Solenopsis invicta transferrin: cDNA cloning, gene architecture, and up-regulation in response to Beauveria bassiana infection

Transferrin genes from several insects have been shown to be induced in response to bacterial or fungal infection. We were interested to know whether transferrin genes in the red imported fire ant, Solenopsis invicta, are similarly induced by microbial challenge. Hence, the cDNA and structure of a gene exhibiting significant homology to insect transferrins were elucidated for S. invicta. The cDNA was comprised of 2417 nucleotides, excluding the poly(A) tail, with a large open reading frame of 2106 nucleotides. The predicted translation product of the S. invicta tranferrin (SiTf) gene was a 702 amino acid polypeptide with an estimated molecular mass of 77.3 kDa and a pI value of 5.66, characteristics consistent with transferrin proteins. Comparative analysis of genomic and cDNA sequences revealed that the SiTf gene was comprised of 8 exons. Quantitative real-time PCR was used to examine the expression of SiTf. Expression of SiTf was induced in worker ants exposed to Beauveria bassiana conidia. Autoclave-killed conidia did not elicit a SiTf induction response from worker ants. Genes, like SiTf, responding to microbe attack or infection may provide a unique approach to assist in the discovery of microbial control organisms for the target insect pest.