Molecular Genetic Investigations of Fungal Pathogenesis in Rice Blast Disease

稻瘟病是由稻瘟病菌引起的一种毁灭性植物病害。对这种真菌病原体的遗传分析表明，感染和破坏水稻植株需要许多遗传位点。由于这种真菌及其栽培寄主植物的遗传和生化易感性，我们认为这种疾病代表了一个独特的机会，通过改变水稻植物感染所需的各种真菌细胞的形状，开始对真菌对水稻的致病性进行详细的遗传和分子分析。我们将这个基因位点命名为SMO，因为SMO突变极大地改变了无性孢子的形状（孢子形态）。在这篇文章中，我们描述了我们克隆和分析SMO基因座功能的方法。我们将通过将SMO突变体与克隆的稻瘟病菌DNA互补来克隆SMO位点。我们将通过遗传分析证明，SMO表现型的DNA片段编码SMO基因。我们将对野生型SMO基因进行测序，并开始分析SMO基因产物的功能。我们还将使用克隆的DNA片段来研究出现频率很高的smo突变的起源。最后，我们将探讨smo突变对稻瘟病菌在水稻植株内生长的影响。本研究结果将为植物病原真菌侵染结构的形成提供新的信息，并为真菌细胞形态的决定机制提供新的见解。

Rice blast is a devastating plant disease caused by the fungus Magnaporthe grisa. Genetic analysis with this fungal pathogen has demonstrated that numerous genetic loci are required for infecting and destroying rice plants. Because of the genetic and biochemical tractability of this fungus and its cultivated host plant, we have decided that this disease represents a unique opportunity to begin a detailed genetic and molecular analysis of fungal pathogenicity on rice by altering the shape of various fungal cells necessary for rice plant infection. We have named this genetic locus, SMO because Smo-mutations dramatically alter the shape of the asexual spores (spore morphology). In this proposal, we described our approach to cloning and analyzing the function of the SMO locus. We shall clone the SMO locus by complementation of Smo-mutants with cloned M.grisea DNA. We will prove by genetic analysis, that DNA fragments that complement the Smo-phenotype encode the SMO gene. We will sequence the wild type SMO gene and begin an analysis of the function of the SMO gene product. We will also use cloned DNA fragments to investigate the origin of Smo-mutations, which appear to occur at a high frequency. Finally we will investigate the consequences of Smo-mutations on M.grisea growth inside rice plants. The results of this research will provide new information on the formation of infection structures in plant pathogenic fungi, as well as provide insights into the mechanisms of cell shape determination in fungi.