Genetic basis for soma is present in undifferentiated volvocine green algae

Somatic cellular differentiation plays a critical role in the transition from unicellular to multicellular life, but the evolution of its genetic basis remains poorly understood. By definition, somatic cells do not reproduce to pass on genes and so constitute an extreme form of altruistic behaviour....

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Bibliographic Details
Published in:Journal of evolutionary biology 2017-06, Vol.30 (6), p.1205-1218
Main Authors: Grochau‐Wright, Z. I., Hanschen, E. R., Ferris, P. J., Hamaji, T., Nozaki, H., Olson, B. J. S. C., Michod, R. E.
Format: Article
Language:English
Subjects:
Adaptation, Physiological
Algae
Biological Evolution
Cell differentiation
Chlorophyta
Clusters
Differentiation (biology)
Divergence
gene duplication
Genes
germ‐soma differentiation
major transitions
multicellularity
Phylogeny
RegA gene
Somatic cells
Stress, Physiological
VARL domain
volvocine algae
Volvox
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Summary:Somatic cellular differentiation plays a critical role in the transition from unicellular to multicellular life, but the evolution of its genetic basis remains poorly understood. By definition, somatic cells do not reproduce to pass on genes and so constitute an extreme form of altruistic behaviour. The volvocine green algae provide an excellent model system to study the evolution of multicellularity and somatic differentiation. In Volvox carteri, somatic cell differentiation is controlled by the regA gene, which is part of a tandem duplication of genes known as the reg cluster. Although previous work found the reg cluster in divergent Volvox species, its origin and distribution in the broader group of volvocine algae has not been known. Here, we show that the reg cluster is present in many species without somatic cells and determine that the genetic basis for soma arose before the phenotype at the origin of the family Volvocaceae approximately 200 million years ago. We hypothesize that the ancestral function was involved in regulating reproduction in response to stress and that this function was later co‐opted to produce soma. Determining that the reg cluster was co‐opted to control somatic cell development provides insight into how cellular differentiation, and with it greater levels of complexity and individuality, evolves.
ISSN:1010-061X
1420-9101
DOI:10.1111/jeb.13100