Cold stress restricts the metabolic and physiological activities of plants, thereby affecting their growth and development. Although broad-complex, tramtrack, and bric-à-brac (BTB) proteins are essential for diverse biological processes and stress responses, the mechanisms underlying BTB-mediated cold responses remain not fully understood. Here, we characterize the function of the cold-induced SlBTB19 protein in tomato (Solanum lycopersicum). Overexpression of SlBTB19 resulted in increased plant sensitivity to cold stress, whereas SlBTB19 knockout mutants exhibited a cold-tolerance phenotype. Further analyses, including protein-protein interaction studies and cell-free degradation assays, revealed that SlBTB19 interacts with and destabilizes the transcription factor SlWRKY2. Using virus-induced gene silencing (VIGS) to silence SlWRKY2 in both wild-type and slbtb19 mutants, we provided genetic evidence that SlWRKY2 acts downstream of SlBTB19 in regulating cold tolerance. Importantly, we demonstrated that SlWRKY2 positively regulates cold tolerance in a CRT/DRE binding factor (CBF)-dependent manner. Under cold stress, SlWRKY2 binds to the W-box in the CBF1 and CBF3 promoters, directly activating their expression. In summary, our findings identify a SlBTB19-SlWRKY2 module that negatively regulates the CBF-dependent cold tolerance pathway in tomato.
Keywords: BTB; CBF; Solanum lycopersicum; WRKY; cold tolerance; transcriptional regulation.
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