Department of Entomology, Pennsylvania State University, University Park, PA 16802, USA.
Proc Natl Acad Sci U S A. 2010 Feb 23;107(8):3600-5. doi: 10.1073/pnas.0907191107. Epub 2010 Feb 3.
Previous studies have shown that vector-borne pathogens can alter the phenotypes of their hosts and vectors in ways that influence the frequency and nature of interactions between them, with significant implications for the transmission and spread of disease. For insect-borne pathogens, host odors are particularly likely targets for manipulation, because both plant- and animal-feeding insects use volatile compounds derived from their hosts as key foraging cues. Here, we document the effects of a widespread plant pathogen, Cucumber mosaic virus (CMV), on the quality and attractiveness of one of its host plants (Cucurbita pepo cv. Dixie) for two aphid vectors, Myzus persicae and Aphis gossypii. Our results indicate that CMV greatly reduces host-plant quality-aphids performed poorly on infected plants and rapidly emigrated from them-but increases the attractiveness of infected plants to aphids by inducing elevated emissions of a plant volatile blend otherwise similar to that emitted by healthy plants. Thus, CMV appears to attract vectors deceptively to infected plants from which they then disperse rapidly, a pattern highly conducive to the nonpersistent transmission mechanism employed by CMV and very different from the pattern previously reported for persistently transmitted viruses that require sustained aphid feeding for transmission. In addition to providing a documented example of a pathogen inducing a deceptive signal of host-plant quality to vectors, our results suggest that the transmission mechanism is a major factor shaping pathogen-induced changes in host-plant phenotypes. Furthermore, our findings yield a general hypothesis that, when vector-borne plant or animal pathogens reduce host quality for vectors, pathogen-induced changes in host phenotypes that enhance vector attraction frequently will involve the exaggeration of existing host-location cues.
先前的研究表明，病媒传播病原体可以改变宿主和病媒的表型，从而影响它们之间相互作用的频率和性质，这对疾病的传播和扩散有重大影响。对于昆虫传播的病原体，宿主气味特别容易成为操纵的目标，因为植物和动物取食的昆虫都使用源自宿主的挥发性化合物作为关键的觅食线索。在这里，我们记录了一种广泛存在的植物病原体黄瓜花叶病毒（CMV）对其宿主植物之一（南瓜 cv. Dixie）的质量和对两种蚜虫媒介（桃蚜和棉蚜）吸引力的影响。我们的结果表明，CMV 大大降低了宿主植物的质量——蚜虫在感染的植物上表现不佳，并迅速从其上迁移——但通过诱导植物挥发性混合物的升高排放，增加了感染植物对蚜虫的吸引力，这种混合物与健康植物释放的混合物相似。因此，CMV 似乎以欺骗性的方式将媒介吸引到感染的植物上，然后它们迅速从中分散，这种模式非常有利于 CMV 采用的非持续传播机制，与先前报道的需要持续蚜虫取食才能传播的持久性传播病毒的模式非常不同。除了提供病原体向媒介诱导宿主植物质量欺骗性信号的实例外，我们的结果还表明，传播机制是塑造宿主植物表型变化的主要因素。此外，我们的发现提出了一个一般假设，即当病媒传播的植物或动物病原体降低宿主对媒介的质量时，病原体诱导的宿主表型变化增强对媒介的吸引力，通常涉及夸大现有的宿主定位线索。
