|_Re: 10월 28일 세미나|
Arabidopsis CPP chaperone family proteins and their targets
Ho-Seok Lee 1,2, Jae-Yong Lee 3, and Hyun-Sook Pai 1
1 Department of Systems biology, Yonsei University, Seoul 03722, South Korea
2 Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna BioCenter (VBC), Dr Bohr-Gasse 3, 1030 Vienna, Austria
3 NongHyup Seed Company, Anseong, Gyeonggi-do 456-824, South Korea
Protochlorophyllide oxidoreductase (POR) catalyzes the protochlorophyllide reduction step in the chlorophyll biosynthetic pathway. POR is activated by light and its substrate and product are photosensitizers. We report that chaperone-like protein of POR 1 (CPP1), a membrane protein containing DnaJ-like domain, interacts with POR isoforms in chloroplast membranes and protects POR proteins from photooxidative damage with its chaperone activity. We also report that CPP2/DE-ETIOLATION IN THE DARK AND YELLOWING IN THE LIGHT (DAY), a CPP1 homolog, plays a dual-role in photomorphogenesis by stabilizing the BR receptor, BRI1, as well as a key enzyme in chlorophyll biosynthesis, POR. DAY localizes to both the endomembrane and chloroplasts via its first transmembrane domain and chloroplast transit peptide, respectively, and interacts with BRI1 and POR in their respective subcellular compartments. Using genetic analysis, we show that DAY acts independently on BR signaling and chlorophyll biogenesis. This work uncovers DAY as a factor that simultaneously regulates BR signaling and chloroplast development, revealing a key regulator of photomorphogenesis that acts across cell compartments. Collectively, these results suggest that CPP family chaperones CPP1 and DAY play critical roles in plant growth and survival.