Medicago Truncatula as the Nodal Species for Comparative and Functional Legume Genomics

豆科植物是世界上最重要的植物类群之一，是人类饮食中蛋白质、动物饲料和饲料作物、油料作物和生物圈中有效氮的重要来源。此外，几种豆类作物是最具特征的植物遗传系统之一，具有许多经典遗传标记，发达的DNA标记图谱和基因组分析的基本工具。然而，尽管私人和公共资源投入了大量资源，但大而复杂的基因组等特征以及引入外源基因的困难严重限制了豆类作物分子分析的步伐。为了响应豆科植物对简单遗传系统的需求，研究者选择了苜蓿（Medicago truncatula）作为豆科植物生物学的模式物种。与主要的豆类作物不同，苜蓿适合进行高效的分子和遗传分析，非常适合研究相关作物豆类物种的重要生物学问题。该项目将对苜蓿的总DNA进行大规模分析，称为“基因组”。特别是，基因的组织图谱（比较基因组学），以及它们在植物生物学中的功能图谱（功能基因组学），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短截紫花苜蓿与豆科作物之间以及短截紫花苜蓿与模式植物拟南芥之间保守的基因组结构。模式植物和相关作物物种之间基因组结构的保守性具有重要意义，因为它有望加快农学上重要基因和性状的克隆和鉴定步伐。本项目下开展的研究活动将包括以下方法：(1)比较基因组学，这将涉及比较苜蓿（豆科植物、豌豆、苜蓿和大豆）与模式植物拟南芥（Arabidopsis thaliana）的基因组织；(2)功能基因组学，构建和表征表达基因序列文库，开展大规模的基因表达分析，研究基因功能；(3)生物信息学，开发鸢尾花基因组信息分析和传播的数据库和数据库资源。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能够比较苜蓿和相关作物豆科植物的农艺和科学兴趣基因。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, as an important source of protein in the human diet, of fodder and forage crops for animals, of oil crops, and for available nitrogen in the biosphere. Moreover, several crop legumes are among the best characterized plant genetic systems, with numerous classical genetic markers, well developed DNA marker maps, and basic tools for genome analysis. Nevertheless, despite the investment of considerable resources from private and public sources, features such as large and complex genomes, and difficulties with introduction of foreign genes have severely limited the pace of molecular analysis in crop legumes. In response to the need for a simple genetic system in legumes, investigators selected Medicago truncatula as a model species for legume biology. Unlike the major crop legumes, Medicago truncatula is amenable to efficient molecular and genetic analyses and it is well suited for study of biological issues important to the related crop legume species. This project will undertake the large scale analysis of Medicago truncatula's total DNA, called its "genome". In particular, a map of the organization of genes (comparative genomics), and of their functions in plant biology (functional genomics), are the emphases of this project. Recent results from this research team document the first indications of conserved genome structure between Medicago truncatula and crop legumes and between Medicago truncatula and the well-characterized model plant Arabidopsis thaliana. Conserved genome structure between model plants and related crop species is significant because it is expected to accelerate the pace of cloning and characterization of agronomically important genes and traits.Research activities conducted under this program will encompass the following approaches: (1) comparative genomics, which will involve comparing the organization of genes between Medicago truncatula the crop legumes pea, alfalfa, and soybean, and the well-characterized model plant Arabidopsis thaliana; (2) functional genomics, which will involve constructing and characterizing a library of expressed gene sequences, and conducting large scale gene expression analysis to study gene function, and (3) bioinformatics, which will involve developing a database and database resources for analysis and dissemination of Medicago truncatula genome information.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 truncatula 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 thaliana. Likewise, completion of the project will benefit not only research on legumes, but the broader scientific community as well.