Meeting Abstract

2.3  Sunday, Jan. 4  Heterogeneity of genome content through the life cycle of Foraminifera PARFREY, Laura Wegener*; KATZ, Laura A.; Univ. of Massachusetts – Amherst; Smith College lwegener@nsm.umass.edu

Genomes are dynamic across the tree of eukaryotes. Animals, plants, and numerous microbial lineages demonstrate widespread variation of genome content within individuals during a life cycle and within populations. Foraminifera a lineage of marine amoebae provide a unique opportunity to study genome dynamics as they have a complex life cycle that alternates between diploid and polyploid phases. As a proxy for genome content, we assess the heterogeneity of nuclear size within two taxonomically diverse species, Allogromia laticollaris and Ammonia beccarii, at different life cycle stages using DAPI staining of nuclei. We find that nuclear size varies nearly 150 fold across life cycle stages, and five fold within a life cycle stage in the population in A laticollaris. The nuclei of A. beccarii vary 30 fold between life cycle stages, and marked heterogeneity exists between nuclei within a single cell. We hypothesize that variation in nuclear size can be explained by a combination of variable levels of polyploidy and amplification of ribosomal DNA. We are measuring the contribution of ribosomal DNA amplification through fluorescence in situ hybridization and quantitative PCR. We also map genome characters elucidated in this study onto a phylogeny of eukaryotes in order to interpret the evolutionary history dynamic genomes.