Why is nature able to mold some phenotypes more readily than others? Investigating the evolutionary constraint of β2 tubulin in Drosophila melanogaster
Sarah R Golconda
While some traits may be able to evolve freely, others may need to await a change in a second trait before they can change themselves. The testis specific beta-2 (β2) tubulin protein, a fundamental component of Drosophila spermtail axonemes, has not evolved in over 60 million years and may exemplify this phenomenon. This study aims to examine what type of evolutionary constraint this protein is experiencing. Previous studies have shown substitutions of the paralogous (related by gene duplication) beta-1 tubulin gene for β2 tubulin disrupts the structure rendering it unable to support reproduction. Here, the substitution of an ortholog, the β2 tubulin gene in a different species which performs the same function, will be examined to see if it can produce a functional sperm in Drosophila melanogaster. Comparing the D. melanogaster β2 tubulin 446 amino acid sequence to various species, the closest relative to D. melanogaster to show a differing sequence was the tsetse fly (Glossina morsitans) which differs in 17 amino acid sites. To determine if tsetse β2 tubulin could replace D. melanogaster β2 tubulin, the tsetse β2 tubulin gene was amplified by PCR, cloned into vectors, and injected in D. melanogaster embryos to be expressed in the spermtail. Its ability to function in place of D. melanogaster β2 will be tested by fertility tests, and viewed under transmission electron microscopy and light microscopy to observe structural similarities and defects from this substitution. If tsetse β2 produces a functional sperm, this could suggest nature is constantly selecting a particular sequence even though other sequences may work, an example of stabilizing selection. Or, if a defective sperm is produced, we can infer co-evolution. Additional changes in the axoneme occurred that allow it to function in G. morsitans but not D. melanogaster.
Graduate Research - Graduate
Mark G Nielsen
Primary Advisor's Department
Stander Symposium poster
"Why is nature able to mold some phenotypes more readily than others? Investigating the evolutionary constraint of β2 tubulin in Drosophila melanogaster" (2017). Stander Symposium Posters. 862.