CAREER: Targeted genome elimination by a selfish B chromosome in the jewel wasp Nasonia vitripennis

Claremont Mckenna College, Claremont CA

Investigators

Abstract

This project seeks to understand how selfish genetic elements can alter patterns of genetic inheritance at the molecular level. In the jewel wasp, Nasonia vitripennis, a special so-called B chromosome can induce elimination of all the genes inherited from the paternal parent, producing progeny that contain genes just from the mother's genome, along with the B chromosome itself. How this happens is not clear, but this research should provide important clues that might shed light on how selfish DNA elements promote their own propagation in this and other systems. The project will provide training opportunities for undergraduate students and a postdoctoral researcher. Data generated by the project will be used for original research in a new module to be incorporated by the PI into his developmental biology course; the new course will provide the students with experience in both bioinformatics and fluorescence microscopy approaches. The course module will also be incorporated into the biology curricula of two-year colleges in the Los Angeles area. A scientific outcome of the collective efforts of students in these courses will be to establish a new gene expression resource for the research community. Educational outcomes of engaging students in research are expected to include: increased student interest and conceptual understanding of scientific inquiry; higher rates of retention as biology majors; higher academic performance of two-year college students in subsequent upper-level biology courses; and enhanced rates of transfer of students from two- to four-year institutions. Normally, all parts of the eukaryotic genome function in unison to insure normal organismal function. However, in some cases, individual chromosome regions and even whole chromosomes can alter normal reproductive processes in order to become transmitted at abnormally high levels to new progeny at the expense of the genome as a whole. Currently little is known about how this condition, known as intragenomic conflict, occurs at the molecular level. This project will employ modern molecular and cytological methods to investigate how a supernumerary ("extra") B chromosome completely destroys the paternal genome in the jewel wasp Nasonia vitripennis, thereby achieving near-perfect B chromosome transmission. Preliminary data suggest that genome elimination is targeted through a mechanism involving differences in the configuration of chromatin associated with the paternal vs. maternal genomes. Experimental approaches will test this hypothesis as follows: (1) define how the B chromosome and the paternal genome differ in their chromatin states when the paternal genome undergoes elimination; (2) determine whether and how the B chromosome initially alters the chromatin state of the paternal genome; and (3) explore the role of novel B chromosome-expressed non-coding RNAs as potential effectors of paternal genome elimination. This research will provide insights into unknown aspects of chromatin dynamics, address whether genome elimination by the selfish B element is mechanistically distinct from genome elimination events in other organisms, and help to discern how intragenomic conflict can arise from a functionally unified genome.