Month: September 2022

SELECTION LEVEL. "The evolution of multicellularity requires an increasing role for natural selection among multicellular individuals, relative to selection among cells within individuals." http://www.pnas.org/content/109/5/1595.full View in LinkedIn

EXPERIMENTAL SETUP. "Experimental evolution of multicellularity. We subjected the unicellular yeast Saccharomyces cerevisiae to an environment in which we expected multicellularity to be adaptive. We observed the rapid evolution of clustering genotypes that display a novel multicellular life history characterized by reproduction via multicellular propagules, a juvenile phase, and determinate growth." http://www.pnas.org/content/109/5/1595.full View in LinkedIn

EVOLVING YEAST CLUSTERS. "The multicellular clusters are uniclonal, minimizing within-cluster genetic conflicts of interest. Simple among-cell division of labor rapidly evolved. Early multicellular strains were composed of physiologically similar cells, but these subsequently evolved higher rates of programmed cell death (apoptosis), an adaptation that increases propagule production." http://www.pnas.org/content/109/5/1595.full View in LinkedIn

EMERGENT TRAITS. "We investigated the transition between unicellular and multicellular life by studying two emergent traits of multicellular snowflake-phenotype yeast, cluster reproduction, and settling survival. New clusters can potentially arise by production of either unicellular or multicellular propagules." http://www.pnas.org/content/109/5/1595.full View in LinkedIn

SNOWFLAKE YEAST. "Snowflake-phenotype yeast have a novel multicellular life history that responds to selection. As snowflake yeast evolved a twofold increase in size at reproduction over 14–60 transfers, propagule size declined from 40 to 20% of parental size." http://www.pnas.org/content/109/5/1595.full View in LinkedIn

PHENOTYPE SHIFT. "We observed adaptation of multicellular traits, indicating a shift in selection from individual cells to multicellular individuals. In response to selection for even more rapid settling, snowflake-phenotype yeast adapted through changes in their multicellular life history, increasing the length of the juvenile phase that precedes production of multicellular propagules." http://www.pnas.org/content/109/5/1595.full View in LinkedIn

YEAST DIVISION OF LABOR. "We also observed the evolution of division of labor within the cluster: most cells remain viable and reproduce, but a minority of cells become apoptotic. Apoptotic cells act as break points within multicellular clusters, allowing snowflake yeast to produce a greater number of propagules from a given number of cells. This is functionally analogous to germ-soma differentiation, where cells specialize into reproductive and nonreproductive tasks. These results demonstrate that multicellular traits readily evolve as a consequence of among-cluster selection." http://www.pnas.org/content/109/5/1595.full View in LinkedIn

YEAST CO-OPTED FUNCTION. "Apoptosis rapidly evolved a new, co-opted function in our multicellular yeast with no obvious parallel in the unicellular ancestor. Similarly, the existence of apoptosis-like cellular suicide in the unicellular ancestors of metazoans may be an important preadaptation, facilitating the evolution of complex multicellularity." http://www.pnas.org/content/109/5/1595.full View in LinkedIn

PUNCTUATED STASIS. "The fossil record shows that long periods of stasis are often punctuated by bursts of rapid evolution, presumably due to shifts in selective conditions and dramatic evolutionary responses. Over the history of life, multicellularity has evolved repeatedly in unrelated phylogenetic groups. The potential for the evolution of multicellularity may be less constrained than is frequently postulated." http://www.pnas.org/content/109/5/1595.full View in LinkedIn

YEAST LAB EVOLUTION. "These results show that key aspects of multicellular complexity, a subject of central importance to biology, can readily evolve from unicellular eukaryotes." http://www.pnas.org/content/109/5/1595.full View in LinkedIn