PARASEXUALITY IN ASEXUAL PATHOGENIC FUNGI

无性致病真菌中的准性行为

基本信息

批准号：
6448510
负责人：
DAVID N KUHN
金额：
$ 7.38万
依托单位：
FLORIDA INTERNATIONAL UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2001
资助国家：
美国
起止时间：
2001-04-01 至 2002-03-31
项目状态：
已结题

项目摘要

Horizontal Genetic Transfer in Asexual Dimorphic Pathogenic Fungi Our long term goal is to determine if parasexuality or some form of horizontal genetic transfer such as an occasional sexual cycle plays a role in altering pathogenicity or drug resistance in asexual dimorphic pathogenic fungi. Such fungi include the human pathogen. Candida albicans and the plant pathogen Fusarium oxysporum. Dimorphic fungi can reproduce as yeast (single cells) or mycelial (filamentous strands of cells). For pathogenic fungi, the mycelial stage is required for penetration into the host. In the mycelial stage, hyphal anastomosis is also possible which would allow the pathogens to form heterokaryons and enable horizontal genetic transfer without sexual structures (parasexuality). We have been studying heterokaryon formation in Fusarium oxysporum f.sp cubense (Foc) because it shares many of the traits of C. albicans. It is however a more convenient model system that C. albicans because it can be grown in the mycelial stage in vitro while C. albicans requires a mucosal membrane to induce the mycelial stage. In this proposal, we will create auxotrophic drug resistant strains of Fox by transformation with a disrupted gene. These mutants will be paired with wild type strain from our mutant after stable or transient heterokaryon formation. If genes can be transferred from one strain to another under our laboratory conditions, it suggests that drug resistance and pathogenicity genes could be transferred from pathogens to non- pathogens in nature. Asexual fungi may also have the ability to occasionally go through a sexual cycle. We have identified on mating type locus in some of our strains. If we find Fox strains on the other mating type, we will try to resurrect the sexual cycle by making heterokaryons between sexual strains of opposite mating type. We have observed that although two different nuclei can exist in a cell, only one mitochondrial genome occurs when heterokaryons are made by protoplast fusion. We have determined what happens in the average heterokaryon by genetic and molecular assays. Now, we propose to determine what happens in a single heterokaryon by microscopic observation. We will label the nucleus and mitochondrion with organelle specific strains and with the gene fluorescent protein and follow their fate after heterokaryon formation. Because only one mitochondrial genome survives after heterokaryon formation, we have a unique opportunity to create strains with unusual combinations of nucleus and mitochondrion. Comparison of the growth and physiology of these strains to the original parental strains will reflect the importance of the interaction of mitochondrion and nucleus.

在无性二态致病真菌中的水平遗传转移我们的长期目标是确定寄生虫性或某种形式的水平遗传转移（例如偶尔的性循环）在改变无性二态性致病真菌中的致病性或耐药性中起作用。这种真菌包括人类病原体。白色念珠菌和植物病原体氧气。二态真菌可以作为酵母（单细胞）或菌丝体（细胞的丝状链）繁殖。对于致病性真菌，渗透到宿主中是必需的。在菌丝阶段，菌丝吻合也可能使病原体形成异性恋，并在没有性结构的情况下实现水平遗传转移（寄生虫）。我们一直在研究氧气孢子菌F.sp cubense（foc）中的杂核形成，因为它具有白色念珠菌的许多特征。然而，这是一个更方便的模型系统，白色念珠菌可以在体外生长，而白色念珠菌则需要粘膜膜来诱导菌丝体阶段。在此提案中，我们将通过破坏基因转化来创建富裕的FOX抗性药物菌株。这些突变体将在稳定或瞬时异质源形成后与我们突变体的野生型应变配对。如果在我们的实验室条件下可以将基因从一种菌株转移到另一种菌株，则表明可以将耐药性和致病性基因从病原体转移到自然病原体。无性真菌也可能偶尔经历性周期。我们已经在某些菌株中确定了交配类型基因座。如果我们发现另一种交配类型的狐狸菌株，我们将尝试通过在相反的交配类型的性菌株之间制作异质菌株来复活性周期。我们已经观察到，尽管细胞中可以存在两个不同的核，但是当通过原生质体融合制成异质核心时，只有一个线粒体基因组发生。我们已经确定了通过遗传和分子测定法中平均异性恋的情况。现在，我们建议通过微观观察来确定单个异性恋中发生的情况。我们将用细胞器特异性菌株和基因荧光蛋白标记细胞核和线粒体，并在异性核对形成后遵循其命运。由于仅一个线粒体基因组在异性恋形成后生存，因此我们有独特的机会来创建具有核和线粒体异常组合的菌株。这些菌株的生长和生理学与原始亲本菌株的比较将反映出线粒体和核的相互作用的重要性。