Data from: Quantifying the coevolutionary potential of multistep immune defenses

Coevolutionary models often assume host infection by parasites depends on a single bout of molecular recognition. As detailed immunological studies accumulate, however, it becomes increasingly apparent that the outcome of host-parasite interactions more generally depends on complex multiple step infection processes. For example, in plant and animal innate immunity, recognition steps are followed by downstream effector steps that kill recognized parasites, with the outcome depending on an escalatory molecular arms race. Here, we explore the consequences of such multi-step infection processes for coevolution using a genetically explicit model. Model analyses reveal that polymorphism is much greater at recognition loci than effector loci, that host-genotype by parasite-genotype (Gh x Gp) interactions are larger for the recognition step, and that the recognition step contributes more to local adaptation than the effector step. These results suggest that (1) local adaptation is more likely when fitness measures are related to recognition versus downstream effectors, (2) effector loci, while mechanistically important, are less likely to harbor the Gh x Gp variation that fuels coevolution, and (3) recognition loci are better candidates for genomic hotspots of coevolution.协同进化模型（Coevolutionary models）通常假定宿主被寄生虫感染仅依赖单次分子识别事件。然而，随着精细免疫学研究的持续积累，学界愈发清晰地认识到，宿主-寄生虫相互作用的结局更广泛地依赖于复杂的多步骤感染过程。例如，在动植物先天免疫（innate immunity）过程中，识别步骤完成后会启动下游效应子步骤以杀灭已被识别的寄生虫，其相互作用结局取决于逐步升级的分子军备竞赛。本研究借助遗传显式模型（genetically explicit model），探究此类多步骤感染过程对协同进化的影响。模型分析结果表明：识别基因座（recognition loci）的多态性显著高于效应子基因座（effector loci）；宿主基因型-寄生虫基因型（Gh × Gp）互作在识别阶段更为强烈；且识别阶段相较效应子阶段对局部适应（local adaptation）的贡献更大。上述研究结果提示：（1）当适合度度量（fitness measures）与识别过程而非下游效应子过程相关时，更易出现局部适应现象；（2）效应子基因座尽管在机制层面发挥关键作用，但却更难携带驱动协同进化的Gh × Gp变异；（3）识别基因座更适合作为协同进化基因组热点区域（genomic hotspots of coevolution）的候选位点