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This Week in PNAS: Dec 30, 2014

A Yale University-led team used data collected over more than three decades for the Framingham Heart Study to look at how factors such as an individual's age and year of birth influence the association between body mass index and an obesity-related variant in the FTO gene. By considering individuals' body mass index over time in relation to their age, birth year, and FTO genotype, the researchers saw increasingly pronounced associations between obesity and FTO genotype depending on birth year, but little to no association in individuals born prior to 1942. "These results suggest genetic influences on complex traits like obesity can vary over time," the study's authors say, "presumably because of global environmental changes that modify allelic penetrance." GenomeWeb has more on this study here.

With the help of small RNA sequencing, an international group profiled Anopheles gambiae mosquito responses to arborovirus exposure and infection. In the mosquito's midgut, where viruses first take hold after being consumed in blood, the researchers saw evidence of antiviral activity associated with immune signaling. On the other hand, antiviral pathways involving small interfering RNAs appeared to be more active during systemic infection of the mosquitoes, showing little in the way of first-line defense at midgut sites, while microbial flora in the midgut seemed to contribute to viral infectivity.

Finally, researchers from Germany and the US describe shifts in expression by a circadian cycle gene called GIGANTEA that seem to contribute to Arabidopsis plant phenotypes. The team tracked transcription of GIGANTEA, a gene typically upregulated in the evening, in plants from 77 Arabidopsis accessions during days of different lengths. The variability they detected in GIGANTEA expression dynamics led the study's authors to conclude that alleles present in different accessions can influence plants' sensitivity and response to light input information. "Such alleles could confer an advantage by adjusting the activity of temporally regulated processes without severely disrupting the circadian system," they write.