Plant HAK/KUP/KT family members function as plasma membrane (PM) H⁺/K⁺ symporters and may modulate chemiosmotically-driven polar auxin transport (PAT). Here, we show that inactivation of OsHAK5, a rice K⁺ transporter gene, decreased rootward and shootward PAT, tiller number, and the length of both lateral roots and root hairs, while OsHAK5 overexpression increased PAT, tiller number, and root hair length, irrespective of the K⁺ supply. Inhibitors of ATP-binding-cassette type-B transporters, NPA and BUM, abolished the OsHAK5-overexpression effect on PAT. The mechanistic basis of these changes included the OsHAK5-mediated decrease of transmembrane potential (depolarization), increase of extracellular pH, and increase of PM-ATPase activity. These findings highlight the dual roles of OsHAK5 in altering cellular chemiosmotic gradients (generated continuously by PM H⁺-ATPase) and regulating ATP-dependent auxin transport. Both functions may underlie the prominent effect of OsHAK5 on rice architecture, which may be exploited in the future to increase crop yield via genetic manipulations.

植物 HAK/KUP/KT 家族成员充当质膜 (PM) H ⁺ /K ⁺同向转运体，并可能调节化学渗透驱动的极性生长素转运 (PAT)。在这里，我们表明OsHAK5（一种水稻 K ⁺转运蛋白基因）的失活降低了根向和地上部 PAT、分蘖数以及侧根和根毛的长度，而OsHAK5过表达增加了 PAT、分蘖数和根毛长度，与 K ⁺供应无关。ATP 结合盒 B 型转运蛋白 NPA 和 BUM 的抑制剂消除了OsHAK5-过表达对 PAT 的影响。这些变化的机制基础包括 OsHAK5 介导的跨膜电位降低（去极化）、细胞外 pH 值增加和 PM-ATPase 活性增加。这些发现强调了 OsHAK5 在改变细胞化学渗透梯度（由 PM H ⁺ -ATPase连续产生）和调节 ATP 依赖性生长素转运方面的双重作用。这两种功能都可能是 OsHAK5 对水稻结构显着影响的基础，未来可能会利用这一点通过遗传操作来提高作物产量。