Bensadia Fatiha, Boudreault Simon, Guay Jean-Frédéric, Michaud Dominique, Cloutier Conrad
Département de Biologie, Université Laval, Cité Universitaire, Que., Canada G1K 7P4.
J Insect Physiol. 2006 Feb;52(2):146-57. doi: 10.1016/j.jinsphys.2005.09.011. Epub 2005 Nov 22.
Parasitoid virulence and host resistance are complex interactions depending on metabolic rate and cellular activity, which in aphids additionally implicate heritable secondary symbionts among the Enterobacteriaceae. As performance of the parasitoid, the aphid host and its symbionts may differentially respond to temperature, the success or failure of aphid parasitism is difficult to predict when temperature varies. We tested the hypothesis that resistance of the pea aphid Acyrthosiphon pisum to the parasitoid Aphidius ervi, which is linked to aphid secondary symbionts, may depend on temperature in several resistant and non-resistant aphid clonal lineages of different geographic origin and of known bacterial symbiosis, using experiments in controlled environments. Complete immunity to A. ervi at 20 degrees C in three different aphid clones whose symbiosis is characterized by the possession of Hamiltonella defensa reversed to high susceptibility at 25 degrees C and especially 30 degrees C, suggesting that the aphid's immune responses to the establishment and early development of the parasitoid is strongly reduced at moderately high temperatures. There was no evidence that a pea aphid control genotype that was susceptible to A. ervi at 20 degrees C could become more resistant as temperature increases, as has been suggested for insect fungal pathogens. By contrast, our results suggest that aphid clonal resistance to A. ervi and related parasitoids is characteristic of cool temperature conditions, similar to various other fitness attributes of aphids. Based on evidence that H. defensa symbionts characterized all three A. ervi resistant pea aphid clones studied, but was absent in control aphids that remained susceptible at all temperatures, we suggest that secondary symbiosis plays a key role in the heat sensitivity of aphid clonal resistance. Our study may also indicate that aphid natural control of variably susceptible host populations by aphid parasitoids is more likely at moderate to high temperatures.
寄生蜂的毒力和宿主抗性是复杂的相互作用，取决于代谢率和细胞活性，而在蚜虫中，这还涉及肠杆菌科中的可遗传次生共生菌。由于寄生蜂、蚜虫宿主及其共生菌的表现可能对温度有不同反应，因此当温度变化时，蚜虫寄生的成败很难预测。我们通过在可控环境中进行实验，检验了以下假设：豌豆蚜对寄生蜂豌豆蚜茧蜂的抗性与蚜虫次生共生菌有关，在几个不同地理来源且已知细菌共生关系的抗性和非抗性蚜虫克隆谱系中，这种抗性可能取决于温度。在20摄氏度时，三种不同的蚜虫克隆对豌豆蚜茧蜂具有完全免疫力，其共生特征是含有防御汉氏菌，但在25摄氏度尤其是30摄氏度时，这种免疫力转变为高易感性，这表明在适度高温下，蚜虫对寄生蜂的建立和早期发育的免疫反应会大大降低。没有证据表明，一种在20摄氏度时对豌豆蚜茧蜂敏感的豌豆蚜对照基因型会随着温度升高而变得更具抗性，昆虫真菌病原体曾有过这样的情况。相比之下，我们的结果表明，蚜虫对豌豆蚜茧蜂及相关寄生蜂的克隆抗性是低温条件下的特征，类似于蚜虫的各种其他适合度属性。基于防御汉氏菌共生菌存在于所有三个被研究的对豌豆蚜茧蜂具有抗性的豌豆蚜克隆中，但在所有温度下都保持易感的对照蚜虫中不存在这一证据，我们认为次生共生在蚜虫克隆抗性的热敏感性中起关键作用。我们的研究还可能表明，在中高温下，蚜虫寄生蜂对不同易感宿主种群的自然控制更有可能实现。
