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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Convergence part 6: the deepest of deep homologies

You are more closely related to a mushroom than a kelp is to a plant. It’s strange to think about, but it’s true. Kelps seem very plant-like, with their root-like holdfasts, stalk-like stipes, and leaf-like blades. But kelps are brown algae, part of the stramenopile (or heterokont) lineage of eukaryotes, which are very distant from the land plants and their green algal relatives, all of which are within the archaeplastida (the direct descendants of the primary origin of chloroplasts). Mushrooms (fungi) and humans (animals), on the other hand, are both opisthokonts, practically cousins at the scale we’re talking about.

Pawlowski 2013 Fig. 1

Figure 1 from Pawlowski 2013. Deep phylogeny of eukaryotes showing the position of small eukaryotic lineages that branch outside the seven supergroups (modified after Burki et al. 2009; drawings S Chraiti). You are represented by a fish, which at this scale you might as well be.

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Flagellar synchronization in Chlamydomonas

The physics is way beyond me, but a new paper by Gary Klindt and colleagues in New Journal of Physics uses Chlamydomonas as a model for flagellar synchronization:

We present a theory of flagellar synchronization in the green alga Chlamydomonas, using full treatment of flagellar hydrodynamics and measured beat patterns. We find that two recently proposed synchronization mechanisms, flagellar waveform compliance and basal coupling, stabilize anti-phase synchronization if operative in isolation. Their nonlinear superposition, however, can stabilize in-phase synchronization for suitable parameter choices, matching experimental observations.

Klindt et al. Fig. 1

Figure 1 from Klindt et al. 2017. In-phase and anti-phase synchronization. (a) In-phase synchronization at high synchronization strength, corresponding to “breast-stroke swimming” Chlamydomonas. (b) For low synchronization strength, anti-phase synchronization is stable, corresponding to a “free-style” gait.

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Chlamydomonas monograph

Chlamydomonas monograph cover

There’s a new Microbiology Monograph on ChlamydomonasChlamydomonas: Molecular Genetics and Physiology, edited by Michael Hippler. It’s actually cheaper to buy it directly from the publisher, but still $149 for an e-book.

This Microbiology Monographs volume covers the current and most recent advances in genomics and genetics, biochemistry, physiology, and molecular biology of C. reinhardtii. Expert international scientists contribute with reviews on the genome, post-genomic techniques, the genetic toolbox development as well as new insights in regulation of photosynthesis and acclimation strategies towards environmental stresses and other structural and genetic aspects, including applicable aspects in biotechnology and biomedicine.

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Chlamy 2018 dates and venue announced

Chlamydomonas zygotes

The dates and location have been announced for the 18th International Conference on the Cell and Molecular Biology of Chlamydomonas:

The 18th International Conference on the Cell and Molecular Biology of Chlamydomonas will be held from June 17-21, 2018 in Washington DC. We look forward to seeing all of you there, so please keep those dates open. The venue will be the historic Carnegie Institution headquarters located in the heart of DC at 1530 P Street NW. To learn more about the venue go to https://rentals.carnegiescience.edu/. More information will be posted concerning the conference over the next couple of months.

I’ll keep you posted as more information becomes available.

MicroRNAs in Chlamydomonas

One of the biggest changes in evolutionary theory in the late 20th century was the growing appreciation for the central role of changes in gene expression in macroevolution. Developmental genes, especially Hox genes, turned out to be remarkably conserved across lineages that diverged over half a billion years ago. The subsequent huge changes in morphology were more often due to changes in when and where those genes were expressed than to changes in the coding sequences of the genes themselves.

Even more recently, an entire new class of regulatory mechanisms was discovered and found to be important in developmental processes. MicroRNAs (miRNAs) are short (21-24 nucleotides) sequences of RNA that reduce gene expression by promoting the breakdown of messenger RNAs (mRNAs) and by repressing translation of mRNAs into proteins. We have only known that microRNAs even existed since the early 1990’s, and their importance in gene regulation and development wasn’t appreciated until the 2000’s.

Although they are structurally similar, plant and animal microRNAs repress gene expression through very different mechanisms. A new paper by Betty Y-W. Chung and colleagues in Nature Plants shows that the regulatory mechanisms of Chlamydomonas microRNAs have both striking similarities and important differences with animal miRNAs:

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A valid point

A reader commented by email about my criticism of the PLoS ONE article that inferred a multigene phylogeny of eukaryotes, with Chlamydomonas reinhardtii as the outgroup (“A cautionary tale on reading phylogenetic trees“).

Although you are of course correct to complain about nearly everything in the paper (esp. re “basal” and node rotations), and I am sure the tree is wrong in more ways than it is right, I think you might reconsider or put in context complaints about the “provides a link between”. My thought is simply that if one has a long branch between two nodes in a tree, if you add a taxon group that branches off in the middle of this long branch, then it does, in a sense, provide a “link” between these two nodes. A more proper way to put it is that it provides information concerning the ancestral state at the two original nodes (i.e., may substantially modify the posterior probability of the states at the two nodes). I doubt that the authors mean it in this sense, but in the general context of teaching people about trees, I would want students to understand this.

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