Potassium (K^+) is an essential macronutrient for plant growth and development. Transporters from the KT/HAK/KUP family play crucial roles in K^+ homeostasis and cell growth in various plant species. However, their ph...Potassium (K^+) is an essential macronutrient for plant growth and development. Transporters from the KT/HAK/KUP family play crucial roles in K^+ homeostasis and cell growth in various plant species. However, their physiological roles in maize are still unknown. In this study, we cloned ZmHAKs and ZmHAKi and investigated their functions in maize (Zea mays L.). In situ hybridization showed that ZmHAKs was mainly expressed in roots, especially in the epidermis, cortex, and vascular bundle. ZmH AK5 was characterized as a high-affinity K^+ transporter. Loss of function of ZmHAK5 led to defective K^+ uptake in maize, under low K^+ conditions, whereas ZmHAK5-over-expressing plants showed increased K^+ uptake activity and improved growth. ZmHAKi was upregulated under low K^+ stress, as revealed by RT-qPCR. ZmHAKi mediated K^+ uptake when heterologously expressed in yeast, but its transport activity was weaker than that of ZmHAK5. Overexpression of ZmHAKi in maize significantly affected K^+ distribution in shoots, leading to chlorosis in older leaves. These findings indicate that ZmHAKs and ZmHAKi play distinct roles in K^+ homeostasis in maize, functioning in K^+ uptake and K^+ distribution, respectively. Genetic manipulation of ZmHAK5 may represent a feasible way to improve K^+ utilization efficiency in maize.展开更多
基金supported by grants from the National Key Research and Development Program of China (2016YFD0100700)the Beijing Nova Program (Z161100004916117)+1 种基金the National Natural Science Foundation of China (31622008)the National Science and Technology Major Project (2016ZX08003-005)
文摘Potassium (K^+) is an essential macronutrient for plant growth and development. Transporters from the KT/HAK/KUP family play crucial roles in K^+ homeostasis and cell growth in various plant species. However, their physiological roles in maize are still unknown. In this study, we cloned ZmHAKs and ZmHAKi and investigated their functions in maize (Zea mays L.). In situ hybridization showed that ZmHAKs was mainly expressed in roots, especially in the epidermis, cortex, and vascular bundle. ZmH AK5 was characterized as a high-affinity K^+ transporter. Loss of function of ZmHAK5 led to defective K^+ uptake in maize, under low K^+ conditions, whereas ZmHAK5-over-expressing plants showed increased K^+ uptake activity and improved growth. ZmHAKi was upregulated under low K^+ stress, as revealed by RT-qPCR. ZmHAKi mediated K^+ uptake when heterologously expressed in yeast, but its transport activity was weaker than that of ZmHAK5. Overexpression of ZmHAKi in maize significantly affected K^+ distribution in shoots, leading to chlorosis in older leaves. These findings indicate that ZmHAKs and ZmHAKi play distinct roles in K^+ homeostasis in maize, functioning in K^+ uptake and K^+ distribution, respectively. Genetic manipulation of ZmHAK5 may represent a feasible way to improve K^+ utilization efficiency in maize.
