Abstract

Shaker potassium (K⁺) channels play essential roles in plant K⁺ uptake, transport, and stress responses. Although some studies have reported Shaker K⁺ channels in cucurbit species, a comprehensive genome-wide analysis across Cucurbitaceae is still lacking. In this study, 59 Shaker K + channel genes were identified from nine cucurbit genomes. These genes were phylogenetically clustered into five distinct classes based on their amino acid sequences, revealing conserved evolutionary relationships. Conserved motif and domain analyses, together with gene structure characterization, revealed structural conservation but also suggested potential functional diversification among family members. Synteny analysis indicated extensive collinearity of Shaker K⁺ channel genes between cucumber and other cucurbit plants, highlighting their evolutionary conservation. Cis -acting elements analysis indicated that many Shaker K⁺ channel genes harbor stress- and hormone- responsive regulatory motifs, particularly those related to abscisic acid, light, and auxin responses, suggesting their involvement in abiotic stress adaptation. Consistent results from qRT-PCR and histochemical GUS staining confirmed tissue-specific expression, with CsK1.1 predominantly in roots and CsK2.1 specifically in leaf guard cells. Subcellular localization analysis revealed that both CsK1.1 and CsK2.1 are localized to the plasma membrane. Functional complementation in yeast verified that both CsK1.1 and CsK2.1 can mediate K⁺ uptake. Our results provide important insights into the characterization of Shaker K + channel gene family in Cucurbitaceae and underscore the roles of cucumber CsK1.1 and CsK2.1 in K + transport.