Abstract:

【Objective】In order to explore the changes of carotenoid content, the transcription level of genes encoding a few key enzymes in carotenoid biosynthetic pathway, and the regulation effect of ethylene in carotenoid biosynthesis in fruits of Valencia orange during the late yellowing and re-greening stages. 【Method】 Fruit late development and maturation process of Valencia orange were divided into four yellowing periods (P1-P4) and three re-greening periods (P5-P7), the carotenoid content and the gene expression of PSY, PDS and ZDS were analyzed accordingly.【Result】 Results demonstrated that peel color during the developmental process from P1 to P7 firstly turns from green to yellow, then to green again, which was consistent with the changes of carotenoid accumulation and PSY, PDS and ZDS gene expression during this process. Ethylene could promote carotenoid accumulation, PSY gene expression in the peel at yellowing stage, but had no significant effects on PDS and ZDS gene expression. However, at the re-greening stage, ethylene treatment had no effects on carotenoid accumulation in the peel, but retarded the decline of PSY and PDS gene expression. 【Conclusion】 Results showed that in the late yellowing and re-greening stages, the regulating effects of ethylene on carotenoid accumulation and PSY, PDS gene expression were varied with fruit development stages of Valencia orange, indicating that the effects of ethylene may relate to other developmental factors. Ethylene could promote peel yellowing at the yellowing stages of Valencia orange, but re-greening was impossible by using ethylene at the re-greening stages.

Key words: Valencia orange, re-greening, carotenoid, ethylene, gene expression