Social defectors may meet diverse cooperators. Genotype-by-genotype interactions may constrain the ranges of cooperators upon which particular defectors can cheat, limiting cheater spread. The bacterium Myxococcus xanthus undergoes cooperative multicellular development, but some developmental defectors cheat on cooperators during this process. In this study, interactions between a cheater disrupted at the signaling gene csgA and allopatrically diversified cooperators reveal a very small cheating range. Expectedly, the cheater failed to cheat on all natural-isolate cooperators owing to non-cheater-specific antagonisms. Surprisingly, lab-evolved cooperators that diverged from their cheating-susceptible ancestor by fewer than 20 mutations and without experiencing cheating had already exited the csgA mutant’s cheating range. Cooperators might also diversify in the potential for a mutation to reduce expression of cooperative trait or generate a cheating phenotype. A new csgA mutation constructed in several highly diverged cooperators generated diverse sporulation phenotypes, ranging from a complete defect to no defect, indicating that genetic backgrounds can limit the set of genomes in which a mutation creates a defector. Our results suggest that natural populations feature geographic mosaics of cooperators that have diversified in their susceptibility to particular cheaters and in the phenotypes generated by any given cooperation-gene mutation.

中文翻译：

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合作者的异域分歧赋予抗欺骗性并限制叛逃者突变的影响

社会叛逃者可能会遇到不同的合作者。基因型之间的相互作用可能会限制特定叛逃者可以作弊的合作者范围，从而限制作弊者的传播。细菌 Myxococcus xanthus 经历了多细胞协同发育，但在此过程中，一些发育背叛者欺骗了合作者。在这项研究中，在信号基因csgA处中断的作弊者与异域多样化合作者之间的相互作用揭示了一个非常小的作弊范围。不出所料，由于非作弊者特异性对抗，作弊者未能欺骗所有自然隔离的合作者。令人惊讶的是，实验室进化的合作者与他们的易作弊祖先相差不到 20 个突变并且没有经历过作弊，已经退出了csgA变种人的作弊范围。合作者也可能使突变的可能性多样化，以减少合作性状的表达或产生作弊表型。在几个高度分化的合作者中构建的新csgA突变产生了不同的孢子形成表型，从完全缺陷到无缺陷，表明遗传背景可以限制突变产生叛逃者的基因组集。我们的研究结果表明，自然种群具有合作者的地理镶嵌特征，这些合作者在对特定作弊者的易感性和任何给定的合作基因突变产生的表型方面具有多样性。