomorphogenesis. In photomorphogenesis, young light grown seedlings of dicot plants exhibit short hypocotyl, open apical hook with fully expanded green cotyledons, and continuous differentiation of the shoot apical meristem. In skotomorphogenesis, due to absence of light, seedlings develo
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