Benzoic acid treated Drosophila melanogaster: the genetic disruption of larval brain stem cells and non-neural cells during metamorphosis

Abstract

It includes the investigation of the toxic effect of the food preservative benzoic acid during the development of Drosophila melanogaster. Male and female flies of Drosophila melanogaster were exposed to various concentrations of benzoic acid (50–3000 mg/l) in culture medium. Total numbers of pupae and young adults generated in each culture tube were counted for 100 h. Ten randomly selected lacto-acetic-orcein stained polytene chromosomes of the third instar larvae of each group were made to assess chromosomal aberrations. Numbers of hemocytes or neuroblasts in third instar larvae with altered nuclear morphologies were scored in 20 randomly selected DAPI stained cells of each group in a single slide. Benzoic acid acted in a dose dependent manner decreasing the population of pupae and young adults but their significant reductions (*p < 0.05, **p < 0.0001) were noticed under the exposure of the flies to ≥ 250 mg/l of this food additive. Developmental inhibition of the flies was accompanied with significant (*p < 0.05, **p < 0.0001) increase in the number of structural abnormalities (ectopic pairing, inversion loops, chromosomal shrinkage, breakage, fusion and asynapsis) of the larval polytene chromosomes due to benzoic acid ≥ 250 mg/l. DAPI staining of the nuclei of larval hemocytes and neuroblasts revealed their significant (*p < 0.05, **p < 0.0001) structural alterations (fragmented, triangular, diffused, spearhead, small globules, etc.) under the dietary exposure of the flies to benzoic acid ≥ 250 mg/l and ≥ 500 mg/l, respectively. Larval Chromosomal abnormalities and damages in the nuclei of the hemocytes and neuroblasts might reflect inhibition of gene expressions that reduced their defensive functions and growth promoting activities. As Drosophila melanogaster possesses substantial similarity with human genome, results of our study emphasize the vulnerability of developing human to this food additive due to maternal dietary intake during pregnancies.