Department of Molecular Biosciences, University of Kansas, Lawrence, KS.
K-INBRE Bioinformatics Core, University of Kansas, Lawrence, KS.
Mol Biol Evol. 2019 Jul 1;36(7):1405-1417. doi: 10.1093/molbev/msz059.
Pathogenic microbes can exert extraordinary evolutionary pressure on their hosts. They can spread rapidly and sicken or even kill their host to promote their own proliferation. Because of this strong selective pressure, immune genes are some of the fastest evolving genes across metazoans, as highlighted in mammals and insects. Drosophila melanogaster serves as a powerful model for studying host/pathogen evolution. While Drosophila melanogaster are frequently exposed to various pathogens, little is known about D. melanogaster's ecology, or if they are representative of other Drosophila species in terms of pathogen pressure. Here, we characterize the genome of Drosophila innubila, a mushroom-feeding species highly diverged from D. melanogaster and investigate the evolution of the immune system. We find substantial differences in the rates of evolution of immune pathways between D. innubila and D. melanogaster. Contrasting what was previously found for D. melanogaster, we find little evidence of rapid evolution of the antiviral RNAi genes and high rates of evolution in the Toll pathway. This suggests that, while immune genes tend to be rapidly evolving in most species, the specific genes that are fastest evolving may depend either on the pathogens faced by the host and/or divergence in the basic architecture of the host's immune system.
病原微生物可以对宿主施加非凡的进化压力。它们可以迅速传播，使宿主患病甚至死亡，从而促进自身的增殖。由于这种强大的选择压力，免疫基因是后生动物中进化最快的基因之一，这在哺乳动物和昆虫中得到了强调。黑腹果蝇是研究宿主/病原体进化的有力模型。虽然黑腹果蝇经常接触各种病原体，但人们对它们的生态知之甚少，也不知道它们在病原体压力方面是否代表其他果蝇物种。在这里，我们描述了蘑菇食性的果蝇 innubila 的基因组，它与黑腹果蝇高度分化，并研究了免疫系统的进化。我们发现，免疫途径在进化速度上，黑腹果蝇和 innubila 之间存在显著差异。与之前在黑腹果蝇中发现的情况相反，我们几乎没有发现抗病毒 RNAi 基因快速进化的证据，而 Toll 途径的进化速度却很高。这表明，虽然免疫基因在大多数物种中往往进化得很快，但进化最快的特定基因可能取决于宿主所面临的病原体，以及宿主免疫系统的基本结构的差异。
