Originally published as Genetics Published Articles Ahead of Print on January 21, 2007.

Genetics, Vol. 176, 309-325, May 2007, Copyright © 2007
doi:10.1534/genetics.106.060897

Concerted Evolution Within the Drosophila dumpy Gene

Amber Carmon*,1, Marian Wilkin{dagger},1, Jana Hassan*, Martin Baron{dagger} and Ross MacIntyre*,2

* Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853 and {dagger} School of Biological Sciences, University of Manchester, Manchester M139PT, United Kingdom

2 Corresponding author: Department of Molecular Biology and Genetics, Cornell University, 409 Biotechnology Bldg., Ithaca, NY 14853.
E-mail: rjm18{at}cornell.edu

We have determined by reverse Southern analysis and direct sequence comparisons that most of the dumpy gene has evolved in the dipteran and other insect orders by purifying selection acting on amino acid replacements. One region, however, is evolving rapidly due to unequal crossing over and/or gene conversion. This region, called "PIGSFEAST," or PF, encodes in D. melanogaster 30–47 repeats of 102 amino acids rich in serines, threonines, and prolines. We show that the processes of concerted evolution have been operating on all species of Drosophila examined to date, but that an adjacent region has expanded in Anopheles gambiae, Aedes aegypti, and Tribolium castaneum, while the PF repeats are reduced in size and number. In addition, processes of concerted evolution have radically altered the codon usage patterns in D. melanogaster, D. pseudoobscura, and D. virilis compared with the rest of the dumpy gene. We show also that the dumpy gene is expressed on the inner surface of the micropyle of the mature oocyte and propose that, as in the abalone system, concerted evolution may be involved in adaptive changes affecting Dumpy's possible role in sperm–egg recognition.