Data from: Outcomes of co-infection by two potyviruses: implications for the evolution of manipulative strategies

Recent studies have documented effects of plant-viruses on host plants that appear to enhance transmission by insect vectors. But, almost no empirical work has explored the implications of such apparent manipulation for interactions among co-infecting pathogens. We examined single and mixed infections of two potyviruses, Watermelon mosaic virus (WMV) and Zucchini yellow mosaic virus (ZYMV), that frequently co-occur in cucurbitaceae populations and share the same aphid vectors. We found that ZYMV isolates replicated at similar rates in single and mixed infections, while WMV strains accumulated to signficantly lower levels in the presence of ZYMV. Furthermore, ZYMV induced changes in leaf colour and volatile emissions that enhanced aphid (Aphis gossypii) recruitment to infected plants. In contrast, WMV did not elicit strong effects on plant-aphid interactions. Nevertheless, WMV was still readily transmitted from mixed infections, despite fairing poorly in in-plant competition. These findings suggest that pathogen effects on host-vector interactions may well influence competition among co-infecting pathogens. For example, if non-manipulative pathogens benefit from the increased vector traffic elicited by manipulative competitors, their costs of competition may be mitigated to some extent. Conversely, the benefits of manipulation may be limited by free-rider effects in systems where there is strong competition among pathogens for host resources and/or access to vectors.

已有研究证实，植物病毒可对宿主植物产生调控效应，且这类效应似乎能够提升昆虫介体的传毒效率。但目前几乎尚无实证研究探讨这类看似操控宿主的现象，对共侵染病原物之间互作的影响。本研究针对两种马铃薯Y病毒属（potyviruses）病毒——西瓜花叶病毒（Watermelon mosaic virus, WMV）和西葫芦黄化花叶病毒（Zucchini yellow mosaic virus, ZYMV）——的单侵染与混合侵染情况展开了调查。这两种病毒常共侵染葫芦科植物种群，且共享相同的蚜虫介体。研究结果显示，ZYMV分离物在单侵染与混合侵染中的复制速率相近；而当存在ZYMV时，WMV株系的病毒积累量显著降低。此外，ZYMV可诱导宿主植物的叶片颜色与挥发性挥发物发生改变，进而提升棉蚜（Aphis gossypii）对染病植株的趋集率。与之相反，WMV并未对植物-蚜虫互作产生显著影响。尽管WMV在植株内的资源竞争中处于劣势，但它仍可顺利从混合侵染的植株中完成传毒。上述研究结果表明，病原物对宿主-介体互作的调控作用，很可能会影响共侵染病原物之间的竞争关系。举例而言，若非操控型病原物能够借助操控型竞争病原物所引发的介体活动频次提升而获益，那么其在竞争中付出的代价可在一定程度上得到缓解。反之，在病原物间针对宿主资源和/或介体接触位点存在激烈竞争的系统中，操控行为所能带来的收益可能会因搭便车效应而受到限制。