Mason Charles J, Rubert-Nason Kennedy F, Lindroth Richard L, Raffa Kenneth F
Department of Entomology, University of Wisconsin-Madison, 1630 Linden Dr., Madison, WI, 53706, USA,
J Chem Ecol. 2015 Jan;41(1):75-84. doi: 10.1007/s10886-014-0530-1. Epub 2014 Dec 5.
Microbial symbionts are becoming increasingly recognized as mediators of many aspects of plant - herbivore interactions. However, the influence of plant chemical defenses on gut associates of insect herbivores is less well understood. We used gypsy moth (Lymantria dispar L.), and differing trembling aspen (Populus tremuloides Michx.) genotypes that vary in chemical defenses, to assess the influence of foliar chemistry on bacterial communities of larval midguts. We evaluated the bacterial community composition of foliage, and of midguts of larvae feeding on those leaves, using next-generation high-throughput sequencing. Plant defense chemicals did not influence the composition of foliar communities. In contrast, both phenolic glycosides and condensed tannins affected the bacterial consortia of gypsy moth midguts. The two most abundant operational taxonomic units were classified as Ralstonia and Acinetobacter. The relative abundance of Ralstonia was higher in midguts than in foliage when phenolic glycoside concentrations were low, but lower in midguts when phenolic glycosides were high. In contrast, the relative abundance of Ralstonia was lower in midguts than in foliage when condensed tannin concentrations were low, but higher in midguts when condensed tannins were high. Acinetobacter showed a different relationship with host chemistry, being relatively more abundant in midguts than with foliage when condensed tannin concentrations were low, but lower in midguts when condensed tannins were high. Acinetobacter tended to have a greater relative abundance in midguts of insects feeding on genotypes with high phenolic glycoside concentrations. These results show that plant defense chemicals influence herbivore midgut communities, which may in turn influence host utilization.
微生物共生体日益被视为植物 - 食草动物相互作用诸多方面的调节者。然而，植物化学防御对食草昆虫肠道共生菌的影响却鲜为人知。我们利用舞毒蛾（Lymantria dispar L.）以及化学防御能力各异的不同基因型美洲山杨（Populus tremuloides Michx.），来评估叶片化学物质对幼虫中肠细菌群落的影响。我们采用新一代高通量测序技术，评估了叶片以及取食这些叶片的幼虫中肠的细菌群落组成。植物防御化学物质并未影响叶片群落的组成。相比之下，酚糖苷和缩合单宁均影响了舞毒蛾中肠的细菌群落。两个最丰富的操作分类单元被归类为罗尔斯通氏菌属和不动杆菌属。当酚糖苷浓度较低时，罗尔斯通氏菌属在中肠中的相对丰度高于叶片，但当酚糖苷浓度较高时，其在中肠中的相对丰度较低。相反，当缩合单宁浓度较低时，罗尔斯通氏菌属在中肠中的相对丰度低于叶片，但当缩合单宁浓度较高时，其在中肠中的相对丰度较高。不动杆菌属与宿主化学物质的关系有所不同，当缩合单宁浓度较低时，它在中肠中的相对丰度相对高于叶片，但当缩合单宁浓度较高时，其在中肠中的相对丰度较低。在取食酚糖苷浓度高的基因型植物的昆虫中肠中，不动杆菌属往往具有更高的相对丰度。这些结果表明，植物防御化学物质会影响食草动物的中肠群落，进而可能影响宿主利用率。
