Tag: Volvox

Posted on
by

Jim Umen and I have published an article in the newest issue of Annual Review of Genetics. We review some green algae that are or have the potential to be models for the evolution of multicellularity, including Volvox, Ulva, Chara, and Caulerpa. Transitions from unicellular to multicellular (or, in the case of Caulerpa, giant, multinucleate unicellular) have been frequent and varied within the green algae, and we argue that studying diverse examples is necessary to understand how and why these transitions have taken place.

Abstract:

The repeated evolution of multicellularity across the tree of life has profoundly affected the ecology and evolution of nearly all life on Earth. Many of these origins were in different groups of photosynthetic eukaryotes, or algae. Here, we review the evolution and genetics of multicellularity in several groups of green algae, which include the closest relatives of land plants. These include millimeter-scale, motile spheroids of up to 50,000 cells in the volvocine algae; decimeter-scale seaweeds in the genus Ulva (sea lettuce); and very plantlike, meter-scale freshwater algae in the genus Chara (stoneworts). We also describe algae in the genus Caulerpa, which are giant, multinucleate, morphologically complex single cells. In each case, we review the life cycle, phylogeny, and genetics of traits relevant to the evolution of multicellularity, and genetic and genomic resources available for the group in question. Finally, we suggest routes toward developing these groups as model organisms for the evolution of multicellularity.

Umen, J. & M.D. Herron. 2021. Green algal models for multicellularity. Annual Review of Genetics  55:603-632. doi: 10.1146/annurev-genet-032321-091533 Free e-print

Posted on
by
Phylogeny

Ross Lindsey’s master’s thesis is now an article in BMC Biology, “Phylotranscriptomics points to multiple independent origins of multicellularity and cellular differentiation in the volvocine algae”:

We performed RNA sequencing (RNA-seq) on 55 strains representing 47 volvocine algal species and obtained similar data from curated databases on 13 additional strains. We then compiled a dataset consisting of transcripts for 40 single-copy, protein-coding, nuclear genes and subjected the predicted amino acid sequences of these genes to maximum likelihood, Bayesian inference, and coalescent-based analyses. These analyses show that multicellularity independently evolved at least twice in the volvocine algae and that the colonial family Goniaceae is not monophyletic. Our data further indicate that cellular differentiation arose independently at least four, and possibly as many as six times, within the volvocine algae.

Altogether, our results demonstrate that multicellularity and cellular differentiation are evolutionarily labile in the volvocine algae, affirming the importance of this group as a model system for the study of major transitions in the history of life.

Lindsey, C.R., F. Rosenzweig, & M.D. Herron. 2021. Phylotranscriptomics points to multiple independent origins of multicellularity and cellular differentiation in the volvocine algae. BMC Biology 19:182, part of the In the Light of Evolution series. doi: 10.1186/s12915-021-01087-0