Genome-Wide Identification, Characterization, and Expression Analysis of BES1 Family Genes in 'Tieguanyin' Tea Under Abiotic Stress

The BRI1-EMS-SUPPRESSOR 1 (BES1) family comprises plant-specific transcription factors, which are distinguished by atypical bHLH domains. Over the past two decades, genetic and biochemical studies have established that members of the BRI1-EMS-SUPPRESSOR 1 (BES1) family are crucial for regulating the expression of genes involved in brassinosteroid (BR) response in rapeseed. Due to the significance of the BES1 gene family, extensive research has been conducted to investigate its functional properties. This study presents a comprehensive identification and computational analysis of BES1 genes in 'Tieguanyin' (TGY) tea (Camellia sinensis). A total of 10 BES1 genes were initially identified in the TGY genome. Through phylogenetic tree analysis, this study uniquely revealed that CsBES1.2 and CsBES1.5 cluster with SlBES1.8 from Solanum lycopersicum, indicating their critical roles in fruit growth and development. Synteny analysis identified 20 syntenic genes, suggesting the conservation of their evolutionary functions. Analysis of the promoter regions revealed two types of light-responsive cis-elements, with CsBES1.4 exhibiting the highest number of light-related cis-elements (13), followed by CsBES1.9 and CsBES1.10. Additional validation via qRT-PCR experiments showed that CsBES1.9 and CsBES1.10 were significantly upregulated under light exposure, with CsBES1.10 reaching approximately six times the expression level of the control after 4 h. These results suggest that CsBES1.9 and CsBES1.4 could play crucial roles in responding to abiotic stress. This study offers novel insights into the functional roles of the BES1 gene family in 'Tieguanyin' tea and establishes a significant foundation for future research, especially in exploring the roles of these genes in response to abiotic stresses, such as light exposure.