RESUMO
Bacterial insecticides like, Bacillus sphaericus and Bacillus thuringiensis serovar israelensis, have been used for the control of nuisance and vector mosquitoes for more than two decades. For many years, it was assumed that the use of microbial larvicides based on B. sphaericus would not lead to resistance in mosquitoes. However, recent reports have shown that B. sphaericus toxins are not free from this problem. Therefore, the resistance of mosquito populations to be will seriously threaten the sustainability of current mosquito control programme using these microbial insecticides. In the present study, we have characterised a novel protein responsible for resistance development in the filariasis vector of Culex quinquefasciatus. Laboratory selection experiments with B. sphaericus against the larvae were carried out up to 17 generations, and the occurrence of resistance was reported (resistance ratio (RR) at lethal concentration (LC)50 and LC90 = 1,987 and 2,051 folds, respectively). The protein profiles of B. sphaericus-resistant and susceptible population have confirmed with the expression of a new polypeptide (80 kDa) in the resistant strain only. Sequence result revealed that the newly expressed protein was 'hexamerin', and this factor might conceivably be responsible for the inheritance of resistance. This study is therefore valuable for comprehending the underlining factor and management of B. sphaericus resistance problem in mosquito population.
Assuntos
Bacillus/fisiologia , Toxinas Bacterianas/farmacologia , Culex/imunologia , Resistência a Medicamentos/genética , Proteínas de Insetos/genética , Sequência de Aminoácidos , Animais , Bacillus/patogenicidade , Toxinas Bacterianas/biossíntese , Toxinas Bacterianas/isolamento & purificação , Agentes de Controle Biológico , Cruzamento , Culex/genética , Culex/microbiologia , Feminino , Regulação da Expressão Gênica/efeitos dos fármacos , Proteínas de Insetos/biossíntese , Larva/genética , Larva/imunologia , Larva/microbiologia , Masculino , Dados de Sequência Molecular , Controle de MosquitosRESUMO
This study involved cloning and sequencing of the coding regions of all 10 Toll-like receptor (TLR) genes of goat. Goat TLR 1-10 gene sequences revealed a high degree of nucleotide identity with sheep and cattle sequences (>90%) and 75-85% with pig, mouse and human sequences. At the amino acid level, 85-99% similarity was observed with sheep and cattle and 60-85% with pig, mouse and human. TLR9c DNA of goat showed the highest amino acid identity to that of sheep (99%) while TLR8 cDNA showed the lowest identity of 88.7% to that of sheep. Variations were seen in the number of leucine rich repeats (LRRs) of goat TLRs as compared to other ruminant species with maximum differences in the TLR3 gene. Phylogenetic analysis through molecular evolution and genetic analysis (MEGA) software and multi dimensional scaling revealed a high degree of conservation of goat TLRs with those from other species. However when the TIR domain of all the TLRs were compared, goat TLR7 TIR alone showed a high divergence of 19.3 as compared to sheep sequences. This is the first report of the full-length cDNA sequences of all the 10 TLR genes of goats which would be a useful tool for the study of evolutionary lineages and for phylogenetic analysis.