Disruption of FW2.2-like Genes Enhances Metallic Micronutrient Accumulation in Brown Rice

Micronutrient deficiencies adversely affect human health and pose a significant global threat. Enhancing the accumulation of micronutrients in the edible parts of crops through genetic breeding is a promising strategy to mitigate micronutrient deficiencies in humans. FW2.2-like (FWL) genes play crucial roles in regulating heavy metal homeostasis in plants. We previously obtained two allelic mutants for each of the rice OsFWL1 (osfwl1a and osfwl1b) and OsFWL2 (osfwl2a and osfwl2b) genes. In this study, we showed that disruption of either OsFWL1 or OsFWL2 significantly enhanced the accumulation of metallic micronutrients in brown rice. Compared with that in the wild type, the iron (Fe) concentration in brown rice was higher in the osfwl1a (+166.7%), osfwl1b (+24.3%), and osfwl2a (+99.2%) mutants; the manganese (Mn) concentration was elevated in all four mutants (+25.1% to 35.6%); the copper (Cu) concentration increased in osfwl2a (+31.0%) and osfwl2b (+29.0%); and the zinc (Zn) concentration increased in osfwl2a (+10.2%). Additionally, disruption of OsFWL1 or OsFWL2 affected the homeostasis of metallic micronutrients in seedlings. Transcriptome analysis suggested that OsFWL1 and OsFWL2 might regulate cell wall polysaccharide metabolism and the expression of heavy metal transporter genes. Protein interaction analysis revealed that OsFWL1 interacted with OsFWL2 on the cell membrane. These findings suggest that OsFWL1 and OsFWL2 can serve as genetic biofortification tools to increase the concentrations of metallic micronutrients in rice grains.