ZmHAK17 encodes a Na+-selective transporter that promotes maize seed germination under salt conditions

Abstract

Elevated sodium ion (Na⁺) in saline farmlands adversely affect crops, notably by inhibiting seed germination. Given the importance of High-Affinity K⁺ Transporter (HAK) family Na⁺ transporters in plant salt tolerance and ZmHAK4 role in maize salt tolerance, our study focuses on characterizing HAK transporters related to ZmHAK4 in maize’s salt stress response. We found that ZmHAK17 is vital for promoting seed germination under saline conditions. Expressed mainly in the germinating embryo’s radicle, ZmHAK17, encodes a Na⁺ transporter located in the plasma membrane. Increased ZmHAK17 transcript levels under salt stress facilitate Na⁺ efflux from the radicle, preventing Na⁺ accumulation in the embryo and reducing salt stress effects on germination. Mutants lacking ZmHAK17 exhibit salt-sensitive germination. This study highlights ZmHAK17 as a key transporter enhancing maize germination in saline conditions, deepening our understanding of HAK family Na⁺ transporters’ role in salt tolerance and offering a new target gene for salt-tolerant maize breeding.