114 Oral - Evolution II
Friday April 08, 5:00 PM - 5:15 PM

Authors:
Sara Guay; Jill O'Toole; Prajal Patel; Geoffrey Findlay

Affiliation: College of the Holy Cross, Worcester, MA, USA

Keywords:
a. genome evolution; a. spermatogenesis

De novo evolved genes arise from previously non-coding DNA regions and are found in only one or a few species. In D. melanogaster, many de novo genes are expressed in the testis, suggesting they may affect male fertility and be subjected to sexual selection. An RNAi and CRISPR knockout screen identified katherine johnson (kj) as one of several putative de novo genes essential for male fertility. Males knocked down or knocked out for kj show a 90% reduction in fertility. Curiously, dissection of mutant testes revealed high numbers of mature sperm in the seminal vesicle. Furthermore, these sperm are transferred to females and enter the seminal receptacle at rates equivalent to sperm of controls. Instead, measurements of egg-to-adult viability showed that the loss of kj causes a fertility defect because of a failure of embryos fathered by kj null males to develop into larvae. Preliminary evidence indicates that embryos fathered by kj nulls initiate mitotic divisions, confirming that kj null male sperm are fertilization competent. However, by 6 hours after fertilization, embryos of kj null males show a significantly reduced rate of developmental progression. To understand the normal function of the KJ protein, and how its loss causes this developmental defect, we constructed a transgenic fly line expressing a 6xHis-tagged kj transgene under the control of its own regulatory sequences. We are currently examining KJ-HA localization and further evaluating the exact stage of embryonic development at which kj null-fathered embryos begin to show defects. While several other putative de novo genes are required for successful sperm production, kj represents the first such gene to our knowledge to be required for the proper use of the paternal genome after fertilization. These findings further establish the ability of newly evolved genes to evolve essential roles in reproduction.