Genetic And Phenotypic Analysis Of Mutations In X Chromosome Of Drosophila Melanogaster And Mutation Of Crop Flies In Fruit Flies

Obesity and diabetes are growing epidemic around the world including China. Studying digestion and absorption is not only important for understanding these diseases and could also provide potential solutions. In order to identify mutations affecting the digestion system, we have performed an EMS mutagenesis screen for the X chromosome in Drosophila. We have generated and screened through 3109 mutant lines. We have further characterized the 55 viable mutants and identified two mutant lines, B86 and A523, which exhibit enlarged crop phenotype. The crop of Drosophila is a bilobed structure capable of extension. Its main function is for temporal storage of ingested liquid food, thus playing an important role in digestion system. To genetically and phenotypically chracterize the enlarged crop mutants, we have conducted a series of experiments. Immunohistochemistry antibody staining experiments indicated that the mutants do not lack the neuronal and muscle systems. The meal volume and the proboscis prints tests on the B86 mutant revealed that enlarged crop phenotype is not due to increased food ingestion. The test with food containing blue dye indicated that enlarged crops are resulted from the failure of clearing up the food due to reduced crop contraction in the mutant animals. Further analysis showed that extracts from the gut, but not the crop of the wild-type animals could rescue the crop contraction defect. These data not only show that the primary defect is in the gut, but also reveals an important feed back system between the crop and the gut. Our work has not only successfully identified the first group of crop contraction mutants, but has also established a powerful model for dissecting molecular, cellular, physiological and genetic mechanisms underlying digestion.