Systematic identification of GST gene family reveals that MYB10.5b–GST21/51 module contributes to leaf coloration in Prunus mume ‘Meiren’

Abstract

Purple–hued foliage is a highly valued ornamental trait in the commercial cultivation of the woody ornamental Prunus mume ‘Meiren’. Glutathione S–transferase (GST) genes are known mediators of anthocyanin accumulation, yet their functional roles in ‘Meiren’ leaf coloration remain unexplored. Here, we systematically identified 88 PmMGST genes, which were classified into eight distinct subfamilies within a large–scale phylogenetic clustering. Gene family analysis revealed conserved exon–intron structures and motif compositions within phylogenetic clades. Duplication and synteny analyses indicated that the expansion of this family was primarily driven by tandem duplication events on chromosomes 3a/b and 6a/b. Moreover, we identified abundant MYB/Myb–binding sites on the PmMGST promoters, suggesting potential regulatory interactions with MYB transcription factors. Expression profiling demonstrated that PmGST17/21/51 were significantly upregulated across development stages accompanied by varying leaf colors. Functional investigations revealed that the overexpression of PmGST21/51 induced purple coloration or deepening in transgenic ‘Meiren’, concomitant with increased anthocyanin accumulation, and elevated transcript levels of anthocyanin synthase genes. PmMYB10.5b, the key regulator of purple–leaf trait formation, directly bounded to PmGST21/51 promoters, establishing a MYB10.5b–GST21/51 regulatory module involved in leaf coloration. Collectively, these results identify PmGST21 and PmGST51 as positive regulators of anthocyanin accumulation and provide foundational insights into the PmGST family in ‘Meiren’. This study offers a novel perspective on anthocyanin regulation in purple-leaved P. mume and contributes to the genetic improvement of foliage color in woody ornamentals.