Transcriptome analysis reveals CsGSTU18 plays an important role in anthocyanin accumulation-induced tender shoot turning purple of tea plant (Camellia sinensis)

Tea plant (Camellia sinensis) is a natural health drink. Because of its unique taste and the health-care effects of natural products, tea is more and more popular and concerned with people. Under the conditions of high temperature and strong light, the young leaves of tea plants are prone to accumulate anthocyanins, which in turn affects the suitability and quality of tea leaves. Here, we screened a key significantly up-regulated glutathione S-transferase 18 (CsGSTU18) gene from both cultivars 'Zi 1' (Z1) and 'Shaanxi Ziyang' (SZ) by RNA-seq. CsGSTU18, which belongs to Tau subfamily, was localized in the endoplasmic reticulum and cytoplasm. The overexpression of CsGSTU18 enhanced anthocyanin accumulation in transgenic Arabidopsis and rescued the anthocyanin-deficient phenotype of strawberry reduced anthocyanins in petioles (rap) mutant. Antisense oligonucleotide (asODN)-mediated transient silencing of CsGSTU18 significantly reduced anthocyanin accumulation in tea plant leaves, whereas the transient overexpression of CsGSTU18 showed the opposite change trend. Overall, these findings suggest that CsGSTU18 plays an important role in anthocyanin accumulation, which result in the tea tender shoot turning purple. This study provides a basis for further research on the molecular mechanism of anthocyanin accumulation in tea plant.