Tonk Miray, Knorr Eileen, Cabezas-Cruz Alejandro, Valdés James J, Kollewe Christian, Vilcinskas Andreas
Fraunhofer Institute for Molecular Biology and Applied Ecology, Department of Bioresources, Winchester Strasse, D-35394 Giessen, Germany.
Center for Infection and Immunity of Lille (CIIL), INSERM U1019 - CNRS UMR 8204, Université Lille Nord de France, Institut Pasteur de Lille, Lille, France.
J Invertebr Pathol. 2015 Nov;132:208-215. doi: 10.1016/j.jip.2015.10.009. Epub 2015 Nov 2.
The red flour beetle Tribolium castaneum is a destructive insect pest of stored food and feed products, and a model organism for development, evolutionary biology and immunity. The insect innate immune system includes antimicrobial peptides (AMPs) with a wide spectrum of targets including viruses, bacteria, fungi and parasites. Defensins are an evolutionarily-conserved class of AMPs and a potential new source of antimicrobial agents. In this context, we report the antimicrobial activity, phylogenetic and structural properties of three T. castaneum defensins (Def1, Def2 and Def3) and their relevance in the immunity of T. castaneum against bacterial pathogens. All three recombinant defensins showed bactericidal activity against Micrococcus luteus and Bacillus thuringiensis serovar tolworthi, but only Def1 and Def2 showed a bacteriostatic effect against Staphylococcus epidermidis. None of the defensins showed activity against the Gram-negative bacteria Escherichia coli and Pseudomonas entomophila or against the yeast Saccharomyces cerevisiae. All three defensins were transcriptionally upregulated following a bacterial challenge, suggesting a key role in the immunity of T. castaneum against bacterial pathogens. Phylogenetic analysis showed that defensins from T. castaneum, mealworms, Udo longhorn beetle and houseflies cluster within a well-defined clade of insect defensins. We conclude that T. castaneum defensins are primarily active against Gram-positive bacteria and that other AMPs may play a more prominent role against Gram-negative species.
赤拟谷盗（Tribolium castaneum）是储存食品和饲料产品的一种毁灭性害虫，也是发育、进化生物学和免疫领域的模式生物。昆虫的先天免疫系统包括抗菌肽（AMPs），其具有广泛的靶标，包括病毒、细菌、真菌和寄生虫。防御素是一类进化上保守的抗菌肽，也是抗菌剂的潜在新来源。在此背景下，我们报告了三种赤拟谷盗防御素（Def1、Def2和Def3）的抗菌活性、系统发育和结构特性，以及它们在赤拟谷盗抵抗细菌病原体免疫中的相关性。所有三种重组防御素均对藤黄微球菌和苏云金芽孢杆菌血清型托尔沃西具有杀菌活性，但只有Def1和Def2对表皮葡萄球菌具有抑菌作用。这些防御素均未对革兰氏阴性菌大肠杆菌和嗜虫假单胞菌或对酵母酿酒酵母表现出活性。在细菌攻击后，所有三种防御素的转录均上调，表明它们在赤拟谷盗抵抗细菌病原体的免疫中起关键作用。系统发育分析表明，来自赤拟谷盗、黄粉虫、乌多天牛和家蝇的防御素聚集在昆虫防御素的一个明确分支内。我们得出结论，赤拟谷盗防御素主要对革兰氏阳性菌有活性，而其他抗菌肽可能在抵抗革兰氏阴性菌方面发挥更突出的作用。
