Table2_Insights into the aroma volatiles and the changes of expression of ester biosynthesis candidate genes during postharvest storage of European pear.xlsx

During the storage period after harvest, the presence of volatile esters is essential for European pear aroma. Nevertheless, the specific molecular process underlying the production of volatile esters in European pear remains elusive. In this research, head space solid phase microextraction and gas chromatography-mass spectrometry were employed to examine the volatile compounds of two varieties of European pear. The results revealed the identification of a collective of 149 volatile compounds, which were categorized into 8 groups: esters (37), alcohols (25), alkanes (24), aldehydes (22), terpenes (15), acids (8), ketones (6) and other categories (12). Notably, there were 79 volatile compounds that coexisted in both varieties, which esters are the primary group of volatile compounds found in both varieties. Through transcriptome analysis, we identified 12 candidate genes associated with ester biosynthesis and established their correlation with firmness, ethylene production, and predominant volatile esters. The results from gene expression analysis revealed significant up-regulation of PcFAD2 and PcLIP2 in both varieties and PcFAD6 exhibits low expression levels. The results indicate that the involvement of these three genes in the synthesis of esters in European pear may have a significant level of importance. This study enhances our understanding of the mechanisms involved in the formation of European pear flavor.

采收后贮藏阶段，挥发性酯类（volatile esters）是欧洲梨香气形成的关键物质。然而，欧洲梨挥发性酯类生成的具体分子机制仍未阐明。本研究采用顶空固相微萃取（head space solid phase microextraction）与气相色谱-质谱联用法（gas chromatography-mass spectrometry），对两个欧洲梨品种的挥发性成分进行了系统分析。结果共鉴定出149种挥发性化合物，可分为8大类：酯类（37种）、醇类（25种）、烷烃类（24种）、醛类（22种）、萜类（15种）、酸类（8种）、酮类（6种）及其他类别（12种）。值得注意的是，两个品种中共存在79种挥发性化合物，且酯类均为两个品种中占主导地位的挥发性化合物类别。通过转录组分析（transcriptome analysis），本研究筛选出12个与酯类生物合成（ester biosynthesis）相关的候选基因，并明确了这些基因与果实硬度、乙烯释放量及主要挥发性酯类之间的相关性。基因表达分析结果显示，两个品种中PcFAD2与PcLIP2均显著上调，而PcFAD6的表达水平较低。研究结果表明，这三个基因在欧洲梨酯类合成过程中可能发挥着关键作用。本研究深化了学界对欧洲梨风味形成机制的理解。