Investigating the Function of Selfish Satellite Sequences through Expression Profiling in the Jewel Wasp testis

• Main Author: Brody, Hanna F
• Format: Others
• Published: Scholarship @ Claremont 2014
• Subjects: Biology; Chromosome; Genetics; Molecular; DNA; Cell and Developmental Biology
• Online Access: http://scholarship.claremont.edu/scripps_theses/391; http://scholarship.claremont.edu/cgi/viewcontent.cgi?article=1398&context=scripps_theses

Highly repetitive, non-protein-coding satellite DNAs are ubiquitous among eukaryotes. In some cases, these sequences make up entire chromosomes, and as much as half of most eukaryotic genomes. Currently, very little is known about the possible roles of satellite DNAs in genome function. In this study I have begun to address the critical issue of satellite DNA function through two different approaches. First, I have used quantitative-RTPCR to address transcriptional levels of three different satellites known to express transcripts in the male germ tissue of the jewel wasp, Nasonia vitripennis. Two of these satellites are located uniquely on a supernumerary (‘extra’), non-essential chromosome known as PSR (for paternal sex ratio), while the third satellite is located on a normal chromosome. These experiments are suggesting that all three of these satellites are not expressed at consistent levels across individuals, arguing against a functional role. Instead, this finding supports the longstanding view of satellites as truly parasitic agents, and their expression may be artifactual. Second, I initiated experiments to determine if conditional mutagenesis through RNA interference is possible; development of this method in the wasp male germ line would be an invaluable tool for further assessing the function of satellite expression. Specifically, I tested the ability of RNAi to deplete the wasp ortholog of cannonball, which plays a testis-specific role in sperm formation in other insects. These experiments resulted in a trend of lower cannonball levels, although non-significant, in RNAi-treated males. These findings suggest that RNAi may be a potentially effective method for conditional mutagenesis in this tissue, but will require further optimization.