Multiomic Analysis Elucidates the Reasons Underlying the Differential Metabolite Accumulation in Citrus Mature Leaves and Fruit Juice Sacs

Fruit and leaf possess distinctly different metabolites. Here, metabolites and transcriptome were compared between mature leaves (ML) and juice sacs (JS) of Citrus grandis "Hirado Buntan" to investigate the possible reasons. Results indicated that the remarkable difference in starch, total flavonoids and carotenoids, l-ascorbate, and jasmonic acid between ML and JS was tightly related to the expression levels of their biosynthesis-related genes, while the significant difference in abscisic acid and citrate was mainly related to the gene expression level(s) of 9-cis-epoxycarotenoid dioxygenase and proton pump genes, respectively. In addition, ATP citrate lyase probably plays a key role in the levels of flavonoids between ML and JS via providing different levels of acetyl-CoA. Taken together, these results identified some key candidate genes responsible for the content of a given metabolite and will contribute to research in regulating such metabolite content in citrus fruits.