The characteristic green-note aroma of Chinese plum (Prunus salicina) is largely defined by C6 aldehydes and alcohols synthesized through the fatty acid pathway involving lipoxygenase (LOX), hydroperoxide lyase (HPL), and alcohol dehydrogenase (ADH). However, the LOX/HPL/ADH gene families and their potential contributions to C6 volatile formation remain poorly characterized in Chinese plum. Here, we integrated genome-wide identification with cultivar-level volatile profiling and RT–qPCR expression analyses to link candidate genes with C6 volatile accumulation. We identified 8 PsLOX, 3 PsHPL, and 13 PsADH genes and classified them into 2, 1, and 3 subfamilies, respectively. Conserved motifs/domains were shared within each family, whereas gene-structure variation suggested functional divergence; segmental duplication was the main driver of family expansion. To explore their functional relevance to aroma biosynthesis, five major C6 aldehydes and alcohols were analyzed in ten cultivars using solid-phase microextraction/gas chromatography-mass spectrometry (SPME/GC–MS), revealing substantial diversity in green-note composition. Combined with reverse transcription quantitative polymerase chain reaction (qRT–PCR) expression profiling, low PsADH2.7 expression was associated with high hexanal content, whereas elevated PsLOX5 and PsADH2.2 expression corresponded to increased 1-hexanol accumulation. High 2-ethyl-1-hexanol levels were linked to increased PsLOX4.1 and PsHPL1.3 but decreased PsADH1.2 expression. In addition, (Z)-3-hexen-1-ol abundance showed strong positive correlations with PsLOX3.1, PsHPL1.2, and PsADH2.6 expression. This integrated genomic and expression–metabolite analysis highlights candidate genes potentially involved in C6 aldehyde/alcohol biosynthesis underlying the green-note aroma of Chinese plum and provides genetic targets for aroma-oriented breeding.

Background: Fruit texture is a major component of plum quality, affecting both consumer acceptance and postharvest behavior. Pectin methylesterases (PMEs) play important roles in cell-wall pectin modification and are therefore likely to contribute to plum fruit texture development and ripening-associated softening. However, the PME gene family has not yet been comprehensively investigated in plum (Prunus salicina L.). Methods: In the present study, a chromosome-level plum genome was used to survey this gene family at the whole-genome scale. Phylogenetic relationships, chromosomal positions, exon–intron organization, conserved motifs, domain architectures, gene duplication, and cis-elements were analyzed. Four flesh texture traits were measured in 55 plum accessions to characterize texture variation and select two representative cultivars with contrasting flesh textures for further molecular analysis. Based on the clustering results, ‘WSCL’ and ‘FR’ were selected for expression profiling during fruit development and subsequent correlation analysis with texture traits. Results: A total of 46 PsPME genes were identified. Phylogenetic analysis classified them into four major subgroups. Structural analyses indicated an overall conserved family framework, although noticeable variation was retained among individual members. Dispersed duplication made the largest contribution to family expansion, and most duplicated pairs appeared to have evolved under purifying selection. Correlation analysis showed that PsPME20, PsPME22, and PsPME25 were significantly negatively correlated with flesh firmness, while PsPME20 was additionally linked to flesh compactness and flesh fragility. Conclusions: Overall, this study clarifies the structural and evolutionary characteristics of the PsPME family and identifies candidate genes that may contribute to texture differences in plum, offering a basis for future functional studies and breeding programs.

Anthocyanins are major determinants of both the color and nutritional quality of fruit. Their accumulation in plant tissues depends on biosynthesis as well as efficient transport into the vacuole, a process in which glutathione S-transferases (GSTs) are believed to play an important role. Through genome-wide identification and analysis, this study identified 39 Chinese plum (Prunus salicina) glutathione S-transferase (PsGST) genes. Phylogenetic analysis grouped these PsGST genes into seven subfamilies. Dispersed duplication appeared to be the main driver of family expansion, and the duplicated genes appear to have largely evolved under purifying selection. The cultivar ‘Fengweimeigui’ (FWMG), with purple peel and red pulp, and the cultivar ‘Fengweihuanghou’ (FWHH), with yellow peel and yellow pulp, were used as contrasting materials because of their distinct anthocyanin pigmentation. We then profiled anthocyanin accumulation and the expression patterns of all PsGST genes across fruit development using quantitative real-time PCR (qRT-PCR). PsGSTF8 was identified as a candidate gene, and its expression patterns in both peel and pulp were consistent with anthocyanin accumulation, with higher relative transcript levels in the deeply colored cultivar ‘FWMG’ and undetectable expression in ‘FWHH’. The transient overexpression of PsGSTF8 in Chinese plum fruit promoted anthocyanin accumulation, and the complementation of the Arabidopsis thaliana transparent testa 19 (tt19) mutant further supported the potential role of PsGSTF8 in anthocyanin accumulation and GST-mediated transport. These results provide new clues for understanding potential GST-mediated anthocyanin transport and accumulation and offer a basis for the further investigation of the molecular mechanisms underlying fruit coloration in Chinese plum.