Abstract: [Objective] Plukenetia volubilis is an oleaginous plant that contains high content of unsaturated fatty acid in the seed oil. It is a potential economically efficient crop with great possibilities for industrialization. There is a significant research gap in regulatory mechanisms of oil synthesis, related key genes and biosynthetic pathways. Therefore, the study of the dynamic changes rule of lipid metabolites and related regulatory genes of fatty acid metabolism of P. volubilis seeds could lay the foundation for further study on raising seed oil yield and improving seed oil quality and provide a valuable example for efficient development and utilization of other woody oil plants.[Method] To investigate the dynamic changes of lipid metabolites content, and search for key genes related to biosynthesis and accumulation of lipid metabolites from differentially expressed genes, gas chromatography mass spectrometry based metabolomics approach and high-throughput sequencing technology platform were used to analyze the P. volubilis seeds collected at different growth stages:initial formation stage, early development stage, middle stage, later stage and maturation stage.[Result] The result of metabolism analysis showed that the high contents of α-linolenic acid and linoleic acid were mainly biosynthesized and accumulated at the seed maturation stage, and the contents of α-linolenic acid and linoleic acid could be the basis for identifying the slow and the rapid accumulation periods. Transcriptome analysis indicated that there were significant differences in gene expression between before and after the stage of seed maturation. The result of combined metabolomics and transcriptomics analysis turned out that the expression patterns of six key enzyme genes related to fatty acid biosynthesis and accumulation were significantly correlated with the biosynthesis and accumulation of fatty acids. And different members of a gene family showed differences and diversity of biological functions. Among them, FAD2-3, FAD7, FATA, KAS2, LACS2, LACS8 and SAD were positively correlated with the contents of total and main fatty acids, indicating that the expression of the seven genes could promote the biosynthesis and accumulation of fatty acids. Moreover, the genes of FAD2-2, KCS1, KCS10 and LACS1 were negatively correlated with the contents of total and main fatty acids, indicating that the expression of the three genes have an inhibitory effect on the biosynthesis and accumulation of fatty acids.[Conclusion] In the study, there were significant differences in the content of fatty acids and the expression of differentially expressed genes between before and after the stage of P.volubilis seed maturation. Based on the content changes of α-linolenic acid and linoleic acid, the seed development process could be divided into the periods of slow and rapid accumulation of fatty acids. We also explored the dynamic changes of the 6 key enzyme genes and correlation analysis in fatty acids biosynthesis. It was found that the expression patterns of key enzyme genes were significantly correlated to the synthesis and accumulation of fatty acids. Different members of the same gene family might have different biological functions. The results laid a theoretical foundation and provided alternative genes on improving the yield of P. volubilis seed oil and changing the composition of fatty acid by technologies of molecular biology.

Key words: Plukenetia volubilis, metabolomics, transcriptomics, biosynthesis of lipids, unsaturated fatty acid