Knockout of OsPHT4;4 enhances thiamethoxam accumulation in rice stems for improved brown planthopper control

The phosphate transporter PHT4 plays a crucial role in nutrient transport within plants. In addition to this fundamental functions, PHT4 may also participate in the uptake and translocation of other compounds, such as ascorbate. However, only a few studies have characterized the functional roles of PHT4. In this study, we identified and functionally characterized the role of the phosphate transporter OsPHT4;4 in thiamethoxam (THX) uptake and transport in rice. Heterologous expression experiments in yeast and Xenopus laevis oocytes (X. laevis oocytes) demonstrated that OsPHT4;4 significantly enhanced THX accumulation in cells. The OsPHT4; 4 proteins contained 11 transmembrane helices and localized primarily to the plasma membrane (PM) and chloroplast envelope. Knockout of OsPHT4;4 reduced the efficiency of THX translocation from stems to leaves, resulting in significant THX accumulation in the stems, which enhanced control of the brown planthopper (BPH), but had no effect on root-to-stem translocation. In contrast, overexpression of OsPHT4;4 increased THX translocation to the leaves, reduced THX accumulation in the stems, and thereby weakened the pest control effect on BPH. Our results indicate that OsPHT4;4 plays a key role in the specific distribution of THX, contributing to pest management while also affecting plant growth. These findings provide a foundation for optimizing pesticide usage in crop management by balancing pest control effectiveness and plant health.