Boosting crop yield and nitrogen use efficiency: the hidden power of nitrogen-iron balance

The macronutrient nitrogen (N) and micronutrient iron (Fe) are essential mineral elements for plant growth and development and participate in multiple vital life activities through intricate interactions. N and Fe fertilizers were found to increase crop yield when applied together. However, the N-Fe balance has not been clearly defined, and the underlying molecular mechanisms have remained unknown until recently. This review summarizes recent advances in N-Fe balance and highlights the critical role of the hub transcription factor NIN-like proteins (NLPs) that integrate N and Fe signals to improve crop yield and nitrogen use efficiency (NUE) as well as the molecular mechanism underlying N-Fe balance-boosted yield and NUE, which provides insight into not only the enhancement of crop yield and NUE but also the innovation of green fertilizers, greatly benefiting global sustainable agriculture and ecosystems.