A single base mutation in promoter of CsTPR enhances the negative regulation on mechanical related leaves droopiness in tea plant

Abstract

Mechanical harvesting in the tea industry has become increasingly essential due to its advantages in increasing productivity and reducing labor costs. Leaves 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 loci, designated as q10.3, along with three lead SNPs located near a TPR gene (TETRATRICOPEPTIDE REPEAT), named CsTPR, through performing a genome-wide association study (GWAS) on 130 tea accessions. Integrated analysis of RNA-seq and ATAC-seq confirmed CsTPR as a droopiness-associated candidate gene at the transcriptional level. CsTPR was then proved to negatively regulate brassinosteroid -induced droopiness by using the CsTPR-silencing tea plant. The whole genome sequencing (WGS) and genome walking cloning further indicated that a single base mutation (T to A) in the promoter of CsTPR. ChIP-seq revealed that this mutation occurred within the binding site, E-box, of CsBES1.2 on the CsTPR promoter. Notably, CsBES1.2 bound the E-box of CsTPR promoter to repress the expression of CsTPR, as demonstrated by 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 CsTPR 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 CsTPR.