Rice Nin-Like Protein 4 Plays A Pivotal Role In Nitrogen Use Efficiency

Nitrogen (N) is one of the key essential macronutrients that affects rice growth and yield. Inorganic N fertilizers are excessively used to boost yield and generate serious collateral environmental pollution. Therefore, improving crop N use efficiency (NUE) is highly desirable and has been a major endeavour in crop improvement. However, only a few regulators have been identified that can be used to improve NUE in rice to date. Here we show that the rice NIN-like protein 4 (OsNLP4) significantly improves the rice NUE and yield. Field trials consistently showed that loss-of-OsNLP4dramatically reduced yield and NUE compared with wild type under different N regimes. In contrast, theOsNLP4overexpression lines remarkably increased yield by 30% and NUE by 47% under moderate N level compared with wild type. Transcriptomic analyses revealed that OsNLP4 orchestrates the expression of a majority of known N uptake, assimilation and signalling genes by directly binding to the nitrate-responsivecis-element in their promoters to regulate their expression. Moreover, overexpression ofOsNLP4can recover the phenotype of Arabidopsisnlp7mutant and enhance its biomass. Our results demonstrate that OsNLP4 plays a pivotal role in rice NUE and sheds light on crop NUE improvement.