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Rice panicles, a major component of yield, are regulated by phytohormones and nutrients. How mineral nutrients promote panicle architecture remains largely unknown. Here, we report that NIN-LIKE PROTEIN3 and 4 (OsNLP3/4) are crucial positive regulators of rice panicle architecture in response to nitrogen (N). Loss-of- function mutants of eitherOsNLP3orOsNLP4produced smaller panicles with reduced primary and secondary branches and fewer grains compared with wild type, whereas their overexpression plants showed the opposite phenotypes. Notably, the OsNLP3/4-regulated panicle architecture was positively correlated with N availability. OsNLP3/4 directly bind to the promoter ofOsRFLand activate its expression to promote inflorescence meristem development. Furthermore, OsRFL activatesOsMOC1expression by binding to its promoter. Our findings reveal the novel N- responsive OsNLP3/4-OsRFL-OsMOC1 module that integrates N availability to regulate panicle architecture, shedding light on how nutrient signals regulate panicle architecture and providing candidate targets for the improvement of crop yield.

Nutrients must be balanced for optimal plant growth. However, the potential significance of balanced nitrogen-iron (N-Fe) for improving crop yield and nitrogen use efficiency (NUE) has never been addressed. Here, we show that balanced N-Fe substantially increases tiller number and boosts yield and NUE in rice and wheat. NIN-like protein 4 plays a pivotal role in maintaining the N-Fe balance by coordinately regulating the expression of multiple genes in N and Fe metabolism and signaling. Moreover, we show that foliar spraying of balanced N-Fe at the tillering stage can effectively increase rice tillers, yield and NUE in the field, which can be reproduced with wheat. Our findings provide guidelines for innovative fertilization to reduce N fertilizer input and promote yield, thus benefitting environment-friendly and sustainable agriculture worldwide.

Nitrogen (N) is an essential macronutrient for crop growth and yield. Improving the N use efficiency (NUE) of crops is important to agriculture. However, the molecular mechanisms underlying NUE regulation remain largely elusive. Here we report that the OsNLP3 (NIN-like protein 3) regulates NUE and grain yield in rice under N sufficient conditions. OsNLP3 transcript level is significantly induced by N starvation and its protein nucleocytosolic shuttling is specifically regulated by nitrate. Loss-of-function of OsNLP3 reduces plant growth, grain yield, and NUE under sufficient nitrate conditions, whereas under low nitrate or different ammonium conditions, osnlp3 mutants show no clear difference from the wild type. Importantly, under sufficient N conditions in the field, OsNLP3 overexpression lines display improved grain yield and NUE compared with the wild type. OsNLP3 orchestrates the expression of multiple N uptake and assimilation genes by directly binding to the nitrate-responsive cis-elements in their promoters. Overall, our study demonstrates that OsNLP3, together with OsNLP1 and OsNLP4, plays overlapping and differential roles in N acquisition and NUE, and modulates NUE and the grain yield increase promoted by N fertilizer. Therefore, OsNLP3 is a promising candidate gene for the genetic improvement of grain yield and NUE in rice.