Molecular Biology of Host-Specific Toxin Biosynthesis

许多植物病原体产生低分子量的 对植物有毒的化学物质。 一些毒素，叫做 “宿主特异性”，在体外具有与 生产有机体在田野里做的事;也就是说，植物 对病原体有抵抗力的人对病原体的 毒素，对病原体敏感的植物对 毒素 真菌产生的寄主特异性毒素 Cochliobolus（也称为Helminthosporium或 双极孢属）与两次灾难性的流行病有关 在过去的四十年里，美国的谷类作物。 而 在过去的几年里，大多数宿主的化学结构- 已经确定了特定的毒素，它们的模式 在某些情况下，行动得到部分澄清，目前没有任何行动得到澄清。 已知的生物合成的植物毒素，也没有关于 病原体获得能力的分子过程， 就自己创造机会 本项目的目标是识别和分离 参与宿主特异性生物合成的酶 毒素，以提高这些酶的抗体，并分离 编码这些酶的基因。 的抗体和 克隆的基因将成为研究生物学的分子基础的工具。 植物病原菌小种特异性与毒素产生 真菌 初期工作将集中在净化和 最近鉴定的两种酶的特性 参与环肽毒素HC-的生物合成 一种毒素，由玉米的真菌病原体旋孢霉属（Cochliobolus）产生 碳。 纯化的酶将用于提高 抗体，并在氨基酸测序后， 合成寡核苷酸。 的抗体和 寡核苷酸将用于克隆这些基因， 内切酶 克隆的基因将用于比较分离株 能不能产生HC毒素的真菌， 最终，在分子水平上研究 致病真菌获得能力的过程， 制造毒素。*/

A number of plant pathogens produce low molecular weight chemicals which are toxic to plants. Some toxins, called "host-specific", have the same host-range in vitro as the producing organism does in the field; that is, plants resistant to the pathogen are insensitive to that pathogen's toxin, and plant susceptible to the pathogen are sensitive to the toxin. Host-specific toxins produced by fungi in the genus Cochliobolus (also known as Helminthosporium or Bipolaris) have been implicated in two catastrophic epidemics of cereal crops in the U.S. in the last forty years. While in the last few years the chemical structures of most host- specific toxins have been determined, and their modes of action in some cases partly clarified, nothing is currently known about the biosynthesis of phytotoxins, nor about the molecular processes by which pathogens acquire the ability to make them. The objectives of this project are to identify and isolate enzymes involved in the biosynthesis of a host-specific toxin, to raise antibodies to these enzymes, and to isolate the genes which code for those enzymes. The antibodies and cloned genes will be tools to study the molecular basis of race specificity and toxin production in plant pathogenic fungi. Initial efforts will focus on the purification and characterization of two enzymes recently identified as being involved in the biosynthesis of a cyclic peptide toxin, HC- toxin, made by the fungal pathogen of maize, Cochliobolus carbonum. The purified enzymes will be used to raise antibodies, and, following amino acid sequencing, to make synthetic oligonucleotides. The antibodies and oligonucleotides will be used to clone the genes for these enzymes. The cloned genes will be used to compare isolates of the fungus which can an cannot make HC-toxin, and ultimately, to study at the molecular level the evolutionary processes by which pathogenic fungi acquire the ability to make toxins.***//