The effect of coinheritance on host-symbiont coevolution

描述(申请人提供)：拟议研究的总体目标是发展进化遗传学理论，以了解宿主和微生物基因组的共同传播如何影响宿主与其共生或致病微生物之间的共同进化。我们的方法是新颖的，因为它将单个基因组内核基因组合的遗传理论扩展到两个基因组之间的基因组合，即寄主和共生体的基因组合。两位点下降理论量化了基因组合的共同遗传，无论是在相同的基因组中还是在不同的基因组中：共同遗传越大，两个基因的进化轨迹连接的程度就越大。我们的结果将使我们能够根据潜在的因果进化过程来解释跨基因组协同变异(物种间不平衡)的模式。我们认为，共遗传决定了宿主-共生体关系是朝着增强毒力进化，还是朝着良性互惠共生进化。当应用于核和线粒体基因组合时，我们成功地预测了从线粒体到核的功能基因转移的频率将是自交程度的函数，并发现功能基因的基因组间转移在近交物种中发生的可能性是异交物种的十倍。在自交交配系统中，线粒体和核基因的共同遗传使选择能够比核基因和线粒体基因独立遗传的交配系统更有效地作用于基因组合。尽管线粒体像一些共生体一样完全垂直传播，但我们预计类似的影响也会在部分垂直传播的系统中或在共生体在宿主之间具有遗传亲缘关系的传染性系统中表现出来。在这项拟议的研究中，我们将提出五个具体目标，以发展理论来解决1)种间不平衡的产生和维持，2)寄主-共生体联合中功能基因的丢失或转移，3)传播方式、毒力和种群遗传结构的共同进化。我们建议在先前NIH资助的基础上发展这一更普遍的理论。

DESCRIPTION (provided by applicant): The overall goal of the proposed research is to develop evolutionary genetic theory for understanding how co-transmission of host and microbial genomes affects co-evolution between hosts and their symbiotic or pathogenic microbes. Our approach is novel in that it extends theory of the inheritance of nuclear gene combinations within single genomes to gene combinations across two genomes, those of host and symbiont. Two-locus descent theory quantifies the coinheritance of gene combinations, whether in the same or in different genomes: the greater the coinheritance, the greater the degree to which the evolutionary trajectories of both genes are conjoined. Our results will allow us to interpret patterns of trans-genomic co- variation (interspecies disequilibria) in terms of th underlying causal evolutionary processes. We propose that coinheritance determines whether a host-symbiont association evolves toward enhanced virulence or toward benign mutualistic symbiosis. When applied to nuclear and mitochondrial gene combinations, we successfully predicted that the frequency of functional gene transfer from the mitochondria to the nucleus would be a function of the degree of selfing and discovered that inter-genomic transfer of functional genes is ten-fold more likely to occur in inbreeding species than in outcrossing species. Coinheritance of mitochondrial and nuclear genes in selfing mating systems allows selection to act more effectively on gene combinations than mating systems where nuclear and mitochondrial genes are inherited independently. Althoughmitochondria are wholly vertically transmitted like some symbionts, we expect similar effects to be manifest in systems with partial vertical transmission or in systems with contagious transmission of symbionts among host that are genetic relatives. In this proposed research we will address five specific aims which will develop theory to address the 1) generation and maintenance of interspecies disequilibria, 2) functional gene loss or transfer in host-symbiont associations, 3) coevolution of transmission mode, virulence, and population genetic structure. We propose to develop this more general theory, building upon progress from prior NIH funding.