Institut für Biologie, Molekulare Ökologie, Martin-Luther-Universität Halle-Wittenberg, Halle, Saale, Germany.
PLoS One. 2011 Mar 29;6(3):e18126. doi: 10.1371/journal.pone.0018126.
The innate immune system which helps individuals to combat pathogens comprises a set of genes representing four immune system pathways (Toll, Imd, JNK and JAK/STAT). There is a lack of immune genes in social insects (e.g. honeybees) when compared to Diptera. Potentially, this might be compensated by an advanced system of social immunity (synergistic action of several individuals). The bumble bee, Bombus terrestris, is a primitively eusocial species with an annual life cycle and colonies headed by a single queen. We used this key pollinator to study the temporal dynamics of immune system gene expression in response to wounding and bacterial challenge.Antimicrobial peptides (AMP) (abaecin, defensin 1, hymenoptaecin) were strongly up-regulated by wounding and bacterial challenge, the latter showing a higher impact on the gene expression level. Sterile wounding down-regulated TEP A, an effector gene of the JAK/STAT pathway, and bacterial infection influenced genes of the Imd (relish) and JNK pathway (basket). Relish was up-regulated within the first hour after bacterial challenge, but decreased strongly afterwards. AMP expression following wounding and bacterial challenge correlates with the expression pattern of relish whereas correlated expression with dorsal was absent. Although expression of AMPs was high, continuous bacterial growth was observed throughout the experiment.Here we demonstrate for the first time the temporal dynamics of immune system gene expression in a social insect. Wounding and bacterial challenge affected the innate immune system significantly. Induction of AMP expression due to wounding might comprise a pre-adaptation to accompanying bacterial infections. Compared with solitary species this social insect exhibits reduced immune system efficiency, as bacterial growth could not be inhibited. A negative feedback loop regulating the Imd-pathway is suggested. AMPs, the end product of the Imd-pathway, inhibited the up-regulation of the transcription factor relish, which is necessary for effector gene expression.
先天免疫系统有助于个体对抗病原体，它包含一套代表四个免疫系统途径（Toll、Imd、JNK 和 JAK/STAT）的基因。与双翅目昆虫相比，社会性昆虫（如蜜蜂）缺乏免疫基因。可能，这可以通过先进的社会免疫系统（几个个体的协同作用）来弥补。熊蜂（Bombus terrestris）是一种原始的真社会性物种，具有一年生的生命周期和由一只蜂王领导的群体。我们利用这种关键的传粉媒介来研究免疫系统基因表达对创伤和细菌挑战的时间动态。抗菌肽（AMP）（abaecin、defensin 1、 hymenoptaecin）被创伤和细菌挑战强烈上调，后者对基因表达水平的影响更大。无菌创伤下调 JAK/STAT 途径的效应基因 TEP A，细菌感染影响 Imd（ relish）和 JNK 途径（basket）的基因。Relish 在细菌挑战后第一个小时内上调，但随后强烈下降。创伤和细菌挑战后的 AMP 表达与 relish 的表达模式相关，而与 dorsal 的相关表达则不存在。尽管 AMP 的表达水平很高，但在整个实验过程中观察到细菌持续生长。本文首次在社会性昆虫中展示了免疫系统基因表达的时间动态。创伤和细菌挑战对先天免疫系统有显著影响。由于创伤诱导的 AMP 表达可能构成对伴随细菌感染的预先适应。与独居物种相比，这种社会性昆虫表现出较低的免疫系统效率，因为无法抑制细菌生长。建议存在一个负反馈回路来调节 Imd 途径。作为 Imd 途径的终产物，抗菌肽抑制转录因子 relish 的上调，而 relish 对于效应基因表达是必需的。
