Molecular Biology of Host-Specific Toxin Biosynthesis

宿主特异性毒素生物合成的分子生物学

• 批准号: 8715608
• 负责人: Jonathan Walton
• 金额: $ 17.5万
• 依托单位: Michigan State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-02-01 至 1991-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8715608&HistoricalAwards=false
• 关键词: Molecular; Biology; Host; Specific; Toxin

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.***//

许多植物病原体产生对植物有毒的低分子化学物质。有些毒素在体外的寄主范围与田间产生的有机体的寄主范围相同，也就是说，对病原体具有抗性的植物对该病原体的毒素不敏感，而对该病原体敏感的植物对该毒素敏感。由Cochliobolus属真菌产生的寄主特异性毒素(又称Helminthosporum或Bipolaris)在过去40年中与美国两次灾难性的谷类作物流行有关。虽然在过去的几年里，大多数寄主特有的毒素的化学结构已经被确定，它们的作用模式在某些情况下也被部分阐明，但目前对植物毒素的生物合成以及病原体获得制造它们的能力的分子过程知之甚少。该项目的目标是鉴定和分离参与宿主特异性毒素生物合成的酶，提高这些酶的抗体，并分离编码这些酶的基因。这些抗体和克隆的基因将成为研究植物病原真菌小种特异性和毒素产生的分子基础的工具。最初的工作将集中在两种酶的纯化和性质上，这两种酶最近被发现参与了由玉米真菌病原菌Cochliobolus Carbon um产生的环肽毒素HC-毒素的生物合成。纯化的酶将被用来提高抗体，并在氨基酸测序后，制造合成的寡核苷酸。抗体和寡核苷酸将被用来克隆这些酶的基因。克隆的基因将用于比较不能产生HC-毒素的真菌菌株，并最终在分子水平上研究病原真菌获得产生毒素能力的进化过程。