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Regulation of N2O emissions from agricultural soil on the transcriptional level

农业土壤 N2O 排放在转录水平上的调控

基本信息

批准号：
229528027
负责人：
Dr. Maren Emmerich
金额：
--
依托单位：
Department of Microbiology
依托单位国家：
德国
项目类别：
Research Fellowships
财政年份：
2012
资助国家：
德国
起止时间：
2011-12-31 至 2013-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/229528027?language=en
关键词：
Regulation N2O emissions agricultural soil

项目摘要

Nitrous oxide (N2O) is an important greenhouse gas and the single most potent ozone-depleting substance of the 21st century. About 62 % of total global N2O emissions stem from soils, a great fraction of which is released as an intermediate of bacterial denitrification, the stepwise reduction of nitrate (NO3-) to di-nitrogen gas (N2). Besides the composition of the denitrifying community, the activities of the gene products that mediate the four steps of denitrification largely determine the efficiency and gaseous end product composition (N2O versus N2) of this process. Previous studies have focused on the role of community composition on denitrification activity in the field or identified detached factors such as pH and O2 partial pressure that have an influence on the expression of the different denitrification genes using laboratory experiments with isolated strains. However, studies elucidating the connection between environmental conditions and expression of denitrification genes in field samples are scarce, even though this kind of studies would provide us with the data we need in order to predict which ways of soil management will lead to an increase or decrease of N2O emissions from denitrification. Consequently, this project aims to identify correlations between different fertilization regimes, denitrification rates and expression of denitrification genes using a more than 50 year-old fertilization experiment as a field site. From this field site, samples from soils which have received two different mineral (ammonium sulfate and calcium nitrate) and two different organic (sewage sludge and cattle manure) fertilizers will be compared to samples from unfertilized soil. Gene and mRNA transcript numbers of two different nitrite (NO2-) reductase genes whose products are involved in N2O production will be quantified in these samples and compared to potential denitrification rates. The same will be done for the N2O reductase gene, the product of which is the only known mediator of N2O consumption. Given the unique role of the N2O reductase, the diversity among the gene and transcript sequences encoding this enzyme within the individual samples will be subject to further analysis, since the differences among the expressed variants of this gene are very likely to play a key role in the regulation of N2O degradation. Once fertilization regimes that lead to an increase or decrease of the expression of the denitrification genes have been identified, the speed with which this effect comes into play will be determined using microcosm experiments. These will further be used in order to elucidate which primary factors increase or decrease the transcription rate of NO2-- and N2O reductase genes. Thus, by sheding light on the regulation of the production and consumption of N2O under different environmental conditions on the genetic level, our study will help to predict more reliably how N2O emissions can be reduced by fertilizing arable soil accordingly.

一氧化二氮（N2 O）是一种重要的温室气体，也是21世纪世纪最强的臭氧消耗物质。全球N2 O排放总量的62%来自土壤，其中很大一部分作为细菌反硝化作用的中间产物释放，硝酸盐（NO3-）逐步还原为二氮气体（N2）。除了反硝化群落的组成，介导反硝化四个步骤的基因产物的活性在很大程度上决定了该过程的效率和气态终产物组成（N2 O与N2）。以前的研究集中在反硝化活性的社区组成的作用，在现场或确定分离的因素，如pH值和O2分压，有不同的反硝化基因的表达，使用实验室实验与分离菌株的影响。然而，研究阐明环境条件和反硝化基因在田间样品中的表达之间的联系是稀缺的，即使这种研究将为我们提供我们需要的数据，以预测哪些方式的土壤管理将导致增加或减少的N2 O排放反硝化。因此，本项目的目的是确定不同施肥制度，反硝化速率和反硝化基因的表达之间的相关性使用超过50年的施肥实验作为现场。在该现场，将接受两种不同矿物质（硫酸铵和硝酸钙）和两种不同有机肥料（污水污泥和牛粪）的土壤样品与未施肥土壤样品进行比较。两种不同的亚硝酸盐（NO2-）还原酶基因的基因和mRNA转录本数量，其产品参与N2 O生产将在这些样品中进行定量，并与潜在的反硝化速率进行比较。N2 O还原酶基因也是如此，其产物是唯一已知的N2 O消耗介质。考虑到N2 O还原酶的独特作用，将对单个样品中编码该酶的基因和转录物序列之间的多样性进行进一步分析，因为该基因的表达变体之间的差异很可能在N2 O降解的调节中发挥关键作用。一旦确定了导致反硝化基因表达增加或减少的施肥制度，将使用微观实验来确定这种效果发挥作用的速度。这些将进一步用于阐明哪些主要因素增加或减少NO2-和N2 O还原酶基因的转录速率。因此，通过揭示不同环境条件下N2 O产生和消耗的遗传调控，我们的研究将有助于更可靠地预测如何减少N2 O排放相应的可耕地土壤。