Functional Analysis Of Rice Nodule Inception-Like Protein 1 And AtNLP7 In Crop Nitrogen Use Efficiency

Nitrogen(N)is an essential macronutrient for normal growth and development of plants and agricultural production.In agricultural production,farmers apply a large amount of N fertilizer to maintain high crop yields.However,due to the low N use efficiency,most N fertilizers are not absorbed by plants and flow to the environment,causing serious environmental pollution and greatly increasing the cost of agricultural production.A desirable and economical solution to cope with these issues is to improve crop NUE,which has been a focal point of intensive research worldwide,yet much more has to be learned about its genetic determinants and regulation.Rice(Oryza sativa)is one of the most important food crops in the world,providing 35%-60%calories for 3 billion people.It is important to improve rice NUE.Here,we show that rice NIN-LIKE PROTEIN 1(OsNLP1)plays a fundamental role in NUE.OsNLP1 protein localizes in nucleus and its transcript level is rapidly induced by N starvation.Overexpression of OsNLP1 improves plant growth,grain yield,and NUE under different N conditions,while knockout of OsNLP1 impairs grain yield and NUE under N limiting conditions.OsNLP1 regulates nitrate and ammonium utilization by cooperatively orchestrating multiple N uptake and assimilation genes.Chromatin immunoprecipitation and yeast-one-hybrid assays show that OsNLP1 can directly bind to the promoter of these genes to activate their expression.Therefore,our results demonstrate that OsNLP1 is a key regulator of N utilization and represents a potential target for improving NUE and yield in rice.In addition,we also demonstrated that the Arabidopsis thaliana NIN-LIKE PROTEIN 7(AtNLP7)was able to improve the growth and development of the cotton plants(Gossypium hirsutum L.),and increase plant biomass under both N-poor and-rich conditions with better-developed root system.The transgenic plants displayed a significant increase in N absorption,key N metabolites,total N content,and expression levels of genes involved in N assimilation and signaling.Our results demonstrate that AtNLP7 can significantly improve both biomass and NUE in cotton plants,indicating the efficacy of AtNLP7 in crop improvement.