Transcriptome analysis reveals the accumulation mechanism of anthocyanins in 'Zijuan' tea (Camellia sinensis var. asssamica (Masters) kitamura) leaves

Anthocyanin biosynthesis in herbaceous plants has been studied widely, but the mechanism of anthocyanin accumulation in 'Zijuan' tea remains unclear. In this study, the leaf transcriptome of 'Zijuan' tea was analyzed at the purple and green stages by using the Illumina HiSeq 2500 platform. A total of 2250 unigenes were differentially expressed at the purple and green stages. Anthocyanin biosynthesis and carbohydrate metabolism were enriched through the KEGG metabolic pathway analysis of the differentially expressed unigenes. The upregulated sucrose synthase gene in the purple leaves may provide hexoses and UDP-glucose for anthocyanin synthesis. The genes encoding the corresponding enzymes in the glycolysis pathway were upregulated, whereas the expression of those genes encoding the enzymes in the TCA cycle showed no obvious change. Increased acetyl-CoA may contribute to anthocyanin accumulation through the upregulated cytosolic acetyl-coenzyme A carboxylase (ACCase) gene in the purple leaves of 'Zijuan' tea, indicating that glycolysis may provide more intermediates as substrates for promoting anthocyanin accumulation. The physiological and qRT-PCR results were consistent with the RNA-Seq data. Our findings expand our knowledge on the metabolic regulation of anthocyanin synthesis in tea plants.