Genome-Wide Identification and Analysis of P-Type Plasma Membrane H+-ATPase Sub-Gene Family in Sunflower and the Role of HHA4 and HHA11 in the Development of Salt Stress Resistance

The P-type plasma membrane (PM) H+-ATPase plays a major role during the growth and development of a plant. It is also involved in plant resistance to a variety of biotic and abiotic factors, including salt stress. The PM H+-ATPase gene family has been well characterized in Arabidopsis and other crop plants such as rice, cucumber, and potato; however, the same cannot be said in sunflower (Helianthus annuus). In this study, a total of thirteen PM H+-ATPase genes were screened from the recently released sunflower genome database with a comprehensive genome-wide analysis. According to a systematic phylogenetic classification with a previously reported species, the sunflower PM H+-ATPase genes (HHAs) were divided into four sub-clusters (I, II, IV, and V). In addition, systematic bioinformatics analyses such as gene structure analysis, chromosome location analysis, subcellular localization predication, conserved motifs, and Cis-acting elements of promoter identification were also done. Semi-quantitative PCR analysis data of HHAs in different sunflower tissues revealed the specificity of gene spatiotemporal expression and sub-cluster grouping. Those belonging to sub-cluster I and II exhibited wide expression in almost all of the tissues studied while sub-cluster IV and V seldom showed expression. In addition, the expression of HHA4, HHA11, and HHA13 was shown to be induced by salt stress. The transgenic plants overexpressing HHA4 and HHA11 showed higher salinity tolerance compared with wild-type plants. Further analysis showed that the Na+ content of transgenic Arabidopsis plants decreased under salt stress, which indicates that PM H+ ATPase participates in the physiological process of Na+ efflux, resulting in salt resistance of the plants. This study is the first to identify and analyze the sunflower PM H+ ATPase gene family. It does not only lay foundation for future research but also demonstrates the role played by HHAs in salt stress tolerance.