A family of methyl esterases converts methyl salicylate to salicylic acid in ripening tomato fruit

Bioinformatics analysis of the tomato (Solanum lycopersicum) methylesterase gene family

BACKGROUND

Methylesterases (MESs) are a class of enzymes responsible for the demethylation of methylated compounds in plants, play a vital role in plant growth and development. However, studies on MES enzymes in tomato (Solanum lycopersicum) are limited.

RESULTS

This study systematically identified MES genes in tomatoes for the first time and studied their physicochemical properties, evolutionary relationships, and expression patterns. Sixteen Solanum lycopersicum methylesterase (SlMES) genes were identified through comprehensive bioinformatics analysis and were categorized into three subfamilies. Members of the same subfamily exhibited similar gene structures, structural domains, and conserved motifs. Chromosomal analysis revealed an uneven distribution of SlMESs across the five chromosomes, with evidence of gene duplication. Cis-acting element analyses suggested that the SlMES family may have important regulatory functions in tomato growth, development, and stress responses. Among them, Solyc02g065260 was further examined for its role in tomato fruit ripening and stress responses. Its tissue-specific expression patterns, dynamic expression during fruit ripening, and responses to pathogens, low temperatures, and hormones, such as methyl jasmonate (MeJA), methyl salicylate (MeSA), abscisic acid (ABA), and ethylene (ET), were analyzed. The results provided further evidence towards understanding the roles of the SlMES family in the tomatoes.

CONCLUSIONS

The results established a theoretical foundation for future investigations into the functional characterization of MES genes during tomato growth and development.

Integrative phenomics, metabolomics, and flavoromics reveal key quality indicators during the formation of flavor and bioactive compounds in Alpinia hainanensis (Zingiberaceae) fruit

Alpinia hainanensis seed (AHS) is a traditional spice and medicinal material with limited studies on its flavor and bioactive chemistry. This study integrated anatomical and microstructural analyses, flavor traits, and full-spectrum metabolome profiling using GC-MS and UPLC-MS/MS to characterize AHS quality. A total of 1543 metabolites were identified, with 41 key flavor compounds showing spatiotemporal specificity. Boiled and dried mature AHS exhibited optimal flavor with large dried fruit, dark and heavy seeds, and strong pungency. Different bioactive compounds peaked across 4-10 weeks post-anthesis, indicating stage-specific medicinal potential. Oil cell traits correlated with bioactive compounds of pinocembrin, cardamonin, and 3-carene accumulation, while bitterness correlated with pinocembrin. Postharvest processing enhanced seed pungency and increased peel terpenoids, supporting value-added utilization. Metabolite accumulation was associated with galactose, fatty acid, terpene, and phenylpropanoid pathways. These findings provide a foundation for refining A. hainanensis harvesting, processing, and utilization.

SlMES1 modulates methyl salicylate to influence fruit volatile profiles in tomato

Methyl salicylate (MeSA), known as phloem-based mobile signal, has been identified as undesirable volatile compounds for tomato fruits due to its medicinal and wintergreen aroma properties. However, the response of most volatile compounds to endogenous MeSA are still unclarified. In this work, we found the concentration of MeSA can be regulated by salicylic acid methyl esterase 1 (SlMES1). We used CRISPR/Cas9 and GC-MS strategies to investigate the effect of SlMES1 on the biosynthesis of flavor compounds during tomato fruit ripening. Our results showed that the loss of function of SlMES1 significantly increased the MeSA content by altering the flux of MeSA and SA interconversion. Although the increased endogenous MeSA did not affect the fruit ripening process, it altered the concentration and proportion of fruit volatiles, mainly reducing the concentration of soluble sugar and volatile substances derived from amino acids and carotenoids. Additionally, the reduction of soluble sugars and volatiles was associated with downregulated the gene encoding Sucrose synthase (SuSy), Alcohol dehydrogenase (ADH), Phenylalanine ammonia lyase (PAL), and β - Carotene hydroxylase (CHY-β) when compared with control. Taken together, SlMES1 plays a crucial role in regulating the MeSA content during fruit ripening and could become a breeding target for improving fruit flavor quality.

Innovative enhancement of flavor profiles and functional metabolites composition in Pandanus amaryllifolius through lactic acid bacteria fermentation

Pandanus amaryllifolius, known as Pandan, serves as a coloring agent and spice in food. The effects of lactic acid bacteria (LAB) on Pandan are underexplored. This study aimed to investigate changes in physicochemical properties, antioxidant activity, volatile compounds and metabolites of Pandan fermented with Lactobacillus acidophilus, Levilactobacillus brevis and Lacticaseibacillus rhamnosus. Fermented Pandan showed increased total phenol (13 %-21 %) and flavonoid (33 %-53 %) content. Pandan fermented with L. rhamnosus exhibited significantly higher antioxidant activity, followed by those fermented with L. brevis and L. acidophilus. Key components like naringenin and volatile compounds such as α-ionone significantly increased after fermentation, with the production of new compounds, including damascenone and linalool. These compounds enhance the flavor and functional properties of fermented Pandan. This research lays a foundation for developing novel LAB-fermented Pandan products.

Function and Evolution of the Plant MES Family of Methylesterases

Land plant evolution has been marked by numerous genetic innovations, including novel catalytic reactions. Plants produce various carboxyl methyl esters using carboxylic acids as substrates, both of which are involved in diverse biological processes. The biosynthesis of methyl esters is catalyzed by SABATH methyltransferases, and understanding of this family has broadened in recent years. Meanwhile, the enzymes catalyzing demethylation-known as methylesterases (MESs)-have received less attention. Here, we present a comprehensive review of the plant MES family, focusing on known biochemical and biological functions, and evolution in the plant kingdom. Thirty-two MES genes have been biochemically characterized, with substrates including methyl esters of plant hormones and several other specialized metabolites. One characterized member demonstrates non-esterase activity, indicating functional diversity in this family. MES genes regulate biological processes, including biotic and abiotic defense, as well as germination and root development. While MES genes are absent in green algae, they are ubiquitous among the land plants analyzed. Extant MES genes belong to three groups of deep origin, implying ancient gene duplication and functional divergence. Two of these groups have yet to have any characterized members. Much remains to be uncovered about the enzymatic functions, biological roles, and evolution of the MES family.

Analysis of Methylesterase Gene Family in Fragaria vesca Unveils Novel Insights into the Role of FvMES2 in Methyl Salicylate-Mediated Resistance against Strawberry Gray Mold

Methylesterases (MESs) hydrolyze carboxylic ester and are important for plant metabolism and defense. However, the understanding of MES' role in strawberries against pathogens remains limited. This study identified 15 FvMESs with a conserved catalytic triad from the Fragaria vesca genome. Spatiotemporal expression data demonstrated the upregulated expression of FvMESs in roots and developing fruits, suggesting growth involvement. The FvMES promoter regions harbored numerous stress-related cis-acting elements and transcription factors associated with plant defense mechanisms. Moreover, FvMES2 exhibited a significant response to Botrytis cinerea stress and showed a remarkable correlation with the salicylic acid (SA) signaling pathway. Molecular docking showed an efficient binding potential between FvMES2 and methyl salicylate (MeSA). The role of FvMES2 in MeSA demethylation to produce SA was further confirmed through in vitro and in vivo assays. After MeSA was applied, the transient overexpression of FvMES2 in strawberries enhanced their resistance to B. cinerea compared to wild-type plants.

Molecular evolution of methylesterase family genes and the BnMES34 is a positive regulator of Plasmodiophora brassicae stress response in Arabidopsis

Methylesterases (MES) are involved in hydrolysis of carboxylic esters, which have substantial roles in plant metabolic activities and defense mechanisms. This study aimed to comprehensively investigate Brassica napus BnMESs and characterize their role in response to Plasmodiophora brassicae stress. Forty-four BnMES members were identified and categorized into three groups based on their phylogenetic relationships and structural similarities. Through functional predictions in the promoter regions and analysis of RNA-Seq data, BnMES emerged as pivotal in growth, development, and stress responses to B. napus, particularly BnMES34, was strongly induced in response to P. brassicae infection. Gene Ontology analyses highlighted BnMES34's role in regulation of plant disease resistance responses. Furthermore, overexpression of BnMES34 in A. thaliana exhibited milder clubroot symptoms, and reduced disease indices, suggesting positive regulatory role of BnMES34 in plant's response to P. brassicae stress. Molecular docking and enzyme activity verification indicated that BnMES34 has the ability to generate salicylic acid via methyl salicylate, and further experimentally validated in vivo. This discovery indicates that the overexpression of BnMES34 in Arabidopsis confers resistance against clubroot disease. Overall, our research suggests that BnMES34 has a beneficial regulatory role in enhancing stress resistance to P. brassicae in B. napus.

Recent Advances in Studying the Regulation of Fruit Ripening in Tomato Using Genetic Engineering Approaches

Tomato (Solanum lycopersicum L.) is one of the most commercially essential vegetable crops cultivated worldwide. In addition to the nutritional value, tomato is an excellent model for studying climacteric fruits' ripening processes. Despite this, the available natural pool of genes that allows expanding phenotypic diversity is limited, and the difficulties of crossing using classical selection methods when stacking traits increase proportionally with each additional feature. Modern methods of the genetic engineering of tomatoes have extensive potential applications, such as enhancing the expression of existing gene(s), integrating artificial and heterologous gene(s), pointing changes in target gene sequences while keeping allelic combinations characteristic of successful commercial varieties, and many others. However, it is necessary to understand the fundamental principles of the gene molecular regulation involved in tomato fruit ripening for its successful use in creating new varieties. Although the candidate genes mediate ripening have been identified, a complete picture of their relationship has yet to be formed. This review summarizes the latest (2017-2023) achievements related to studying the ripening processes of tomato fruits. This work attempts to systematize the results of various research articles and display the interaction pattern of genes regulating the process of tomato fruit ripening.

Metabolomics reveals the effects of different storage times on the acidity quality and metabolites of large-leaf black tea

Most aged tea has superior sensory qualities and good health benefits. The content of organic acids determines of the quality and biological effects of aged tea, but there are no reports of the effect of storage on the composition and relative proportion of acidic compounds in black tea. This study analyzed and compared the sourness and metabolite profile of black tea produced in 2015, 2017, 2019 and 2021 using pH determination and UPLC-MS/MS. In total, 28 acidic substances were detected, with 17 organic acids predominating. The pH of black tea decreased significantly during storage from pH 4.64 to pH 4.25 with significantly increased in l-ascorbic acid, salicylic acid, benzoic acid and 4-hydroxybenzoic acid. The metabolic pathways ascorbate biosynthesis, salicylate degradation, toluene degradation, etc. were mainly enriched. These findings provide a theoretical basis to regulate the acidity of aged black tea.

The dissection of tomato flavor: biochemistry, genetics, and omics

Flavor and quality are the major drivers of fruit consumption in the US. However, the poor flavor of modern commercial tomato varieties is a major cause of consumer dissatisfaction. Studies in flavor research have informed the role of volatile organic compounds in improving overall liking and sweetness of tomatoes. These studies have utilized and applied the tools of molecular biology, genetics, biochemistry, omics, machine learning, and gene editing to elucidate the compounds and biochemical pathways essential for good tasting fruit. Here, we discuss the progress in identifying the biosynthetic pathways and chemical modifications of important tomato volatile compounds. We also summarize the advances in developing highly flavorful tomato varieties and future steps toward developing a "perfect tomato".