Identification of putative promoter elements for epsilon glutathione s-transferases genes associated with resistance to DDT in the malaria vector mosquito anopheles arabiensis

Abstract

The purpose of this study was to identify the putative regulatory elements in the promoter region of An. arabiensis strains which differed in susceptibility to DDT and compare with those identified in its sibling An. gambaie. Basal expression level of Epsilon class GSTs (Glutathione S – transferases) GSTe1 gene was 0.512 – 0.658 (95% CI) and GSTe2 0.672 – 1.204 (95% CI) in adults of DDT resistant KGB compared to 0.031 – 0.04 (95% CI) and 0.148 – 0.199 (95% CI) respectively in susceptible MAT strains of An. arabiensis. Induced mean expression of GSTe2 in larvae exposed to DDT for one hour was 0.901 – 1.172 (95% CI) in KGB and 0.475 – 0.724 (95% CI) in MAT strain. In present work, strain specific primers were used to amplify and sequenced the promoter regions of GSTe1 and GSTe2 in the KGB, MAT and field specimens. Computational analysis revealed presence of classical arthropod initiator sequence TCAGT and putative core promoter elements, GC, CAAT, TATA boxes. A typical TATA box was identified at 35 bp upstream Transcription Start Site (TSS) in GSTe1 but was absent in GSTe2. Several binding sites for regulatory elements downstream and multiple polymorphic sites were identified between strains. The role of these regulatory elements in transcription of these genes has not been determined. However, on comparison the 2 bp adenosine indel (insertion/deletion) which was essential in driving the promoter activity in An. gambiae was identified only DDT resistant KGB strain.

Keywords

• Promoter
• glutathione transferases (GSTs)
• insecticide resistance
• DDT
• Anopheles arabiensis