Architecture and Evolution of a Minimal Plant Genome

The carnivorous plant Utricularia gibba (family Lentibulariaceae) is a small species of bladderwort in the same order as mints (Lamiales). Commonly known as the humped bladderwort, this species forms floating mats, and in order to supplement their nitrogen and phosphorous intake, the plant captures small organisms as prey using bladder-like suction traps.  While remarkable for its natural history, U. gibba also has one of the smallest known angiosperm genomes at 82 megabases, which is approximately two-thirds the size of Arabidopsis thaliana. Here we focus on the structural analyses of its genome sequence using the genome of tomato (Solanum lycopersicum), the evolutionarily closest species with a non-restricted genome available, as an outgroup. As expected, nearly all nonessential inter- and intra-genomic sequences have been removed, leaving behind a remarkably compact extant genome. However, despite its small size, the genome of U. gibba held a surprise: its lineage had undergone three independent whole genome duplication events since its divergence with tomato. Following each of these events, the genome underwent massive fractionation which removed the majority of duplicated homeologous genes. This repeated pattern of whole genome duplication followed by subsequent fractionation made deciphering the evolution of U. gibba quite difficult. This talk will focus on the analytical process for revealing the genomic evolution of U. gibba using the comparative genomics platform CoGe (http://genomevolution.org), which may be used for the analysis of other genomes with similarly dynamic evolutionary processes.