Data for: Impact of rearing temperature on encapsulation and the accumulation of transcripts putatively involved in capsule formation in a parasitized lepidopteran host

Encapsulation and melanisation are innate immune reactions of insects against foreign intruders such as parasitoids. In an earlier study, we observed that immature life stages of the endoparasitoid Tranosema rostrale (Hymenoptera: Ichneumonidae) parasitizing Choristoneura fumiferana (Lepidoptera: Tortricidae) larvae experienced higher mortality due to encapsulation and melanisation when reared at high (30°C) than at lower (10°C, 20°C) temperatures. Downregulation of T. rostrale polydnavirus genes in parasitized hosts and upregulation of two genes involved in the spruce budworm’s melanisation process were identified as likely contributors to parasitoid mortality at high temperature. However, levels of transcripts of genes involved in the spruce budworm’s cellular encapsulation process were not measured inasmuch as candidate genes, in the spruce budworm, had not yet been identified. In addition, our assessment of temperature-dependent encapsulation and melanisation of foreign objects in spruce budworm larvae was only partial. To fill these knowledge gaps, we injected SephadexTM beads into unparasitized spruce budworm larvae and assessed their encapsulation/melanisation after the insects had been held at three different temperatures (10, 20, and 30°C), and we identified spruce budworm genes putatively involved in the encapsulation process and quantified their transcripts at the same three temperatures, using a qPCR approach. As expected, both encapsulation and melanisation of SephadexTM beads increased as a function of temperature. At the molecular level, three of the five genes examined (Integrin β1, Hopscotch, Stat92E) clearly displayed temperature-dependent upregulation. The results of this study further support the hypothesis that a temperature-dependent increase in the encapsulation response of C. fumiferana against T. rostrale is due to the combined effects of reduced expression of polydnavirus genes and enhanced expression of host immune genes.

包囊作用（encapsulation）与黑化反应（melanisation）是昆虫针对寄生性天敌等外来入侵者的先天免疫反应。在此前的一项研究中，我们观察到：内寄生蜂（endoparasitoid）云杉卷叶蛾寄生蜂（Tranosema rostrale，膜翅目：姬蜂科）的未成熟虫态，在寄生云杉芽卷蛾（Choristoneura fumiferana，鳞翅目：卷蛾科）幼虫后，于30℃高温环境下的死亡率显著高于10℃、20℃的低温环境，其死亡诱因即为宿主的包囊与黑化反应。研究发现，寄生宿主体内的T. rostrale多分DNA病毒（polydnavirus）基因表达下调，同时云杉芽卷蛾黑化过程相关的两个基因表达上调，这被认为是高温下寄生蜂死亡率升高的潜在驱动因素。然而，由于当时尚未鉴定出云杉芽卷蛾细胞包囊作用相关的候选基因，因此并未对该过程相关基因的转录本水平进行检测。此外，此前针对云杉芽卷蛾幼虫对外来异物的温度依赖性包囊与黑化反应的评估并不完整。为填补上述研究空白，本研究将葡聚糖微球（Sephadex™）注射入未被寄生的云杉芽卷蛾幼虫体内，将幼虫分别置于10℃、20℃、30℃三种温度下培养后，评估其对外来异物的包囊与黑化反应；同时采用实时定量PCR（qPCR）技术，鉴定云杉芽卷蛾中与包囊作用相关的候选基因，并在上述三种温度下对这些基因的转录本进行定量分析。正如预期，葡聚糖微球的包囊与黑化反应程度随温度升高而显著增强。在分子层面，所检测的5个基因中，整合素β1（Integrin β1）、Hopscotch及Stat92E这3个基因呈现出明显的温度依赖性上调表达。本研究结果进一步支持了以下假说：云杉芽卷蛾（C. fumiferana）对云杉卷叶蛾寄生蜂（T. rostrale）的包囊免疫反应随温度升高而增强，这一现象是由寄生蜂多分DNA病毒基因表达下调与宿主免疫基因表达上调共同作用所导致的。