Chromosomal Phylogeny of the Anopheles gambiae Complex

描述(申请人提供)：冈比亚按蚊复合体的形态难以区分的成员具有显著不同的生态适应、地理分布和行为。该复合体包括主要的疟疾媒介(阿拉伯疟原虫、冈比亚疟原虫)，也包括次要媒介(A.bwambae、A.melas、A.merus)和非媒介(A.quriannulatus A、A.quriannulatus B)。开发疟疾管理的新方法意味着要找到通过用非病媒取代媒介种群来阻断传播的方法。我们目前对载体和非载体之间的基因构成差异的了解不足以实施成功的种群替换。推断冈比亚按蚊复合体的祖先基因组特征对于识别与人类血液选择的起源和丧失、生态和行为适应以及与人类栖息地的关联相关的进化变化至关重要。这些基因组变化应该有针对性并加以操纵，以便减少并最终消除疟疾传播。尽管冈比亚按蚊的分子标记和基因组序列已有，但成员间的系统发育关系尚未完全解决。由于该复合体的起源是最近的，高度的序列相似性、遗传渗透和共享的分子祖先多态混淆了明确确定进化方向的能力。这个探索性的R21项目的主要目标是确定冈比亚按蚊复合体中的祖先和衍生的染色体排列。我们的方法的优点是，它是基于观察到的祖先排列是在群内和群外物种之间共享的，并且断点结构可以指示染色体进化的方向。我们计划(1)鉴定冈比亚按蚊复合体和外群物种A.stephensi之间共享的染色体安排，(2)确定反转断点的衍生结构特征，如转座/重复元件和基因复制的存在。对群内断点和群外断点的对比分析将首次评估反转的唯一性，并明确确定复合体中祖先的X和2R排列。尽管识别和测序断点在技术上是具有挑战性的任务，但2LA断点的成功表征和我们的初步研究表明，我们的研究目标是可以实现的。我们的建议有两个具体的目标：1.将固定倒位XAG、Xbcd、2Rop的断裂点物理定位到冈比亚按蚊复合体和斯氏按蚊的染色体上，并计算群内和群外物种之间的倒位距离。2.对阿拉伯沙棘中的Xc、四环沙棘中的Xa+、Xc+、沙棘中的2Ro以及斯氏沙棘中的同源序列进行序列测定和特征分析。与公共卫生相关：这项建议将推断冈比亚按蚊复合体中的祖先染色体安排。它们在确定与人类血液选择的起源和丧失、生态和行为适应以及与人类栖息地相关的进化基因组变化方面至关重要。这些基因组变化应该有针对性并加以操纵，以便减少并最终消除疟疾传播。

DESCRIPTION (provided by applicant): Morphologically indistinguishable members of the Anopheles gambiae complex have remarkably distinct ecological adaptations, geographical distributions, and behaviors. This complex includes the major malaria vectors (A. arabiensis, A. gambiae), as well as minor vectors (A. bwambae, A. melas, A. merus) and nonvectors (A. quadriannulatus A, A. quadriannulatus B). Development of novel approaches to malaria management implies finding the ways to interrupt transmission by replacing populations of vectors with nonvectors. Our current knowledge about differences in genetic make-up among vectors and nonvectors is insufficient for implementing the successful population replacement. Inferring ancestral genomic features in the A. gambiae complex is crucial in identifying the evolutionary changes associated with the origin and loss of human blood choice, ecological and behavioral adaptations, and association with human habitats. These genomic changes should be targeted and manipulated so that malaria transmission can be reduced and eventually eliminated. Despite the availability of molecular markers and the genome sequence for A. gambiae, the phylogenetic relationships among the members are not fully resolved. Because of the recent origin of the complex, the high level of sequence similarity, genetic introgression, and shared molecular ancestral polymorphisms confound the ability to determine the direction of evolution unambiguously. The major goal of this exploratory R21 project is to determine the ancestral and derived chromosomal arrangements in the A. gambiae complex. The advantage of our approach is that it is based on observations that the ancestral arrangements are shared between ingroup and outgroup species and that the breakpoint structure can indicate the direction of chromosomal evolution. We plan to (1) identify chromosomal arrangements shared between the A. gambiae complex and the outgroup species A. stephensi and (2) determine derived structural features of inversion breakpoints such as the presence of transposable/repetitive elements and gene duplications. The comparative analysis of the ingroup and outgroup breakpoints will for the first time assess the uniqueness of the inversions and unambiguously determine the ancestral X and 2R arrangements in the complex. Although identifying and sequencing breakpoints are technically challenging tasks, the successful characterization of the 2La breakpoints and our preliminary studies suggest that our research aims are achievable. Our proposal has two specific aims: 1. To physically map the breakpoints of fixed inversions Xag, Xbcd, 2Rop to the chromosomes of the A. gambiae complex and A. stephensi and to calculate the inversion distances between ingroup and outgroup species. 2. To sequence and characterize the inversion breakpoints of Xc in A. arabiensis, Xa+, Xc+ in A. quadriannulatus, and 2Ro in A. merus, and the homologous sequences in A. stephensi. PUBLIC HEALTH RELEVANCE: This proposal will infer ancestral chromosome arrangements in the Anopheles gambiae complex. They are crucial in identifying the evolutionary genomic changes associated with the origin and loss of human blood choice, ecological and behavioral adaptations, and association with human habitats. These genomic changes should be targeted and manipulated so that malaria transmission can be reduced and eventually eliminated.