Data from: Repeatability and contingency in the evolution of a key innovation in phage lambda

The processes responsible for the evolution of key innovations, whereby lineages acquire qualitatively new functions that expand their ecological opportunities, remain poorly understood. We examined how a virus, bacteriophage λ, evolved to infect its host, Escherichia coli, through a novel pathway. Natural selection promoted the fixation of mutations in the virus’s host-recognition protein, J, that improved fitness on the original receptor, LamB, and set the stage for other mutations that allowed infection through a new receptor, OmpF. These viral mutations arose only after the host evolved reduced expression of LamB, whereas certain other host mutations prevented the phage from evolving the new function. This study shows the complex interplay between genomic processes and ecological conditions that favor the emergence of evolutionary innovations.目前学界对驱动关键创新演化的过程仍缺乏充分认知——此类过程可使物种谱系获得质变性的全新功能，进而拓展其生态机遇。本研究以λ噬菌体（bacteriophage λ）为研究对象，探究其如何通过全新途径演化出感染宿主大肠埃希氏菌（Escherichia coli）的能力。自然选择推动了该病毒宿主识别蛋白J（protein J）中突变的固定，这些突变提升了病毒在原始受体LamB上的适合度，并为后续其他允许病毒通过新受体OmpF完成感染的突变奠定了基础。而这些病毒突变仅在宿主演化出LamB表达下调后才会出现；与此同时，部分宿主突变会阻碍噬菌体获得这一新功能。本研究揭示了助力演化创新出现的基因组过程与生态条件之间的复杂相互作用。