Chengbo Shen, Zhe Ji, Wu Jiao, Siyu Zhang, Yunzhi Huang, Yaojun Qin, Menghan Huang, Shuming Kang, Zulong Mo, Bingyu Jiang, Ying Yu, Yajing Song, Yue Li, Jiayi Xu, Yanan Tian, Yuchen Xie, Guosheng Xiong, Shaokui Wang, Guohua Xu, Xiangdong Fu, Shan Li
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 OsWRI1a 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.