Correlation of the temporal and spatial expression patterns of HQT with the biosynthesis and accumulation of chlorogenic acid in flowers.

Hydroxycinnamoyl-CoA quinate transferase (HQT) is one of the key enzymes in the biosynthesis of chlorogenic acid (CGA) in the flowers of . However, the spatiotemporal expression patterns of and its relationship to the dynamics of CGA biosynthesis, transport, and storage remain largely unknown. In this study, we collected flower samples at different growth stages (S1-S6) and examined the spatiotemporal expression pattern of and the dynamic accumulation patterns of CGA using a combination of molecular and cytological techniques. Our results suggest that the spatiotemporal expression pattern of is directly correlated with dynamic changes in CGA accumulation and distribution in flowers. We further show that CGA is synthesized primarily in the cytoplasm and chloroplasts. CGA synthesized in the cytoplasm first accumulates in specialized vesicles and is then transferred to large central vacuoles for storage by fusion of CGA-containing vesicles with vacuoles. Furthermore, CGA synthesized in the chloroplasts appears to be transferred into the vacuoles for storage by direct membrane fusion between the tonoplast and the disrupted chloroplast membranes. Collectively, our results suggest that CGA is synthesized in chloroplasts and cytoplasm and finally transferred to the vacuole for long-term storage.