Silencing of GhKEA4 and GhKEA12 Revealed Their Potential Functions Under Salt and Potassium Stresses in Upland Cotton

The K(+) efflux antiporter (KEA) mediates intracellular K(+) and H(+) homeostasis to improve salt tolerance in plants. However, the knowledge of KEA gene family in cotton is largely absent. In the present study, 8, 8, 15, and 16 putative KEA genes were identified in Gossypium arboreum, G. raimondii, G. hirsutum, and G. barbadense, respectively. These KEA genes were classified into three subfamilies, and members from the same subfamilies showed similar motif compositions and gene structure characteristics. Some hormone response elements and stress response elements were identified in the upstream 2000 bp sequence of GhKEAs. Transcriptome data showed that most of the GhKEAs were highly expressed in roots and stems. The quantificational real-time polymerase chain reaction (qRT-PCR) results showed that most of the GhKEAs responded to low potassium, salt and drought stresses. Virus-induced gene silencing (VIGS) experiments demonstrated that under salt stress, after silencing genes GhKEA4 and GhKEA12, the chlorophyll content, proline content, soluble sugar content, peroxidase (POD) activity and catalase (CAT) activity were significantly decreased, and the Na(+)/K(+) ratio was extremely significantly increased in leaves, leading to greater salt sensitivity. Under high potassium stress, cotton plants silenced for the GhKEA4 could still maintain a more stable Na(+) and K(+) balance, and the activity of transporting potassium ions from roots into leaves was reduced silenced for GhKEA12. Under low potassium stress, silencing the GhKEA4 increased the activity of transporting potassium ions to shoots, and silencing the GhKEA12 increased the ability of absorbing potassium ions, but accumulated more Na(+) in leaves. These results provided a basis for further studies on the biological roles of KEA genes in cotton development and adaptation to stress conditions.