Undergraduate summer internships at the Danforth Center

This is an unbelievable opportunity: an NSF-funded, paid summer internship at the Donald Danforth Plant Science Center in St. Louis. Ru Zhang is at the Danforth Center. Jim Umen is at the Danforth Center. The Fourth International Volvox Conference was at the Danforth Center. If you’re an undergraduate and you think you might want to study Volvox or Chlamydomonas (or plants), this would be a great way to get started.

Danforth Internship

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Volvox newsletter

Volvox newsletter cover

As David Kirk pointed out, what we normally call the First through Fourth International Volvox Meetings are really about the fifth through eighth, as they were preceded by several meetings in the ’70s. The very first meeting was hosted by David and Marilyn Kirk at Washington University in St. Louis. Richard Starr, then at Indiana University, reported on the meeting in the first Volvox Newsletter (Dr. Starr would later move to the University of Texas, and his strains would form the beginning of the UTEX Culture Collection, which is still in operation).

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More Volvox correspondence

I previously corresponded with a science teacher in India, who wrote me with some questions about Volvox. After our initial exchange, my correspondent wrote

Can you please name if there is any unicellular colonial microorganism found?

I asked for clarification and received this reply:

I read about colonial organisms being unicellular and multicellular. Few people think Volvox as colonial organism which is unicellular while Phylum Bryozoa has colonial organisms which are multicellular. The confusion started here. What are colonial microorganisms really? If they are unicellular and multicellular why are they called as colonial then? Bacteria being unicellular which form colonies thought Can bacteria be called as colonial organism? I tried to look for the same but I have not found something solid which says bacteria can be called as colonial organisms. I want to explain colonial organisms to children and don’t want to provide wrong information.

Can you please help in understanding do colonial unicellular microorganism exist? I asked one of the microbiologist I know in here she is also not clear with the concept or probably I might have read something wrong. Need guidance.

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Mary Agard Pocock

Alexey Desnitskiy, Stuart Sym, and Pierre Durand have published a new paper in Transactions of the Royal Society of South Africa recounting the contributions of South African phycologist Mary Agard Pocock to Volvox research [full disclosure: Pierre Durand and I were labmates in Rick Michod’s lab at the University of Arizona for a time, and Alexey Desnitskiy is a friend and collaborator].

Pocock, who defended her Ph.D. in 1932, made careful observations of both sexual and asexual development in several species of Volvox that she collected in southern Africa: V. africanus, V. capensis,V. rousseletii, and V. gigas (which she originally described). For some of these species, hers are still the only detailed descriptions of their ontogeny:

Pocock studied almost all aspects of asexual and sexual development in several African Volvox species, with the exception of sexual differentiation control…Pocock’s data on embryonic inversion in V. africanus, V. capensis, V. gigas and V. rousseletii retain their importance today. Her description of inversion during asexual development in V. africanus and V. capensis remains the only detailed study of this process in these two species and her observations of embryonic inversion in V. gigas and V. rousseletii were corroborated almost 40 years later. [references omitted]

Pocock 1933 Fig. 2L-O

Figure 2L-O from Pocock 1933. Inversion in Volvox gigas.

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I was in Canada

I have been disloyal to the fierce roller. After grad school, I stepped away from Volvox for a couple of years to do a postdoc with Michael Doebeli at the University of British Columbia. I thought I was going to transition to mathematical modeling, and Dr. Doebeli and I did do a bit of that together. I also got my first exposure to next-generation sequencing in his lab. I eventually returned to the fold, but during my time in Canada I wasn’t paying much attention to the Volvox world.

As a result, I missed Jerry Coyne’s coverage of the Volvox genome, which was published in 2010, just as I was discovering Jericho Beach, enjoying cheap sushi, and struggling to understand adaptive dynamics.

What does it take to become multicellular?

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CRISPR/Cas9 mutagenesis in Volvox

Researchers in Stephen Miller’s lab at the University of Maryland, Baltimore County have successfully used CRISPR/Cas9 to knock out several developmentally important genes in Volvox carteri. CRISPR/Cas9 is a relatively new technology that allows heritable mutations to be introduced into living cells at specific locations within the genome.

This advance was announced in a new paper in The Plant Journal by José A. Ortega-Escalante, Robyn Jasper, and Stephen M. Miller (Jasper and Ortega-Escalante are listed as equal contributors). They were able to transform wild-type V. carteri with inversion-deficient and somatic-regenerator mutations, and they transformed somatic regenerator mutants with a gonidialess (no specialized reproductive cells) mutation.

I have never used CRISPR/Cas9, and I don’t know as much about it as I should, so I’m sure any explanation I gave would be riddled with errors. Here’s someone who seems to know what she’s talking about:

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Repost: Message from David Kirk

After last week’s sad news that one of the founding fathers of Volvox research, David Kirk, had passed away, I thought it would be relevant to repost a message he sent a couple of years ago. The modern series of Volvox meetings started in 2011 in Arizona, and we’ve been calling them the First through Fourth International Volvox Conferences, with the Fifth scheduled for July 26-29, 2019. Dr. Kirk wrote in with some interesting historical insight about Volvox meetings that long preceded the current series:

I got an email out of the blue from David Kirk, and I thought some of it would be of interest. Dr. Kirk is one of the biggest names in Volvox research: he carried out much of the developmental genetics that forms the foundation of our field, he literally wrote the book on Volvox evo-devo, and my impression is that most of the PIs currently studying Volvox spent time in his lab as students and postdocs.

VolvoxBookCover

The email was prompted by the meeting review from the 2015 meeting in Cambridge (he liked it, whew! :-D), and he said that he’s looking forward to the 2017 meeting in St. Louis. The email also had a footnote with some interesting information, which I quote here with Dr. Kirk’s permission:

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Are the multicellular volvocine algae monophyletic?

One of the strengths of the volvocine algae as a model system is that they span a range of sizes and degrees of complexity. Sizes range from tens of microns to a couple of millimeters, cell numbers range from one to 50,000 or so, some species do and some don’t have cellular differentiation, and some do and some don’t undergo inversion during development. This variation makes the volvocine algae ripe for comparative analyses, which I and many others have done. It also allows many of the intermediate steps between unicellular and complex multicellular life to be identified, as David Kirk did in his “twelve-step” paper.

The volvocine algae have clearly taken some of those steps more than once. Cellular differentiation, for example, has evolved at least three times, in the genus Astrephomene, in the so-called Volvox section Volvox (a.k.a. Euvolvox), and in the lineage that includes Pleodorina and the other Volvox species. One thing they seem to have only done once, though, is to evolve multicellularity itself.

There have been dozens of studies addressing the evolutionary relationships among various species of volvocine algae. Most have been from Hisayoshi Nozaki’s lab, though I and many others have weighed in as well. Nearly all of them, at least those that address the topic, agree that the three families that make up the multicellular volvocine algae–the Tetrabaenaceae, Goniaceae, and Volvocaceae–uniquely descend from a common ancestor. In other words, the multicellular volvocine algae are monophyletic.

Three important cladistic terms are used to summarize the evolutionary relationships among a group of species. If all of the members of the group descend from a common ancestor, and nothing else descends from that ancestor, the group is called monophyletic. Mammals, for example, are monophyletic. A monophyletic group is also called a clade. If all group members are descended from a common ancestor, but so are some non-group members, the group is called paraphyletic. Reptiles, for example, are paraphyletic, because there is no clade that includes all reptiles that doesn’t also include birds. The word ‘paraphyletic’ should nearly always be followed by ‘with respect to’: reptiles are paraphyletic with respect to birds.

The bottom of the barrel, in terms of evolutionary relationships, is polyphyly. A group is considered polyphyletic if its members don’t share a recent common ancestor at all, in other words, if they have multiple evolutionary origins. Flying animals are polyphyletic. Algae are polyphyletic. The genus Volvox is polyphyletic. Polyphyletic taxa are the scum of the phylogenetic Earth. Telling a taxonomist that a group she has named is polyphyletic is a deadly insult.

The prevailing view of volvocine evolutionary relationships is that the family Volvocaceae is sister to the Goniaceae (that is, each is the other’s closest relative), and the Tetrabaenaceae are sister to the Volvocaceae + Goniaceae. Two new papers infer relationships among volvocine algae and their unicellular relatives, and one of them challenges the view of multicellular monophyly.

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Volvox inversion review

Alexey Desnitskiy from St. Petersburg State University has published a short review of the process of embryonic inversion in the genus Volvox. It is a translation, by the author, of his Russian-language paper in the journal Ontogenez (Desnitskiy, AG. 2018. Ontogenez 49:147-152). The article, in the Russian Journal of Developmental Biology, isn’t listed as open access, but it also doesn’t seem to be paywalled.

Inversion occurs during the development of all known species in the family Volvocaceae (Colemanosphaera, Eudorina, Pandorina, Platydorina, Pleodorina, Volvox, Volvulina, and Yamagishiella), where it serves to turn the embryo inside-out and get the flagella on the outer surface of the colony. The paper discusses the two distinct inversion processes found in different Volvox species:

…the inversion of “type A” and the inversion of “type B,” represented by the two species most thoroughly studied, respectively V. carteri f. nagariensis and V. globator (Hallmann, 2006; Höhn and Hallmann, 2011). The principal difference between these two types of inversion is that this process begins at the anterior pole of the embryo in the first case, while in its posterior hemisphere in the second case. Coordinated displacements of cells relative to the system of intercellular cytoplasmic bridges play, along with changes of the cell shape, an important role in the inversion process in embryos of both Volvox species. In V. globator, though, the spindle-shaped cells could be observed not in the entire embryo but only in the posterior hemisphere at the stage of its compression.

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