Route of entry and mode of action of protein in the larvae and pupae of mosquitoes exposed to the toxin of Pseudomonas fluorescens Migula
The aim of the study is to find out the route of entry and mode of action of protein in the larvae and pupae of mosquitoes exposed to the toxins. Laboratory bioassay of the crude proteins was also carried against 4th instar larvae and pupae of A. stephensi Liston, Cx. quinquefasciatus Say and Ae. aegypti (L) and in vivo-binding of FITC conjugated mosquitocidal protein into the larvae and pupae of Cx. quinquefasciatus to study the route of entry. Among the three species of mosquitoes, the larvae and pupae of An. stephensi were more susceptible to the crude protein than those of Cx. quinquefasciatus or Ae. aegypti. Probit regression analysis was carried out to calculate the LC50 values for the larvae of An. stephensi, Cx. quinquefasciatus and Ae. aegypti of three mosquitoes species were 1.6, 2.29, and 4.9 and LC90 values for the larvae of three mosquitoes species were 7.0, 7.7 and 14.35 respectively. The LC50 and LC90 values for the pupae of three mosquito’s species were 0.18, 0.33, 0.93 and 0.53, 0.83, 2.8 respectively. The LC50 and LC90 values for the crude and pure protein against the pupae of Cx. quinquefasciatus were 0.33, 0.031 and 0.85 and 0.086 respectively. The FITC conjugated mosquitocidal protein was found binding to the head, thorax and midgut regions of larvae and pupae of Cx. quinquefasciatus. The present study revealed that the chitin is the target substrate for the mosquitocidal toxin and leads to degradation of peritrophic membrane of the mosquito species and thereby supports the proposed mode of action for mosquitocidal metabolites. This study provides the first evidence with a novel concept that the mosquitocidal metabolite hydrolysis various substrates there by degrading the cuticular region of the mosquito.