WHAT GENE(S) SPECIFY EGG SIZE VARIATION AMONG DROSOPHILA SPECIES?

Abstract

There exists great variation in egg morphology among Drosophila species. However, little is known about the mechanism(s) that specify egg shape and size of Drosophila. Some studies suggest that pre-embryonic gene expression might influence egg size variability. Drosophila sechellia is known to produce much larger eggs, and Drosophila sechellia is also known to produce fewer eggs compared to its sister species D. mauritiana, D. melanogaster, and D. simulans. This egg size difference presents an opportunity to leverage the arsenal of genetic tools available among these species to understand the molecular bases of egg size variation. Here, we study a collection of interspecific genetic introgression that have a mostly D. sechellia genomic background with a small segment of D. mauritiana genomic material. We collected, measured, and analyzed egg length data and discovered that 3Q1(A) was one of the three introgression lines had an effect on egg length size. 3Q1(A), produces much smaller eggs compared to D. sechellia pure species. To identify the gene(s) that causes these differences in egg length, we sequenced the genome of 3Q1(A) and compared it to the genomes of the parental D. sechellia and D. mauritiana lines used to create the introgression. We have identified the limits of the D. mauritiana genetic material within the 3Q1(A) introgression region and we have performed functional genetic tests of these candidates using resources available in D. melanogaster and identified genes that have an effect on egg length. We anticipate that our results will provide direction for future developmental studies of oogenesis among these species.