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Systematics and molecular pathogenesis of oomycetes with emphasis on flagellar genes.

机译：卵菌的系统学和分子发病机制，重点是鞭毛基因。

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摘要

Oomycetes are ubiquitous fungus-like protists which include serious pathogens of agricultural, horticultural, and aquatic commodities. Proper identification to the species level is a critical first step in any investigation of oomycetes, and the use of DNA for oomycete species identification is well established, but DNA barcoding with cytochrome c oxidase (COI) is a relatively new and potentially useful approach that had yet to be assessed over a significant sample of oomycete genera. DNA sequencing of COI from 1205 isolates representing 23 genera and a comparison to internal transcribed spacer (ITS) sequences from the same isolates showed that COI-based identification and the dataset generated are a valuable addition to the currently available oomycete taxonomy resources. Due to the fact that studies of oomycete evolution and taxonomy have traditionally been heavily reliant on ribosomal RNA and mitochondrial cytochrome oxidase sequencing to infer species boundaries and higher level phylogenetic relationships, a new approach to oomycete molecular systematics was undertaken using two single-copy protein-coding flagellar genes, PF16 and OCM1, showing their utility in species delimitation and in phylogenetic reconstruction of oomycete evolution. This approach also demonstrates a recently proposed codon substitution-based phylogenetic method. Using the codon model, the phylogenetic relationships inferred by flagellar genes are largely in agreement with the current views of oomycete evolution, whereas nucleotide and amino acid models failed to reconstruct monophyly in several clades. Interesting parallels exist between the molecular evolution of flagellar genes and zoospore ontology, supporting the tree obtained using the codon model. Sequencing of OCM1 in particular revealed high variability among oomycetes and indicated a potential role of this protein in host-interaction of zoospores. A hypothesized role of OCM1 in host recognition, possibly through interaction with host C-type lectin was tested, and although the role of OCM1 was not confirmed, plant C-type lectin was shown to contribute to susceptibility of Arabidopsis seedlings to Pythium zoospores. This is a novel and important finding which helps to understand the unknown function of C-type lectin in plants. As a whole, this thesis contributes new resources and knowledge to the study of oomycetes, molecular evolution, and plant pathology.
机译：卵菌是无处不在的真菌样生物，其包括农业，园艺和水生商品的严重病原体。在卵菌种的任何研究中，正确鉴定物种水平是关键的第一步，DNA在卵菌种鉴定中的应用已得到公认，但是使用细胞色素C氧化酶（COI）进行DNA条形码编码是一种相对较新且可能有用的方法，尚未对卵菌属的大量样本进行评估。来自代表23个属的1205个分离株的COI的DNA测序以及与来自同一分离株的内部转录间隔区（ITS）序列的比较表明，基于COI的鉴定和生成的数据集是当前可用的卵菌类分类资源的宝贵补充。由于卵母细胞进化和分类学的研究传统上高度依赖核糖体RNA和线粒体细胞色素氧化酶测序来推断物种边界和更高水平的系统发生关系，因此，我们采用了两种单拷贝蛋白-编码鞭毛基因PF16和OCM1，显示它们在物种定界和卵菌进化的系统发育重建中的效用。该方法还证明了最近提出的基于密码子取代的系统发生方法。使用密码子模型，鞭毛基因推断的系统发育关系与卵菌进化的当前观点基本吻合，而核苷酸和氨基酸模型未能在多个进化枝中重建单亲。鞭毛基因的分子进化与游动孢子本体之间存在有趣的相似之处，这支持使用密码子模型获得的树。特别是OCM1的测序显示卵母细胞之间存在很高的变异性，并表明该蛋白在游动孢子宿主相互作用中的潜在作用。测试了OCM1在宿主识别中的假设作用，可能是通过与宿主C型凝集素相互作用而进行的，尽管未确认OCM1的作用，但植物C型凝集素已显示出对拟南芥幼苗对腐霉菌游动孢子的敏感性。这是一个新颖而重要的发现，有助于理解C型凝集素在植物中的未知功能。总体而言，本论文为卵菌，分子进化和植物病理学的研究提供了新的资源和知识。

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  • 作者

    Robideau, Gregg P.;

  • 作者单位

    Carleton University (Canada).;

  • 授予单位 Carleton University (Canada).;
  • 学科 Biology Molecular.;Agriculture Plant Pathology.;Biology Microbiology.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 139 p.
  • 总页数 139
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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