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This Week in PNAS: Jun 16, 2009

In PNAS this week, there's a series of articles in reference to the Two Centuries of Darwin Sackler Colloquium, most taking a closer look at natural selection and its relationship to key scientific questions today. In one, zoologists from the University of British Columbia check in on the role genetics plays in ecological speciation. Using the threespine stickleback (Gasterosteus aculeatus) as a model, they propose that adaptation to freshwater environments has happened several times "via a 'transporter' process in which selection in freshwater environments repeatedly acts on standing genetic variation that is maintained in marine populations by export of freshwater-adapted alleles from elsewhere in the range."

In other work, scientists looked at adaptive radiations, which, they say, "were central to Darwin's formation of his theory of natural selection," and how they affect speciation. Using sequence searches, phylogenetic analyses, and finding novel sequences with degenerate PCR and RACE, they identified 34 genes that are likely involved in the flavonoid pathway in Aquilegia, whose flowers change color due to changes in the types of anthocyanin pigments. The flavonoid pathway produces anthocyanins. "Future studies will be able to use these sequences along with next-generation sequencing technologies to follow expression and sequence variation at the population level," they say in the abstract.

Work led by the Max Planck Institute for Chemical Ecology's Rohit Shroff studied the application of MALDI-MS to metabolomics. Using an ionization mode of MALDI, based on Brønsted-Lowry acid-base theory, they were able to detect many metabolites covering important metabolic pathways such as the Krebs cycle, fatty acid and glucosinolate biosynthesis, out of extracts, biofluids, and in biological tissues from Arabidopsis thaliana, Drosophila melanogaster, Acyrthosiphon pisum, and human blood.

Finally, University of Pittsburgh researchers employed immunohistochemical and in situ hybridization analyses of 30 primary glioblastoma tissues to find that expression of Dicer, miR-222, or miR-339 was inversely associated with intercellular cell adhesion molecule (ICAM-1) expression. Their work suggests that "Dicer is responsible for the generation of the mature miR-222 and -339, which suppress ICAM-1 expression on tumor cells, thereby down-regulating the susceptibility of tumor cells to CTL-mediated cytolysis."

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