Jasmonate-induced MdMYC2 improves fruit aroma during storage of ‘Ruixue’ apple based on transcriptomic, metabolic and functional analyses

Abundant volatile compounds are predominant contributors to fruit aroma in various species. Plant hormones and transcription factors are pivotal for volatile compound production in fruit. Jasmonate (JA) regulates the biosynthesis of volatiles such as aldehydes and alcohols, but a possible mechanism by which JA-induced MdMYC2 regulates aldehyde and alcohol biosynthesis in apple fruit has not been described. To study the effects of JA on the critical volatiles of ‘Ruixue’ fruit, gas chromatography‒mass spectrometry (GC‒MS) was used to determine the content of volatiles in fruits treated with JA. Our results showed that JA treatment effectively improved fruit quality during storage of ‘Ruixue’ fruit; for instance, sweetness increased and aroma volatiles accumulated. Furthermore, we identified the transcription factor (TF) MdMYC2 (MD16G1274200), whose expression increased 1.5- to 2.0-fold in JA-treated fruits. Subsequently, MdMYC2 overexpression dramatically increased volatile biosynthesis in apple calli (1.6-fold) and tomato calli (2.1-fold). Furthermore, MdMYC2 upregulated MdLOX5a transcription (3-fold) by binding to its promoter according to dual-luciferase and yeast one-hybrid (Y1H) assays. Collectively, these findings provide beneficial information to illustrate the mechanisms by which JA regulates volatile biosynthesis in fruit.