GENETICS OF USTILAGO HORDEI

大麦黑粉菌（Ustilago hordei）是引起大麦黑穗病的一种担子菌。 无性生长以非致病性、单倍体、出芽的形式发生 酵母样孢子虫 孢子的融合，由一个单一的 具有两个等位基因的交配型基因座，导致致病性菌丝体 双核体 我们已经证明了交配涉及到细胞之间的交流 相反的交配类型，导致接合的形成 管. 一个非常令人兴奋的发现是小分子量化合物， 或信息素，作为信号。 我们已经分离出许多变种人， 这两种交配类型都不能交配。 其中一些变种人 不能产生活跃的信息素，而其他人则不能产生 接合管 这项研究工作的长期目标是 生物化学表征纯化的信息素和克隆相关基因 在这种信息素介导的细胞间相互作用中， 了解非转换中涉及的基本机制， 病原体对病原体 参与该项目的MBRS学生将 继续在以前的赠款下开始的工作。 形成稳定 联合通过营养缺陷型突变体的互补获得大麦二倍体， 演示。 这为利用准性遗传学 分析宿主和病原体的相互作用 以前的遗传分析 表明这种相互作用是由基因对基因的关系控制的。 MBRS的学生在这个项目中工作将分离出U. 显示红色表型大麦。 由于这种突变是 隐性，二倍体透明。 然而，再单倍体化将 在二倍体细胞的集落中产生红色扇区。 这些红色的单倍体 分离并分析以确定营养缺陷型标记的分离， 交配型和毒力基因。 这将是迈向 克隆与该病原真菌毒力直接相关的基因 和它的真核宿主。

Ustilago hordei is a basidiomycetes which causes covered smut of barley. Asexual growth occurs in the form of non-pathogenic, haploid, budding yeast-like sporidia. Fusion of sporidia, which is controlled by a single mating-type locus with two alleles, results in a pathogenic, mycelial dikaryon. We have shown that mating involves communication between cells of the opposite mating type, resulting in the formation of conjugation tubes. A very exciting finding is that small molecular weight compounds, or pheromones, act as signals. We have isolated numerous mutants from both mating types which are incapable of mating. Some of these mutants are unable to produce active pheromone and others are incapable of making conjugation tubes. The long range goal of this research effort is to biochemically characterize purified pheromones and clone genes involved in this pheromone mediated cell-cell interaction in order to better understand the basic mechanisms involved in the conversion of a non- pathogen to a pathogen. The MBRS student involved in this project will continue work started under the previous grant. The formation of stable U. hordei diploids by complementation of auxotrophic mutants was demonstrated. This opens the door to using parasexual genetics to analyze this host-pathogen interaction. Previous genetic analyses have shown this interaction to be governed by a gene-for-gene relationship. The MBRS student working on this project will isolate ade mutants of U. hordei which display a red color phenotype. Since this mutation is recessive, diploids will be hyaline. However, rehaploidization will yield red sectors in colonies of diploid cells. These red haploids will be isolated and analyzed to determine segregation of auxotrophic markers, mating-type and a virulence genes. This will be the first step toward cloning genes directly involved in virulence of this pathogenic fungus and its eukaryotic host.