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Thesis Examination: MSc Student Gurman Grewal

Thu. Nov. 28 09:00 AM - Thu. Nov. 28 11:00 AM
Contact: Dylan Armitage
Location: Room 1RC028

Gurman Grewal - MSc Student in Bioscience, Technology, and Public Policy 


Drosophila females mate with multiple males leading to sperm competition within the female reproductive tract. In such a scenario, the last male to mate with the female fathers the majority of the progeny. However, if females mate with males from different species, the conspecific male father the majority of the progeny regardless of the mating order in a process known as conspecific sperm precedence (CSP). Previously, CSP candidate genes between D. simulans and D. mauritiana as well as genes involved in the maintenance of last male sperm precedence have been show to cluster in the 89B cytogenetic map position. Further, there is some evidence to suggests that genes that mediate CSP can also influence intraspecific sperm competition. Here I tested 12 genes located within the 89B region that are highly expressed in the testes and/or accessory glands for their role in intraspecific sperm competition using D. melanogaster. Testes-specific knockdown of Manf, bor, or CSN5 resulted in more first male sperm being present in sperm storage organs of doubly mated females. Conversely, there were fewer first male sperm in sperm storage organs of females for whom the second mating was with males that had CG14891 or Mst89B knocked down in their testes. The apparent poor displacement by males with the knockdown of Manf, bor, or CSN5 can be attributed to differences in fertility as knocking down the latter two genes led to complete sterility and males with knockdown of Manf fathered only 31% of the progeny when compared to females mated to wild-type males. Males with a knockdown of Mst89B also only fathered 6.5% of the expected progeny (compared to wild-type males). Given that males with a Mst89B knockdown appeared as if they are better displacers of resident sperm, further research needs to be conducted to evaluate whether these males are truly better at displacing sperm or if other dynamics of sperm storage and/or transfer may be the cause of the observed results. Nonetheless, my results suggest an essential role of bor and CSN5 in D. melanogaster fertility and possibly a divergent role of Mst89B in terms of displacement and fecundity.