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Ranjan Ganguly F231 Walters Life Sciences |
Keywords:
Gene structure, Gene regulation, Cis-regulatory elements, Trans-regulatory factors, Cytochrome P450 genes, Insecticide resistance, Drosophila genetics, DNA microarray
Research Area:
Molecular and Genetic basis of Cytochrome P450 gene regulation and Cytochrome P450-mediated insecticide resistance.
Description of Research:
The major focus of my laboratory is to understand the molecular and genetic basis of insecticide resistance. It is a common knowledge that insects cause lot of damages to the society by destroying crops in the fields and carrying germs for various diseases. Hundreds of different chemicals have been synthesized to control insects. However, the battle seems to be never ending because eventually insects become resistant to these chemicals.
Most resistance phenomena are genetically determined and mediated by a group of microsomal enzymes called cytochrome P450 monooxygenases or CYPs. CYPs comprise a large multigene family and they are found in all living organisms. These enzymes are involved in the degradation of various kinds of cellular metabolites and exogenous chemicals or xenobiotic compounds. CYPs are the enzymes that also metabolically activate procarcinogens into carcinogens and promutagens into mutagens. In insects, CYPs confer metabolic resistance to various kinds of insecticides. It has been well documented that resistant insects have higher levels of one or more CYPs compared to the susceptible insects, and resistant insects can be rendered susceptible by inhibiting their CYPs. However, it is not known how insects control their CYP levels. The long-term goal of our research is to understand the molecular and genetic mechanisms that regulate CYP levels and help evolve insecticide resistance in insects.
We are using Drosophila as a model insect, and Cyp6a2 and Cyp6a8 as prototype Cyp genes to understand the mechanism of insect CYP gene regulation. It has been shown that CYP6A2 can metabolize diazinon and DDT in heterologous expression system. We have shown that the level of expression of both these genes is much higher in the resistant strains compared to the susceptible ones. We have discovered that the third chromosome carries a repressor gene(s) that downregulates 2nd chromosome-linked Cyp6a2 and Cyp6a8 genes. Recent experiments suggest that the repressor locus is mutant in the strains that are overproducers of CYP6A2 and CYP6A8 enzymes. Our objectives are to map and clone the repressor gene, purify the repressor protein and understand how does the repressor regulate Cyp gene expression in Drosophila. Recently, Drosophila genome has been sequenced completely and analysis of the sequence data suggests that there are 90 Cyp genes in Drosophila. We also plan to use DNA microarray technique to understand whether all Cyp genes in Drosophila are controlled by a common regulatory mechanism. The results of these investigations may help understand Cyp gene regulation in economically important insects in future.
Selected Publications:
- Boake CRB, McDona K, Maitra S and Ganguly R (2003) Forty years of solitude: life-history divergence and behavioral isolation between laboratory lines of Drosophila melanogaster. J. Evol. Biol. 16:83-90.
- Maitra S, Price C and Ganguly R (2002) Cyp6a8 of Drosophila melanogaster: Gene structure, and sequence and functional analysis of the upstream DNA. Insect Biochem. Mol. Biol 32: 859-870.
- Maitra S, Dombrowski SM, Basu M, Raustol O, Waters LC and Ganguly R (2000) Factors on the third chromosome affect the level of Cyp6a2 and Cyp6a8 expression in Drosophila melanogaster. Gene 248:147-156.
- Dombrowski SM, Krishnan R, Witte M, Maitra S, Diesing C, Waters LC and Ganguly R (1998) Constitutive and barbital-induced expression of the Cyp6a2 allele of a high producer strain of CYP6A2 in the genetic background of a low producer strain. Gene 221:69-77.
- Maitra S, Dombrowski SM, Waters LC and Ganguly R (1996) Three second chromosome-linked clustered Cyp6 genes show differential constitutive and barbital-inducible expression in DDT-resistant and susceptible strains of Drosophila melanogaster. Gene 180:165-171.
- Krishnan R and Ganguly R (1995) A 3.5-kb DNA fragment contains the cis-regulatory elements for retina-specific expression and partial male-specific hypertranscription of the X1R-linked Arrestin B (ArrB) gene of Drosophila miranda. Gene 160:185-190.
- Ray K and Ganguly R (1994). Organization and expression of the Drosophila melanogaster G protein gamma subunit gene (D-Gg1). Gene 148: 315-319.
- Swanson KD and Ganguly R (1992) Characterization of a Drosophila melanogaster gene similar to the mammalian genes encoding tyrosine/tryptophan activator and protein kinase C inhibitor proteins. Gene 113: 183 - 190.
- Ray K and Ganguly R (1992) The Drosophila G protein gamma subunit gene (D-Gg1) produces three developmentally regulated transcripts and is expressed in the central nervous system. J. Biol. Chem. 267: 6086 - 6092.
- Ganguly R Swanson KD, Ray K and Krishnan R (1992) A BamHI repeat is predominantly associated with the degenerating neo-Y chromosome of D.miranda but absent in D.melanogaster genome. Proc. Natl. Acad. Sci., USA 89: 1340 -1344.
- Krishnan R, Swanson KD and Ganguly R. (1991) Dosage compensation of a retina-specific gene in Drosophila miranda. Chromosoma. 100: 123-131.