Chandler S M, Wilkinson T L, Douglas A E
Department of Biology, University of York, York, UK.
Proc Biol Sci. 2008 Mar 7;275(1634):565-70. doi: 10.1098/rspb.2007.1478.
The interactions between herbivorous insects and their symbiotic micro-organisms can be influenced by the plant species on which the insects are reared, but the underlying mechanisms are not understood. Here, we identify plant nutrients, specifically amino acids, as a candidate factor affecting the impact of symbiotic bacteria on the performance of the phloem-feeding aphid Aphis fabae. Aphis fabae grew more slowly on the labiate plant Lamium purpureum than on an alternative host plant Vicia faba, and the negative effect of L. purpureum on aphid growth was consistently exacerbated by the bacterial secondary symbionts Regiella insecticola and Hamiltonella defensa, which attained high densities in L. purpureum-reared aphids. The amino acid content of the phloem sap of L. purpureum was very low; and A. fabae on chemically defined diets of low amino acid content also grew slowly and had elevated secondary symbiont densities. It is suggested that the phloem nutrient profile of L. purpureum promotes deleterious traits in the secondary symbionts and disturbs insect controls over bacterial abundance.
植食性昆虫与其共生微生物之间的相互作用会受到昆虫所取食植物种类的影响，但其潜在机制尚不清楚。在此，我们确定植物养分，特别是氨基酸，是影响共生细菌对吸食韧皮部的豌豆蚜生长性能影响的一个候选因素。豌豆蚜在唇形科植物紫花野芝麻上的生长速度比在替代寄主植物蚕豆上慢，并且紫花野芝麻对蚜虫生长的负面影响会因细菌次生共生菌昆虫雷吉氏菌和防御哈氏菌而持续加剧，这两种菌在取食紫花野芝麻的蚜虫体内密度很高。紫花野芝麻韧皮部汁液中的氨基酸含量非常低；而取食低氨基酸含量化学定义食物的豌豆蚜生长也很缓慢，且次生共生菌密度升高。研究表明，紫花野芝麻的韧皮部养分特征促进了次生共生菌中的有害特性，并扰乱了昆虫对细菌数量的控制。
