Comparative transcriptome profiling analysis provides insight into the mechanisms for sugar change in Chinese jujube (Ziziphus jujuba Mill.) under rain-proof cultivation.

Chinese jujube (Ziziphus jujuba Mill.) is a globally popular and economically important fruit that is rich in bioactive compounds with strong anti-cancer effects. Rain-proof cultivation is widely used to cultivate Chinese jujube, as it helps avoid rainfall damage during fruit harvest. Although the sugar content of jujube fruits differs between rain-proof and open-field cultivation, the underlying molecular mechanisms are unknown. Here, we analyzed the levels of sugar content, sugar accumulation pattern, and transcriptome profiles of jujube fruits at five developmental stages grown under rain-proof and open-field cultivation modes. The sugar content of jujube fruits was significantly higher under rain-proof cultivation than under open-field cultivation, although the sugar composition and sugar accumulation patterns were comparable. Comparative analysis of transcriptomic profiles showed that rain-proof cultivation enhanced the intrinsic metabolic activity of fruit development. Gene expression and correlation analyses suggested that ZjSPS, ZjSS, ZjHXK, and ZjINV regulate the development-related changes in sugar content in jujube fruits grown under rain-proof cultivation. Temperature, humidity, and moisture conditions were key climatic factors affecting sugar accumulation. Our results provide insights into the molecular mechanisms regulating sugar content and sugar accumulation in Chinese jujube fruits grown under rain-proof cultivation, and we provide genetic resources for studying the development mechanism of Chinese jujube fruit.