Mechanisms of Fungal Pathogenesis: Analysis of a Meiotically Unstable, Dispensable Chromosome

真菌发病机制：减数分裂不稳定、可有可无的染色体的分析

• 批准号: 9507263
• 负责人: Sarah Covert
• 金额: $ 10.16万
• 依托单位: University of Georgia Research Foundation Inc
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-08-01 至 1998-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9507263&HistoricalAwards=false
• 关键词: Mechanisms; Fungal; Pathogenesis; Analysis; Meiotically

9507263 Covert Certain isolates of Nectria haematococca, a fungal pathogen of plants, contain a chromosome that is often rearranged, partially deleted or completely lost during meiosis. Changes in the structure of the chromosome can be visualized, and the sizes of the resulting chromosome derivatives measured on pulsed field gels. The pattern of chromosomal alterations suggests that this chromosome contains sites that are particularly susceptible to breakage and reunion. The first goal of this proposal is to determine if this chromosome contains hotspots for meiotic breakage and reunion, and if so, to map the position of these sites on the chromosome. The unstable chromosome in N. haematococca is of further interest because it contains a gene, Makl, believed to be essential for pathogenicity on chickpea. The product of Makl detoxifies an antimicrobial compound produced by chickpea in response to infection. Genetic analysis of Makl indicated that it is either linked to genes for, or is itself responsible for high virulence on chickpea. Makl has been cloned and sequenced. The second goal of this research proposal is to directly test the importance of Makl in pathogenicity by disrupting it and assaying the resulting mutants for their ability to cause disease symptoms on chickpea. If the gene disruption experiment indicates that Makl is not essential for high virulence on chickpea, it will imply that additional genes involved in chickpea pathogenicity are on the same chromosome as Makl. In this case, the third goal of this proposal, mapping novel genes for chickpea pathogenicity on the 1.6 Meg abase Makl chromosome, will be pursued. %%% This research proposal focuses on a fungal pathogen of plants, Nectria haematococca. Two aspects of N. haematococca's biology are particularly interesting: (1) it has an unusual chromosome that is unstable during meiosis as well as dispensable for saprophytic growth, and (2) according to genetic evidence, genes on this chromosome are responsible for high virulenc e of N. haematococca on chickpea (Cicer arietinum). Because the unstable chromosome is present in field populations, it appears to confer a significant adaptive advantage to the isolates that contain it. Its instability may be a mechanism for shedding it in habitats in which it is extraneous. This research into chromosomal instability and plant pathogenicity will contribute to scientific knowledge on a number of fronts. The role of unstable, dispensable chromosomes in fungal-plant interactions will be clarified, the genetic machinery underlying pathogenicity in a model fungus will be characterized further, and perhaps most significantly, scholarship on the general mechanisms of chromosome instability will be advanced. ***

9507263隐蔽的某些赤壳菌（Nectria haematococca）分离株是一种植物真菌病原体，含有一条染色体，在减数分裂过程中经常重排、部分缺失或完全丢失。染色体结构的变化可以被可视化，并且在脉冲场凝胶上测量所得染色体衍生物的大小。染色体改变的模式表明，这条染色体含有特别容易断裂和团聚的位点。这个建议的第一个目标是确定这条染色体是否包含减数分裂断裂和团聚的热点，如果是这样，绘制这些位点在染色体上的位置。N.红球菌是更令人感兴趣的，因为它含有一个基因Makl，据信对鹰嘴豆的致病性是必需的。Makl的产品解毒鹰嘴豆在应对感染时产生的抗菌化合物。Makl的遗传分析表明，它要么与鹰嘴豆的高毒力基因相关，要么本身就是导致鹰嘴豆高毒力的原因。Makl已被克隆和测序。本研究提案的第二个目标是通过破坏Makl并测定所得突变体在鹰嘴豆上引起疾病症状的能力来直接测试Makl在致病性中的重要性。如果基因破坏实验表明Makl对于鹰嘴豆上的高毒力不是必需的，则这将意味着参与鹰嘴豆致病性的另外的基因与Makl在相同的染色体上。在这种情况下，该提案的第三个目标，映射1.6兆碱基Makl染色体上的鹰嘴豆致病性的新基因，将被追求。 这项研究计划的重点是植物的真菌病原体，赤壳菌。N.红球藻的生物学特性特别令人感兴趣：（1）它有一条不寻常的染色体，在减数分裂期间不稳定，并且不适于嗜盐生长;（2）根据遗传学证据，该染色体上的基因负责N.鹰嘴豆上的红球藻（Cicer arietinum）。由于不稳定染色体存在于田间种群中，它似乎赋予了含有它的分离物显著的适应性优势，它的不稳定性可能是它在外来生境中脱落的一种机制。对染色体不稳定性和植物致病性的研究将有助于在许多方面的科学知识。不稳定的，染色体在真菌-植物相互作用中的作用将得到澄清，致病性的遗传机制在一个模型真菌将进一步的特点，也许最重要的是，奖学金染色体不稳定的一般机制将被推进。 ***