Collaborative Research: Genomic Evolution in the Endosymbiotic Bacteria (Buchnera) of Aphids

合作研究：蚜虫内共生细菌（Buchnera）的基因组进化许多无脊椎动物含有特殊的细胞内细菌，这些细菌通过卵子从母体传播给后代，并在宿主谱系中持续存在数百万年。通常，动物宿主和细菌不能分开生活，这种情况减缓了共生细菌的遗传特征。目前的项目扩展了之前昆虫生物学家和细菌学家之间的合作，他们利用现代分子方法来表征蚜虫共生体中的单个基因。这些细菌经历了基因修饰，提高了它们为宿主提供生长和繁殖所需氨基酸的能力。这项新的研究旨在解决共生体与相关非共生体细菌在整体基因组特征上的差异。在蚜虫共生体的基因组结构的动态分析将使用新开发的分子方法来确定大的染色体片段的大小和确定特定基因的染色体位置共生体从几个已知关系的蚜虫宿主。此外，特定基因的进化速率将被确定为具有已知分化日期的对共生体。这些结果将与来自遗传数据库的相关非共生细菌的相应信息进行比较。蚜虫的共生体具有一些独特的遗传特征，这些特征似乎代表了细胞内细菌的一般综合征，包括农业害虫的有益共生体和感染人类、其他动物和植物的致病菌。这些特征包括基因数量和基因组大小的减少，随着时间的推移，基因变化的速度更快，DNA分子的组成有偏差。因此，拟议的调查将增加对包括各种农业和医学上重要细菌的遗传综合征的理解。对这些生物的基本生物学的进一步了解，有助于找到控制农业害虫和/或致病因子的新方法。

Nontechnical AbstractCollaborative Research: Genomic Evolution in the Endosymbiotic Bacteria(Buchnera) of AphidsNancy A. Moran, University of ArizonaPaul Baumann, University of California-DavisMany invertebrates contain specialized intracellular bacteria that are transmitted from mother to offspring in eggs and that persist in host lineages for millions of years. Typically, animal hosts and bacteria are unable to live apart, a situation that has slowed genetic characterization of symbiotic bacteria. The current project extends a previous collaboration, between an insect biologist and a bacteriologist, which has exploited modern molecular methods to characterize individual genes in symbionts of aphids. These bacteria have undergone genetic modifications that improve their ability to provide hosts with amino acids that are required for growth and reproduction. The new research is designed to address the question of how symbionts differ from related nonsymbiotic bacteria in overall genome characteristics. The dynamics of genome structure in aphid symbionts will be analyzed using newly developed molecular methods for determining sizes of large chromosomal fragments and for determining chromosomal locations of specific genes in symbionts from several aphid hosts of known relationships. In addition, rates of evolution of specific genes will be determined for pairs of symbionts with known dates of divergence. These results will be compared to corresponding information, from genetic databases, for closely related nonsymbiotic bacteria.The symbionts of aphids possess some distinctive genetic traits that appear to represent a general syndrome in intracellular bacteria, including both beneficial symbionts of agricultural pests and pathogenic bacteria infecting humans, other animals, and plants. These characteristics include a reduced number of genes and reduced genome size, faster rates of genetic change over time, and biased composition of DNA molecules. Thus, the proposed investigations will increase understanding of a genetic syndrome that encompasses a variety of agriculturally and medically important bacteria. The additional knowledge of the basic biology of these organisms could contribute to new methods of controlling both agricultural pests and/or agents of disease.