Knocking Out OsPT4 Gene Decreases Arsenate Uptake by Rice Plants and Inorganic Arsenic Accumulation in Rice Grains

Abstract

Arsenic (As) accumulation in rice grains poses health risk to humans. Plants including rice take up arsenate (AsV) by phosphate transporters. In this study, rice phosphate transporter OsPT4 (OsPht1;4) was investigated based on two independent T-DNA insertion mutants of OsPT4 (M1 and M2), which displayed stronger AsV resistance than wild types WT1 and WT2. When cultivated in medium (+P or -P) with AsV, ospt4 mutants accumulated 16-32% lower As in plants, suggesting that OsPT4 mediates AsV uptake. Analysis of the xylem sap showed that AsV concentrations in ospt4 mutants was 20-40% lower than WT controls under -P condition, indicating OsPT4 may also mediate AsV translocation. Moreover, kinetics analysis showed that ospt4 mutants had lower AsV uptake rates than the WT controls, further proving that OsPT4 functions as an AsV transporter in rice. When grown in flooded soils with As, AsV concentrations in rice grains of ospt4 mutants decreased by 50-55%. More importantly, knocking out OsPT4 in M1 and M2 reduced inorganic As accumulation in rice grains by 20-44%, significant for controlling As exposure risk from rice. Taken together, our findings revealed a critical role of OsPT4 in AsV uptake and translocation in rice. Knocking out OsPT4 effectively decreased inorganic As accumulation in rice grains, shedding light on engineering low-As rice to enhance food safety.