Integrated analysis of transcriptome and metabolome reveals the mechanism of lignin biosynthesis in fruit abscission of Chinese bayberry (Myrica rubra).

Chinese bayberry is a distinctive fruit tree native to southern China. However, it suffers from severe fruit abscission at mature stage, while the molecular mechanism of which remain unclear. In this study, two varieties (BQ and DA) with significant difference in fruit abscission were performed as the materials, and the results indicated the lignin content of fruit stalk was considered as the major cause of fruit abscission in Chinese bayberry. BQ with low fruit abscission rates exhibited thicker and shorter fruit stalks, along with correspondingly higher lignin content in the fruit stalk, when compared to DA. On this basis, the molecular mechanism of lignin biosynthesis through integrated transcriptomic and metabolomic analyses was further investigated. 65 DEGs and 29 DAMs were identified to be potentially involved in lignin biosynthesis. Among those DEGs and DAMs, nine structural genes (MrCOMT1/2/3, MrCCR1/2/3, Mr4CL1/2, and MrCAD) and four important metabolites (coniferaldehyde, coniferyl alcohol, sinapaldehyde, and 5-hydroxyconiferyl alcohol) associated with lignin biosynthesis were identified through enrichment pathway analysis and qPCR validation. Overall, this study revealed the regulatory network composing key DEGs and DAMs involved in lignin biosynthesis, thereby providing valuable insights into the mechanism of fruit abscission and informing the molecular breeding efforts in Chinese bayberry.