Isolation and characterization of a termite transferrin gene up-regulated on infection.
PCR-based subtractive hybridization was used to isolate genes preferentially expressed in a termite (Mastotermes darwiniensis) following exposure to an entomopathogenic fungus. The subtraction procedure yielded a cDNA clone encoding a putative transferrin that, when sequenced to its ends, is the largest (728 amino acids) for any insect transferrin characterized to date. Cysteines and residues comprising putative iron-binding sites are conserved in both N- and C-terminal lobes, suggesting structural and functional similarity to diferric vertebrate transferrins. A quantitative PCR assay confirmed a significant increase in transferrin expression following infection, suggesting its up-regulation is part of the innate immune response. However, codon-based tests for selection among known insect transferrins revealed only a small proportion of codon-sites positively selected. Thus, unlike certain vertebrate transferrin lineages, no widespread evidence for pathogen-mediated positive selection was detected at this locus.
Thompson
Graham J
GJ
School of Tropical Biology, James Cook University, Townsville, Queensland, Australia. gjt@sfu.ca
Crozier
Y Ching
YC
Crozier
Ross H
RH
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D003062:Codon / Q000235:genetics; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D020049:Isoptera / Q000235:genetics* / Q000276:immunology / Q000382:microbiology; D003904:Mitosporic Fungi / Q000254:growth & development*; D008969:Molecular Sequence Data; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012641:Selection, Genetic; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014168:Transferrin / Q000235:genetics* / Q000276:immunology; D015854:Up-Regulation / Q000276:immunology
D003062:Codon; D018076:DNA, Complementary; D014168:Transferrin