OsHMA3overexpression works more efficiently in generating low-Cd rice grain thanOsNramp5knockout mutation

Abstract

ABSTRACTCadmium (Cd) is highly toxic and a carcinogen to humans. Rice is prone to absorbing Cd and accumulating it in the grain, which raises health concerns for rice consumers. OsNramp5 is a major transporter for Cd and manganese (Mn) uptake in rice, whereas OsHMA3 is a tonoplast-localized transporter for Cd detoxification. In this study, we compared the efficiency ofOsNramp5knockout mutation andOsHAM3overexpression in reducing Cd content in the rice grain. The grain Cd content of theOsNramp5knockout mutants was significantly lower than that of the wild-type rice T5105. However, theOsNramp5knockout mutants still had much higher grain Cd content than the similarOsNramp5mutants reported previously or theOsHAM3overexpression line developed in our previous study. Pyramiding theOsNramp5mutant allele and theOsHAM3transgene in a double homozygous line could not further reduce grain Cd content. TheOsNramp5gene in T5105 has a haplotype II promoter, and its knockout mutation partially impairs Mn uptake in rice. Our results demonstrate thatOsHMA3overexpression works more efficiently in generating low-Cd rice grain thanOsNramp5knockout mutation without affecting Mn uptake in rice.