Gene expression plasticity across hosts of an invasive scale insect species

Most plant-eating insects eat only a few plant species. How do some eat many? For plant-eating insects, we still have only a nascent understanding of the genetic basis of host-use promiscuity. Here, to improve that situation, we investigated host-induced gene expression plasticity in the invasive lobate lac scale insect, Paratachardina pseudolobata (Hemiptera: Keriidae). We were particularly interested in the differential expression of detoxification and effector genes, which are thought to be critical for overcoming a plant’s chemical defenses. We collected RNA samples from P. pseudolobata on three different host plant species, assembled transcriptomes de novo, and identified transcripts with significant host-induced gene expression changes. Gene expression plasticity was pervasive, but the expression of most detoxification and effector genes was insensitive to the host environment. Nevertheless, some types of detoxification genes were more differentially expressed than expected by chance. Moreover, we found evidence of a trade-off between expression of genes involved in primary and secondary metabolism; hosts that induced less expression of genes for detoxification induced more expression of genes for growth. Our findings are largely consonant with those of several recently published studies of other plant-eating insect species. Thus, across plant-eating insect species, there may be a common set of gene expression changes that enable host-use promiscuity.

绝大多数植食性昆虫仅取食少量植物物种，而为何部分类群能够取食大量宿主植物？针对植食性昆虫宿主利用广谱性的遗传基础，目前我们的认知仍处于初步阶段。为此，本研究以入侵性害虫假叶状胶蚧（Paratachardina pseudolobata，半翅目：胶蚧科）为对象，探究其宿主诱导的基因表达可塑性。我们重点关注了解毒基因与效应基因的差异表达——这类基因被认为是突破植物化学防御的关键因子。我们从取食3种不同宿主植物的假叶状胶蚧中采集RNA样本，从头拼接获得转录组，并筛选出受宿主诱导发生显著表达变化的转录本。研究发现基因表达可塑性普遍存在，但多数解毒基因与效应基因的表达并不受宿主环境的影响。尽管如此，部分类型的解毒基因的差异表达水平显著高于随机预期。此外，我们还发现参与初级代谢与次级代谢的基因表达存在权衡关系：当宿主诱导解毒基因的表达水平降低时，其生长相关基因的表达水平则会升高。我们的研究结果与近期多项针对其他植食性昆虫类群的已发表研究结论基本一致。由此推测，在不同植食性昆虫类群中，可能存在一套共通的基因表达变化模式，赋予其宿主利用的广谱性。