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Genetic and physiological parameters associated with cadmium toxicity in Drosophila melanogaster
Abstract:
Two strains of Drosophila melanogaster represent the extremes in resistance and sensitivity to the lethal effects of CdCl2. The strain containing the mutations vermilion and brown (v; bw) and the strain Austin had LC50's of 3.3 and 1.3 mM CdCl2, respectively. The three major chromosomes from these two strains were assorted genetically into the six possible combinations. The measured LC50's for CdCl2 for these six genotypes fell into two groups according to the X chromosome; those containing the X chromosome from v; bw had LC50's 0.5-1.0 mM greater than those in which the X chromosome was from Austin. Since the parent strains differed by 2 mM, we suggest that the X chromosome is a major, but not the sole, site of genes to produce resistance to CdCl2. When 109Cd was in the diet the uptake by v; bw and Austin over 2 days was the same. After 4 days of uptake, the Austin strain excreted the 109Cd five times faster than v; bw but the six genotypes did not differ appreciably in excretion rate from one another and resembled the sensitive parent Austin more than the resistant one. Thus a second process is indicated that distinguishes resistance to CdCl2 that apparently is not associated with the X chromosome.
Insights
The X chromosome plays a key role in cadmium chloride (CdCl2) resistance in Drosophila melanogaster, but it is not the only factor. Further research indicates a second, unlinked genetic process also influences CdCl2 resistance.
Area of Science:
- Genetics
- Toxicology
- Drosophila research
Background:
- Cadmium chloride (CdCl2) exhibits lethal effects on organisms.
- Drosophila melanogaster strains display varying sensitivities to CdCl2.
Purpose of the Study:
- To investigate the genetic basis of CdCl2 resistance in Drosophila melanogaster.
- To identify chromosomal locations and mechanisms contributing to CdCl2 resistance.
Main Methods:
- Genetic analysis of Drosophila melanogaster strains with extreme CdCl2 resistance and sensitivity.
- Assortment of major chromosomes to create six distinct genotypes.
- Measurement of lethal concentrations (LC50) for CdCl2.
- Radioisotope tracing (109Cd) to assess metal uptake and excretion.
Main Results:
- The X chromosome significantly influences CdCl2 resistance, with the resistant strain's X chromosome conferring higher LC50 values.
- Uptake of 109Cd was similar between resistant and sensitive strains.
- Excretion rates differed, with the sensitive strain excreting cadmium faster, suggesting a non-X-linked mechanism.
Conclusions:
- The X chromosome is a major determinant of CdCl2 resistance in Drosophila, but not the sole contributor.
- A second, independent genetic factor likely influences cadmium excretion and overall resistance.
- Further research is needed to elucidate the non-X-linked mechanisms of CdCl2 resistance.