Cloning and overexpression of transferrin gene from cypermethrin-resistant Culex quinquefasciatus

The complete sequence of transferrin has been cloned from cypermethrin-resistant strain of Culex pipiens quinquefasciatus (Cr-Q strain). Quantitative RT-PCR analysis indicated that the transferrin transcription level was 12.6 times higher in Cr-C strain than in susceptible strain at 4th instar larvae. The transferrin expression was also found to be consistently higher throughout the life cycle of Cr-C strain. A protein of predicted size 19.6kDa has been detected by Western blotting in transferrin-transfected mosquito C6/36 cells. These transferrin-transfected cells also showed enhanced cypermethrin resistance compared to null-transfected or plasmid vector-transfected cells as determined by methyl tritiated thymidine(³H-TdR) incorporation. These results indicate that transferrin is expressed at higher levels in Cr-Q strain, and may confer some insecticide resistance in Culex pipiens quinquefasciatus.