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This Week in PLOS: Jun 30, 2014

In PLOS Genetics, an American team including investigators from Monsanto and the Universities of California, Minnesota, and Georgia used population genomics to explore the roots of divergence and speciation in ecologically distinct sister species of yellow monkeyflower, called Mimulus guttatus and M. nasutus. Based on genomic data for 13 M. guttatus plants, five plants from a M. nasutus population, and a single representative from the outgroup species M. dentilobus, the researchers estimate that M. guttatus and M. nasutus diverged from one another in central California some 200,000 to 500,000 years. While M. nasutus began acquiring genomic features associated with self-fertilization at around that time, the study's authors also saw signs of persistent introgression between the sister species.

A PLOS Pathogens study implicates a microRNA called miR-146a in arthritic complications in Lyme disease, but not with Lyme disease-associated carditis. Through microarray-based screening, researchers from the University of Utah and elsewhere saw a rise in miR-146a expression in joint tissue from three different strains of mice infected with the Lyme disease-causing spirochete bacteria Borrelia burgdorferi. Their follow-up experiments indicated that mice missing the miRNA — a negative regulator of NF-kappaB signaling — were more prone to developing arthritis, though miR-146a deficiency did not appear to affect risk of carditis during Lyme disease.

A Japanese and Ghanaian team reporting in PLOS One describes a new strain of group A rotavirus detected by sequencing samples from two Ghanaian children with acute gastroenteritis. The samples, collected before the rotavirus vaccine Rotarix became more widespread in Ghana in 2012, contained new combinations of human and bovine rotavirus genes, consistent with mixing and reassortment between the strains. "These findings highlight the contribution of reassortment and interspecies transmission events to the high rotavirus diversity in this region of Africa," the study's authors write, "and justify the need for simultaneous monitoring of animal and human rotavirus strains."