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Biological sciences; Evolution; Genetics
Abstract:
Complex life has arisen through a series of ‘major transitions’ in which collectives of formerly
autonomous individuals evolve into a single, integrated organism. A key step in this process is
the origin of higher-level evolvability, but little is known about how higher-level entities
originate and gain the capacity to evolve as an individual. Here we report a single mutation
that not only creates a new level of biological organization, but also potentiates higher-level
evolvability. Disrupting the transcription factor ACE2 in Saccharomyces cerevisiae prevents
mother–daughter cell separation, generating multicellular ‘snowflake’ yeast. Snowflake yeast
develop through deterministic rules that produce geometrically defined clusters that preclude
genetic conflict and display a high broad-sense heritability for multicellular traits; as a result
they are preadapted to multicellular adaptation. This work demonstrates that simple microevolutionary
changes can have profound macroevolutionary consequences, and suggests that
the formation of clonally developing clusters may often be the first step to multicellularity.
