【Objective】Prunus mume, a renowned traditional ornamental flower in China, is extensively utilized in landscape gardening due to its high aesthetic value. Developing P. mume cultivars with colorful foliage represents a pivotal objective in current genetic improvement programs. Among them, the ‘Meiren’ cultivar group, distinguished by its unique purple-leaf phenotype, serves as an ideal model for investigating the genetic regulation of anthocyanin biosynthesis. Anthocyanin accumulation is the primary determinant of the purple-leaf trait. Although glutathione S-transferases (GSTs) play a crucial role in the anthocyanin transport process, research on GSTs in P. mume remains scarce. This study aimed to clone and functionally characterize PmMGST81, a member of the GST gene family from P. mume ‘Meiren’, to elucidate the role of GST genes in anthocyanin accumulation and lay a theoretical foundation for understanding the coloration mechanism of P. mume.【Method】The PmMGST81 gene was cloned using the homology-based cloning method. Bioinformatics analyses, including prediction of signal peptides and transmembrane domains, gene structure analysis, and prediction of cis-acting elements in the 2 000 bp upstream promoter region, were conducted. Amino acid sequences of homologous proteins in Rosaceae were retrieved for multiple sequence alignment. RNA was extracted from leaves at different developmental stages (S1. apical leaves; S2. middle leaves; S3. basal leaves) of the same annual shoots of P. mume ‘Meiren’and reverse-transcribed into cDNA. The expression patterns of PmMGST81 and structural genes in the anthocyanin synthesis pathway were analyzed by quantitative real time PCR (qPCR) to explore the correlation between the expression of PmMGST81 and anthocyanin content phenotypes. Agrobacterium tumefaciens strains harboring the empty vector plasmid pSuper1300-GFP and the recombinant plasmid PmMGST81-pSuper1300-GFP were injected into Nicotiana benthamiana leaves. Fluorescent signals were observed and photographed using a laser confocal microscope to confirm the subcellular localization of PmMGST81 protein based on the position of GFP green fluorescence.The flower color phenotypes of transgenic tobacco(N. tabacum) plants overexpressing PmMGST81 were observed. Anthocyanins were extracted from tobacco petals, and their contents were determined by spectrophotometry. Five structural genes related to the anthocyanin synthesis pathway in tobacco, namely NtF3'H, NtFLS, NtANS, NtDFR, and NtUFGT, were selected. qPCR was employed to detect their expression levels in the over expressed PmMGST81 lines, verifying the function of PmMGST81 in anthocyanin accumulation through stable genetic transformation of tobacco.【Result】(1) The full-length coding sequence (CDS) of PmMGST81, which was 642 bp and encoded 213 amino acids, was successfully cloned. It was classified as a stable protein, and subcellular localization prediction indicated that it was located in both the cytoplasm and nucleus. The PmMGST81 protein lacked signal peptides and obvious transmembrane structures but contained the typical GST-C and GST-N conserved domains of GST family proteins. The predicted cis-acting elements in the upstream promoter were predominantly light-responsive and hormone-responsive elements, and numerous binding sites for MYB genes were present in the promoter sequence. Sequence alignment of the PmMGST81 protein with homologous proteins from Rosaceae plants revealed that it had the closest genetic relationship with those of Prunus species, indicating its conservation during evolution. (2)qPCR results showed that the expression patterns of structural genes in the anthocyanin synthesis pathway, such as PmMF3'H, generally exhibited a decreasing trend from S1 to S3 in P. mume ‘Meiren’ leaves. The leaf color gradually changed from purple to green during the S1—S3 stages. Similarly, the expression levels of PmMGST81 differed significantly among the three stages, and a significant positive correlation was observed between the expression of PmMGST81 and anthocyanin content. (3)Subcellular localization demonstrated that the PmMGST81 protein was distributed in both the nucleus and cytoplasm. (4)In the transgenic tobacco lines overexpressing PmMGST81, the expression level of PmMGST81 was significantly higher than that in the control group. The corolla color deepened, and the anthocyanin content was significantly increased. Expression analysis of anthocyanin synthesis pathway genes showed that, except for NtFLS, whose expression level did not differ significantly from that of the wild-type, the expression levels of NtF3'H, NtANS, NtDFR, and NtUFGT were upregulated to varying degrees. This indicated that the deepening of tobacco flower color was due to increased anthocyanin accumulation. 【Conclusion】In this study, the GST family gene PmMGST81 (with a CDS length of 642 bp) was cloned from P. mume ‘Meiren’, and its protein was found to be distributed in both the nucleus and cytoplasm. The expression of PmMGST81 at different developmental stages of purple leaves was significantly positively correlated with anthocyanin content. Overexpression of PmMGST81 in tobacco promoted anthocyanin accumulation in the corolla and upregulated the expression of structural genes in the anthocyanin biosynthesis pathway, suggesting that PmMGST81 regulates the purple leaf phenotype of P. mume ‘Meiren’ by positively modulating anthocyanin metabolism.