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Abstract The Antarctic sea urchin Sterechinus neumayeri (Echinoida; Echinidae) is routinely used as a model organism for Antarctic biology. Here, we present a high-quality genome of S. neumayeri. This chromosomal-level assembly was generated using PacBio long-read sequencing and Hi-C chromatin conformation capture sequencing. This 885.3-Mb assembly exhibits high contiguity with a scaffold length N50 of 36.7 Mb assembled into 20 chromosomal length scaffolds. These putative chromosomes exhibit a high degree of synteny compared to other sea urchin models. We used transcript evidence gene modeling combined with sequence homology to identify 21,638 gene models that capture 97.4% of BUSCO orthologs. Among these, we were able to identify and annotate conserved developmental gene regulatory network orthologs, positioning S. neumayeri as a tractable model for comparative studies on evolution and development. 

Abstract Gene gains and losses are a major driver of genome evolution; their precise characterization can provide insights into the origin and diversification of major lineages. Here, we examined gene family evolution of 1154 genomes from nearly all known species in the medically and technologically important yeast subphylum Saccharomycotina. We found that yeast gene family evolution differs from that of plants, animals, and filamentous ascomycetes, and is characterized by smaller overall gene numbers yet larger gene family sizes for a given gene number. Faster-evolving lineages (FELs) in yeasts experienced significantly higher rates of gene losses—commensurate with a narrowing of metabolic niche breadth—but higher speciation rates than their slower-evolving sister lineages (SELs). Gene families most often lost are those involved in mRNA splicing, carbohydrate metabolism, and cell division and are likely associated with intron loss, metabolic breadth, and non-canonical cell cycle processes. Our results highlight the significant role of gene family contractions in the evolution of yeast metabolism, genome function, and speciation, and suggest that gene family evolutionary trajectories have differed markedly across major eukaryotic lineages.