Towards the Complete Gene Inventory and Function of the Medicago Truncatula Genome

豆科植物是世界上最重要的植物群之一，因为它们对现代农业系统的发展至关重要。农艺学上的重要成员包括亚洲的大豆和大米，以及美洲的玉米和豆类。豆科植物也是开花植物的第三大家族。在世界范围内，这种植物家族为人类提供了33%的蛋白质摄入量，同时也是动物饲料和饲料以及食用油和工业用油的重要来源。豆科植物还以其独特的共生固氮特性而闻名，是生物圈中有效氮的主要来源之一。仅在美国，豆科植物的种植面积就超过8000万英亩，它们固定了大约600万吨氮，价值约45亿美元。为了满足豆科植物对遗传系统的需求，科学家们开发了一种对豆科植物重要的生物学和农艺学问题进行研究的模式种。特别重要的是，与主要作物豆科植物不同，紫花苜蓿适合进行高效的分子、遗传和反向遗传分析。这个项目涉及对苜蓿基因组的大规模分析。基因的组织图谱（比较基因组学），它们在豆类生物学中的功能图谱（功能基因组学），以及利用计算工具（生物信息学）对数据进行分析和公开分发，是这个项目的重点。该研究小组最近的研究结果首次证明了紫花苜蓿和豆科作物之间，以及紫花苜蓿和模式植物拟南芥之间保守的基因组结构。我们描述了抗性基因类似物的基因组结构，并发现了豆类抗性基因的新谱系。我们参与开发了包含超过127,000个序列的公共表达序列标签（EST）资源，并创建了可公开访问的数据库，将这些信息与其他科学家和公众联系起来。这些信息已经加快了在苜蓿和其他豆科植物中发现和鉴定重要的农学豆类基因和性状的步伐。这项研究的目标是通过促进多机构的国际努力来扩展这些分析，以开发一个完整的基因清单和Medicago基因组的功能分析。本研究的具体目标包括(1)创建基因组的全面物理图谱，(2)分析(a)植物发育，(b)与微生物相互作用，(c)营养胁迫条件下数千个基因的协调表达，以及(3)继续实施和改进可公开访问的数据库活动。这项研究的长期影响将是整合整个豆科植物的遗传和功能信息，从而扩大对具有重要经济意义的豆科植物进行基础和应用研究的机会。这项研究将使科学家们能够比较苜蓿和相关作物豆科植物的农艺和科学基因。这方面的知识将使有价值的基因和性状（如抗病性和作物生产力）的克隆和鉴定更加有效，并最终将促进改良作物品种的发展。通过本研究产生的表达基因数据库，可以详细分析特定基因在植物生长发育中的作用。在这项研究过程中鉴定的许多基因将成为作物改良策略和豆科生物学家继续科学研究的重点。拟议的工作极大地受益于先前由nsf资助的模式植物拟南芥的研究。同样，该项目的完成不仅有利于豆科研究，也有利于更广泛的科学界。

The legume family is one of the most important groups of plants worldwide because they have been fundamental to development of modern agricultural systems. Agronomically important members include soybean and rice in Asia, and maize and beans in the Americas. Legumes are also the third largest family of flowering plants. On a worldwide basis, this plant family contributes 33% of humankind's protein intake, while also serving as an important source of fodder and forage for animals, and of edible and industrial oils. Legumes are also distinguished by their unique property of symbiotic nitrogen fixation, providing one of the major sources of available nitrogen in the biosphere. In the US alone, legumes are grown on over 80 million acres, where they fix approximately 6 million metric tons of nitrogen worth an estimated $4.5 billion. In response to the need for a tractable genetic system in legumes, scientists have developed Medicago truncatula as a model species for study of biological and agronomic issues important to legumes. Of particular significance, Medicago is amenable to efficient molecular, genetic and reverse-genetic analyses, unlike the major crop legumes.This project involves the large-scale analysis of the genome of Medicago. A map of the organization of genes (comparative genomics), of their functions in legume biology (functional genomics), and analysis and public distribution of the data by means of computational tools (bioinformatics), are the emphases of this project. Recent results from this research team document the first indications of conserved genome structure between Medicago and crop legumes, and between Medicago and the well-characterized model plant Arabidopsis thaliana. We have described the genomic architecture of resistance gene analogs and discovered new lineages of legume resistance genes. We have contributed to the development of a public Expressed Sequence Tag (EST) resource containing in excess of 127,000 sequences, and created publicly accessible databases to relate this information to other scientists and to the public. Already this information has accelerated the pace of discovery and characterization of agronomically important legume genes and traits, in both Medicago and crop legume species.The goal of this research is to extend these analyses by contributing to a multi-institutional, international effort to develop a complete gene inventory and functional analysis of the Medicago genome. The specific objectives of this research include (1) creating a comprehensive physical map of the genome, (2) assaying the coordinate expression of thousands of genes under conditions of (a) plant development, (b) interactions with microorganisms, and (c) nutrient stress, and (3) continuing to implement and improve publicly accessible database activities.The long-term impact of this research will be to integrate genetic and functional information across legumes, and thereby expand opportunities for basic and applied research in economically important legume species. This research will allow scientists to compare genes of agronomic and scientific interest in Medicago and the related crop legumes. This knowledge will enable more efficient cloning and characterization of valuable genes and traits, such as disease resistance and crop productivity, and it will ultimately facilitate the development of improved crop varieties. The database of expressed genes generated by this research will enable the detailed analysis of the role of specific genes in plant growth and development. Many of the genes identified in the course of this research will become the focus of crop improvement strategies and of continued scientific investigation by legume biologists. The proposed work benefits enormously from previous NSF-sponsored research on the model plant Arabidopsis. Likewise, completion of the project will benefit not only research on legumes, but the broader scientific community as well.