Multicellularity rundown

Too many papers, not enough time: each of these deserves a deep dive, but my list just keeps getting longer, so I’m going to have to settle for a quick survey instead. To give you an idea of what I’m up against, these papers were all published (or posted to bioRxiv) in July and August, 2016. By the time I could possibly write full-length posts about them all, there would probably be ten more!

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Retrogenes in Volvox and Chlamy

The evolution of multicellularity in the volvocine algae appears to have happened primarily through co-option of existing genes for new functions. For example, the initial transition from a unicellular life cycle to a simple multicellular one involved the retinoblastoma gene, as Hanschen and colleagues elegantly demonstrated (see “The evolution of undifferentiated multicellularity: the Gonium genome“). A Volvox gene involved in cellular differentiation, regA, was likely co-opted from an ancestral role in environmental sensing, and a similar origin appears to explain the use of cyclic AMP for the signaling that causes multicellular aggregation in cellular slime molds (see “Volvox 2015: evolution“). 

Some of the changes leading to complex multicellularity, though, clearly did involve new genes. Two gene families involved in building the extracellular matrix that makes up most of a Volvox colony, the pherophorins and metalloproteinases, have undergone multiple duplication events leading to greatly expanded gene families (see “Heads I win; tails you lose: Evolution News & Views on Gonium, part 2“). One mechanism by which genes are duplicated is retroposition, in which a messenger RNA is reverse transcribed into DNA and inserted into the genome:

Fig S1A from Jakalski et al. 2016. Basic mechanism of retroposition. DNA is transcribed into a pre-mRNA by RNA polymerase, introns are spliced out, and a poly(A) tail is added to the 3′ end, resulting in a mature messenger RNA. The mRNA is then reverse-transcribed to DNA and inserted into a new genomic location.

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Teach lies to schoolchildren, because it used to be easy to cross the border

Photo by John Minchillo.

Photo by John Minchillo, downloaded from New Scientist.

Someone over at Uncommon Descent is unhappy with a New Scientist article criticizing Ken Ham’s Ark Park, an explicitly creationist-themed attraction dedicated to Biblical literalism. In the New Scientist article (“School field trips to creationist Ark? Sink that idea right now“), Josh Rosenau argues that teaching school children that the Earth is 6,000 years old, and that a vengeful creator committed genocide by drowning against his creation, is a bad idea.

Uncommon Descent objects, in a post that reveals more about its (unnamed) author than it presents any coherent argument (“New Scientist stomps on Noah’s Ark“) [PG-13 below the fold]:

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New position at Georgia Tech

GATechLogo

Part of the reason posts at Fierce Roller have been so sparse lately is that I’ve been busy moving across the country. I’m now a Senior Research Scientist in the School of Biology at Georgia Tech. I’ll be running a small lab, with two (soon three) postdocs and a very talented grad student.

I spent exactly one day on campus before I left for the ASM Experimental Microbial Evolution meeting, on which I managed to meet with the grad student and one postdoc and to get hooked up to the campus wifi. I have not yet attended new employee orientation or been assigned an employee ID number, so the degree to which I’m actually employed at this moment is a bit murky. Hopefully I’ll get this all sorted next week.

The long-term evolution experiment

I’m attending the 2nd ASM Conference on Experimental Microbial Evolution (#ASMEME) in Washington, DC. The meeting opened last night with a keynote address by Rich Lenski on the long-term evolution experiment (LTEE). If you’re not familiar with it, the LTEE involves twelve populations of E. coli bacteria that have been transferred every damn day for the last 28 years. That’s right, twelve transfers every day since Ronald Reagan was President.

Since E. coli undergoes about 6.6 doublings per day under the experimental conditions, that means that the bacteria in this experiment have been evolving for over 65,000 generations. In that time, it has produced a wealth of information about evolutionary processes and spun out countless related experiments. The LTEE is so iconic that you usually don’t have to explain, at least to evolutionary biologists, which long-term evolution experiment you’re talking about. It has also played a role in some controversies, not least the “Lenski affair.”

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