The R2R3-MYB transcription factor CsMYB42 regulates theanine biosynthesis in albino tea leaves

MYB transcription factors in plants: A comprehensive review of their discovery, structure, classification, functional diversity and regulatory mechanism

The MYB transcription factor (TF) family is one of the largest families in plants and performs highly diverse regulatory functions, particularly in relation to pathogen/pest resistance, nutrient/noxious substance absorption, drought/salt resistance, trichome growth, stamen development, leaf senescence, and flavonoid/terpenoid biosynthesis. Owing to their vital role in various biological regulatory processes, the mechanisms of MYB TFs have been extensively studied. Notably, MYB TFs not only directly regulate targets, such as phytohormones, reactive oxygen species signaling and secondary cell wall formation, but also serve as crucial points of crosstalk between these signaling networks. Here, we have comprehensively described the structures, classifications, and biological functions of MYB TFs, with a specific focus on their roles and mechanisms in the response to biotic and abiotic stresses, plant morphogenesis, and secondary metabolite biosynthesis. Different from other reported reviews, this review provides comprehensive knowledge on plant MYB TFs and will provide valuable insights in understanding regulatory networks and associated functions of plant MYB TFs to apply in resistance breeding and crop improvement.

CsMOF1-guided regulation of drought-induced theanine biosynthesis in Camellia sinensis

The distinctive flavor and numerous health benefits of tea are attributed to the presence of theanine, a special amino acid found in tea plants. Nitrogen metabolite is greatly impacted by drought; however, the molecular mechanism underlying the synthesis of theanine in drought-stricken tea plants is still not clear. Through the drought transcriptome data of tea plants, we have identified a gene CsMOF1 that appears to play a role in theanine biosynthesis under drought stress, presenting a significantly negative correlation with both theanine content and the expression of CsGS1. Further found that CsMOF1 is a transcription factor containing a MYB binding domain, localized in the nucleus. Upon silencing CsMOF1, there was a prominent increase in the level of the theanine and glutamine, as well as the expression of CsGS1, while glutamic acid content decreased significantly. Conversely, overexpression of CsMOF1 yielded opposite effects. Dual luciferase reporter assay and electromobility shift assays demonstrated that CsMOF1 binds to the promoter of CsGS1, thereby inhibiting its activity. These results indicate that CsMOF1 plays a crucial role in theanine biosynthesis in tea plants under drought stress, acting as a transcriptional repressor related to theanine biosynthesis. This study provides new insights into the tissue-specific regulation of theanine biosynthesis and aids with the cultivation of new varieties of tea plants.

Genome-wide identification of tea plant (Camellia sinensis) BAHD acyltransferases reveals their role in response to herbivorous pests

BACKGROUND

BAHD acyltransferases are among the largest metabolic protein domain families in the genomes of terrestrial plants and play important roles in plant growth and development, aroma formation, and biotic and abiotic stress responses. Little is known about the BAHDs in the tea plant, a cash crop rich in secondary metabolites.

RESULTS

In this study, 112 BAHD genes (CsBAHD01-CsBAHD112) were identified from the tea plant genome, with 85% (98/112) unevenly distributed across the 15 chromosomes. The number of BAHD gene family members has significantly expanded from wild tea plants to the assamica type to the sinensis type. Phylogenetic analysis showed that they could be classified into seven subgroups. Promoter cis-acting element analysis revealed that they contain a large number of light, phytohormones, and stress-responsive elements. Many members displayed tissue-specific expression patterns. CsBAHD05 was expressed at more than 500-fold higher levels in purple tea leaves than in green tea leaves. The genes exhibiting the most significant response to MeJA treatment and feeding by herbivorous pests were primarily concentrated in subgroups 5 and 6. The expression of 23 members of these two subgroups at different time points after feeding by tea green leafhoppers and tea geometrids was examined via qPCR, and the results revealed that the expression of CsBAHD93, CsBAHD94 and CsBAHD95 was significantly induced after the tea plants were subjected to feeding by both pricking and chewing pests. Moreover, based on the transcriptome data for tea plants being fed on by these two pests, a transcriptional regulatory network of different transcription factor genes coexpressed with these 23 members was constructed.

CONCLUSIONS

Our study provides new insights into the role of BAHDs in the defense response of tea plants, and will facilitate in-depth studies of the molecular function of BAHDs in resistance to herbivorous pests.

Differential Response of MYB Transcription Factor Gene Transcripts to Circadian Rhythm in Tea Plants (Camellia sinensis)

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.