Biological Sciences, Florida Gulf Coast University, Fort Myers, Florida, United States of America.
PLoS One. 2010 Jun 28;5(6):e11339. doi: 10.1371/journal.pone.0011339.
Diabrotica virgifera virgifera larvae are root-feeding insects and significant pests to maize in North America and Europe. Little is known regarding how plants respond to insect attack of roots, thus complicating the selection for plant defense targets. Diabrotica virgifera virgifera is the most successful species in its genus and is the only Diabrotica beetle harboring an almost species-wide Wolbachia infection. Diabrotica virgifera virgifera are infected with Wolbachia and the typical gut flora found in soil-living, phytophagous insects. Diabrotica virgifera virgifera larvae cannot be reared aseptically and thus, it is not possible to observe the response of maize to effects of insect gut flora or other transient microbes. Because Wolbachia are heritable, it is possible to investigate whether Wolbachia infection affects the regulation of maize defenses. To answer if the success of Diabrotica virgifera virgifera is the result of microbial infection, Diabrotica virgifera virgifera were treated with antibiotics to eliminate Wolbachia and a microarray experiment was performed. Direct comparisons made between the response of maize root tissue to the feeding of antibiotic treated and untreated Diabrotica virgifera virgifera show down-regulation of plant defenses in the untreated insects compared to the antibiotic treated and control treatments. Results were confirmed via QRT-PCR. Biological and behavioral assays indicate that microbes have integrated into Diabrotica virgifera virgifera physiology without inducing negative effects and that antibiotic treatment did not affect the behavior or biology of the insect. The expression data and suggest that the pressure of microbes, which are most likely Wolbachia, mediate the down-regulation of many maize defenses via their insect hosts. This is the first report of a potential link between a microbial symbiont of an insect and a silencing effect in the insect host plant. This is also the first expression profile for a plant attacked by a root-feeding insect.
玉米根叶甲幼虫是一种以植物根部为食的昆虫，也是北美洲和欧洲玉米的重要害虫。目前人们对于植物如何应对根部昆虫侵害知之甚少，这使得选择植物防御目标变得复杂。玉米根叶甲是该属中最成功的物种，也是唯一一种携带几乎全种范围沃尔巴克氏体感染的玉米根叶甲。玉米根叶甲感染了沃尔巴克氏体和在土壤中生活的植食性昆虫中发现的典型肠道菌群。玉米根叶甲幼虫不能在无菌条件下饲养，因此，无法观察玉米对昆虫肠道菌群或其他瞬态微生物的反应。由于沃尔巴克氏体是可遗传的，因此可以研究沃尔巴克氏体感染是否影响玉米防御的调节。为了确定玉米根叶甲的成功是否是微生物感染的结果，用抗生素处理玉米根叶甲以消除沃尔巴克氏体，并进行了微阵列实验。直接比较经抗生素处理和未经处理的玉米根叶甲取食对玉米根组织的反应，结果表明未经处理的昆虫与抗生素处理和对照处理相比，植物防御能力下降。通过 QRT-PCR 进行了验证。生物和行为学测定表明，微生物已经整合到玉米根叶甲的生理机能中，而不会产生负面影响，抗生素处理也不会影响昆虫的行为或生物学特性。表达数据表明，微生物（很可能是沃尔巴克氏体）的压力通过其昆虫宿主介导了许多玉米防御的下调。这是第一个报道昆虫的微生物共生体与昆虫宿主植物沉默效应之间存在潜在联系的报告。这也是第一个对受根食性昆虫侵害的植物进行的表达谱分析。
