Meitotic Purification of AMN1 from DB146

Multicellularity has evolved dozens of times in many branches across the Tree of Life, in eachcase producing a new kind of individual that has the potential for division of labor among itsconstituent cells. In many of these instances nascent multicellularity has remained facultative,manifesting only under conditions where it provides a decisive fitness advantage to the genomein which it has arisen. Here we investigate the mechanistic basis for, and the selective advantagesassociated with, cryptic multicellularity in wild strains of the yeast Saccharomyces cerevisiae.Meiotic purification of this trait followed by genome sequencing indicates that the genome ofdiploid champagne yeast DB146 is heterozygous at the AMN1 (antagonist of mitotic exitnetwork) for an allele that dysregulates post-mitotic cell separation. Expression of this trait inhaploid DB146 results in clonal multicellular clusters in which daughters remain attached tomother cell walls.