Roles of Lateral Gene Transfer and Gene Recruitment in the Convergent Evolution of Pathogens of a Common Host

横向基因转移和基因招募在共同宿主病原体趋同进化中的作用

• 批准号: 0641808
• 负责人: Hans. VanEtten
• 金额: $ 48万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-06-01 至 2012-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0641808&HistoricalAwards=false
• 关键词: Roles; Lateral; Gene; Transfer; Recruitment

The contribution of horizontal gene transfer (HGT) to the evolution of prokaryotic genomes has been substantial. However, the existence of this phenomenon and its relative role in shaping eukaryotic genomes is controversial. This research aims to elucidate how fungi become pathogens of plants. The specific fungus and disease that serve as the primary model are Nectria haematococca and the disease it causes on pea (Pisum sativum). Past research has established that pathogenic isolates of this fungus have a specific enzyme, a cytochrome P450, that demethylates and thus detoxifies the antimicrobial chemical pisatin produced by the pea. The gene (PDA) encoding pisatin demethylase (pda) has been shown to serve as a virulence factor in N. haematococca. Research funded by NSF has lead to the discovery that PDA is clustered with three other genes that also function independently as virulence traits on pea. This cluster of pea pathogenicity genes (the PEP cluster) is on a "conditionally dispensable" chromosome in N. haematococca. Recent results have shown that a complete PEP cluster is found only in pea-pathogenic isolates of this fungus and that the PEP genes are distinguished from the genes located in the other regions of the genome by their G+C content and codon usage. Although the PEP cluster is present in two other related pea pathogens (Neocosmospora and Fusarium oxysporum), it is not present in Nectria species that are more closely related to N. haematococca. The dispensability, uneven distribution within a species, difference in codon usage and a discontinuous phylogenetic distribution are traits that have been associated with HGT in prokaryotic organisms. Biochemical studies indicate that other more distantly related pea pathogens lack PDA homologs but have paralogous cytochrome P450s with pda activity. These pea pathogens may have convergently evolved their pisatin-detoxifying ability by gene recruitment. The distribution of this enzymatic capacity is also restricted to the pea pathogens and not found in intervening lineages. Thus, two parallel systems are available to assess the role of gene recruitment and the relative roles of HGT versus vertical gene evolution in the evolution of pathogenicity in these eukaryotes. The role of gene recruitment will be evaluated by determining the evolutionary history of the PDA P450 genes that have evolved to detoxify pisatin. This research addresses basic questions on the evolution of eukaryotic genomes. In addition, the identification of pathogenicity traits and knowledge about how fungi acquire them will directly affect the current methods for the control of pathogenic fungi and aid in the design of new strategies to prevent plant diseases. The research will also allow undergraduates from the University of Arizona and from the Dept. of Plant Science's Winter Internship Program to continue to participate in research. This internship program involves ten liberal arts colleges and funds from this grant will expand the collaboration between the University of Arizona and one of these colleges, Luther College, thus providing undergraduates at Luther College with hands-on research experience along with training in contemporary technologies, all at their home institution.

水平基因转移（HGT）对原核生物基因组进化的贡献是巨大的。 然而，这种现象的存在及其在真核生物基因组形成中的相对作用是有争议的。 本研究旨在阐明真菌如何成为植物病原体。 作为主要模型的特定真菌和疾病是赤壳菌及其在豌豆（豌豆）上引起的疾病。 过去的研究已经确定，这种真菌的致病性分离物具有一种特异性酶，细胞色素P450，可以使豌豆产生的抗菌化学品pisatin去甲基化，从而解毒。 已证明编码pisatin去甲基化酶（pda）的基因（pda）是N.红球菌属 由NSF资助的研究发现，PDA与其他三个基因聚集在一起，这些基因也作为豌豆的毒力性状独立发挥作用。 豌豆致病基因簇（PEP簇）位于N.红球菌属 最近的研究结果表明，一个完整的PEP集群被发现，只有在豌豆致病性分离物的这种真菌和PEP基因是区别于基因组的其他区域的基因，其G+C含量和密码子使用。 尽管PEP簇存在于另外两种相关的豌豆病原体（新宇宙孢菌和尖孢镰刀菌）中，但它不存在于与N.红球菌属 原核生物中HGT的可免除性、种内分布不均匀性、密码子使用的差异性和系统发育分布的不连续性是与HGT相关的特征。 生化研究表明，其他更远的相关豌豆病原体缺乏PDA同源物，但有旁系同源细胞色素P450与PDA活动。 这些豌豆病原体可能已经收敛进化的pisatin解毒能力的基因招募。这种酶的能力的分布也仅限于豌豆病原体，并没有发现在干预谱系。 因此，两个平行的系统可用于评估基因招募的作用和相对的作用，HGT与垂直基因进化的致病性在这些真核生物的进化。 基因募集的作用将通过确定PDA P450基因的进化历史来评估，该基因已经进化到使鱼红解毒。这项研究解决了真核生物基因组进化的基本问题。 此外，致病性性状的鉴定和真菌如何获得它们的知识将直接影响目前控制病原真菌的方法，并有助于设计预防植物病害的新策略。 这项研究也将允许亚利桑那大学和系里的本科生。植物科学的冬季实习计划继续参与研究。这项实习计划涉及十所文理学院，这笔赠款的资金将扩大亚利桑那大学与其中一所学院路德学院之间的合作，从而为路德学院的本科生提供实践研究经验沿着当代技术培训，所有这些都在他们的家乡机构。