Objective  Transcriptomes of differentially expressed genes related to flavonoids synthesis in tubers of two Huaiyushan cultivated varieties of Tetrastigma hemsleyanum Diels et Gilg were compared.

  Method   Tubers from Huaiyu 1 (HY1) and Huaiyu 2 (HY2) were used for the transcriptome analysis.

  Result  HY1 and HY2 had clean reads of 42 311 662 and 41 411 202, respectively, and no less than 95.75% of Q30 base. Their transcription factors basically belonged to the MYB-superfamily, bHLH, AP2/ERF, NAC, C2C2, WRKY, etc. The paired values of FPKM in HY1 and HY2 were between 0 and 2; the expression densities, between 0 and 0.7; the number of commonly expressed genes, 22 367; and, the number of uniquely expressed genes in HY1, 18 196, while 8 137 in HY2. The correlation between the expressions of the two had a coefficient of 0.913, and that between the samples was high. There were 12 199 differentially expressed genes between the two, with 3 551 upregulated and 8 648 downregulated in HY2 as compared to HY1. The GO enrichment analysis showed that the differential genes were mainly annotated into photosynthesis, light harvesting in photosystem I, photosynthesis, light harvesting, chlorophyll metabolic process, protein-chromophore linkage, generation of precursor metabolites and energy, chlorophyll biosynthetic process, response to oxidative stress, alpha-amino acid metabolic process, photosynthesis, plastoglobule, photosystem I, photosystem II, plastid nucleoid, photosystem, chlorophyll binding, monooxygenase activity, iron ion binding, heme binding, lyase activity, etc. Whereas, the KEGG enrichment analysis indicated the differential genes to be mainly annotated into photosynthesis-antenna proteins, ribosome, glyoxylate and dicarboxylate metabolism, phenylpropanoid biosynthesis, stilbenoid, diarylheptanoid and gingerol biosynthesis, flavonoid biosynthesis, photosynthesis, carbon fixation in photosynthetic organisms, glycine, serine and threonine metabolism, plant hormone signal transduction, glutathione metabolism, pyruvate metabolism, phenylalanine metabolism, circadian rhythm-plant, flavone and flavonol biosynthesis, cysteine and methionine metabolism, cyanoamino acid metabolism, carotenoid biosynthesis, alpha-linolenic acid metabolism, porphyrin and chlorophyll metabolism, and other metabolic pathways.

  Conclusion  The differentially expressed genes related to flavonoids synthesis, such as stilbene synthase, leucoanthocyanidin dioxygenase, CHI protein, chalcone synthase 2, flavanone 3-hydroxylase and lleucoanthocyanidin reductase 1 and flavonoid 3’- hydroxylase gene were upregulated in HY2, while chalcone synthase, flavonol synthase and flavonoid 3’, 5’-methyltransferase downregulated. The variations apparently resulted in the differences shown on the total flavonoid content between the HY1 and HY2 tubers.