BRZ-INSENSITIVE-PALE GREEN 1 is encoded by chlorophyll biosynthesis enzyme gene that functions in the downstream of brassinosteroid signaling

Brassinosteroids (BRs), a kind of phytohormone, have various biological activities such as promoting of plant growth, increasing of stress resistance, and chloroplast development. Though BRs have been known to have physiological effects on chloroplast, the detailed mechanism of chloroplast development and chlorophyll biosynthesis in BR signaling remains unknown. Here we identified a recessive pale green Arabidopsis mutant, Brz-insensitive-pale green1 (bpg1), which was insensitive to promoting of greening by BR biosynthesis-specific inhibitor Brz in the light. BPG1 gene encoded chlorophyll biosynthesis enzyme, 3, 8-divinyl protochlorophyllide a 8-vinyl reductase (DVR), and bpg1 accumulated divinyl chlorophylls. Chloroplast development was suppressed in bpg1. Brz dramatically increased the expression of chlorophyll biosynthesis enzyme genes, including BPG1. These results suggest that chlorophyll biosynthesis enzymes are regulated by BR signaling in the aspect of gene expression and BPG1 plays an important role in regulating of chloroplast development.