Data from: Delayed transmission selects for increased survival of vesicular stomatitis virus

Life-history theory predicts that traits for survival and reproduction cannot be simultaneous maximized in evolving populations. For this reason, in obligate parasites such as infectious viruses, selection for improved between-host survival during transmission may lead to evolution of decreased within-host reproduction. We tested this idea using experimental evolution of RNA virus populations, passaged under differing transmission times in the laboratory. A single ancestral genotype of Vesicular Stomatitis Virus (VSV), a negative-sense RNA Rhabdovirus, was used to found multiple virus lineages evolved in either ordinary 24-hour cell-culture passage, or in delayed passages of 48 hours. After 30 passages (120 generations of viral evolution), we observed that delayed transmission selected for improved extracellular survival, which traded-off with lowered viral fecundity (slower exponential population growth, and smaller mean plaque size). To further examine the confirmed evolutionary trade-off, we obtained consensus whole-genome sequences of evolved virus populations, to infer phenotype-genotype associations. Results implied that increased virus survival did not occur via convergence; rather, improved virion stability was gained via independent mutations in various VSV structural proteins. Our study suggests that RNA viruses can evolve different molecular solutions for enhanced survival despite their limited genetic architecture, but suffer generalized reproductive trade-offs that limit overall fitness gains.生活史理论（Life-history theory）预测，在演化种群中，生存与繁殖相关性状无法同时实现最大化。针对感染性病毒这类专性寄生物，传播过程中宿主间存活能力提升的选择压力，可能会导致宿主内繁殖能力的演化衰退。我们借助实验室中不同传播时间条件下传代的RNA病毒种群（RNA virus populations）的实验演化（experimental evolution），对该假说展开了验证。本研究以水疱性口炎病毒（Vesicular Stomatitis Virus, VSV）——一种负链RNA弹状病毒（negative-sense RNA Rhabdovirus）的单一祖先基因型为起始，构建了多个病毒谱系，分别在常规24小时细胞培养传代（cell-culture passage）或48小时延迟传代的条件下进行演化。经过30次传代（对应病毒演化120个世代）后，我们观察到延迟传代选择出了胞外存活能力提升的病毒种群，但该性状以病毒繁殖力下降为代价，具体表现为更慢的指数种群增长以及更小的平均噬斑大小（plaque size）。为进一步验证该演化权衡关系，我们获取了演化后病毒种群的共识全基因组序列（consensus whole-genome sequence），以推断表型-基因型关联（phenotype-genotype association）。结果显示，病毒存活能力的提升并非通过趋同演化实现；相反，病毒粒子稳定性（virion stability）的改善来自不同水疱性口炎病毒结构蛋白（structural protein）上的独立突变。本研究表明，尽管遗传结构有限，RNA病毒仍可演化出不同的分子通路以提升存活能力，但会面临普遍存在的繁殖权衡，进而限制了整体适合度增益（fitness gain）。