Researchers identify the mechanism by which a selfish genetic element in C. elegans kills embryos. The toxin, known as peel-1, is carried by the father’s sperm and disrupts embryonic development of muscle and epidermal tissue. Only those embryos with zeel-1, an antidote to the poison that's located next to peel-1 in the genome and expressed during embryogenesis, survive. The results suggest that tight physical linkage of the genes was key to their co-evolution, and their ability to spread despite the cost they impose on their hosts.
Comparing the genomes of a Chinese male, a Korean male, three European individuals, and two Yoruba males, researchers estimate the population sizes of ancient human populations, from a million years ago to about 8,000 BCE. As suggested by previous studies, the results point to a severe bottleneck in European and Chinese populations between 10,000 and 60,000 years ago, while African populations show evidence of an earlier and much less severe bottleneck. The data also suggest that modern humans may have started to diverge as early as 100,000 to 120,000 years ago.
Comparing the sequence of the E. coli strain responsible for this year’s devastating European outbreak with archival data reveals genes characteristic of two pathogenic E. coli types—enteroaggregative E. coli (EAEC) and enterohemorrhagic E. coli (EHEC)—and suggests the new strain is a hybrid of the two, formed via the gain and loss of specific chromosomal and plasmid-encoded virulence factors.
A. Mellmann, et al., “Prospective genomic characterization of the German enterohemorrhagic Escherichia coli O104:H4 outbreak by rapid next generation sequencing technology,” PLoS One, 6:e22751, 2011. Free F1000 Evaluation
Over the past 10 years, the concept of adaptive radiation—when new ecological niches drive rapid evolution and speciation—has been questioned. Here, researchers demonstrate that within two clades of pupfish, introduction into novel niches can accelerate the rates of morphological change up to 131 times faster than related fish, suggesting that niche invasion indeed drives high rates of morphological diversification.
C.H. Martin and P.C. Wainwright, “Trophic novelty is linked to exceptional rates of morphological diversification in two adaptive radiations of cyprinodon pupfish,” Evolution, 65:2197-212, 2011. Free F1000 Evaluation
While the interactions between deleterious mutations and other genes in the genome are well studied, the results of interactions with beneficial mutations are less clear. Comparing the effects of beneficial mutations in isolation and in combination in a bacteriophage, researchers find that phages carrying multiple beneficial mutations are not as fit as would be predicted by the simple addition of the fitness benefits afforded by the individual mutations, suggesting that epistatic interactions between beneficial mutations are antagonistic. In some cases, beneficial mutations could even become deleterious in the presence of another beneficial mutation.
Genome comparisons of Mycobacterium avium subspecies paratuberculosis (MAP), the pathogenic bacteria that causes Johne's disease in cattle and is suspected to play a role in Crohn's disease, reveals two large tandem duplications that varied in prevalence from 0.01 to 15 percent of isolates. The authors propose that overrepresentation of one of these duplications, vGI-17, in MAP strains isolated from human Crohn’s patients may play a role the bacterium’s pathogenicity, enhancing its ability to infect human hosts or persist following infection.
Researchers identify an enzyme that may be responsible for the establishment of small intergenic palindromic sequences called repetitive extragenic palindromes (REPs) in bacterial genomes. REP-associated tyrosine transposase (RAYT) shows high sequence similarity to single-strand DNA transposases, suggesting it could play a role in the proliferation and mobilization of the repeated elements, which are suspected to contribute to chromosome organization and transcription termination.
J. Nunvar, et al., “Identification and characterization of repetitive extragenic palindromes (REP)-associated tyrosine transposases: implications for REP evolution and dynamics in bacterial genomes,” BMC Genomics, 11:44, 2010. Free F1000 Evaluation
The F1000 Top 7 is a snapshot of the highest ranked articles from a 30-day period on Faculty of 1000 Evolutionary Biology, as calculated on August 25, 2011. Faculty Members evaluate and rate the most important papers in their field. To see the latest rankings, search the database, and read daily evaluations, visit http://f1000.com.