Cloning and characterization of prophenoloxidase A3 (proPOA3) from Culex pipiens pallens

Abstract The prophenoloxidase subunit A3 ( proPOA3 ) gene was cloned from Culex pipiens pallens , which had an open reading frame of 2061 bp encoding a putative 686 amino acid protein. The deduced amino acid sequence shares 98% with proPOA3 from Culex quinquefasciatus . ProPOA3 is expressed at all developmental stages of C. pipiens pallens . Significant negative correlation was observed between proPOA3 expression and deltamethrin resistance in resistant C. pipiens pallens . Furthermore, proPOA3 expression levels were significantly lower in deltamethrin-resistant mosquitoes than in susceptible mosquitoes collected at four locations in Eastern China. However, we did not find any substantial change in proPOA3 expression in field-collected resistant Anopheles mosquitoes. Moreover, overexpressing proPOA3 in C6/36 cells led to more sensitivity to deltamethrin treatment. In laboratory and field-collected resistant C. pipiens pallens , a valine to isoleucine mutation (769G>A) and two synonymous mutations (1116G>C and 1116G>A) were identified in proPOA3 . In addition, the mutation frequency of 769G>A and 1116G>C increased gradually, which corresponded with raised deltamethrin resistance levels. Taken together, our study provides the first evidence that proPOA3 may play a role in the regulation of deltamethrin-resistance in C. pipiens pallens .