Genome Organization and Transmission Genetics of Arbuscular Mycorrhizal Fungi

本项目的目标是利用遗传学、群体遗传学和细胞学方法揭示丛枝菌根真菌(AM真菌、球孢菌门)的基因组结构(大小和倍性)和繁殖模式。AM真菌在包括许多作物在内的大多数陆地植物的根上定居，在那里它们有助于从土壤中吸收矿物质。因此，它们是陆地生态系统的关键组成部分。然而，AM真菌仍然是基因上了解最少的微生物之一。AM真菌没有有性形态，被假设为克隆繁殖，但有理论和经验上的理由来怀疑这一假设。为了选择挑战克隆假说所需的工具，将对基因组组织进行彻底的分析。接下来，将分析AM真菌田间种群的遗传变异模式，以检测重组或克隆的特征。这项工作将得到一项细胞学研究的补充，该研究追踪AM真菌生命周期中细胞核的命运，为此将构建表达GFP标记组蛋白的基因转化菌株，以使活细胞中的细胞核可视化。了解AM真菌的基因组结构对于未来AM真菌基因组的测序是至关重要的。繁殖方式是发展AM真菌传递遗传学所需的最重要信息，本研究建立的遗传转化系统将为AM真菌遗传转化提供很大的帮助。这项工作的另一个产品，遗传标记，将加强AM真菌基于表型的分类。所有这些工具将使系统评估AM真菌在自然界和农业系统中的作用，并促进AM真菌的育种(如果繁殖是有性繁殖)或选择(如果繁殖是克隆)，用于改善植物矿质营养、防治虫害、保护免受干旱、盐碱或有毒金属胁迫的特定目的。如果被证实是克隆的，它可能代表一个古老的无性世系，它们可能提供一个系统来研究在没有减数分裂重组的情况下长期进化生存的机制。

The goal of this project is to uncover genome organization (size and ploidy) and the reproductive mode of arbuscular mycorrhizal fungi (AM fungi, Glomeromycota) using genetic, population genetic and cytological approaches. AM fungi colonize roots of most land plants, including many crop species, where they facilitate uptake of minerals from the soil. Consequently, they are a key component of terrestrial ecosystems. Yet, AM fungi remain one of the least genetically understood microorganisms. With no sexual morphology, AM fungi are hypothesized to reproduce clonally, but there are theoretical and empirical reasons to doubt this hypothesis. To select tools needed to challenge the hypothesis of clonality, a thorough analysis of genome organization will be performed. Next, patterns of genetic variation in a field population of an AM fungus will be analyzed to detect signatures of recombination or clonality. This work will be supplemented by a cytological study tracing the fate of nuclei during AM fungal life cycle, for which genetically transformed strains expressing GFP-labeled histone will be constructed to enable visualization of nuclei in living cells. Understanding the genome organization of AM fungi is essential for future sequencing of AM fungal genomes. Reproductive mode is a single most important piece of information needed to develop transmission genetics of AM fungi, which will be greatly aided by the genetic transformation system developed in this study. Another product of this work, genetic markers, will augment the phenotype-based taxonomy of AM fungi. All these tools will enable systematic evaluation of the role of AM fungi in nature and agrosystems, and facilitate breeding (if reproduction is sexual) or selection (if reproduction is clonal) of AM fungi for specific purposes of improved plant mineral nutrition, pest control, protection from drought, salinity, or toxic metal stress. Glomeromycota, if proven clonal, may represent an ancient asexual lineage and they may offer a system to study mechanisms of long-term evolutionary survival in the absence of meiotic recombination.