Molecular Phylogenetics of the Sternorrhyncha (Insecta: Homoptera) and Their Bacterial Endosymbionts

9306495种莫兰蚜虫、粉虱和相关昆虫包括一些对农业和林业最具破坏性的害虫。所有这些昆虫的生存和繁殖都依赖于被称为内共生体的独特细菌。这些细菌生活在昆虫宿主的特殊细胞内，它们制造的必要营养物质是这些昆虫唯一的食物--植物汁液中所没有的。内共生体通常从母昆虫传给后代，并在内部传播。研究这些昆虫的科学家长期以来一直推测，这种昆虫的特性，如攻击特定植物品种的能力，可能取决于内共生菌的性质。此外，与一种细菌菌株的关联有时可能会丢失，取而代之的是与另一种菌株的关联。事实上，获得新的细菌伴生体被怀疑是昆虫攻击以前抗病的植物品种的新能力的基础。直到最近，这些怀疑还无法得到检验，因为内共生菌不能在昆虫宿主之外生长，因此很难或不可能确定其特征。现代分子生物学方法现在使我们能够探索这些以前神秘的有机体。该项目是昆虫学家和细菌学家的合作项目，使用昆虫基因和细菌基因的DNA序列，以回答有关这些昆虫与其内共生细菌之间联系的起源和持久性的问题。初步结果表明，蚜虫和它们的主要内共生菌之间的联系是非常持久的，持续了数百万年。对农业害虫管理的一个启示是，新的蚜虫品系的出现并不是像之前推测的那样是由于获得了新的细菌同系物。此外，在之前获得NSF奖励的第一年的初步工作表明，一种新的粉虱已经成为蔬菜作物的毁灭性害虫，并不是像农业昆虫学家之前推测的那样，是通过获得一种新的细菌伴生物而产生的。描述这些专门化细菌与其寄主昆虫之间内共生关系的长期历史将增加这些重要昆虫群体生物学的基本知识，其中包括许多经济上重要的害虫物种。这项研究利用了分子生物学和DNA序列计算机处理的最新发展。***

9306495 Moran Aphids, whiteflies and related insects include some of the most devastating pests of agriculture and forestry. The survival and reproduction of all of these insects depend on distinctive bacteria called endosymbionts. These bacteria live inside special cells of their insect hosts and they manufacture essential nutrients that are absent from the plant sap that is the sole diet of these insects. Endosymbionts are normally passed from mother insect to offspring, with transmission occurring internally. Scientists studying these insects have long speculated that properties of the insects, such as ability to attack particular varieties of plants, might depend on the nature of the endosymbionts. Furthermore, associations with one strain of bacteria might sometimes be lost and replaced by associations with a different strain. In fact, acquisition of new bacterial associates has been suspected to be the basis of new abilities of insects to attack previously resistant plant varieties. Until recently, these suspicions could not be tested because the endosymbiont bacteria cannot be grown outside their insect hosts and were therefore difficult or impossible to characterize. Modern methods of molecular biology now allow us to explore these previously mysterious organisms. This project, a collaboration between an entomologist and a bacteriologist, uses DNA sequences from both the insect genes and the bacterial genes in order to answer questions regarding the origin and persistence of the associations between these insects and their endosymbiotic bacteria. Preliminary results have shown that the association between aphids and their primary endosymbion ts is extremely long lived, persisting for millions of years. An implication for agricultural pest management is that the appearance of new strains of aphid pests is not due to the acquisition od new bacterial associates, as previously speculated. Also, initial work during the first year of funding with a prior NSF award showed that a new strain of whitefly that has become a devastating pest of vegetable crops did not originate through the gain of a new bacterial associate, as speculated previously by agricultural entomologists. %%% Characterization of the long term history of the endosymbiotic associations between these specialized bacteria and their host insects will add to basic knowledge of an essential aspect of the biology of these important insect groups which include many economically important pest species. This research takes advantage of recent developments in molecular biology and also in computer processing of the DNA sequences. ***