Abstract
As social insects, termites live in densely populated colonies with specialized castes under conditions conducive to microbial growth and transmission. Furthermore, termites are exposed to xenobiotics in soil and their lignocellulose diet. Therefore, termites are valuable models for studying gene expression involved in response to septic injury, immunity and detoxification in relation to caste membership. In this study, workers and soldiers of the Formosan subterranean termite, Coptotermes formosanus, were challenged by bacterial injection or by no-choice feeding with a sublethal concentration (0.5%) of phenobarbital. Constitutive and induced expression of six putative immune response genes (two encoding for lectin-like proteins, one for a ficolin-precursor, one for the Down syndrome cell adhesion molecule, one for a chitin binding protein, and one for the gram-negative binding protein 2) and four putative detoxification genes (two encoding for cytochrome P450s, one for glutathione S-transferase, and one for the multi antimicrobial extrusion protein), were measured via quantitative real time polymerase chain reaction and compared within and among 1) colonies, 2) treatment types and 3) castes via ANOVA. Eight genes were inducible by septic injury, feeding with phenobarbital or both. Colony origin had no effect on inducibility or differential gene expression. However, treatment type showed significant effects on the expression of the eight inducible genes. Caste effects on expression levels were significant in five of the eight inducible genes with constitutive and induced expression of most target genes being higher in workers than in soldiers.
Highlights
As social insects, termites live in densely populated colonies with a specialized caste system characterized by morphological differentiation and division of labor between worker, soldier and reproductive castes
The genes inducible by xenobiotic and septic injury/immune challenge encoded for CYP15A1, Chitin-binding protein (CBP), two lectin-related proteins (LECT-like, Ctype lectin gene (CLECT)), the Ficolin-2 precursor (FICO-2) and the gram-negative binding protein 2 (GNBP-2)
The gene encoding for glutathione S-transferase (GST) was exclusively induced by 0.5% PB treatment, while the gene for the Multi antimicrobial extrusion protein (MatE) was induced predominantly with the E. coli/P. termitis treatment
Summary
Termites (order Blattaria, formerly Isoptera [1]) live in densely populated colonies with a specialized caste system characterized by morphological differentiation and division of labor between worker, soldier and reproductive castes. Relatedness within termite colonies is usually high since members of all castes are the offspring of a limited number of reproductives (kings and queens [2]). Termites must have evolved strong and versatile defense mechanisms against toxic xenobiotics and pathogens in adaptation to living in densely populated colonies of closely related individuals, with intense social interactions in nest conditions conducive to microbial growth and transmission as well as being exposed to contaminants in the soil, insecticides and a lignocellulosic diet containing secondary metabolites produced by plants. Previous studies using purification and biochemical characterization showed that termites possess multiple cytochrome
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