Tea is an economically important plant characterized by a large genome, high heterozygosity, and high species diversity. In this study, we assemble a 3.26-Gb high-quality chromosome-scale genome for the ‘Longjing 43’ cultivar of Camellia sinensis var. sinensis. Genomic resequencing of 139 tea accessions from around the world is used to investigate the evolution and phylogenetic relationships of tea accessions. We find that hybridization has increased the heterozygosity and wide-ranging gene flow among tea populations with the spread of tea cultivation. Population genetic and transcriptomic analyses reveal that during domestication, selection for disease resistance and flavor in C. sinensis var. sinensis populations has been stronger than that in C. sinensis var. assamica populations. This study provides resources for marker-assisted breeding of tea and sets the foundation for further research on tea genetics and evolution.

As a vital beverage crop, tea has been extensively planted in tropical and subtropical regions. Nitrogen (N) levels and forms are closely related to tea quality. Based on different N levels and forms, we studied changes in NO₃⁻ and NH₄⁺ fluxes in tea roots utilizing scanning ion-selective electrode technique. Our results showed that under both single and mixed N forms, influx rates of NO₃⁻ were much lower than those of NH₄⁺, suggesting a preference for NH₄⁺ in tea. With the increase in N concentration, the influx rate of NO₃⁻ increased more than that of NH₄⁺. The NH₄⁺ influx rates in a solution without NO₃⁻ were much higher than those in a solution with NO₃⁻, while the NO₃⁻ influx rates in a solution without NH₄⁺ were much lower than those in a solution with NH₄⁺. We concluded that (1) tea roots showed a preference for NH₄⁺, (2) presence of NO₃⁻ had a negative effect on NH₄⁺ influx, and (3) NH₄⁺ had a positive effect on NO₃⁻ influx. Our findings not only may help advance hydroponic tea experiments but also may be used to develop efficient fertilization protocols for soil-grown tea in the future.

Adventitious root (AR) formation is essential for the successful propagation of Camellia sinensis and auxins play promotive effects on this process. Nowadays, the mechanism of auxin-induced AR formation in tea cuttings is widely studied. However, a lack of global view of the underlying mechanism has largely inhibited further studies. In this paper, recent advances including endogenous hormone changes, nitric oxide (NO) and hydrogen peroxide (H₂O₂) signals, secondary metabolism, cell wall reconstruction, and mechanisms involved in auxin signaling are reviewed. A further time course analysis of transcriptome changes in tea cuttings during AR formation is also suggested to deepen our understanding. The purpose of this paper is to offer an overview on the most recent developments especially on those key aspects affected by auxins and that play important roles in AR formation in tea plants.

Catechins are the main polyphenol compounds in tea (Camellia sinensis). To understand the relationship between gene expression and product accumulation, the levels of catechins and relative expressions of key genes in tea leaves of different developmental stages were analyzed. The amounts of catechins differed significantly in leaves of different stages, except for gallocatechin gallate. Close correlations between the expression of synthesis genes and the accumulation of catechins were identified. Correlation analysis showed that the expressions of chalcone synthase 1, chalcone synthase 3, anthocyanidin reductase 1, anthocyanidin reductase 2 and leucoanthocyanidin reductase genes were significantly and positively correlated with total catechin contents, suggesting their expression may largely affect total catechin accumulation. Anthocyanidin synthase was significantly correlated with catechin. While both ANRs and LAR were significantly and positively correlated with the contents of (−)-epigallocatechin gallate and (−)-epicatechin gallate. Our results suggest synergistic changes between the expression of synthetic genes and the accumulation of catechins. Based on our findings, anthocyanidin synthase may regulate earlier steps in the conversion of catechin, while the anthocyanidin reductase and leucoanthocyanidin reductase genes may both play important roles in the biosynthesis of galloylated catechins.