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类群之一，因为它们是现代农业系统发展的基础。农艺学上重要的成员包括亚洲的大豆和水稻，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，这种植物家族贡献了人类蛋白质摄入量的33%，同时也是动物饲料和饲料以及食用油和工业油的重要来源。 豆科植物还具有独特的共生固氮特性，是生物圈中可用氮的主要来源之一。 仅在美国，豆类种植面积就超过8000万英亩，在那里它们固定了大约600万公吨的氮，价值估计为45亿美元。为了满足豆科植物对易处理遗传系统的需求，科学家们开发了蒺藜苜蓿作为研究豆科植物重要生物学和农艺学问题的模式物种。 特别重要的是，与主要作物豆类不同，苜蓿可进行有效的分子、遗传和反向遗传分析，该项目涉及对苜蓿基因组的大规模分析。 该项目的重点是基因组织图（比较基因组学）、基因在豆类生物学中的功能图（功能基因组学）以及通过计算工具（生物信息学）分析和公开分发数据。 该研究小组的最新结果首次证明了苜蓿和豆科作物之间以及苜蓿和特征良好的模式植物拟南芥之间保守的基因组结构。 我们已经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。 我们为开发包含超过127，000个序列的公共表达序列标签（EST）资源做出了贡献，并创建了可公开访问的数据库，以便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发现和表征苜蓿和作物豆科物种中具有重要农艺学意义的豆科基因和性状的步伐，本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，以开发苜蓿基因组的完整基因库和功能分析。 这项研究的具体目标包括：（1）创建基因组的综合物理图谱，（2）在（a）植物发育，（B）与微生物相互作用和（c）营养胁迫的条件下测定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豆类的遗传和功能信息，从而扩大对经济上重要的豆类物种进行基础和应用研究的机会。 这项研究将使科学家能够比较苜蓿和相关作物豆类的农艺学和科学兴趣的基因。 这些知识将使人们能够更有效地克隆和鉴定抗病性和作物产量等有价值的基因和性状，并最终促进改良作物品种的开发。 通过这项研究产生的表达基因数据库将能够详细分析特定基因在植物生长和发育中的作用。 在这项研究过程中发现的许多基因将成为作物改良策略和豆类生物学家继续科学研究的重点。 拟议的工作极大地受益于以前的NSF赞助的研究模式植物拟南芥。 同样，该项目的完成不仅有利于豆类研究，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.