Combined metabolome and transcriptome analysis revealed the distribution characteristics of secondary metabolites in Citrus reticulata 'Ponkan'

Citrus contains abundant secondary metabolites distributed in various tissues, playing an important role in human health. A total of 512 secondary metabolites were detected in 12 tissues of Citrus reticulata 'Ponkan', showing that different tissues had unique secondary metabolic profiles. Leaf, tender bine and flavedo were flavonoids-enriched tissues, while the root was coumarins-enriched tissue. Combined transcriptome and metabolite analysis showed that the differential expression of some structural genes may be the cause of metabolite specific accumulation among different tissues, and from which we identified two OMTs involved in coumarin methoxylation modification. Weighted gene co-expression network analysis (WGCNA) revealed the modules related to flavonoids and coumarins content and predicted related transcription factors. The antioxidant capacity of 12 tissues appeared significant difference, with the strongest in the young leaf and the lowest in juice sacs, seed and segment membrane. Our research described the metabolic profile of citrus plants in detail and provided rich references for the development of medicinal value and resource utilization of citrus.