Transcriptional repressor RST1 controls salt tolerance and grain yield in rice by regulating gene expression of asparagine synthetase.

Abstract

Salt stress impairs nutrient metabolism in plant cells, leading to growth and yield penalties. However, the mechanism by which plants alter their nutrient metabolism processes in response to salt stress remains elusive. In this study, we identified and characterized the rice (<i>Oryza sativa</i>) <i>rice salt tolerant 1 </i>(<i>rst1</i>) mutant, which displayed improved salt tolerance and grain yield. Map-based cloning revealed that the gene <i>RST1</i> encoded an auxin response factor (OsARF18). Molecular analyses showed that RST1 directly repressed the expression of the gene encoding asparagine synthetase 1 (OsAS1). Loss of <i>RST1</i> function increased the expression of <i>OsAS1</i> and improved nitrogen (N) utilization by promoting asparagine production and avoiding excess ammonium (NH₄⁺) accumulation. <i>RST1</i> was undergoing directional selection during domestication. The superior haplotype RST1^{Hap III} decreased its transcriptional repression activity and contributed to salt tolerance and grain weight. Together, our findings unravel a synergistic regulator of growth and salt tolerance associated with N metabolism and provide a new strategy for the development of tolerant cultivars.