Analysis of brassinosteroid signalling mutant that related to chloroplast development

Abstract

Brz (brassinazole) was synthesized as the first specific inhibitor of brassinosteroid biosynthesis by Asami et al. Target of Brz220 is the cytochrome P450 enzyme encoded by DWF4. In the light, plants treated with Brz display dwarfism with the dark-green leaves. Brassinosteroid deficiency in the dark with Brz caused not only the deetiolation but also the acceleration to chloroplast from etioplast after the short-term-light treatment to cotyledon that germinated in the dark with Brz. Many chloroplast genes that were encoded on the both of nuclei and plastid genome were expressed in the dark with Brz higher than the control plant without Brz. We identified a pale green mutant that could not be recovered to high green by Brz. As the dark-grown hypocotyl of the mutant was normal short-dwarf by Brz, the mutants can be thought as specific on the signalling from brassinosteroid to chloroplast development.