Unveiling the unique aroma of Morus macroura through integrated volatile metabolome and transcriptome analysis

• γ -decalactone is the key aroma component of 'Baichang' mulberries. • Differential expression of ester synthesis genes is the formation of the unique aroma. • Transcription factors are involved in the regulation of aroma formation. Mulberries, especially the ‘BaiChang’ ( Morus macroura ) variety known for its creamy flavour, are highly valued by consumers and the market for their high nutritional value and unique aroma. However, the formation mechanism of its unique aroma compounds remains unclear. This study employed a combination of volatile metabolomics and transcriptomics analyses to examine volatile organic compounds (VOCs) and transcriptional changes at different developmental stages of ‘BaiChang’ mulberries. A total of 663 VOCs were identified, with 342 of annotated with different odours. Differential analysis revealed that the three comparison groups shared 56 differential metabolites, and each group contained 35, 56 and 17 unique differential metabolites. Among them, the 69 differential metabolites related to sweet, waxy, coconut and oil were screened. The content of 2(3H)-furanone, 5-hexyldihydro drastically increased during the S3 stage, and its aroma characteristics are consistent with the sensory phenotype. Among these, γ-decalactone is inferred to be the key VOC in ‘BaiChang’ mulberries. By integrating transcriptome data, 13 key structural genes were identified as potentially related to the synthesis of γ-decalactone, including CYPs, FAE, FAH, ACXs and EHLs. Most of these genes are highly expressed during the later stages of fruit development. Additionally, a preliminary dynamic relationship between lactones and esters was inferred during the development of ‘BaiChang’ mulberries. Furthermore, by combining weighted gene coexpression and K-means analyses, it was found that the biosynthesis of lactones and esters may be regulated by ethylene induction and transcription factors such as MYB, NAC, MDDS and bZIP . This study lays the foundation for understanding of the regulatory mechanisms underlying the formation of the unique aroma of ‘BaiChang’ mulberries and provides new insights for the further exploration of superior mulberry varieties.