D'Amico Katherine M, Horton Thomas R, Maynard Charles A, Stehman Stephen V, Oakes Allison D, Powell William A
Department of Environmental and Forest Biology, State University of New York College of Environmental Science and Forestry, Syracuse, New York, USA.
Department of Forest and Natural Resources Management, State University of New York College of Environmental Science and Forestry, Syracuse, New York, USA.
Appl Environ Microbiol. 2015 Jan;81(1):100-8. doi: 10.1128/AEM.02169-14. Epub 2014 Oct 17.
American chestnut (Castanea dentata [Marsh.] Borkh.) dominated the eastern forests of North America, serving as a keystone species both ecologically and economically until the introduction of the chestnut blight, Cryphonectria parasitica, functionally eradicated the species. Restoration efforts include genetic transformation utilizing genes such as oxalate oxidase to produce potentially blight-resistant chestnut trees that could be released back into the native range. However, before such a release can be undertaken, it is necessary to assess nontarget impacts. Since oxalate oxidase is meant to combat a fungal pathogen, we are particularly interested in potential impacts of this transgene on beneficial fungi. This study compares ectomycorrhizal fungal colonization on a transgenic American chestnut clone expressing enhanced blight resistance to a wild-type American chestnut, a conventionally bred American-Chinese hybrid chestnut, and other Fagaceae species. A greenhouse bioassay used soil from two field sites with different soil types and land use histories. The number of colonized root tips was counted, and fungal species were identified using morphology, restriction fragment length polymorphism (RFLP), and DNA sequencing. Results showed that total ectomycorrhizal colonization varied more by soil type than by tree species. Individual fungal species varied in their colonization rates, but there were no significant differences between colonization on transgenic and wild-type chestnuts. This study shows that the oxalate oxidase gene can increase resistance against Cryphonectria parasitica without changing the colonization rate for ectomycorrhizal species. These findings will be crucial for a potential deregulation of blight-resistant American chestnuts containing the oxalate oxidase gene.
美国栗（Castanea dentata [Marsh.] Borkh.）曾在北美东部森林中占据主导地位，在生态和经济方面都是关键物种，直到栗疫病（Cryphonectria parasitica）的引入，该物种在功能上被根除。恢复工作包括利用草酸氧化酶等基因进行遗传转化，以培育出可能抗枯萎病的栗树，这些栗树可重新引入原生栖息地。然而，在进行此类引入之前，有必要评估其对非目标生物的影响。由于草酸氧化酶旨在对抗真菌病原体，我们特别关注该转基因对有益真菌的潜在影响。本研究比较了表达增强抗枯萎病能力的转基因美国栗克隆与野生型美国栗、传统培育的美中杂交栗以及其他壳斗科物种的外生菌根真菌定殖情况。一项温室生物测定使用了来自两个具有不同土壤类型和土地利用历史的田间地点的土壤。统计了定殖根尖的数量，并通过形态学、限制性片段长度多态性（RFLP）和DNA测序鉴定真菌物种。结果表明，外生菌根的总定殖情况因土壤类型的差异大于树种差异。个别真菌物种的定殖率有所不同，但转基因栗和野生型栗的定殖情况没有显著差异。本研究表明，草酸氧化酶基因可增强对栗疫病的抗性，而不会改变外生菌根物种的定殖率。这些发现对于可能解除对含有草酸氧化酶基因的抗枯萎病美国栗的监管至关重要。
