Biological photoreceptors of light-dependent regulatory processes

Abstract

Progress in understanding primary mechanisms of light reception in photoregulatory processes is achieved through discovering new biological photoreceptors, chiefly the regulatory sensors of blue/UV-A light. Among them are LOV domain-containing proteins and DNA photolyase-like cryptochromes, which constitute two widespread groups of photoreceptors that use flavin cofactors (FMN or FAD) as the photoactive chromophores. Bacterial LOV domain modules are connected in photoreceptor proteins with regulatory domains such as diguanylate cyclases/phosphodiesterases, histidine kinases, and DNA-binding domains that are activated by photoconversions of flavin. Identification of red/far-red light sensors in chemotrophic bacteria (bacteriophytochromes) and crystal structures of their photosensor module with bilin chromophore are significant for decoding the mechanisms of phytochrome receptor photoconversion and early step mechanisms of phytochrome-mediated signaling. The only UV-B regulatory photon sensor, UVR8, recently identified in plants, unlike other photoreceptors functions without a prosthetic chromophore: tryptophans of the unique UVR8 protein structure provide a "UV-B antenna". Our analysis of new data on photosensory properties of the identified photoreceptors in conjunction with their structure opens insight on the influence of the molecular microenvironment on light-induced chromophore reactions, the mechanisms by which the photoactivated chromophores trigger conformational changes in the surrounding protein structure, and structural bases of propagation of these changes to the interacting effector domains/proteins.

UV-B Photoreceptors, Their Role in Photosignaling, Physiological Responses, and Abiotic Stress in Plants

“…Plants use the UVR8 photoreceptor to sense UV-B radiation and perform appropriate acclimation responses (Fraikin et al 2013 ;Jenkins 2014 ;Tilbrook et al 2013 ). A UV-B hypersensitive mutant, UV resistance locus 8-1, from a genetic screen for UV-sensitivity showed reduced expression of fl avinoid-biosynthesis pathway genes and chalcone synthase gene as well as an increased levels of PR1 and PR5 (pathogenesis-related genes) proteins (Kliebenstein et al 2002 ).…”

Elucidation of Abiotic Stress Signaling in Plants

“…Plants use the UVR8 photoreceptor to sense UV-B radiation and perform appropriate acclimation responses (Fraikin et al 2013 ;Jenkins 2014 ;Tilbrook et al 2013 ). A UV-B hypersensitive mutant, UV resistance locus 8-1, from a genetic screen for UV-sensitivity showed reduced expression of fl avinoid-biosynthesis pathway genes and chalcone synthase gene as well as an increased levels of PR1 and PR5 (pathogenesis-related genes) proteins .…”

“…When light interacts with these small molecules, they undergo photochemical changes like isomerization, bond formation, photoreduction or cyclic electron transfer, etc. leading to conformational changes in the apoprotein part, which in turn leads to signal propagation and the resulting physiological functions (Fraikin et al 2013 ;Jenkins 2014 ;Losi and Gartner 2012 ;Sineshchekov et al 2013 ). Photoreceptors are classifi ed primarily based on the chemical nature of their chromophore as 1.…”

Interaction of light quality and fertility on biomass, shoot pigmentation and xanthophyll cycle flux in Chinese kale

“…Specialized plant photoreceptor pigment–protein complexes capture light energy to drive photosynthetic processes, as well as to respond to environmental changes in light quality and quantity. Following light interception, conformational changes in chromophore molecules result in chromophore–protein interactions that transform light signals into biological signals capable of regulating gene expression and altering plant metabolism . Cryptochromes and phototropins are two specialized photoreceptors in plants that respond to higher energy blue/ultraviolet light wavelengths.…”

“…Following light interception, conformational changes in chromophore molecules result in chromophore-protein interactions that transform light signals into biological signals capable of regulating gene expression and altering plant metabolism. 1 Cryptochromes and phototropins are two specialized photoreceptors in plants that respond to higher energy blue/ultraviolet light wavelengths. Cryptochromes regulate responses such as circadian rhythms and stem elongation, whereas phototropins control chloroplastic movements to maximize the absorption of light.…”