Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 4, 2005
Publication Date: April 1, 2006
Citation: Valles, S.M., Perera, O.P., Strong, C.A. 2006. Gene Structure and Expression of the Glutathione S-transferase, SiGSTS1, from the Red Imported Fire Ant, Solenopsis invicta. Archives of Insect Biochemistry and Physiology. 61: 239-245. Interpretive Summary: The red imported fire ant was introduced into the United States in the 1930s and currently infests about 300 million acres. It causes significant economic losses in livestock and agricultural production and poses a serious threat to human health. Annually, 50% of people in infested areas are stung, occasionally with fatal consequences. Although insecticides have been used to control fire ants for decades, very little research has been conducted on their detoxification systems. Scientists at the Center for Medical, Agricultural and Veterinary Entomology have elucidated the genetic architecture and developmental expression of the first glutathione transferase gene in the imported fire ant. Understanding insecticide disposition in fire ants is crucial to the development of insect-specific insecticides and possibly novel methods of ant control.
Technical Abstract: The structural organization and developmental expression of a previously described glutathione S-transferase cDNA from the red imported fire ant, Solenopsis invicta, was elucidated. The gene was previously named Solenopsis invicta, glutathione S-transferase, sigma class, #1 (SiGSTS1). Comparison of genomic and cDNA sequences showed that the gene was comprised of 5 exons and 4 introns. All of the introns possessed the 5’GT and 3’AG splicing sites characteristic of eukaryotes. The comparative CT method of quantitative-polymerase chain reaction was employed to examine the developmental expression of the SiGSTS1 transcript in monogyne and polygyne S. invicta. Polygyne queen and late instars exhibited 3.5-fold and 4.7-fold increased expression of SiGSTS1, respectively, compared with pupae. Expression in early instars (13.1-fold) and workers (9.6-fold) exhibited the highest, and statistically significant, levels of expression of all polygyne developmental stages examined. A similar pattern of expression was observed for the monogyne social form. However, the queen showed the lowest expression level, followed by pupae (1.2-fold), late larvae (5.8-fold), early larvae (9.4-fold) and workers (10.1-fold). No differences were observed in the SiGSTS1gene sequences between fire ant social forms.