Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, United Kingdom.
Evolution. 2012 Jul;66(7):2030-41. doi: 10.1111/j.1558-5646.2012.01578.x. Epub 2012 Feb 23.
There is growing evidence that successful infection of hosts by pathogens requires a series of independent steps. However, how multistep infection processes affect host-pathogen coevolution is unclear. We present a coevolutionary model, inspired by empirical observations from a range of host-pathogen systems, where the infection process consists of the following two steps: the first is for the pathogen to recognize and locate a suitable host, and the second is to exploit the host while evading immunity. Importantly, these two steps conform to different models of infection genetics: inverse-gene-for-gene (IGFG) and gene-for-gene (GFG), respectively. We show that coevolution under this scenario can lead to coupled gene frequency changes across these two systems. In particular, selection often favors pathogens that are infective at the first, IGFG, step and hosts that are resistant at the second, GFG, step. Hence, there may be signals of positive selection between functionally independent systems whenever there are multistep processes determining resistance and infectivity. Such multistep infection processes are a fundamental, but overlooked feature of many host-pathogen interactions, and have important consequences for our understanding of host-pathogen coevolution.
越来越多的证据表明，病原体成功感染宿主需要一系列独立的步骤。然而，多步骤感染过程如何影响宿主-病原体共同进化尚不清楚。我们提出了一个共同进化模型，该模型受到了来自一系列宿主-病原体系统的经验观察的启发，其中感染过程包括以下两个步骤：第一步是病原体识别和定位合适的宿主，第二步是在逃避免疫的同时利用宿主。重要的是，这两个步骤符合不同的感染遗传模型：反向基因对基因（IGFG）和基因对基因（GFG）。我们表明，在这种情况下的共同进化可以导致这两个系统中基因频率的耦合变化。特别是，选择往往有利于在第一步 IGFG 中具有感染性的病原体和在第二步 GFG 中具有抗性的宿主。因此，只要有决定抗性和感染性的多步骤过程，在功能上独立的系统之间可能存在正选择的信号。这种多步骤感染过程是许多宿主-病原体相互作用的一个基本但被忽视的特征，对我们理解宿主-病原体共同进化具有重要意义。
