A single-base mutation in promoter of enhances the negative regulation on mechanical-related leaf drooping in tea plants.

Mechanical harvesting in the tea industry has become increasingly essential due to its advantages in increasing productivity and reducing labor costs. Leaf droopiness caused a high rate of broken leaves, hindering the mechanized harvesting quality. However, the underlying mechanisms remain unclear. We herein identified a quantitative trait locus, designated as , along with three lead single nucleotide polymorphisms (SNPs) located near a gene (), named , through performing a genome-wide association study (GWAS) on 130 tea accessions. Integrated analysis of RNA-seq and ATAC-seq confirmed as a droopiness-associated candidate gene at the transcriptional level. was then proved to negatively regulate brassinosteroid-induced droopiness by using the -silencing tea plant. Whole-genome sequencing (WGS) combined with genome walking further indicated that a single-base mutation (T-A) in the promoter of . ChIP-seq revealed that this mutation occurred within the binding site, E-box, of CsBES1.2 on the promoter. Notably, CsBES1.2 bound the E-box of promoter to repress the expression of , as demonstrated by chromatin immunoprecipitation quantitative polymerase chain reaction (ChIP-qPCR), electrophoretic mobility shift assays (EMSA), and transient assays. The single-base mutation strengthened the inhibitory effect of CsBES1.2 on the expression of via enhancing the binding affinity to the E-box. Altogether, our findings suggest that CsTPR negatively regulates droopiness in tea plants under the transcriptional repression of CsBES1.2 and that a single-base mutation within E-box amplifies the suppression of CsBES1.2 on the expression of .