Brassinosteroid signaling mutants that related to chloroplast development

Abstract

Brz(brassinazole) was synthesized as the first specific inhibitor for brassinosteroid biosynthesis. In the dark germination, Brz-treated plant expressed chloroplastic genes that are expressed as very low level in dark-grown cotyledon without Brz. When the dark-germinated plant with Brz was transferred to the light conditions, chloroplast development was accelerated as compared to the cotyledon without Brz. In the light, Brz treated adult plant showed high-green leaves as compared to leaves without Brz. We screened a mutant that showed pale green phenotype with Brz in the light as bpg2 (Brz-insensitive-pale green2). A T-DNA insertion that related to mutant phenotype in any back crossed bpg2 mutants were identified in an ORF of a novel gene. Possible candidate gene of bpg2 possessed at least 4 hydrophobic regions, and localization of bpg2 into chloroplast was predicted by TargetP program.