Affiliations: * BIOTEC Central Research Unit, National Center for Genetic Engineering and Biotechnology, 113 Phaholyothin Road, Klong 1, Klong Luang, Pathumthani 12120, Thailand
** National Institute of Health, Department of Medical Sciences, Ministry of Public Health, 88/7 Tiwanon Road, Nonthaburi 11000, Thailand
*** Department of Biochemistry and Molecular Biology & Genetics, Mahidol University, Rama VI Rd, Bangkok, 10400 Thailand
**** Department of Entomology, University of California, Riverside, CA 92521, U.S.A.
Source: Presented in the 4th International Congress of Vector Ecology (SOVE),Reno, Nevada, U.S.A., 2 – 7 October 2005
Application of Bacillus sphaericus (BS) strain 2362 in low-income communities in Thailand rapidly triggers higher than 100,000-fold resistance of Culex quinquefasciatus to the bacteria. In this study, DNA sequences of a-glucosidase gene, which encodes for a putative receptor for the bacterial binary toxin, from both BS-susceptible and resistant Cx. quinquefasciatus larvae were analyzed. The gene from both mosquito larvae was encoded in a 1,911-bp DNA fragment and consists of 3 short introns. When mRNA was used as a template in RT-PCR, a 1,743-bp DNA fragment encoding for 580 amino acids was obtained. Comparison of a-glucosidase gene from susceptible and resistant larvae reveals 2 groups of the gene. The first group consists of Ala141 ® Asp, Thr172 ® Gln, and Trp339 ® Stop. The second group shows several point mutation; Asp29 ® Asn, Ala 95 ® Asp, Ser113 ® Ala, Thr172 ® Gln, Tyr369 ® Asp, and Gly541 ® Ser. Therefore, resistance mechanism of Cx. quinquefasciatus against B. sphaericus might include both point mutation and the mutations that leads to premature termination of translation.