The defensin-like protein OsCDT5 reduces Cd accumulation in rice (Oryza sativa L.)

Rice (Oryza sativa L.) is one of the most important food crops worldwide, with a strong capacity for Cd accumulation. Cd accumulation in rice is regulated by multiple genes. Clarifying the roles of these genes in controlling Cd accumulation is beneficial for breeding rice varieties with low Cd accumulation in brown rice, thereby reducing human Cd intake. In this study, a defensin-like protein, OsCDT5, which localized to the apoplast and exhibits Cd-chelating ability, we identified. The Cd-to-protein binding ratios for MBP-OsCDT5 were 3.16-fold and 5.77-fold higher than those of the control, respectively, under pH 5.5 and pH 7.5 conditions. The yeast strain expressing OsCDT5 exhibited a Cd concentration that was 78.5 % of that in the control strain, and showed a significantly enhanced Cd tolerance. At the seedling stage, OsCDT5 was primarily localized in the outer epidermis of rice roots. Meanwhile, OsCDT5 reduces Cd concentration in both the roots and shoots of rice at the seedling stage. Compared to the wild-type, the oscdt5 knockout mutants exhibited increased Cd concentration in roots and shoots by ≥ 21.9 % and ≥12.8 %, respectively. Conversely, in OsCDT5 overexpression lines, Cd concentration in roots and shoots was reduced by ≥ 4.5 % and ≥19.1 %, respectively. These findings demonstrate that OsCDT5 is a critical regulatory locus governing Cd accumulation in rice.