Plasticity and the evolution of group-level regulation of cellular differentiation in the volvocine algae

During the evolution of multicellularity, the unit of selection transitions from single cells to integrated multicellular cell groups, necessitating the evolution of group-level traits such as somatic differentiation. However, the processes involved in this change in units of selection are poorly understood. We propose that the evolution of soma in the volvocine algae included an intermediate step involving the plastic development of somatic-like cells. We show that Eudorina elegans, a multicellular volvocine algae species previously thought to be undifferentiated, can develop somatic-like cells following environmental stress (i.e., cold shock). These cells resemble obligate soma in closely related species. We find that somatic-like cells can differentiate directly from cold-shocked cells. This differentiation is a cell-level trait, and the differentiated colony phenotype is a cross-level byproduct of cell-level processes. The offspring of cold-shocked colonies also develop somatic-like..., Induction of somatic-like cells over multiple generations
In order to determine whether somatic-like cells develop in response to cold shock, we inoculated a 250 mL flask of Standard Volvox Media (SVM) with E. elegans UTEX 1201 and grew the cultures on a shaker at 25°C with a 16:8 hour light:dark cycle. After 5 days, we transferred 0.5 mL of the culture to a new 250 mL flask with fresh SVM and allowed the culture to grow for 10 days. We then placed 1 mL of the culture with young unexpanded colonies in six Eppendorf tubes. Three of the tubes were cold-shocked in a covered ice bath at 1° C for two hours while the other three control tubes were placed in the dark at 25° C for two hours. The contents of each tube were then transferred to fresh media in separate wells of a 6 well plate.
 To assess the development of somatic cells over multiple generations following cold shock, we imaged the cold-shocked colonies (which we refer to as generation 1; G1), their offspring (generation 2; G2), and..., , # Plasticity and the evolution of group-level regulation of cellular differentiation in the volvocine algae

[https://doi.org/10.5061/dryad.ns1rn8q1h](https://doi.org/10.5061/dryad.ns1rn8q1h)

#### Description of the data and file structure

The datasets and code associated with the manuscript \"Plasticity and the evolution of group-level regulation of cellular differentiation in the volvocine algae\" are deposited here. There are five datasets associated with this manuscript:

1. Supplementary_data_S1.csv provides the data used to examine the number of plastic somatic-like cells per colony for replicates of two generations in cold-shocked and control conditions in flasks. 
2. Supplementary_data_S2.csv provides the data used to follow three generations of cold-shocked and control colonies and to assess the inheritence of the differentiated phenotype.
3. Supplementary_data_S3.csv provides the data used to examine the number of living plastic somatic-like cells per colony for three generati...