Musa paradisica RCI complements AtRCI and confers Na+ tolerance and K+ sensitivity in Arabidopsis

The mechanisms involved in Na+/K+ uptake and extrusion are important in plant salt tolerance. In this study, we investigated the physiological role of a plasma membrane (PM)-localized protein, MpRCI, from plantain in transgenic Arabidopsis under NaCl and KCl stress and determined its effect on PM fluidity and H+-ATPase activity. The MpRCI gene exhibited high homology to the AtRCI2 gene family in Arabidopsis and was therefore able to complement for loss of the yeast AtRCI2-related PMP3 gene. Results of phenotypic espial and atomic emission spectrophotometer (AES) assays indicated that MpRCI overexpression in the AtRCI2A knockout mutant with reduced shoot Na+ and increased K+ exhibited increased Na+-tolerance and K+-sensitivity under NaCl or KCl treatments, respectively. Furthermore, comparisons of PM fluidity and H+-ATPase activity in shoots, with expression or absence of MpRCI/AtRCI2A expression under NaCl or KCl stress, showed MpRCI maintained PM fluidity and H+-ATPase activity under stress conditions. Results suggest that MpRCI plays an essential role in Na+/K+ flux in plant cells.

► MpRCI was able to complement for the loss of yeast PMP3 gene and AtRCI2A gene. ► MpRCI could enhance the Na+ tolerance and K+ sensitivity of plant. ► MpRCI could protect the PM fluidity and H+-ATPase activity of plant.