determination of glutathione s-transferase e2 region (gste2) in ddt susceptible and resistant anopheles stephensi populations: significance and application of nucleotide and amino acid comparison

glutathione s-transferases (gsts) are a major family of detoxification enzymes which possess a wide range of substrate specificities. interest in insect gsts has primarily focused on their role in insecticide resistance. in this study, following world health organization (who) routine susceptibility test, dna was extracted from specimens of anopheles stephensi collected from the kazeroon district in the fars province as control area and saravan, chabahar, nikshahr districts in sistan and baluchistan province representing major malarious areas under insecticide treatment, in iran. the (glutathion s-transferase epsilon class 2) gste2 gene including exon i and ii and the full sequence of intron i, belonging to an. stephensi specimens were then amplified. the size of the resulting amplicons from the control area and the insecticide treated areas were 492 and 489 bp, respectively. these fragments were purified and then sequenced from both ends. the comparison of total amplified fragments among kazeroon and nikshahr and/or other populations of the sistan and baluchistan province (saravan and chabahar) showed 98% and 97% similarities, including 9-11 nucleotide substitutions, none of which had led to any amino acid change, within these populations. comparison of the nucleotide sequence of gste2 in an. stephensi populations with that of the major world malaria vector, anopheles gambiae revealed 86% homology, while amino acid similarity between the two species was approximately 90%. however, the main difference between the two susceptible and resistance groups in an. stephensi populations is related to their intron sequence with a distance of 8-9%, while this distance among resistance populations from the sistan and baluchistan province varied by approximately 0-4%.  the results obtained from this study serve as a first report and baseline data regarding the structure of gste2 gene, including exon i, exon ii and intron i in susceptible and resistance field specimens of an. stephensi. however, the integration of these data into the malaria control program still remains a challenge in iran and neighboring countries, especially afghanistan and pakistan.