Plasmid biology of Rhizobium leguminosarum

豆科根瘤菌的质粒生物学

• 批准号: RGPIN-2015-03926
• 负责人: Hynes, Michael
• 金额: $ 3.28万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=612662
• 关键词: Plasmid; biology; Rhizobium; leguminosarum

Rhizobia are bacteria that are notable for their ability to form nitrogen-fixing nodules on the roots of legume plants, such as peas, beans, lentils and alfalfa. Their ability to allow these plants to grow without addition of synthetic nitrogen-containing fertilizers, whose production and application has a high cost in fossil fuel consumption, makes them extremely important in sustainable agriculture. Production of more efficient and more competitive rhizobial strains for use as legume inoculants is a major goal in biotechnology. However, the interactions of introduced rhizobial strains, and the potential for genetic transfer between strains in the environment, are not well understood. Rhizobia are unusual among bacteria in that they have large and complex genomes that usually consist of one chromosome and several very large extrachromosomal genetic elements known as plasmids. The plasmids tend to be very stable, and some of them exhibit properties intermediate between those expected of a plasmid and those of a chromosome. This proposal will focus on the plasmids of Rhizobium leguminosarum biovar viciae strains VF39 and 3841, both of which have six plasmids and can form nodules on peas, lentils, faba beans, vetches, and various Lathyrus species. The emphasis will be on the genes that determine the mechanisms and consequences of transfer by conjugation between bacterial strains, and on the role of plasmid-encoded genes in carbon catabolism and rhizosphere competition. The research builds on previous expertise in the lab studying large plasmids, and the availability of genome sequences for both strains. The two main themes will be 1) detailed analysis of the novel plasmid transfer and type IV secretion systems encoded on plasmids pRleVF39b, pRleVF39a and pRL7JI and 2) analysis of the two distinct, alternate, plasmid-encoded systems for ribitol transport and catabolism that are present in the genomes of both strains. Theme 1 will identify all genes required for transfer of the plasmids, and identify the pathways regulating plasmid transfer. Theme 2 will study the role of ribitol catabolism in rhizosphere colonization and nodule infection, and will determine the contributions each of the two degradation pathways makes in ribitol metabolism. The possible reasons for the existence of two parallel pathways will be investigated.This research should provide important information about diversity, survival and competition, and horizontal gene transfer in an agriculturally important bacterium. This information could be very valuable for the design and application of superior legume inoculant strains for use in sustainable crop production.

根瘤菌是以其在豆科植物如豌豆、菜豆、扁豆和苜蓿的根部形成固氮根瘤的能力而闻名的细菌。它们允许这些植物在不添加合成含氮肥料的情况下生长的能力，其生产和应用在化石燃料消耗中具有高成本，使得它们在可持续农业中极其重要。生产更有效和更有竞争力的根瘤菌菌株用作豆类接种剂是生物技术的主要目标。然而，引入的根瘤菌菌株的相互作用，并在环境中的菌株之间的遗传转移的潜力，没有得到很好的理解。根瘤菌在细菌中是不寻常的，因为它们具有大而复杂的基因组，通常由一条染色体和几个非常大的染色体外遗传元件（称为质粒）组成。质粒往往非常稳定，其中一些质粒的性质介于质粒和染色体之间。该提案将集中于根瘤菌蚕豆生物变种菌株VF 39和3841的质粒，这两种菌株都具有六种质粒，并且可以在豌豆、扁豆、蚕豆、野豌豆和各种山豌豆属物种上形成根瘤。重点将是决定细菌菌株之间的接合转移的机制和后果的基因，以及质粒编码的基因在碳催化剂和根际竞争中的作用。这项研究建立在实验室先前研究大质粒的专业知识以及两种菌株基因组序列的可用性基础上。两个主要主题将是1）详细分析质粒pRleVF 39 b、pRleVF 39 a和pRL7 JI上编码的新型质粒转移和IV型分泌系统，以及2）分析两种菌株基因组中存在的核糖醇转运和催化剂的两种不同的、交替的质粒编码系统。主题1将确定质粒转移所需的所有基因，并确定调节质粒转移的途径。主题2将研究核糖醇催化剂在根际定殖和根瘤感染中的作用，并确定两种降解途径在核糖醇代谢中的贡献。这一研究将为农业上重要的细菌的多样性、生存和竞争以及水平基因转移提供重要信息。这些信息对于设计和应用用于可持续作物生产的上级豆类接种菌株非常有价值。