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This Week in PNAS: Apr 16, 2014

In the early, online edition of the Proceedings of the National Academy of Sciences, an international team led by investigators in the US present findings from a population sequencing study of group A Streptococcus strain belonging to the Emm protein 1 serotype, commonly dubbed "flesh-eating bacteria." By sequencing the genomes of more than 3,600 of these "M1" strains, the researchers retraced the evolution and spread of epidemic group A Streptococcus. For instance, their results suggest that the current epidemic clone arose as a result of stepwise genetic changes that introduced increased virulence and other incremental advantages. "Compared with a pre-epidemic reference strain," study authors say, "the contemporary clone is significantly more virulent in non-human primate models of pharyngitis and necrotizing fasciitis." GenomeWeb Daily News has more on the study, here.

An international team takes a look at horizontal gene transfer events contributing to low-light capabilities of fern plants. Using transcriptome and genome sequences generated for various plants as part of the One Thousand Plants Project, the researchers found clues suggesting that the unusual fern photoreceptor neochrome was originally nabbed from hornworts in the bryophyte lineage through horizontal gene transfer before being modified to meet fern plants' low-light light harvesting needs. That notion was further supported by the group's efforts to sequence and analyze a draft version of the hornwort Anthoceros punctatus genome.

Washington University's Joseph Jez and colleagues from WashU and the University of Missouri describe the manner in which a regulatory protein known as NolR regulates root nodulation by rhizobial microbes and related gene expression patterns by these microbes and their host plants. With the help of X-ray crystal structure, biochemical, and other experiments, the researchers developed models for protein-DNA interactions and conformational switches that the soybean symbiont Sinorhizobium fredii version of NolR uses to regulate root nodulation and plant symbiosis.