Genome-wide identification and expression analysis of anthocyanin synthesis-related R2R3-MYB gene family in purple passion fruit (Passiflora edulis)

Abstract

The myeloblastosis (MYB) transcription factors (TFs) participate in a variety of physiological and biochemical processes, especially in the anthocyanin biosynthesis in plants. However, the comprehensive functional study of MYB TFs, especially in regulating anthocyanin accumulation in passion fruit (Passiflora edulis) remains limited. To gain a better understanding of the evolutionary history of this family, we conducted a genome-wide analysis of MYB TFs in passion fruit, including phylogenetic analysis, gene structure, conserved motifs, chromosomal locations, and collinearity analysis. A total of 254 MYB genes were identified in the passion fruit genome, comprising 128 1R-MYBs, 119 R2R3-MYBs, 5 3R-MYBs and 2 4R-MYBs. Based on the classification of Arabidopsis thaliana MYB (AtMYB) genes, the passion fruit R2R3-MYB (PeMYB) genes were further divided into 37 subgroups, which were dispersed in 9 chromosomes. The analyses of gene structure and protein conserved motif analyses further supports the clustering results of the phylogenetic tree. RT-qPCR validation revealed that the relative expression of PeMYB67 and PeMYB86 increased during fruit development, while PeMYB95 exhibited no significant changes. The expression levels of other eight MYB genes involving PeMYB4, PeMYB13, PeMYB32, PeMYB40, PeMYB78, PeMYB115, PeMYB25 and PeMYB118 manifested declining regulation alongside fruit ripening. They were either positively or negatively correlated with the accumulation of anthocyanins during fruit growth. Overall, this study provides a comprehensive overview of the passion fruit MYB superfamily genes and lays a foundation for future cloning and functional analysis of PeMYB genes related to anthocyanin accumulation in passion fruit.