Experimental Evolution of the Bacteriophage Group Leviviridae

适应性的遗传学将在一组单链RNA噬菌体-选择噬菌体在高温下生长。高温抑制野生型噬菌体的生长。然而，在高温下繁殖噬菌体几代后，噬菌体适应性恢复。在这项研究中，八种不同的噬菌体物种将在高温下繁殖（通过连续转移）。与适应高温快速生长相关的遗传变化将通过对进化的噬菌体进行完全测序并将这些序列与每个物种的祖先序列进行比较来测定。将讨论的具体问题包括：（1）与适应高温相关的遗传变化是什么，（2）遗传变化的适应性效应是什么，（3）在适应性进化过程中固定的突变的适应性效应的分布是什么，（4）进化在噬菌体物种内是可重复的，（5）在何种程度上，物种的进化预测与适应高温生长相关的特定变化，（6）在何种程度上，RNA分子的变化增加了重要的茎环结构在高温下的稳定性？光滑病毒科的独特之处在于它们具有非常高的突变率，并且RNA分子的大部分二级结构的功能已经被研究出来;因此，许多适应性变化的功能意义可以被理解。此外，由于存在一个得到充分支持的组的同源性，遗传变化可以放置到一个系统发育的背景下。

The genetics of adaptation will be examined in the Leviviridae, a group of single stranded RNA phage. The phage will be selected for growth at high temperature. High temperature inhibits the growth of the wild-type phage. However, after propagating the phage at high temperature for several generations, phage fitness recovers. In this study, eight different phage species will be propagated (via serial transfer) at high temperature. The genetic changes associated with adaptation to fast growth at high temperature will be assayed by completely sequencing the evolved phage and comparing these sequences to the ancestral sequence for each species. The specific questions that will be addressed include: (1) what are the genetic changes associated with adaptation to high temperature, (2) what are the fitness effects of the genetic changes, (3) what is the distribution of fitness effects of mutations that are fixed during the course of adaptive evolution, (4) is the evolution repeatable within a phage species, (5) to what extent does the phylogeny of the species predict specific change associated with adaptation to growth at high temperature, and, (6) to what extent do changes in the RNA molecule increase the stability of important stem-loop structures at high temperature? The Leviviridae are unique in that they have a very high mutation rate and the function of much of the secondary structure of the RNA molecule has been worked out; hence, the functional significance of many adaptive changes can be understood. Moreover, because a well-supported phylogeny of the group exists, the genetic changes can be placed into a phylogenetic context.