Gene inactivation of SmHQT simultaneously improved the browning tolerance and the accumulation of anthocyanins and flavonols of eggplant fruit

The biosynthesis of CGA can occur following different routes in plant species, and hydroxycinnamoyl CoA:quinate hydroxycinnamoyl transferase (HQT) are important enzymes in these pathways. However, the spatiotemporal expression patterns of SmHQT and its relationship to the CGA biosynthesis in eggplant remain largely unclear. In this study, 89 BAHDs were identified from the eggplant genome using PF02458 (transferase) as Hidden Markov Model (HMM) to screen the BAHDs and divided into 7 subfamilies according to the phylogenetic tree. Six eggplant acyltransferases clustered in a subgroup of Clade Ib, clustered with StHQT. We examined the expression patterns of 6 BAHDs in clade Ib in 14 eggplant tissues, and screened out SmHQT for further study. RNAi suppression of SmHQT resulted in over a 90% reduction in CGA, but no change in antioxidant activity suggests that flux was rerouted into other phenylpropanoids. LCMS results showed that flavonols were significantly increased in young leaves, mature leaves, flesh and peel, and anthocyanins were significantly increased in leaves and peel. The genotypes of knockout were chimeric, suggesting that our multiplex gene knockout CRISPR/Cas9 system worked in later stages of plant regeneration. Collectively, those results showed that CGA in eggplant is synthesized through SmHQT, and SmHQT suppression redirected phenylpropanoid flux and altered phenotype.