A transposon insertion in the 5' UTR of OsPT1 reprograms its expression pattern and promotes cadmium accumulation in...

Cadmium (Cd) accumulation in rice grains presents a serious risk to human health; however, the mechanisms underlying this process remain incompletely understood. In this study, a genome-wide association analysis identified 29 loci associated with grain Cd content (LAGCCs). Among these, one of the most strongly associated loci, LAGCC4, contains the transporter gene OsPT1, whose haplotypes show a strong correlation with Cd content in rice grains. A transposon, H-MITE, inserts into the 5' untranslated region (UTR) of OsPT1, altering its expression pattern and leading to increased Cd accumulation. Furthermore, we identified the transcription factor OsbHLH35, which specifically binds to the OsPT1^H-MITE promoter to regulate its transcription in response to Cd stress. Targeted knockout of either OsPT1^H-MITE or OsbHLH35 via CRISPR-Cas9 gene editing significantly reduced grain Cd content, with reductions ranging from 61.7% to 80.6%. This study reveals a previously unrecognized mechanism contributing to high Cd accumulation in rice and identifies genetic targets for breeding rice varieties with reduced Cd content.