Abstract

The antagonism between ABA and GA in regulating accumulation of anthocyanin has been well documented. Lately we showed both ABA and GA 3 alleviated litchi browning, but the underlying molecular mechanism remains unclear. Here we showed 6-d storage caused obvious browning in litchi, but ABA and GA 3 increased anthocyanin and reduced color fading relative to the control. LC-MS analysis identified 21 anthocyanins from litchi, of which seven were upregulated and 14 downregulated for ABA treatment after storage relative to before, and four upregulated and 17 downregulated for GA 3 treatment. Among the upregulated anthocyanins were three shared by ABA and GA 3 treatments. RNA-seq revealed that ABA and GA 3 upregulated genes for 7 anthocyanin biosynthetic enzymes, including LcPAL and LcCHS , whose expression patterns were consistent with that of LcNAC90 . Moreover, ABA and GA 3 activated transcription of LcNAC90 transiently expressed in tobacco, verifying the responsiveness of LcNAC90 to ABA and GA 3 . The regulatory network analysis suggested that LcPAL and LcCHS transcripts were highly correlated with LcNAC90. Sequence analysis revealed NAC binding sites in promoters of LcPAL and LcCHS . Biochemical evidences showed LcNAC90 specifically bound to the promoters and activated transcription of LcPAL and LcCHS . LcNAC90 overexpression in Arabidopsis increased leaf pigmentation and upregulated anthocyanin biosynthetic genes in Arabidopsis , e.g. AtPAL and AtCHS . Collectively, this work suggests that ABA and GA 3 activate LcNAC90 to enhance anthocyanin biosynthesis in litchi during storage. The findings provide novel insight into mechanism underlying anthocyanin accumulation regulated by ABA and GA.