Gene structure and expression of the glutathione S-transferase, SiGSTS1, from the red imported fire ant, Solenopsis invicta.

The structural organization and developmental expression of a previously described glutathione S-transferase cDNA from the red imported fire ant, Solenopsis invicta, were elucidated. The gene was previously named Solenopsis invicta, glutathione S-transferase, sigma class no. 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 C(T) 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- and 4.7-fold increased expression of SiGSTS1, respectively, compared with pupae. 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 SiGSTS1 gene sequences between fire ant social forms. Although obviously developmentally expressed, the function of SiGSTS1 in S. invicta is not known.