Shaker potassium channel OsKAT1 regulates root K⁺ uptake and lodging resistance in rice under low K⁺ stress

Widespread potassium (K) deficiency in paddy soils, coupled with the low potassium use efficiency (KUE) of rice, has driven research on genetically improving KUE for sustainable rice production. Breeding high-KUE rice cultivars requires thorough understanding of root K⁺ uptake molecular mechanisms mediated by specific K⁺ channels and transporters. Here, we characterize the Shaker-type K⁺ channel OsKAT1 in rice. Disruption of OsKAT1 impairs root K⁺ uptake, resulting in reduced K⁺ accumulation and severe growth retardation under low-K⁺ stress. Conversely, overexpression of OsKAT1 enhances root K⁺ acquisition and promotes rice growth. Notably, OsKAT1-overexpressing lines exhibit increased culm diameter and improved bending resistance, thereby enhancing lodging tolerance. OsKAT1 overexpression also significantly increases grain size and weight under both K⁺-sufficient and low-K⁺ conditions. Natural variation at the OsKAT1 locus correlates with differential gene expression among haplotypes, with Hap 2 and Hap 3 conferring superior tolerance to low-K⁺ stress. Additionally, our results suggest that the expression pattern and physiological function of OsKAT1 may be cultivar-dependent. Collectively, these findings establish OsKAT1 as a key integrator of low-K⁺ adaptation, lodging resistance, and yield enhancement in rice, offering a promising genetic target for breeding rice varieties with improved KUE and yield potential.