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This Week in PLOS: Aug 17, 2015

The time to most recent common ancestor, as gauged through DNA sequence data, doesn't always correspond to the time of divergence, writes James Pettengill from the US Food and Drug Administration in PLOS One. Through coalescent simulations, he shows that incomplete lineage sorting and taxon sampling can influence such estimations. In particular, he found that a recent analysis of Salmonella enterica serovar Agona, which reported a 1932 divergence time, conflated time to most recent common ancestor among the samples they analyzed with divergence date. Instead, he argues that the date of divergence for Agona cannot be determined without the addition of a closely related serovar in the analysis. Further, he notes determining such divergence times properly can be crucial in public health settings.

University of California, Riverside, researchers report in PLOS Genetics that some 7,500 transcripts are differentially expressed in female mosquito during its 72-hour reproduction period. Using RNAi and in vitro organ culture approaches, the researchers further uncovered the major regulators of the four waves of gene expression that occur: 20-hydroxyecdysone and the ecdysone receptor; HR3; and juvenile hormone and its receptor methoprene tolerant. These regulators, they note, activate and repress sets of co-regulated gene sets.

For another PLOS Genetics paper, a trio of researchers from Croatia and Italy report that satellite DNA appears to modulate gene expression in the beetle Tribolium castaneum under certain environmental conditions. The trio found that genes associated with the major satellite DNA TCAST1 have enhanced suppression and a slower return to their previous expression levels after heat stress than do the same genes when not associated with TCAST1 satellite DNA elements. "Based on this, the impact of satellite DNAs on adaptation to different environmental conditions as well as their role in the evolution of gene regulatory networks is proposed," the trio adds.