MYB77 regulates high‐affinity potassium uptake by promoting expression of HAK5

Summary In Arabidopsis, the high‐affinity K + transporter HAK5 is the major pathway for root K + uptake when below 100 µM; HAK5 responds to Low‐K + (LK) stress by strongly and rapidly increasing its expression during K + ‐deficiency. Therefore, positive regulators of HAK5 expression have the potential to improve K + uptake under LK. Here, we show that mutants of the transcription factor MYB77 share a LK‐induced leaf chlorosis phenotype, lower K + content, and lower Rb + uptake of the hak5 mutant, but not the shorter root growth, and that overexpression of MYB77 enhanced K + uptake and improved tolerance to LK stress. Furthermore, we demonstrated that MYB77 positively regulates the expression of HAK5 , by binding to the HAK5 promoter and enhances high‐affinity K + uptake of roots. As such, our results reveal a novel pathway for enhancing HAK5 expression under LK stress, and provides a candidate for increasing the tolerance of plants to LK.