HY5-COP1: the central module of light signaling pathway

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.

Illuminating the COP1/SPA Ubiquitin Ligase: Fresh Insights Into Its Structure and Functions During Plant Photomorphogenesis

“…HY5 is a bZIP transcription factor that was recently shown to function mainly by activation of gene expression rather than by gene repression ( Burko et al, 2020 ). Along with HYH and HFR1, HY5 suppresses the elongation of hypocotyls in light-grown seedlings ( Lau and Deng, 2012 ; Hoecker, 2017 ; Yuan et al, 2018 ; Bhatnagar et al, 2020 ). HY5 is a non-canonical transcriptional regulator that carries a DNA-binding domain but no transcriptional activation domain.…”

Anything New under the Sun? An Update on Modulation of Bioactive Compounds by Different Wavelengths in Agricultural Plants

“…Please refer to some recent reviews [ 37 , 38 , 39 , 40 ] for a detailed summary of the current knowledge of the transcriptional network and mechanisms regulating the response to the different light spectral composition. Interestingly, CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), which promotes the proteasome-mediates degradation of key factors involved in light signalling, is involved in the response to any light radiation, from UV to far-red wavelengths [ 41 ]. Similarly, the transcription factor ELONGATED HYOCOTYL 5 (HY5) has a central role as a final effector of all the light-dependent signalling routes, being able to bind to the promoters of about 4000 genes in Arabidopsis [ 41 ].…”

Red and blue light treatments of ripening bilberry fruits reveal differences in signalling through abscisic acid‐regulated anthocyanin biosynthesis

“…After light perception, phytochrome and cryptochrome interact with the E3 ubiquitin ligase constitutive photomorphogenesis protein 1 (COP1), which is the key light signalling regulator (Lau & Deng, 2012). In the dark, COP1 directly interacts and represses the action of elongated hypocotyl 5 ( HY5 ) gene inhibiting light signal transmittance and circadian clock genes, also the flowering regulators, such as CONSTANS (CO) via the proteasomal degradation complex (Bhatnagar, Singh, Khurana, & Burman, 2020; Zoratti, Karppinen, et al, 2014). Under light, COP1 activity is repressed, allowing the expression of HY5 and positive transcriptional regulators in a number of developmental processes and metabolic pathways, including anthocyanin biosynthesis (Wu et al, 2019).…”