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群之一，是人类饮食中蛋白质的重要来源，也是动物饲料和饲料作物、油料作物以及生物圈有效氮的重要来源。此外，几种豆科作物是最具特色的植物遗传系统之一，拥有众多的经典遗传标记、发展良好的DNA标记图谱和基本的基因组分析工具。然而，尽管来自私人和公共来源的大量资源投入，但大而复杂的基因组和难以引入外源基因等特点严重限制了豆类作物分子分析的步伐。为了应对豆科植物对简单遗传系统的需求，研究人员选择了元宝紫花苜蓿作为豆科生物学的模式物种。与主要的豆科作物不同，紫花苜蓿能够进行有效的分子和遗传分析，非常适合于研究对相关豆科作物物种重要的生物学问题。该项目将对元宝山紫花苜蓿的总DNA进行大规模的分析，这种DNA被称为“基因组”。特别是，基因组织图(比较基因组学)及其在植物生物学中的功能图(功能基因组学)是该项目的重点。该研究小组的最新研究结果首次表明，元胞紫花苜蓿和豆类作物之间以及元胞紫花苜蓿和特征良好的模式植物拟南芥之间存在保守的基因组结构。模式植物和相关作物物种之间保守的基因组结构具有重要意义，因为它有望加快农学上重要基因和基因的克隆和鉴定的步伐。在该计划下开展的研究活动将包括以下方法：(1)比较基因组学，将涉及比较豆类作物紫花苜蓿、豌豆、紫花苜蓿和大豆以及特征良好的模式植物拟南芥之间的基因组织；(2)功能基因组学，它将包括构建和表征一个表达基因序列的文库，并进行大规模的基因表达分析，以研究基因功能；(3)生物信息学，将包括开发一个数据库和数据库资源，用于分析和传播紫花苜蓿基因组信息。这项研究的长期影响将是整合豆科植物的遗传和功能信息，从而扩大对重要经济豆科植物的基础和应用研究的机会。这项研究将使科学家能够比较元宝紫花苜蓿和相关豆类作物中具有农学和科学意义的基因。这些知识将能够更有效地克隆有价值的基因和特征，如抗病和作物生产力，并最终促进改良作物品种的开发。这项研究产生的表达基因数据库将使详细分析特定基因在植物生长发育中的作用成为可能。在这项研究过程中确定的许多基因将成为作物改良战略和豆科生物学家继续科学研究的重点。这项拟议的工作极大地得益于美国国家科学基金会以前对模式植物拟南芥的研究。同样，该项目的完成不仅将使豆类研究受益，也将使更广泛的科学界受益。

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.