Regulation of midgut defensin production in the blood-sucking insect Stomoxys calcitrans

School of Biological Sciences, University of Wales, Bangor LL57 2UW, Wales, UK.
Insect Molecular Biology (Impact Factor: 2.59). 01/2002; 10(6):561-71. DOI: 10.1046/j.0962-1075.2001.00296.x
Source: PubMed


The Stomoxys midgut defensin (Smd) family of genes are exclusively expressed in the anterior midgut of adult flies. Their putative function is protection of the stored bloodmeal from microbial attack. Smd genes are constitutively expressed, up-regulated in response to a bloodmeal and further up-regulated by immune stimulation per os but only in the presence of a bloodmeal not a sugar meal. Smd genes are down-regulated in response to a systemic immune challenge. Smd gene constructs transfected into l(2)mbn cells undertake constitutive expression but are not up-regulated by immune challenge. Electrophoretic mobility shift assays (EMSA) suggest the rel-like sites in the proximal promoter region of Smd genes do not bind midgut factors and so are non-functional.

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    • "Exon–intron genomic structure has been previously described for vector arthropod defensins including those of I. ricinus (Rudenko et al., 2007), O. moubata (Nakajima et al., 2002a,b), Aedes aegypti (Lowenberger et al., 1999) and Anopheles gambiae (Eggleston et al., 2000). Intronless defensins have also been previously reported in I. scapularis (Hynes et al., 2005), D. variabilis (Hynes et al., 2005) and Stomoxys calcitrans (Munks et al., 2001). We found that I. ricinus contains both variants with DefMT3 and DefMT4 containing two introns, and DefMT7 identified as being intronless. "
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    • "We examined expression of these genes in infected and uninfected fleas in a four-day time course as described above. Analysis of these experiments suggest that transcript abundance for defensin, lectin and SERPIN increase in response to feeding (defensin, P < 0.0001; lectin, P < 0.0001 and P < 0.001; serpin, P < 0.018, Table S2), which is consistent with observations for defensin gene expression in the stable fly, Stomoxys calcitrans, and the sheep tick, Ixodes ricinus (Lehane et al., 1997; Munks et al., 2001; Boulanger et al., 2002; Hamilton et al., 2002; Rudenko et al., 2005) (Table S2). Interestingly, none of these genes show a significant treatment effect on gene expression due to infection (Table S2). "
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