(full paper is archived in the Miller Library)
Title: Genetic characterization of a DnaJ-related gene in the colonial ascidian, Botryllus schlosseri.
Student Author(s): Hoang, Tinya Audrey
Faculty Advisor(s): De Tomaso, Anthony
Location: Final Papers Biology 175H
Date: June 2008
Abstract: When two colonies of the tunicate, Botryllus schlosseri, encounter one another, they can either undergo vascular fusion or trigger a rejection reaction that blocks fusion. This interaction is a form of allorecognition. Allorecognition is the ability to recognize self from non-self, and in B. schlosseri, the outcome of the allorecognition process is determined by a single, highly-polymorphic fusion-histocompatibility (FuHC) locus. Another highly polymorphic gene that encodes a DnaJ-related protein has been found in the FuHC locus. The function of this gene is unknown, but the gene is of particular interest because it shows a high level of polymorphism and it may also function in allorecognition. In this study, DnaJ was characterized genetically in order to look for patterns of polymorphism and population structure. The DnaJ gene was sequenced from three California populations and two Woods Hole populations. The sequences showed a high level of polymorphism, with an average of 82.6 polymorphic sites and 33.35 pairwise differences within populations. However, the gene showed no population structure (FST=0) and 100% of the variation was attributable to within population variation. A locus by locus AMOVA showed the least amount of variation was attributable to variation between the California and Woods Hole groups. These results suggest either incomplete lineage sorting or balancing selection for genetic diversity. The high amount of variation in this gene is unprecedented and may indicate a particular role in its function.