CAREER: Evolution of allosomes and dosage compensation in terrestrial isopods

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Allosomes are chromosomes that determine sex, like the X and Y chromosomes in mammals, and they play crucial roles in the evolutionary biology of species. They have evolved independently in a wide array of species, and while these chromosomes in different groups share many similarities, they also exhibit important differences. Explaining these differences, however, remains difficult. While a strong body of theoretical work makes several important predictions regarding the evolution of allosomes, conclusively testing those predictions has been difficult because most prior research has focused on a small subset of model organisms. This project will address this problem by examining allosomes in terrestrial isopod crustaceans, which include woodlice and pillbugs. Terrestrial isopods are an ideal group for these questions because they exhibit considerable variation in sex-determining mechanisms, but, surprisingly, their genomes have received little attention. The proposed experiments are designed to help explain why these chromosomes are so unique, and how they contribute to vital biological processes. Importantly, this project will also promote diversity in science and create hands-on educational opportunities for students, especially engaging those from under-served groups. First, a project-based genomics course will be developed, and course materials made publicly available. Second, an international summer program will be established that provides undergraduates at SUNY Oswego with opportunities to conduct research abroad. Finally, this work will generate interest in research on campus by allowing incoming freshmen participating in an existing science and math summer 'bridge' camp to take part in interdisciplinary laboratory activities.This project will address key questions on the evolution of allosomes in three species of terrestrial isopod crustaceans (Trachelipus rathkei, Porcellio laevis, and Armadillidium vulgare). This research will (i) identify where changes in sex-determining chromosomes have occurred on the isopod evolutionary tree; (ii) test whether genes on these chromosomes are affected more strongly than autosomal genes by natural selection and genetic drift; and (iii) test whether these species exhibit dosage compensation. A comparative approach using whole genome sequencing and gene annotation via RNA sequencing will be used to address the first two aims. Fluorescent in-situ hybridization (FISH) will also be used to determine homology of allosomes among species. The sex of terrestrial isopods can be experimentally manipulated through surgical ablation or implantation of androgenic glands, which offers a unique opportunity to accurately test for dosage compensation using RNA sequencing in manipulated and unmanipulated individuals of the same and opposite sex. By studying a unique taxonomic group, this research will help examine the generality of patterns suggested by earlier work on allosomes, providing significant insights into these influential components of so many organisms' genomes, including those of humans.