Identification of Shaker Potassium Channel Family Members and Functional Characterization of SsKAT1.1 in Stenotaphrum secundatum Suggest That SsKAT1.1 Contributes to Cold Resistance

<i>Stenotaphrum secundatum</i> is an excellent shade-tolerant warm-season turfgrass. Its poor cold resistance severely limits its promotion and application in temperate regions. Mining cold resistance genes is highly important for the cultivation of cold-resistant <i>Stenotaphrum secundatum</i>. Although there have been many reports on the role of the Shaker potassium channel family under abiotic stress, such as drought and salt stress, there is still a lack of research on their role in cold resistance. In this study, the transcriptome database of <i>Stenotaphrum secundatum</i> was aligned with the whole genome of Setaria italica, and eight members of the Shaker potassium channel family in <i>Stenotaphrum secundatum</i> were identified and named <i>SsKAT1.1</i>, <i>SsKAT1.2</i>, <i>SsKAT2.1</i>, <i>SsKAT2.2</i>, <i>SsAKT1.1</i>, <i>SsAKT2.1</i>, <i>SsAKT2.2</i>, and <i>SsKOR1</i>. The <i>KAT3</i>-like gene, <i>KOR2</i> homologous gene, and part of the AKT-type weakly inwardly rectifying channel have not been identified in the <i>Stenotaphrum secundatum</i> transcriptome database. A bioinformatics analysis revealed that the potassium channels of <i>Stenotaphrum secundatum</i> are highly conserved in terms of protein structure but have more homologous members in the same group than those of other species. Among the three species of <i>Oryza sativa</i>, <i>Arabidopsis thaliana</i>, and <i>Setaria italica</i>, the potassium channel of <i>Stenotaphrum secundatum</i> is more closely related to the potassium channel of <i>Setaria italica</i>, which is consistent with the taxonomic results of these species belonging to Paniceae. Subcellular location experiments demonstrate that SsKAT1.1 is a plasma membrane protein. The expression of <i>SsKAT1.1</i> reversed the growth defect of the potassium absorption-deficient yeast strain R5421 under a low potassium supply, indicating that <i>SsKAT1.1</i> is a functional potassium channel. The transformation of <i>SsKAT1.1</i> into the cold-sensitive yeast strain INVSC1 increased the cold resistance of the yeast, indicating that <i>SsKAT1.1</i> confers cold resistance. The transformation of <i>SsKAT1.1</i> into the salt-sensitive yeast strain G19 increased the resistance of yeast to salt, indicating that <i>SsKAT1.1</i> is involved in salt tolerance. These results suggest that the manipulation of <i>SsKAT1.1</i> will improve the cold and salt stress resistance of <i>Stenotaphrum secundatum</i>.