Genetic and molecular analysis of light-regulated plant development

Abstract

Light regulates many physiological and developmental events in plants through the action of multiple sensory pigment systems. Although our understanding of the regulatory photoreceptors, including phytochromes (that principally absorb red and far-red energy) and blue light receptors, has advanced considerably in the recent past, the mechanisms of light signal transduction in higher plants are poorly understood. To unravel the molecular events associated with light-regulated plant development, a large number of photomorphogenic mutants have been isolated in several different plant species, including Arabidopsis, cucumber, tomato, pea, Brassica and Sorghum, which are either impaired in normal perception of light signal (photoreceptor mutants) or are affected in some specific or a sub-set of phenotypic traits (signal transduction mutants). Their physiological and molecular analysis is proving to be valuable in (1) assigning specific function to discrete phytochrome species, (2) elucidation of elements that constitute the transduction pathway downstream of signal perception, and (3) determining how different photosensory systems regulate many diverse responses. The progress made in the analysis of photomorphogenic mutants, as reviewed in this article, clearly indicates that multiple photoreceptors, either of the same or different class, interact through an intricate network of signal transduction pathways to finally determine the light-dependent phenotype of both monocots and dicots.