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This Week in PNAS: Apr 3, 2018

Researchers from Australia and the UK search for signs of hybridization, gene flow, and population structure in moth pests from the Helicoverpa genus with whole-genome sequencing and re-sequencing on representatives from half a dozen Helicoverpa species, including the cotton bollworm moth H. armigera that has become invasive in South America. Based on sequences for 76 Helicoverpa moths from H. armigera, H. zea, H. punctigera, H. gelotopoeon, H. hardwicki, and H. assulta moths collected in 16 countries, the team saw relatively high levels of genetic diversity in the heavily sampled H. armigera species. Although the authors did not see widespread gene flow between the six species, they note that nine moths in Brazil appeared to be hybrids formed by multiple rounds of H. armigera-H. zea mixing over time and/or introgression by H. zea into the H. armigera genome.

A team from Switzerland and the UK considers the consequences of altered evolutionary clock rate estimates when using genetic sequence data and phylogenetic analyses for epidemiologic applications during an infectious disease outbreak. The researchers used simulated data, together with real data for Ebola virus isolates collected in Guinea and in the early stages of a Sierra Leone outbreak, to explore methodological biases that affect epidemiological dynamic models. "During the West African Ebola virus disease epidemic, an unusually high evolutionary rate was initially estimated," the authors say, though their latest results suggest "high evolutionary rates are not necessarily real but can stem from methodological biases in the analyses."

University of Pennsylvania and Johns Hopkins University researchers describe AMP-activated protein kinase (AMPK) pathway activation in the hippocampus of mice that have been chronically exposed to nicotine, which they suspect may contribute to nicotine withdrawal symptoms and problems with kicking the nicotine habit in humans. Using Western blot analyses and other approaches, the team tracked phosphorylated AMPK (pAMPK) and AMPK levels in mouse hippocampal samples after chronic nicotine exposure and a day of nicotine withdrawal, identifying nicotine-associated hippocampal AMPK activation that quickly dissipated without nicotine. The authors note that they could combat post-nicotine withdrawal anxiety behaviors in mice by pharmacologically boosting AMPK levels with pAMPK or by peripheral tissue application of metformin, a documented AMPK activator.