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

TLDR

Salt stress disrupts plant nutrient metabolism, causing growth and yield penalties, yet the mechanisms underlying these metabolic adjustments remain unclear. The study aimed to identify and characterize the rice salt‑tolerant 1 (rst1) mutant that exhibits enhanced salt tolerance and grain yield. RST1 encodes an auxin response factor (OsARF18) that directly represses asparagine synthetase 1 (OsAS1), linking auxin signaling to nitrogen metabolism. Loss of RST1 function upregulates OsAS1, boosts asparagine production, improves nitrogen utilization, reduces excess ammonium, and the domestication‑selected haplotype RST1Hap III, with reduced repression activity, confers salt tolerance and higher grain weight, establishing RST1 as a synergistic regulator of growth and salt tolerance via N metabolism.

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 (Oryza sativa) rice salt tolerant 1 (rst1) mutant, which displayed improved salt tolerance and grain yield. Map-based cloning revealed that the gene RST1 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 RST1 function increased the expression of OsAS1 and improved nitrogen (N) utilization by promoting asparagine production and avoiding excess ammonium (NH4+) accumulation. RST1 was undergoing directional selection during domestication. The superior haplotype RST1Hap 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.