Benzaldehyde (BAld) is one of the most widely distributed volatiles that contributes to flavor and defense in plants. Plants regulate BAld levels through various pathways, including biosynthesis from trans-cinnamic acid (free BAld), release from hydrolysis of glycoside precursors (BAld-H) via multiple enzymatic action steps, and conversion into downstream chemicals. Here, we show that BAld-H content in peach (Prunus persica) fruit is up to 100-fold higher than that of free BAld. By integrating transcriptome, metabolomic and biochemical approaches, we identified glycoside hydrolase PpGH28BG1 as being involved in the production of BAld-H through the hydrolysis of glycoside precursors. Overexpressing and silencing of PpGH28BG1 significantly altered BAld-H content in peach fruit. Transgenic tomatoes heterologously expressing PpGH28BG1 exhibited a decrease in BAld-H content and an increase in SA accumulation, while maintaining fruit weight, pigmentation, and ethylene production. These transgenic tomato fruits displayed enhanced immunity against Botrytis cinerea compared to wild type (WT). Induced expression of PpGH28BG1 and increased SA content were also observed in peach fruit when exposed to Monilinia fructicola infection. Additionally, elevated expression of PpGH28BG1 promoted fruit softening in transgenic tomatoes, resulting in a significantly increased emission of BAld compared to WT. Most untrained taste panelists preferred the transgenic tomatoes over WT fruit. Our study suggests that it is feasible to enhance aroma and immunity in fruit through metabolic engineering of PpGH28BG1 without causing visible changes in the fruit ripening process.

Bayberry is the most economically significant fruit within the Myricaceae family, having high nutritional and medicinal value. The AP2/ERF family is a class of transcription factors found mainly in plants. However, the bayberry AP2/ERF gene family has not previously been studied. In this study, 113 members of the bayberry AP2/ERF gene family were identified. According to the phylogenetic tree, the members of this group are divided into three subfamilies, namely AP2, ERF, and DREB. The gene structure and conserved motifs were analyzed. Chromosome localization showed that 95 genes were unevenly distributed on 8 chromosomes and 18 genes were located on the skeleton. Gene collinearity analysis of the bayberry AP2/ERF gene family showed 12 segmental duplication events, involving 21 AP2/ERFs. In addition, we further investigated the evolutionary relationship of the AP2/ERF gene family between bayberry and six other species. It was found that bayberry was most closely related to Populus trichocarpa and Malus pumila, with 153 and 141 homologous gene pairs, respectively. Cis-acting elements indicated that AP2/ERFs were related to phytohormone responses, light response, abiotic and biotic stress tolerance. Transcriptomic data showed that the expression pattern of AP2/ERF gene was different in bayberry space electric field treatment and at different stages of fruit development. The results of GO annotation revealed the biological processes, cellular component and molecular function that the AP2/ERF genes were involved. And KEGG enrichment analysis indicated that these genes were mainly clustered in genetic information processing and metabolism pathways. The AP2/ERF gene was identified in the genome of bayberry, and its structure, conserved motif, and phylogenetic relationship were analyzed. These findings of this study serve as a reference for the genome-wide identification of the AP2/ERF gene family in other species and groundwork for future research on the function of AP2/ERF genes in bayberry.

Bayberry (Myrica rubra) is a significant subtropical fruit tree, renowned for its distinctive flavor and high nutritional value. WRKY transcription factors are a class of plant-specific zinc-finger proteins that play critical roles in plant growth and development, secondary metabolism, and responses to abiotic stress. However, there is currently limited information about the WRKY gene family in bayberry. This study conducted a systematic bioinformatics analysis of 55 WRKY genes in bayberry, elucidating their phylogenetic relationships, gene structures, conserved motifs, and syntenic characteristics. The results demonstrated that these WRKY family members could be classified into five subfamilies, with each gene containing at least one WRKY domain. The bayberry WRKY genes exhibited significant variations in gene length and intron-exon numbers, while maintaining relatively conserved gene structures within each subfamily. The promoters of WRKY gene members contained multiple regulatory elements, including hormone-responsive elements, light-responsive elements, and abiotic stress-responsive elements. Collinearity analysis revealed that the WRKY family in bayberry experienced six segmental duplication events. Inter-species synteny analysis demonstrated high collinearity between bayberry and Actinidia spp., indicating evolutionary conservation of WRKY genes across different plant species. It was observed that bayberry WRKY genes exhibited significant differential expression across different cultivars and developmental stages of fruits through expression pattern analysis. Further research indicated that MrWRKY14, a member of the bayberry WRKY family, significantly enhanced the promoter activity of MrSWEET1, thereby influencing the process of sugar accumulation. These findings not only provide an important reference for the genome-wide identification of WRKY gene families in plants but also lay a solid foundation for future in-depth functional analysis of bayberry WRKY genes.

The harvest period of bayberry fruit cultivated in the open field is short and often suffers from continuous cloudy and rainy days, leading to a decrease in yield and a decline in fruit quality. However, cultivating bayberries in greenhouses could avoid the harm due to rain, improve fruit quality and prolong the supply period, thus significantly increasing economic returns. Bayberry fruit quality, assessed by single fruit weight, vertical and horizontal diameters, soluble solids content and sugar-acid ratios, was significantly superior in fruit produced under greenhouse conditions than in fruit produced in the open field. Analysis of the soluble sugar components and the related enzyme activities indicated that the sucrose accumulation and metabolism of bayberry fruit were significantly improved by greenhouse cultivation, possibly owing to differences in sucrose-phosphate synthase and acid invertase activities.

Loquat (Eriobotrya japonica) is a subtropical evergreen fruit tree with high economic benefits and nutritional value. AP2/ERF (APETALA2/ethylene responsive factor) are a wide range of transcription factors found in plants, which play an important role in regulating plant development and biological processes. However, the systematic identification and characterization of AP2/ERF genes in loquat remains unclear. In the present research, a total of 189 loquat AP2/ERF members were identified. According to the phylogenetic tree, these members were divided into three subfamilies, including AP2 (42), ERF (96), and DREB (51). Except for three genes located on the skeleton, most of the loquat AP2/ERF genes were unevenly distributed across all chromosomes. The collinearity results showed that 175 duplicate gene pairs were found in the AP2/ERF gene family of loquat. Ka/Ks results indicated that these genes underwent purification selection pressure. The syntenic analysis of AP2/ERF genes between Arabidopsis, pomegranate, peach, and loquat provided valuable clues for the potential evolution of AP2/ERF family in loquat. Cis-element analysis showed that most of the AP2/ERF genes in loquat had multiple cis-elements related to stress response, plant hormone signal transduction, and plant growth and development. Transcriptomic data indicated that the expression patterns of AP2/ERF genes exhibited diversity in different loquat cultivars during fruit development and ripening. The results of this study displayed the first comprehensive analysis of AP2/ERF genes in loquat, which provides a solid foundation for future research on the function of AP2/ERF genes in loquat.

Flesh fruits are essential for human health, but pathogen infection poses a threat to fruit production and postharvest storage. The hormone salicylic acid (SA) and its metabolites, such as sugar conjugates and methyl salicylate (MeSA), play a crucial role in regulating plant immune responses. However, the UDP-glycosyltransferases (UGTs) responsible for modulating SA metabolism in fruit have yet to be identified, and further investigation is needed to elucidate its involvement in fruit immune response. Here, we identified PpUGT74F2 as an enzyme with the highest transcription level in peach fruit, responsible for catalyzing the biosynthesis of SA glucoside (SAG), but not for MeSAG formation in fruit. Furthermore, infection of peach fruit with Monilinia fructicola, which causes brown rot disease, led to reduced expression of PpUGT74F2, resulting in a significant decrease in SAG content and an increase in MeSA levels. Transgenic tomatoes expressing heterologous PpUGT74F2 increased susceptibility to gray mold. Interestingly, overexpressing PpUGT74F2 did not affect SA levels but dramatically reduced MeSA levels in response to pathogen infection, accompanied by significantly reduced expression of pathogen-related (PR) genes in transgenic tomatoes. This study highlights that PpUGT74F2 acts as a negative regulatory factor for fruit immunity through a distinct mechanism not previously reported in plants.