Integration of transcriptome and metabolome analysis reveals that alternative splicing of TT8 modulates anthocyanin biosynthesis in postharvest blood orange stored at moderate temperature.

Abstract

To address the problem of lower anthocyanin contents in blood oranges at the ripening stage in local orchards, we compared the effects of postharvest storage at different temperatures on anthocyanin production in the pulps of fruit. Transcriptome sequencing and non-targeted metabolomics methods were used to analyze the dynamic changes in differentially expressed genes and differentially accumulated metabolites, respectively, during storage at 8 ℃ or room temperature (15 ℃). The results indicated that anthocyanin and citrate contents in fruit were higher at 8 ℃ than at other storage temperatures. The mRNA levels of TT8, a bHLH transcription factor, were higher in fruits stored at 8 ℃ than at room temperature throughout the entire storage period. Conversely, alternative splicing transcripts of TT8△, lacking a partial coding sequence, exhibited lower expression levels in fruit stored at 8 ℃. During postharvest storage, the genes involved in flavonoid biosynthesis and proton pumping were activated by TT8 and its partners. So that the increasing anthocyanin contents in juice sac tissues were attributed partially to TT8 expression changes caused by the alternative splicing during postharvest storage at a moderate temperature.