In the Light of Evolution Volume V: Cooperation and Conflict (2011) / Chapter Skim
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9 Evolution of Cooperation and Control of Cheating in a Social Microbe--JOAN E. STRASSMANN and DAVID C. QUELLER
9 Evolution of Cooperation and Control of Cheating in a Social Microbe--JOAN E. STRASSMANN and DAVID C. QUELLER
Pages 191-212
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From page 191... ...
Cheaters are limited from exploiting other clones by high relatedness, kin discrimination, pleiotropy, noble resistance, and lottery-like role assignment. The active nature of these limits is reflected in the elevated rates of change in social genes compared with nonsocial genes.
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From page 192... ...
. Microorganisms evaluate their numbers with quorum sensing, kill nonclonemates with bacteriocins, hunt in groups, and cooperatively swarm through their environment, to name just a few examples of their social attributes (Crespi, 2001; Riley and Wertz, 2002; Diggle et al., 2007a; West et al., 2007a)
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From page 193... ...
The major transitions can thus be categorized as fraternal, with like cooperating with like, or egalitarian, where the cooperating units bring different things to the collaboration (Queller, 1997)
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From page 194... ...
This makes it easier to interpret the actions of different partners. Other attributes of the ideal social Drosophila include feasibility of study in a fairly natural environment, placement in a rich phylogeny with related species that vary in social traits, a sequenced set of genomes, and a collegial com munity of fellow investigators.
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From page 195... ...
. Although this is usually viewed as a solitary stage, they are always able to sense the density of nearby amoebae with a molecule called prestarvation f actor (Kessin, 2001)
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From page 196... ...
The stalk cells vacuolate and die, forming sturdy cellulose walls in the process that give them the strength to hold up the spherical ball of spores. The final fruiting body consists of about 20% stalk cells and 80% spore cells.
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From page 197... ...
The third advantage to grouping is slug movement; slugs move farther than amoebae, which could position them into a better place for dispersal. The complex orchestration of fruiting body formation could only have arisen through natural selection, but more work on the actual advantages is needed.
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From page 198... ...
Later, we were able to find and genotype individual wild-fruiting bodies collected from the very rich resource of deer dung and nearby soil. This approach gave much higher relatednesses, between 0.86 and 0.98 depending on the sample and technique (Gilbert et al., 2007)
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From page 199... ...
They may modify their behavior in chi mera to take advantage of their part ner, facultative cheating. Third, a social parasite can only make fruiting bodies in chimera with a victim.
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From page 200... ...
Other evidence for social conflict among wild clones in the social stage comes from comparing chimeras with pure clones in their ability to migrate as slugs and to form tall fruiting bodies (Fig.
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From page 201... ...
The fbxA knockout cheats its ancestor but cannot make spores on its own. Pools of REMI mutants can also be screened to obtain cheaters that are able to make normal fruiting bodies on their own but cheat their ancestor in a chimera.
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From page 202... ...
ness because at high relatedness, it is selected against by its own com promised spore production. We expect social parasites like this one to fail in nature because of the high relatedness within fruiting bodies found in the wild.
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From page 203... ...
Tiny soil samples have multiple clones of D discoideum, but fruiting bodies are nearly clonal.
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From page 204... ...
This could be true if they trans differentiate from prespore cells to prestalk cells later in development, and this was shown to be the case (Foster et al., 2004)
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From page 205... ...
This result was derived from careful observation of the fate of sister cells through videography. Every time a cell divided, one sister cell became prestalk or prespore according to the above musi cal chairs lottery mechanism, whereas the sister cell became a null cell, a third cell type that stained with neither prespore nor prestalk markers (Gomer and Firtel, 1987)
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From page 206... ...
Queller counterforces might achieve a compromise that could support altruism under a wide variety of conditions in D discoideum, if one of two recently divided cells becomes stalk and the other becomes spore.
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From page 207... ...
The condition variants resulting from position in the cell cycle or glucose feeding are tied to DIF-1 levels with weaker, more recently divided cells more vulnerable to DIF-1. There are single-gene knockouts with an
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From page 208... ...
. Cells that have rtoA knocked out lose the specificity toward stalk of the M and/or S cell cycle phase, producing fruiting bodies that are mostly stalk with tiny spore heads (Wood et al., 1996)
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From page 209... ...
The second set of genes we used was based on a social index, which was higher when a gene was more expressed in the social stage compared with the nonsocial stage. In this analysis, the more social genes had a lower probability of having homologs, an elevated rate of amino acid change, and a lower conservation score, supporting our hypothesis (Sucgang et al., 2011)
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From page 210... ...
In D discoideum, we have shown that conflict exists in the form of shorter stalk lengths, reduced migration distances, and cheat
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From page 211... ...
We thank many colleagues for helpful discussions of these points, especially Sandie Baldauf, Koos Boomsma, Kevin Foster, Richard Gomer, Ashleigh Griffin, Rob Kay, Richard Kessin, Adam Kuspa, Gene Robinson, Gadi Shaulsky, Chris Thompson, Greg Velicer, and Stuart West as well as our own laboratory group. Our research is supported by the U.S.
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