Integration of volatile and non-volatile metabolites and the transcriptome reveals the formation mechanisms of differential aroma compounds between Pyrus communis and Pyrus pyrifolia cultivars

In this study, volatile and non-volatile metabolites and transcriptome analysis were combined to explore the formation mechanism of differential aroma compounds between 3 P. communis and 3 P. pyrifolia cultivars. A total of 510 volatile compounds were identified in 6 cultivars. Sixteen ester and alcohol compounds, including butyl acetate, hexyl acetate, 2-methylbutyrate, ethanol, butanol, propanol, and 2-methylbutanol, with higher contents in the P. communis cultivars than in the P. pyrifolia cultivars, were identified as the main differential aroma compounds. Among the possible synthesis pathways for these 16 aroma compounds, certain amino acid degradation processes, such as isoleucine, valine, and alanine oxidation and threonine dehydration were found to provide important intermediate substances for synthesis. Within the key enzyme genes in the synthesis pathway, several critical enzyme genes, including monoacylglycerol lipase (PcMAGL, pycom08g09340), threonine dehydrase (PcTD, pycom12g10020), and acyl CoA dehydrogenase (PcLCAD, pycom16g13880), might play an important role in the synthesis of these differential aroma compounds. The aforementioned results provide valuable information into the formation mechanisms of differential aroma compounds and offer novel target sites for enhancing pear aroma quality through gene editing.

本研究结合挥发性与非挥发性代谢组分析及转录组分析，探究3个西洋梨（P. communis）品种与3个砂梨（P. pyrifolia）品种间差异香气物质的形成机制。6个供试梨品种中共鉴定出510种挥发性化合物。其中16种酯类与醇类化合物（包括乙酸丁酯、乙酸己酯、2-甲基丁酸酯、乙醇、丁醇、丙醇及2-甲基丁醇）在西洋梨品种中的含量显著高于砂梨品种，被鉴定为主要差异香气物质。在该16种香气物质的潜在合成通路中，部分氨基酸降解过程（如异亮氨酸、缬氨酸、丙氨酸的氧化反应及苏氨酸脱水反应）可为其合成提供关键中间产物。在合成通路的关键酶基因中，单酰甘油脂肪酶（monoacylglycerol lipase, PcMAGL, pycom08g09340）、苏氨酸脱水酶（threonine dehydrase, PcTD, pycom12g10020）及酰基辅酶A脱氢酶（acyl CoA dehydrogenase, PcLCAD, pycom16g13880）等关键酶基因可能在上述差异香气物质的合成中发挥重要作用。上述研究结果为解析差异香气物质的形成机制提供了宝贵参考，同时为通过基因编辑技术提升梨果实香气品质提供了全新的靶标位点。