HY5 regulates GLK and GNC transcription factors to orchestrate photomorphogenesis inArabidopsis thaliana

Abstract

AbstractLight induced de-etiolation is an important aspect of seedling photomorphogenesis. GOLDEN2 LIKE (GLK) and GATA NITRATE-INDUCIBLE CARBON-METABOLISM-INVOLVED (GNC) are master transcriptional regulators involved in chloroplast development, but whether they participate in photomorphogenesis is largely unknown. Here we show that ELONGATED HYPOCOTYL5 (HY5) binds toGLKandGNCpromoters and activates their expression. HY5 also interacts with GLK proteins. Chlorophyll content in the de-etiolating seedlings of thehy5 glk2andhy5 gncdouble mutants was lower than that in the single mutants. It was further found that GLK inhibited hypocotyl elongation, whereas GNC promoted hypocotyl elongation, and that both could superimpose on thehy5phenotype. Correspondingly, GLK and GNC differentially regulate the expression of cell elongation genes. DE-ETIOLATED 1 (DET1) destabilises GLK proteins. The light-grown traits exhibited by etioplast ofdet1mutant were attenuated indet1 glk2double mutant, while similar todet1mutant, photosystem genes were up-regulated to different extent in etiolated seedlings overexpressingGLK2orGNC. Our study reveals that GLK and GNC act downstream of HY5 and likely cooperate with HY5 and DET1 to orchestrate multiple developmental traits during the light-induced skotomorphogenesis to photomorphogenesis transition.One-sentence summaryGLK and GNC act downstream of HY5, and cooperate with HY5 and DET1, to regulate both chloroplast development and hypocotyl elongation during the transition from skotomorphogenesis to photomorphogenesis.