PARASEXUALITY IN ASEXUAL PATHOGENIC FUNGI

无性致病真菌中的准性行为

• 批准号: 6217816
• 负责人: DAVID N KUHN
• 金额: $ 11.4万
• 依托单位: FLORIDA INTERNATIONAL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-01-01 至 1999-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6217816
• 关键词: DNA; Fusarium; cell nucleus; complementary DNA; cytoplasm; fungal genetics; genetic recombination; genetic transcription; heterokaryon; microorganism conjugation; microorganism culture; microorganism sexual dimorphism; mitochondrial DNA; molecular cloning; nucleic acid sequence; plant growth /development; polymerase chain reaction; restriction fragment length polymorphism; single strand conformation polymorphism

Parasexuality in fungi is believed by many to be a rare and insignificant process. On the contrary, we have observed that the process occurs regularly and may account for significant genetic exchange on asexual fungi. Asexual pathogens may use parasexuality to generate genetic diversity without disrupting favorable allele combinations. This would have important implications in agriculture and medicine since it may facilitate the transfer of genes for resistance to multiple fungicides or drugs. The importance of reevaluating the role and mechanism of parasexuality in asexual pathogens increases as the number of immunocompromised humans experiencing serious fungal infections increases. In addition to transferring drug resistance, parasexuality may transfer host range genes between pathogens thereby altering host range specificity. If horizontal transfer is possible between unrelated fungi, nonpathogenic fungi normally present in the host could acquire genes conferring pathogenicity. Using Fusarium oxysporum f. sp. cubense (Foc), a haploid imperfect fungus associated with the Ascomycota, as our model system we have isolated 106 auxotrophic and drug resistant mutants. By inducing heterokaryon formation between these mutants, we have observed all the stages of the parasexual cycle in Foc. We have created a new and efficient method for form heterokaryons (double pick) which led to our discovery of mutants which can overcome incompatibility barriers to form heterokaryons with strains outside their own vegetative compatibility groups (VCG) and forma species. We have also developed benomyl resistant double auxotroph strains to induce heterokaryon formation with wild type strains (wild type testers). Some of these strains are also capable of overcoming incompatibility barriers. Such results have encouraged us to reevaluate when transfer of nuclear and cytoplasmic genetic information can occur in the parasexual cycle. In addition to our nuclear encoded auxotrophs, we have identified mitochondrial genome types (mitotypes) by amplification of mitochondrial intergenic regions and analysis of restriction fragment length polymorphisms (RFLP) and single strand conformational polymorphisms (SSCP). We propose to use these advances to assess horizontal transfer of nuclear and cytoplasmic genetic information in heterokaryons, to find mutants showing altered heterokaryon formation, and to assess the wild type testers both as a taxonomic tool and as a means to study in planta formation of heterokaryons.

许多人认为真菌中的寄生虫是一种罕见而微不足道的 过程。 相反，我们观察到该过程发生 定期，可能会说明无性遗传交换 真菌。 无性病原体可能会使用寄生虫来产生遗传 多样性而不会破坏有利的等位基因组合。 这会 在农业和医学上具有重要意义，因为它可能 促进基因转移以抗多种杀菌剂或 毒品。 重新评估角色和机制的重要性 无性病原体中的阵营性随着数量的增加而增加 经历严重真菌感染的免疫功能低下的人会增加。 除了转移耐药性外，阵营性还可以转移 病原体之间的宿主范围基因，从而改变宿主范围 特异性。 如果在无关的真菌之间进行水平转移， 通常存在于宿主中的非致病真菌可以获取基因 赋予致病性。 使用镰刀菌f。 sp。 cubense（foc），单倍体不完美的真菌 与Ascomycota相关，作为我们的模型系统，我们已经隔离了106 营养营养和耐药突变体。 通过诱导异性恋 这些突变体之间的形成，我们观察到了 焦点中的寄生虫周期。 我们为 形成异性恋（双重选择），这导致了我们发现突变体 可以克服与形成异性虫的不兼容障碍 他们自己的营养兼容组（VCG）和FORMA之外的菌株 物种。 我们还开发了抗苯胺抗性双增强剂 用野生型菌株（野生型 测试人员）。 这些菌株中的一些也能够克服 不兼容的障碍。 这样的结果鼓励我们重新评估 当核和细胞质遗传信息的转移可能发生在 阵营周期。 除了我们的核编码性相互营养外，我们还 通过放大的线粒体基因组类型（Mitotypes）已经鉴定 线粒体间区域和限制片段的分析 长度多态性（RFLP）和单链构象多态性 （SSCP）。 我们建议利用这些进步来评估核的水平转移 和杂质者中的细胞质遗传信息，以找到突变体 显示异质构成的改变，并评估野生类型 测试人员既是分类工具，又是在planta中学习的手段 异性虫的形成。