Identification of Shaker K+ channel family members in sweetpotato and functional exploration of IbAKT1.

The Shaker K+ channel family plays a vital role in potassium absorption and stress resistance in plants. However little information on the genes family is available about sweetpotato. In the present study, eleven sweetpotato Shaker K+ channel genes were identified and classified into five groups based on phylogenetic relationships, conserved motifs, and gene structure analyses. Based on synteny analysis, four duplicated gene pairs were identified, derived from both ancient and recent duplication, whereas only one resulted from tandem duplication events. Different expression pattern of Shaker K+ channel genes in roots of Xu32 and NZ1 resulted in different K+ deficiency tolerances, suggesting there is different mechanism of K+ uptake in sweetpotato cultivars with different K+-tolerance levels. Quantitative real-time PCR analysis revealed that the shaker K+ channel genes responded to drought and high salt stresses. Higher K+ influx under normal condition and lower K+ efflux under K+ deficiency stress were observed in IbAKT1 overexpressing transgenic roots than in adventitious roots, which indicated that IbAKT1 may play an important role in the regulation of K+ deficiency tolerance in sweetpotato. This is the first genome-wide analysis of Shaker K+ channel genes and the first functional analysis of IbAKT1 in sweetpotato. Our results provide valuable information on the gene structure, evolution, expression and functions of the Shaker K+ channel gene family in sweetpotato.