Chlorpyrifos-induced hsp70 expression and effect on reproductive performance in transgenic Drosophila melanogaster (hsp70-lacZ) Bg(9)

Expression of hsp70 in the third-instar larval tissues of transgenic Drosop hila melanogaster (hsp70-lacZ) following dietary exposure to organophosphat e insecticide chlorpyrifos for various time intervals was investigated. Eff ect of the chemical on different developmental stages of the fly was also e valuated by looking at survivorship, hatchability, emergence, fecundity, fe rtility, and reproductive performance. Our results showed that the toxicant evokes profound cytotoxic effect as evidenced by dark blue staining in sal ivary gland, proventriculus, brain ganglia, and midgut in the lowest concen tration of the chemical following 24 and 48 h of exposure. On the other han d, a significant increase (61%) in hsp70 expression in the above larval tis sues was observed in the next higher concentration of the toxicant after 6 h exposure when compared with that of the lowest dose. A further increase i n exposure time caused 100% larval mortality. Similarly, larvae exposed to higher concentrations of the toxicant, exhibited 100% mortality within 1 h of treatment. The insecticide caused a delay in emergence and a severe redu ction in survivorship of the flies in a dose-dependent manner with 100% mor tality within a day of exposure in the highest dosed group. A delay in emer gence by 3 days was evident even in the lowest concentration of the chemica l. A drastic effect of the chemical on hatchability was found in the highes t dosed group with 100% embryonic mortality at post-16 stage of the embryo. Reproductive performance was significantly affected even in the lowest dos ed group. The present study suggests that certain larval tissues of Drosoph ila, a nontarget organism, are vulnerable to chlorpyrifos as evidenced by h sp70 expression. Further, the adverse effect of the toxicant is reflected o n various stages of development of the fly including reproductive performan ce.