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This Week in PNAS: Dec 27, 2016

In the early, online edition of the Proceedings of the National Academy of Sciences, an international team describes apparent ties between gene flow restriction and pyrethroid insecticide resistance in Anopheles funestus, a mosquito that can carry malaria-causing parasites. Using microarrays and PCR-based microsatellite marker genotyping, the researchers assessed genome-wide transcription profiles and genetic diversity in An. funestus mosquitoes from sites in Zambia, Malawi, and Mozambique. Along with restricted gene flow between populations, the analysis revealed differences in the cytochrome P450 genes expressed to bolster resistance to pyrethroid insecticides such as permethrin or deltamethrin. "[M]ultiple CYP450s, genes linked to xenobiotic metabolism, are responsible for insecticide resistance, but their impact varies significantly depending on geography," the authors note. "Genetic diversity analysis revealed that this genomic variation is associated with barriers to gene flow between southern African populations of An. funestus."

Researchers from North Carolina State University, the US Department of Agriculture's Agriculture Research Service, and Cotton Incorporated consider leaf shape genetics in the cultivated Upland cotton plant, Gossypium hirsutum, with an eye to cotton crop improvement. The team investigated a locus previously linked to lobed leaf morphology, analyzing more than 1,500 leaves from hundreds of cotton lines and fine-mapping the locus in characterized cotton lines and crosses. In the process, the group identified a causal role for a transcription factor related to the LMI1 gene in Arabidopsis in leaf shape that was explored in more detail using genomic data and gene silencing experiments. "This study, identifying a single locus responsible for cotton leaf shape, expands the genetic toolbox for breeders to produce superior cotton varieties," the authors write.

Finally, a Virginia Commonwealth University-led team looks at ways of curbing the invasiveness of radiation-induced forms of glioblastoma multiforme (GBM) brain tumors in cell lines and mouse models. Based on results from past studies, and from their own analyses of available expression data, the researchers focused on a gene called MDA-9, which shows increased expression in some human GBM tumors from cases with poor outcomes or treatment response. Their results suggest that GBM response to radiation was enhanced, and invasiveness decreased, when the MDA-9 was silenced using small hairpin RNA or a small molecule inhibitor known as PDZ1i.