禾本科作物联合固氮研究进展

Research progress on associative nitrogen fixation of gramineous crops

生物固氮是唯一能将空气中“免费”的氮气转化为化合态氮的生物学过程。一般认为豆科作物具有共生固氮能力,间套种豆科作物已成为补充农田氮素的重要方式。越来越多的证据证明禾本科作物也具有较高的联合固氮潜力,大量联合固氮菌不仅定殖在根际、根内,还可以定殖在植株地上部如茎维管束、叶际中,表明禾本科作物固氮微生物可能为避免复杂的土壤环境,开辟了一条“体内高效固氮”的新途径。本文回顾了近年来玉米、小麦、水稻、甘蔗等禾本科作物在联合固氮部位、调控途径、菌群构建等方向取得的创新进展,重点介绍了固氮菌除了与宿主植物存在互作关系外,还与其他功能细菌、真菌和病毒之间存在潜在的相互作用。基于生物固氮多功能合成菌群在植物营养和促生等领域表现出的巨大应用前景和潜力,提出了当前禾本科作物联合固氮研究的前沿热点和难点,即如何综合利用“自上而下”和“自下而上”策略,筛选关键功能类群并结合基因组尺度代谢模型,构建群落稳定、功能多样、效果显著的合成菌剂,为生物固氮在农业生产中广泛应用提供强有力的技术支撑。

Biological nitrogen fixation(BNF)is the only biological process that can convert the“free”atmospheric nitrogen into chemical nitrogen for the utilization of plant and microorganism.Leguminous crops are widely known about their high efficiency in symbiotic nitrogen fixation,and have been used in agriculture as a supplement of nitrogen for other crops.Recent studies found that gramineous crops also had powerful associative nitrogen fixation capacity.In particular,large numbers of associative nitrogen-fixing bacteria have been identified in root,rhizosphere,and the above ground compartments of plants,like stem vascular bundle and phyllosphere,suggesting that nitrogen-fixing microorganisms in gramineous crops may have created a new pathway for“efficient nitrogen fixation in vivo”to avoid complex soil environments.This article presents an overview of the recent advancements in the associative nitrogen fixation compartments,regulatory pathways,and microbial community construction of gramineous crops,such as maize,wheat,rice,and sugarcane.This review focuses on the potential interactions between nitrogen-fixing bacteria and other functional bacteria,fungi,and viruses,beyond their interactions with host plants.Based on the promising application prospects of multifunctional synthetic microbial community in the fields of plant nutrition and growth promotion,this paper outlines the current research frontiers and challenges in associative nitrogen fixation of gramineous crops. The ultimate aim is to integrate the “top-down” and “bottom-up” strategies to identify key functional groups, combine genome-scale metabolic models, and construct stable, functionally diverse, and effective synthetic microbial community, and to provide robust technical support for the widespread application of BNF in agricultural production.