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.