Tiny Gene Edit Cuts Toxic Cadmium in Rice by Half

Researchers from Japan's Okayama University and the Chinese Academy of Sciences have developed a genome-edited rice variety that drastically reduces the accumulation of toxic cadmium in rice grains without compromising crop yields or essential nutrient levels. Cadmium is a carcinogenic heavy metal found in contaminated agricultural soils that easily accumulates in cereal crops, making rice one of the largest dietary sources of cadmium exposure worldwide.

In a study published in the Proceedings of the National Academy of Sciences (PNAS), the team used precise base-editing technology to screen over 1,600 genome-edited lines targeting the metal transporter gene OsNramp5. They identified a specific point mutation, dubbed OsNramp5I441T, that swaps a single amino acid (isoleucine to threonine at position 441). In field trials on cadmium-contaminated soil, this subtle tweak reduced cadmium levels in brown rice by 48%, from 0.14 mg/kg in the wild-type plants to 0.07 mg/kg in the edited plants, while keeping grain yields and crucial micronutrients like iron, zinc, and manganese completely intact.

The breakthrough solves a long-standing challenge in agricultural science, as earlier methods to block cadmium typically stunted plant growth or disrupted the uptake of essential minerals. The researchers discovered that the mutation increases the transporter's preference for zinc, allowing zinc to outcompete cadmium as it moves through the plant toward the grain. Led by Dr. Sheng Huang and Professor Jian Feng Ma, the team believes this genetic modification offers a practical precision-breeding strategy to produce safer rice on affected soils globally.

For more details, read the news article in the Okayama University website.