MaHAK5, a Potassium Transporter of Banana, Enhanced Potassium Uptake in Transgenic Arabidopsis under Low Potassium Conditions

Potassium (K+) is one of the most important macronutrients for plant growth and development. It is generally accepted that the KUP/HAK/KT transporters play essential roles in K+ uptake at low concentrations. However, their physiological functions in bananas remain unknown. Here, we cloned MaHAK5 and analyzed its functions in banana (Musa acuminata). Gene expression analysis showed that MaHAK5 was upregulated in the roots and leaves in the early stage of low K+ (LK) stress. MaHAK5 was localized in the cytomembrane. The expression of MaHAK5 improved the growth of the low K+-sensitive yeast mutant R5421 at different K+ supply levels. Overexpression of MaHAK5 in Arabidopsis thaliana significantly enhanced the ability for K+ uptake and increased the chlorophyll content under LK stress. These results indicate that MaHAK5 plays a crucial role in maintaining K+ uptake in bananas.