Phytochromes and Other (Photo)Receptors of Information in Plants

Abstract

In land plants, at least five groups of photoreceptors perceive information about light conditions and diurnal rhythm, as well as about ambient temperature, presence of pathogens or competing neighbors, direction of the gravity vector and other factors. The photoreceptor toolkit allows plants to integrate environmental information and “make decisions” necessary for survival and successful reproduction, i.e., whether to enter or exit dormancy, accelerate or stop growth, promote or delay flowering; choose the direction of growth, induce or suppress the formation of side shoots, as well as regulate the synthesis of volatile substances affecting the growth of neighbors or pathogens. These photoreceptors include phytochromes, cryptochromes, phototropins, the ZTL (ZEITLUPE) family proteins, and the ultraviolet-B receptor UVR8. In spite of the diversity of plants photoreceptors, their functionality follows several “common rules.” Transformation of the information on light quality and quantity into metabolic and morphogenetic responses occurs via controlled degradation of transcription factors mediated by interactions of the active form of a photoreceptor and the СОР1-SPA1 E3-ubiquitine ligase complex in the nucleus. Apart from interacting with СОР1, the active forms of photoreceptors in the nucleus can directly bind to transcription factors and trigger their degradation. Phytochromes belong to the largest (the molecular mass of a monomer is ca. 125 kD) and most sophisticated plant photoreceptors. In addition to the abovementioned mechanisms, they also regulate alternative splicing and the selection of alternative promoters for thousands of plant genes. The interaction of phytochrome with jasmonate signaling is of special interest, as phytochromes regulate the jasmonate-mediated cessation of growth in response to stress. This review focuses on data revealing the potential for the application of novel information on plant photoreceptors for the generation of crop varieties capable of high performance under stress conditions.