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This Week in PNAS: May 13, 2014

In the early, online edition of the Proceedings of the National Academy of Sciences, an American team took a transcriptome sequencing-based look at gene expression shifts that occur in the maize endosperm as that storage organ transits through the development process. Using RNA sequence data generated for maize endosperm and kernel samples from eight different developmental stages, the investigators identified subsets of genes that are specifically expressed at various time points, producing what they call a "preliminary atlas of spatiotemporal patterns of endosperm gene expression in support of future efforts for understanding the underlying mechanisms that control seed yield and quality."

Researchers from the UK, Italy, and France reported on findings from a Y chromosome study of the mosquito species Anopheles gambiae, which is known for carrying malaria-causing Plasmodium parasites. By tinkering with typical Y chromosome function in A. gambiae mosquitoes, the team created a model system that's expected to enable more detailed studies of the Y chromosome's role, if any, in sex determination in that species. "Our findings will aid studies of sex chromosome function," the study's authors write, "and enable the development of male-exclusive genetic traits for vector control."

In another study slated to appear online in PNAS, University of Toronto researchers turned to the flowering plant Rumex hastatulus for their study of Y chromosome degeneration. The team used SNP patterns, phylogeny, and other approaches to assess gene loss and mutations in Y-linked genes in the dioecious plant, which contains both ancestral and derived sex chromosome systems and versions of the X and Y chromosomes that evolved relatively recently. Along with signs of Y chromosome degeneration in general, for instance, results of the study suggest that amino acid substitutions, declining expression, and other degeneration-related features are more pronounced in genes that have gone without recombination for longer stretches of evolutionary time.