Alternative splicing and developmental regulation of glutathione transferases in Culex quinquefasciatus Say

We identified and characterized an alternatively spliced gene that encodes delta glutathione transferases (GSTs) (CqGSTdelta1) in Culex quinquefasciatus.CqGSTdelta1 contains six exons that produce four mature GST transcripts, each sharing exons 1 and 2, and containing a different exon 3 variant (exons 3A, 3B, 3C, or 3D). The exon/intron composition of CqGSTdelta1 showed high similarity with the delta GST genes adgst1AS1 and aggst1α identified from Anopheles dirus and Anopheles gambiae, respectively. Thus, alternative splicing in delta GSTs possibly occurred before the divergence of the Anopheles and Culex mosquitoes. Gene expression analysis clarified that CqGSTd1-1 and CqGSTd1-4 are constitutively and highly expressed in the larvae, pupae, and adults, while CqGSTd1-2 and CqGSTd1-3 are suppressed at all developmental stages, except the pupal stage. Thus, at least two factors may be associated with the transcriptional regulation of these genes. Microarray analysis revealed that none of the genes were overexpressed in a DDT-resistant Cx. quinquefasciatus strain.