CsWRKY17 enhances Al accumulation by promoting pectin deesterification in tea plant

The tea plant (Camellia sinensis) is a typical crop that accumulates aluminum (Al). Although the physiological mechanisms by which this occurs are well understood, their molecular mechanisms remain elusive. Here, an integrative approach combining quantitative trait locus (QTL) mapping of controlled hybridized populations and comparative transcriptomic analysis using samples treated with different Al concentrations was applied to identify candidate genes associated with Al accumulation in tea plants. Consequently, 41 candidate genes were selected using genome functional annotation of the qAl09 locus in the region of 35 256 594-57 378 817 bp on chromosome 7. Finally, a key gene, CsWRKY17, was identified as encoding a nucleus-localized transcription factor involved in regulating Al accumulation in tea plants, given the finding of a high correlation between its expression level and Al content in leaves. Overexpression of CsWRKY17 in Arabidopsis increased pectin deesterification, sensitivity to Al stress, and Al accumulation in leaves. Expression of the pectin methylesterase gene CsPME6 was found to be highly consistent with CsWRKY17 expression under various Al concentrations. In addition, experiments using a yeast monoclonal, electrophoresis mobility shift assay and dual-luciferase reporter (DLR) system confirmed that CsWRKY17 activated CsPME6 promoter activity. Antisense oligodeoxynucleotide silencing revealed a positive association between CsPME6 expression and Al accumulation in tea shoots. In conclusion, this study suggests that CsWRKY17 promoted the process of pectin deesterification by binding to the CsPME6 promoter, thereby enhancing Al enrichment in tea plants. Our findings lay the foundation for studying the precise mechanisms through which Al enriched in tea leaves.