Immune system responses and fitness costs associated with consumption of bacteria in larvae of Trichoplusia ni
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BioMed Central
Open Access
Research article
Immune system responses and fitness costs associated with consumption of bacteria in larvae of Trichoplusia ni Dalial Freitak1, Christopher W Wheat2, David G Heckel1 and Heiko Vogel*1 Address: 1Max Planck Institute for Chemical Ecology, Department of Entomology, Hans-Knoell – Strasse 8, 07745 Jena, Germany and 2University of Helsinki, Department of Biological and Environmental Sciences, Helsinki FI-00014, Finland Email: Dalial Freitak - [email protected]; Christopher W Wheat - [email protected]; David G Heckel - [email protected]; Heiko Vogel* - [email protected] * Corresponding author
Published: 21 December 2007 BMC Biology 2007, 5:56
doi:10.1186/1741-7007-5-56
Received: 11 May 2007 Accepted: 21 December 2007
This article is available from: http://www.biomedcentral.com/1741-7007/5/56 © 2007 Freitak et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract Background: Insects helped pioneer, and persist as model organisms for, the study of specific aspects of immunity. Although they lack an adaptive immune system, insects possess an innate immune system that recognizes and destroys intruding microorganisms. Its operation under natural conditions has not been well studied, as most studies have introduced microbes to laboratoryreared insects via artificial mechanical wounding. One of the most common routes of natural exposure and infection, however, is via food; thus, the role of dietary microbial communities in herbivorous insect immune system evolution invites study. Here, we examine the immune system response and consequences of exposing a lepidopteran agricultural pest to non-infectious microorganisms via simple oral consumption. Results: Immune system response was compared between Trichoplusia ni larvae reared on diets with or without non-pathogenic bacteria (Escherichia coli and Micrococcus luteus). Two major immune response-related enzymatic activities responded to diets differently – phenoloxidase activity was inhibited in the bacteria-fed larvae, whereas general antibacterial activity was enhanced. Eight proteins were highly expressed in the hemolymph of the bacteria fed larvae, among them immune response related proteins arylphorin, apolipophorin III and gloverin. Expression response among 25 putative immune response-related genes were assayed via RT-qPCR. Seven showed more than fivefold up regulation in the presence of bacterial diet, with 22 in total being differentially expressed, among them apolipophorin III, cecropin, gallerimycin, gloverin, lysozyme, and phenoloxidase inhibiting enzyme. Finally, potential life-history trade-offs were studied, with pupation time and pupal mass being negatively affected in bacteria fed larvae. Conclusion: The presence of bacteria in food, even if non-pathogenic, can
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