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 condition without Brz. In the light, Brz treated adult plant showed high-green leaves as compared to leaves without Brz. So we tried to screen for a mutant that showed pale green phenotype with Brz in the light, and isolated bpg2 (Brz-insensitive-pale green2) mutant. A T-DNA insertion site of bpg2 mutant was identified in an ORF of novel gene. TargetP program predicted that BPG2 localized to chloroplast. Expression of bpg2 gene was induced by light, and was highest in leaves. These results might suggest that BPG2 has an important role for regulation of chloroplast differentiation.