Regulation of gene expression by light.

Light signals perceived mainly by phytochromes and cryptochromes regulate plant growth and development by driving dramatic shifts of the transcriptome. Early light-responsive genes include a large proportion of transcripton factors of different DNA binding motifs. Mutations at loci encoding several transcriptional regulators, including some of those showing rapid changes in transcript levels, impair responses to light in Arabidopsis thaliana. Proteasome-mediated degradation involving the E3 ligase COP1 provides an additional layer of control of the levels of transcription factors. Some transcriptional regulators are shared by light, circadian and/or hormonal signalling circuits creating complex networks that interactively integrate environmental and endogenous cues.