The circadian clock refers to the formation of a certain rule in the long-term evolution of an organism, which is an invisible ‘clock’ in the body of an organism. As one of the largest TF families in higher plants, the MYB transcription factor is involved in plant growth and development. MYB is also inextricably correlated with the circadian rhythm. In this study, the transcriptome data of the tea plant ‘Baiyeyihao’ were measured at a photoperiod interval of 4 h (24 h). A total of 25,306 unigenes were obtained, including 14,615 unigenes that were annotated across 20 functional categories within the GO classification. Additionally, 10,443 single-gene clusters were annotated to 11 sublevels of metabolic pathways using KEGG. Based on the results of gene annotation and differential gene transcript analysis, 22 genes encoding MYB transcription factors were identified. The G10 group in the phylogenetic tree had 13 members, of which 5 were related to the circadian rhythm, accounting for 39%. The G1, G2, G8, G9, G15, G16, G18, G19, G20, G21 and G23 groups had no members associated with the circadian rhythm. Among the 22 differentially expressed MYB transcription factors, 3 members of LHY, RVE1 and RVE8 were core circadian rhythm genes belonging to the G10, G12 and G10 groups, respectively. Real-time fluorescence quantitative PCR was used to detect and validate the expression of the gene transcripts encoding MYB transcription factors associated with the circadian rhythm.

Ni Yang, Jing-Wen Li, Yuan-Jie Deng, Rui-Min Teng, Wei Luo, Gui-Nan Li, Zhi-Hang Hu, Hui Liu, Ai-Sheng Xiong, Jian Zhang, Quan-Hong Yao, Jing Zhuang; Ectop

Theanine, a unique non-protein amino acid, is specifically accumulated in tea plants during winter. This study explored the theanine accumulation patterns in ‘Longjing 43’ and ‘Huangjinya’ under different N supply conditions and analyzed the expression of genes involved in theanine biosynthesis during winter dormancy. We found that the two tea plant cultivars shared similar theanine accumulation patterns in winter. After 30 d of cultivation with various N forms and N deficiency, the theanine content in the tissues of both cultivars was highest in the control group, followed by NH₄⁺ treatment. Furthermore, we noted that root growth of tea plants was inhibited to varying degrees under different N sources and N-deficient conditions. Gene expression analysis revealed that both N forms can induce the transcription of key genes, including CsADC, CsALT, CsCuAO, CsGDH2, CsPAO, CsNiR, CsNR, and CsTS1 in ‘Longjing 43’ and ‘Huangjinya’. The expression of these genes was strongly correlated with theanine levels under the N treatments. The winter theanine accumulation was finely tuned by the interplay of multiple related genes, with expression levels varying across different cultivars and tissues.