Genome editing enables reverse genetics of multicellular development in the choanoflagellate <i>Salpingoeca rosetta</i>.

Abstract

In a previous study, we established a forward genetic screen to identify genes required for multicellular development in the choanoflagellate, <i>Salpingoeca rosetta</i> (Levin et al., 2014). Yet, the paucity of reverse genetic tools for choanoflagellates has hampered direct tests of gene function and impeded the establishment of choanoflagellates as a model for reconstructing the origin of their closest living relatives, the animals. Here we establish CRISPR/Cas9-mediated genome editing in <i>S. rosetta</i> by engineering a selectable marker to enrich for edited cells. We then use genome editing to disrupt the coding sequence of a <i>S. rosetta</i> C-type lectin gene, <i>rosetteless</i>, and thereby demonstrate its necessity for multicellular rosette development. This work advances <i>S. rosetta</i> as a model system in which to investigate how genes identified from genetic screens and genomic surveys function in choanoflagellates and evolved as critical regulators of animal biology.