Transformation of fruit flies: How transposons helped decode the fruit fly genome

Genetic transformation of Drosophila with transposable element vectors. Rubin GM, Spradling AC. Science. 1982 Oct 22;218(4570):348-53. doi: 10.1126/science.6289436.

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The completion of the Drosophila melanogaster genome sequence in 2000 was a ground-breaking discovery in the field of genetics, taking over nine years to be completed. Join us today to hear Daisy the Drosophila explain how scientists uncovered a gene transfer tool which would help them understand a quarter of the vital Drosophila genes!

You may think of Drosophila as simple fruit flies, but discovering a reliable and efficient method for molecular genetic modifications to the genome proved more difficult than expected. This all changed when strange genetic traits were observed in the progeny of specific crosses of Drosophila. This phenomenon was termed ‘hybrid dysgenesis’ with scientists believing that a DNA sequence called P elements introduced from the male Drosophila was responsible. They believed that these P elements shared similar properties to the transposable elements discovered by Barbara McClintock in maize decades prior.

The discovery of P element action gave scientists Gerald M. Rubin and Allan C. Spradling the opportunity to harness the transposable nature of this DNA sequence for a means of gene transfer, enabling transformation of fruit flies. In their experiment, they attempted to prove they could restore wildtype red eye colour in the progeny of Drosophila which had the mutant brown eye colour phenotype. To do this, they injected their wildtype gene with the P element into Drosophila embryos and waited to see if their proposed method of gene transfer was in fact successful. Their results showed that 18 out of 40 of their injected embryos produced progeny which had restoration of their red eye colour. This showed that their method of gene transfer was a success and it proved to be even more useful to help decode the genomic sequence of the fruit fly. They used P-element gene transfer to tag thousands of genes in Drosophila by inserting mutations into genes targeted by specifically created P elements. The discovery of P-element mediated gene transfer in Drosophila has played a vital role in understanding its complex genome sequence, paving the way for the expansion of knowledge on other organisms and their sequences.

Creator: Renee Chen

References:
Bingham PM, Kidwell MG, Rubin GM. The molecular basis of P-M hybrid dysgenesis: the role of the P element, a P-strain-specific transposon family. Cell. 1982;29(3):995-1004.
Karess RE, Rubin GM. Analysis of P transposable element functions in Drosophila. Cell. 1984;38(1):135-146.
McClintock B. The origin and behavior of mutable loci in maize. Proc Natl Acad Sci U S A. 1950;36(6):344-355.
O'Hare K, Rubin GM. Structures of P transposable elements and their sites of insertion and excision in the Drosophila melanogaster genome. Cell. 1983;34(1):25-35.
Rubin GM, Spradling AC. Genetic transformation of Drosophila with transposable element vectors. Science. 1982;218(4570):348-353.
Spradling AC, Rubin GM. Transposition of cloned P elements into Drosophila germ line chromosomes. Science. 1982;218(4570):341-347.
Spradling AC, Stern D, Beaton A, Rhem EJ, Laverty T, Mozden N, Misra S, Rubin GM. The Berkeley Drosophila Genome Project gene disruption project: Single P-element insertions mutating 25% of vital Drosophila genes. Genetics. 1999;153(1):135-177.