Genomic organization and immune regulation of the defensin gene from the mosquito, Anopheles gambiae

Abstract

The defensin gene from the mosquito, Anopheles gambiae, is present as a single copy per haploid genome. Two exons, encoding a 102 residue preprodefensin, are separated by a 105 bp intron bounded by consensus splice sites. The upstream regulatory sequence includes a TATA box, arthropod initiator and numerous motifs homologous to insect and mammalian immune response elements. This promoter is capable of upregulation by immune challenge in cultured cells and activity is further stimulated by Gambif1, a mosquito Rel protein known to translocate to the nucleus and bind NF-kappa B sites in target promoters. Activity is inhibited by p50, a mammalian Rel protein that competitively binds NF-kappa B sites, and virtually abolished by p40, an avian I kappa B protein that inhibits nuclear translocation.

Supplementation with Abscisic Acid Reduces Malaria Disease Severity and Parasite Transmission

“…57 Coincident with this response were induced levels of defensin and APL1 transcripts, suggesting that ABA signaling regulates NF-κB-dependent gene expression in a manner analogous to that observed in mammalian cells. [58][59][60] The impact of immune genes other than AsNOS, however, remains to be determined. Given the significant reduction in parasitemia in ABA-treated mice by 3-4 days postinfection ( Figures 1B and 4A), ABA may function to promote early inflammatory responses in both hosts to reduce parasite development and then feedback to promote restoration from inflammation as observed in the mouse.…”

Polymorphism at the defensin gene in the Anopheles gambiae complex: Testing different selection hypotheses

“…gambiae defensin sequence (Eggleston et al, 2000; GenBank Accession number: AF063402). A 1.4 Kb region (position 1524-2972 in the published sequence) encompassing the whole transcribed region of defensin as well as 5′ and 3′ non-transcribed flanking regions, was amplified with forward primer Df1524L (5′ GCG GGG TGA ATG TTA TCT CT 3′) and reverse primer Df2972R (5′ ACA ATA AAA GGA ACG CAA GC 3′).…”

“…Defensin is synthesized mainly in the fat body of both larvae and adults and secreted into the haemolymph. It is expressed constitutively at low rates in adults and larvae, but following an infection challenge expression increases dramatically (Richman et al, 1997;Dimopoulos et al, 1998;Eggleston et al, 2000). Sporozoites of Plasmodium gallinaceum (and oocysts to a lower extent) are killed by defensin, but the relevance of this in-vitro study to natural defense needs to be determined (Shahabuddin et al, 1998).…”

“…The promoter region is rich with sequence motifs similar to transcription regulatory elements of insect and mammalian immune response genes. These include binding sites for nuclear factor kappa B, GATA factors, nuclear factor interleukin 6 and interferon consensus elements among others (Eggleston et al, 2000). Induction of defensin transcription can be mediated by Gambif1 , a member of the Rel protein group that mediates transcription regulation of immune response of Drosophila and other insects.…”

Molecular characterization of a defensin in the IZD‐MB‐0503 cell line derived from immunocytes of the insect Mamestra brassicae (Lepidoptera)

“…Various papers have reported the isolation and description of anti-microbial defensins in different insects, but not in Lepidoptera (Chalk et al, 1995;Lowenberger et al, 1995;Cho et al, 1996Cho et al, , 1997Miyanoshita et al, 1996;Richman et al, 1996;Dimopoulos et al, 1997;Gao et al, 1999;Muller et al, 1999;Eggleston et al, 2000). The only data available on defensin in Lepidoptera concern Heliothis virescens, in which the inducible molecule, heliomicin, has been found.…”