Co-expression network analysis identifies AtrANS, a gene essential for anthocyanin pigmentation in Akebia trifoliata pericarp

Pericarp coloration is an important trait in Akebia trifoliata breeding which influences consumer choice. To better understand the molecular mechanisms underlying its formation, three varieties of A. trifoliata with different pericarp colors: Luoyang white pericarp (LW), Guida No.3 pink pericarp (GP), and Za No.30 purple pericarp (ZP) were used. The pigment content of the pericarp of these three varieties during the colour change period was determined, and anthocyanins were determined as the main reason for the different colors. RNA-Seq analysis was performed on the pericarps of different varieties over several periods. Using LW as a control, 13,807 differently expressed genes (DEGs) were identified by comparing the GP and ZP. KEGG enrichment analysis revealed that phenylalanine and flavonoid biosynthesis were significantly enriched, and anthocyanin regulatory genes such as AtrPAL, AtrCHS, AtrCHI and AtrANS were identified. Weighted gene coexpression network analysis (WGCNA) identified two modules highly related to anthocyanin biosynthesis and showed that AtrANS plays a vital role in anthocyanin biosynthesis in the pericarp of A. trifoliata. Exogenous overexpression of the AtrANS increases and promotes the accumulation of anthocyanins and the expression of anthocyanin biosynthetic regulatory genes. Virus-induced gene silencing (VIGS) of the AtrANS resulted in the reduction of anthocyanin accumulation in the pericarp of A. trifoliata. In conclusion, our study revealed transcriptional events during pericarp coloration in A. trifoliata. Studies have also shown that AtrANS plays an important role in the regulation of anthocyanin biosynthesis.