The high-affinity K+ transporter IbHAK5 enhances potassium ion absorption and improves root morphology in sweetpotato (Ipomoea batatas).

Potassium is a vital element in sweetpotato that plays important roles during its growth and development. In this study, potassium transporter IbHAK5, which is homologous to Arabidopsis HAK5, was cloned and overexpressed in sweetpotato. IbHAK5 encoded a protein of 739 amino acids and localized in the plasma membrane. Two IbHAK5-overexpressing transgenic lines with the highest expression level of IbHAK5 were screened for K⁺-deficiency stress tolerant assay. Compared with wild type sweetpotato plants, transgenic plants grew well with higher chlorophyll content, and maintain great higher K⁺ contents via decreasing more K⁺ effluxes under low potassium ion (- K⁺) stress condition. Additionally, IbHAK5 can help plants improve root morphology and increase endogenous hormone IAA content under both normal condition and - K⁺ stress, which may result in the increased root K⁺ absorption ability. The results indicated that IbHAK5 play an important role in sweetpotato response to - K⁺ stress, as well as support molecular-assisted breeding with the IbHAK5 gene.