RESUMO
The present study aims to characterize the Cry2Ad toxin protein isolated from a Bacillus thuringiensis strain, BRC-HZP10, which have a potential insecticidal activity against larvae of the diamondback moth, Plutella xylostella (L.). The crude Bt toxin proteins were isolated and purified by cation exchange chromatography, then equilibrated with 0.2 M NaOH buffer, pH 4.0, followed by ultraviolet detection at 280 nm and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A refined Cry2Ad toxin protein with 88.34% purity was eventually obtained and used for a bioassay by feeding it to P. xylostella. The results showed conspicuous insecticidal activity towards P. xylostella with 50% lethal concentration of 6.84 µg/mL and 95% confidence interval of 5.77-7.91 mg/mL. At a concentration of 16.38 µg/mL, the intake of Cry2Ad protein significantly shortened the oviposition period and larval developmental duration, but significantly reduced the fecundity and egg hatchability of the population compared to those of control (without treatment with Cry2Ad protein) (P < 0.05). These results indicate that the Cry2Ad protein plays an effective role in controlling the population of P. xylostella.
Assuntos
Bacillus thuringiensis/química , Proteínas de Bactérias/isolamento & purificação , Proteínas de Bactérias/toxicidade , Endotoxinas/isolamento & purificação , Endotoxinas/toxicidade , Proteínas Hemolisinas/isolamento & purificação , Proteínas Hemolisinas/toxicidade , Inseticidas/toxicidade , Mariposas/crescimento & desenvolvimento , Testes de Toxicidade , Animais , Toxinas de Bacillus thuringiensis , Cátions , Cromatografia por Troca Iônica , Eletroforese em Gel de Poliacrilamida , Mariposas/efeitos dos fármacos , Padrões de Referência , Análise de Regressão , Soroalbumina Bovina/metabolismo , Fatores de TempoRESUMO
Molecular evidence that suggests the possible role of the ixodid tick, Haemaphysalis longicornis and its eggs in the transmission of equine Babesia caballi parasites is presented herein. Using polymerase chain reaction (PCR) to assay for DNA in parasites, presumably acquired by ticks that were allowed to feed on splenectomized-SCID mice, experimentally exposed to in vitro-cultivated B. caballi, we have obtained positive bands that corresponded to the expected B. caballi-specific 430bp gene fragment in 50% of female ticks used, and in 75 and 25% of eggs and larval progeny, respectively. Also, parasite DNA was detected in ticks, eggs and larvae as late as the 16th to the 20th day post-host infestation. Present findings support to the potential role of H. longicornis in the transmission of B. caballi parasites. Its capability, however, to successfully transmit the infection to horses under natural conditions in the field needs to be further ascertained. To our knowledge, this is the first documented study incriminating H. longicornis as a most and likely biological vector of equine babesias.