OsNRAMP7 positively regulates heat tolerance at seedling and reproductive stages in rice

Abstract

Heat stress is a significant environmental threat that affects the growth and productivity of rice. However, there is currently limited understanding of heat tolerance. Natural resistance-associated macrophage proteins (NRAMPs) are known for their roles in ions uptake, transportation, and disease resistance, but their role in heat resistance is still unknown. In this study, we demonstrated that OsNRAMP7, a member of the NRAMP family in rice, positively regulates heat resistance at both vegetative and reproductive stages by generation of knockout and overexpression transgenic lines. OsNRAMP7 was highly expressed in leaf blades, roots, immature panicles, flag leaf sheaths, and husks. The expression of OsNRAMP7 was strongly induced in rice shoots when exposed to heat stress. Under heat stress, OsNRAMP7 knockout plants exhibited more severe leaf damage and lower survival rates at the seedling stage, and decreased seed-setting rates and seed weight per plant at the reproductive stage compared to the wild type. Conversely, the OsNRAMP7 overexpression plants exhibited enhanced heat tolerance across these phenotypic parameters. OsNRAMP7 is co-localized in the Endoplasmic Reticulum and Golgi. Transcriptome analysis revealed significant changes in the ribosome pathway in transgenic plants under heat stress. The OsNRAMP7 overexpression plants increased the total antioxidant capacity and water content in rice after heat stress, and exhibited stronger heat tolerance. There are three main distinct haplotypes of OsNRAMP7 in natural populations that are unevenly distributed across various cultivated rice regions and showed differentiation among subpopulations. This study reports for the first time the biological function of NRAMP family member OsNRAMP7 in heat tolerance and lays the foundation for expanding the molecular regulation mechanism of heat tolerance in rice.