College Honors Program

Investigating the function and evolution of two putative de novo evolved genes essential for Drosophila melanogaster fertility

Date of Creation

5-17-2024

Document Type

Campus Access Only

Department

Biology

First Advisor

Geoffrey Findlay

Abstract

De novo evolved genes emerge from previously non-coding DNA regions. Many de novo genes in Drosophila melanogaster show preferential expression in the testes, suggesting potential functions in fertility. RNA interference and CRISPR knockout experiments identified two such genes, goddard and katherine johnson (kj), as essential for male fertility. goddard null males fail to produce mature sperm. kj mutants produce and transfer normal levels of sperm, but have ~90 percent lower fertilization rates. To identify functionally important regions of the Goddard protein, we tested the ability of orthologous goddard genes from other Drosophila species to restore fertility in goddard null males. Interestingly, while most orthologs showed the same localization patterns as Goddard from D. melanogaster, fertility rescue did not correlate with evolutionary distance. To investigate how kj may contribute to fertilization ability, we created transgenic D. melanogaster flies knocked out for endogenous kj and containing either of two tagged kj sequences, an N-terminal HA tag or an N-terminal GFP tag. Tagged KJ protein is present in spermatid nuclei through the canoe stage of nuclear condensation but is not detected in the needle stage of mature sperm, suggesting that KJ may play a role in how mature sperm are shaped. Since nuclear shape may be important for sperm entry into the egg, loss of KJ function may result in improper shaping of sperm and thus impair sperm fertilization ability. These findings show how newly evolved genes develop essential roles in reproduction.

Comments

Reader: Robert Bellin

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