Comparative Transcriptomic Analysis Reveals Carotenoids Biosynthesis Genes in Peach

Carotenoids are important substances for the yellow color of peach flesh. In this study, the contents of carotenoids in two yellow flesh peach varieties ('Zhongtao Jinmi' and 'Jinxiang') and one white flesh peach variety ('Bairuyu') were determined by high-performance liquid chromatography. The results showed that the carotenoid content in the two yellow flesh peach varieties increased with fruit development and reached the maximum of 25.80 and 27.63 μg.g-1 at the mature stage, while that of the white flesh peach variety remained at a very low level during the whole fruit development period. Furthermore, transcriptome sequencing was performed to analyze the differentially expressed genes (DEGs) during fruit development among the three peach varieties. Among these DEGs, four candidate genes were identified to be potentially involved in the biosynthesis of carotenoids, including LOC18774744 (encoding UDP-glycosyltransferase 87A1 (UGT87A1)), LOC18792568 (encoding the carotenoid cleavage dioxygenase 4 gene (CCD4)), LOC109949966 (an unannotated gene), and LOC18779468 (encoding xyloglucan endoglucosylase/hydrolase protein 8. qRT-PCR confirmed that the expression of LOC109949966 and LOC18779468 in two yellow flesh varieties was significantly higher than that in the white flesh variety, while it was the opposite case for UGT87A1 and CCD4. Therefore, we speculate that CCD4 is directly involved in regulating carotenoid synthesis, while other three genes may play some indirect roles in the process. Our findings are expected to improve the understanding on the mechanism of carotenoid biosynthesis in peach. © 2022 Friends Science Publishers