The genome of S. mediterranea and the evolution of cellular core mechanisms

The planarian Schmidtea mediterranea is an important model for stem cell research and regeneration. We report the first highly contiguous genome assembly of Schmidtea mediterranea, using long-read sequencing and a de novo assembler (MARVEL) enhanced for low complexity reads. The S. mediterranea genome is highly polymorphic and repetitive genome, and harbors a novel class of giant Gypsy retroelements. Further, the genome assembly lacks a number of highly conserved genes, including critical components of the mitotic spindle assembly checkpoint, yet planarians maintain checkpoint function. Our genome assembly provides a key model system resource that will be useful for studying regeneration and the evolutionary plasticity of cell biological core mechanisms.