CRISPR-mediated BnaNRAMP1 homologous copies editing create a low Cd-accumulation oilseed rape germplasm with unaffected yield

Abstract

Brassica napus, one of the most important oil crops cultivated globally, is severely impacted by prolonged soil contamination with cadmium (Cd), resulting in decreased yields and poor seed quality. This crop exhibits a high adsorption capacity for Cd, thereby making the creation of seed resources with low Cd-accumulation as an essential strategy to alleviate this challenge. To address this issue, we genetically edited BnaNRAMP1 in B. napus by targeting three different exon regions, resulting in new germplasm resources with significant differences in Cd accumulation capacity and unaffected yield. Among these, the mutant K140-22, specifically targeting the seventh exon, is distinguished by its substantially reduced Cd accumulation. Further, enzyme assays of the antioxidant defense system in both roots and shoots of K140-22 revealed its enhanced antioxidant activity, which contributes to elucidate the molecular mechanisms of plant tolerance to heavy metal stress. Remarkably, this mutant also maintained equivalent agronomic traits and seed quality, which highlights its potential as a germplasm resource for rapeseed breeding for low Cd accumulation, as well as for elevating rapeseed economic value in Cd contaminated soil.