Enzymatic diversity of biological nitrogen fixation in a changing world

不断变化的世界中生物固氮的酶多样性

• 批准号: RGPIN-2016-03660
• 负责人: Bellenger, JeanPhilippe
• 金额: $ 3.5万
• 依托单位: Université de Sherbrooke
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=689679
• 关键词: Enzymatic; diversity; biological; nitrogen; fixation

The boreal forest is one of the largest untouched terrestrial ecosystem in the world and supports essential economic sectors (i.e forestry, tourism) in Canada. Understanding boreal ecosystems function is thus of prime ecological and economical importance. In boreal forests, nitrogen is the nutrient that is most often reported as limiting primary productivity. While boreal forest soils are often rich in total nitrogen, this nitrogen is bound in recalcitrant forms that are not readily available to plants. Therefore, forest growth strongly relies on rapidly cycling nitrogen and new nitrogen inputs. The last arises from biological nitrogen fixation by microorganisms, especially cyanobacteria, involved in symbiotic and mutualistic associations with mosses and lichens or living freely in soil. In the next decades, the boreal forest will undergo unprecedented perturbations (e.g. increased temperature, humidity) due to global climate change. Recent studies reported that nitrogen availability to plants will likely play a critical role in the response of the boreal forest to global climate change. ******Understanding processes controlling biological nitrogen fixation in boreal forest is thus essential to the management of boreal natural resources in a sustainable manner. Biological nitrogen fixation relies on the activity of the enzyme nitrogenase which reduces atmospheric dinitrogen into bioavailable ammonium. While three isoforms of the enzyme nitrogenase have been identified, biological nitrogen fixation is assumed to depend primarily on the molybdenum isoform. Recent research, conducted by my laboratory and colleagues, have highlighted that the two other isoforms, using vanadium and iron, play a more significant role on biological nitrogen fixation than previously accepted. These findings significantly alter the traditional views that molybdenum is the predominant metal sustaining biological nitrogen fixation and invite us to integrate nitrogenase diversity in our conceptual models linking metal dynamics and biological nitrogen fixation. ******This research program will address critical questions regarding biological nitrogen fixation in boreal ecosystems. It will significantly improve our conceptual models linking micronutrient dynamics and biological nitrogen fixation by providing new insights into the contribution of alternative nitrogenases to biological nitrogen fixation in boreal forests as well as their potential role in the response of boreal forests to global climate change. The determination of the real importance of nitrogenase diversity in the environment is potentially transformative as it deeply affects the way we comprehend and estimate biological nitrogen fixation in the field. This research will ultimately help boreal forest end-users (e.g. forestry) and decision makers to improve Canadian natural resources management policies and practices.**

北方森林是世界上最大的未受破坏的陆地生态系统之一，支撑着加拿大的重要经济部门（即林业、旅游业）。因此，了解北方生态系统的功能具有首要的生态和经济重要性。在北方森林中，氮是最常被报道为限制初级生产力的养分。虽然北方森林土壤通常富含总氮，但这些氮以难以被植物利用的顽固形式结合。因此，森林生长强烈依赖快速循环的氮和新的氮输入。最后一个来自微生物的生物固氮，特别是蓝藻，与苔藓和地衣共生互利，或在土壤中自由生活。未来几十年，由于全球气候变化，北方森林将经历前所未有的扰动（例如温度、湿度升高）。最近的研究报告称，植物的氮利用率可能在北方森林应对全球气候变化中发挥关键作用。 ******了解控制北方森林生物固氮的过程对于以可持续方式管理北方自然资源至关重要。生物固氮依赖于固氮酶的活性，该酶将大气中的二氮还原成生物可利用的铵。虽然已经鉴定出固氮酶的三种异构体，但生物固氮被认为主要取决于钼异构体。我的实验室和同事最近进行的研究强调，使用钒和铁的另外两种异构体在生物固氮方面发挥的作用比以前所接受的更为重要。这些发现显着改变了传统观点，即钼是维持生物固氮的主要金属，并邀请我们将固氮酶多样性整合到连接金属动力学和生物固氮的概念模型中。 ******该研究计划将解决有关北方生态系统生物固氮的关键问题。它将通过提供新的见解来了解替代固氮酶对北方森林生物固氮的贡献以及它们在北方森林应对全球气候变化中的潜在作用，从而显着改进我们连接微量营养素动态和生物固氮的概念模型。确定环境中固氮酶多样性的真正重要性具有潜在的变革性，因为它深刻影响着我们理解和估计现场生物固氮的方式。这项研究最终将帮助北方森林最终用户（例如林业）和决策者改进加拿大自然资源管理政策和实践。**