Dinoflagellates are diverse, ecologically important phytoplankton in marine and freshwater environments. Here, we present two draft de novo diploid genome assemblies of the free-living dinoflagellate Polarella glacialis, isolated from the Arctic and Antarctica. For each genome, we predicted >50,000 high-quality genes supported by full-length transcriptome data. About 68% of the total genome sequence is repetitive, and includes long terminal repeats that likely contribute to intra-species

more »

... ral divergence and distinct genome sizes (3.0 and 2.7 Gbp). In each genome, ~40% of genes are encoded unidirectionally and ~25% are single exonic; these include tandemly repeated genes that encode functions related to cold adaptation and photosynthesis. Multi-genome comparison unveiled genes specific to P. glacialis and a common ancestral origin of ice-binding domains in cold-adapted dinoflagellates. Our results provide insights into how dinoflagellate genomes may enhance the transcriptional efficiency of critical genes as a mechanism of environmental adaption and niche specialisation.