A rice SOUL family heme-binding protein REAC1 enhances the antioxidative capacity of C. elegans through modulation of ROS-related gene expression.

The development and identification of beneficial components from crop resources are vital for individuals, especially the elderly, as they are capable of facilitating health. Red rice is widely consumed and possesses potential therapeutic effects to some extent, but it is important to discover the specific roles of each component when consumed purposefully. In this context, the REAC1/rHBP2, a red rice heme-binding protein (HBP) from the SOUL family, was revealed that possesses a role in boosting the antioxidative capacity of C. elegans that consume this protein. The Arabidopsis plants overexpressing REAC1 presented more tolerance to oxidative stress related to the wild-type plants. Furthermore, REAC1 derived from engineered bacteria exhibited clear activities of heme-binding and hydroxy radical inhibition in vitro. While no adverse effects were observed in the nematodes that were treated with REAC1, they exhibited enhanced motility and improved survival under oxidative conditions simulated by treatment with 5 mM H₂O₂ compared to the control group. Additionally, the levels of endogenous reactive oxygen species (ROS) were significantly reduced, and the expression of redox-related genes, such as SOD-3 and CAT-1, was evidently upregulated in the treated nematodes. Taken together, these results suggest that the red rice heme-binding protein REAC1 plays a critical role in the enhancement of the antioxidative capacity of C. elegans through ROS-related regulation, thereby offering a promising approach for individuals to combat oxidative stress.