OsWRI1a coordinates systemic growth responses to nitrogen availability in rice

Nitrogen (N) deficiency-induced increases in the root-to-shoot biomass ratio in plants are adaptive in nature but suboptimal for agriculture. Understanding the regulatory mechanisms governing this developmental plasticity could help improve crop performance while reducing fertilizer application. We identified OsWRI1a (WRINKLED1a) as a regulatory hub coordinating rice root and shoot growth in response to external N supply, thereby stabilizing the root-to-shoot ratio. In roots, OsWRI1a enhances N-responsive development by promoting auxin accumulation. Meanwhile, shoot OsWRI1a stimulates tiller development and therefore shoot growth. We identified an elite <i>OsWRI1a</i> haplotype that minimizes root-to-shoot ratio fluctuation under N deficiency, improving N-use efficiency and grain yield. Our findings reveal a central mechanism coordinating N-responsive growth allocation for sustainable agriculture.