Comparative transcriptome analysis and transient assays revealed AaGST and AaBGAL, respectively, contribute to skin and flesh coloration in A. arguta.

Abstract

Actinidia arguta possesses different colors in the fruit skin and flesh, but the underlying mechanism has not yet been clarified. In this study, we conducted 36 samples RNA-seq to investigate the phenotypic expression of different fruit tissues (skin and flesh) in red and green A. arguta varieties during different coloring phases. GO and KEGG enrichment results of differentially expressed genes (DEGs) suggested that the red color of the skin and flesh was derived from anthocyanin transport and flesh softening, respectively. Weighted gene co-expression network analysis (WGCNA) revealed MEyellow and MEblack modules significantly correlated with skin and flesh coloration, and two genes, Glutathione S-transferases (AaGST) and β-galactosidases (AaBGAL), were identified as hub genes involved in different tissue-specific coloration. Transient overexpression in apples and kiwifruits confirmed the role of AaGST and AaBGAL in color formation. Our results preliminarily explore the mechanism of red color formation in different A. arguta fruit tissues and provide novel insights into red color formation.