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This Week in PNAS: Dec 15, 2015

In the early, online edition of the Proceedings of the National Academy of Sciences, researchers from the US, Spain, and Denmark describe lineages identified in the human follicle mite Demodex folliculorum using hundreds of mitochondrial DNA sequences from 70 individuals of European, Asian, African, or Latin American descent. Based on 241 mite mitochondrial DNA sequences from these individuals, the team found that mites with the same mitochondrial haplotypes tend to be shared between individuals in close contact with one another, though mites from lineages found in an individual's ancestral region appear capable of persisting for long periods of time. GenomeWeb has more on the study, here.

A team from the US, Australia, and Sweden introduce evidence of copy number expansions involving the NK-lysin gene in cattle. By delving into a database of bovine sequences, the researchers unearthed seven types of sequences that appeared capable of coding for NK-lysin, an antimicrobial protein and effector molecule pumped out by certain cells in the innate immune system. Their phylogenetic analysis suggest these sequences belong to four NK-lysin genes, all found on chromosome 11 of the cattle genome, while follow-up experiments hinted that each of the genes is functional, but shows slightly different tissue-specific expression patterns.

Finally, Mexican researchers follow the epigenetic and gene expression effects of low phosphate availability in Arabidopsis plants. The team tracked cytosine methylation and gene expression differences in the roots and shoots of Arabidopsis thaliana seedlings grown under with different phosphate treatments, creating a range of low- or high-phosphate conditions. The results pointed to methylation shifts in plants grown with little phosphate, leading to altered expression of genes that help respond to such conditions. "[T]he expression of a subset of low Pi-responsive genes is modulated by methylation changes," the study's authors write, "and … DNA methylation is required for the proper establishment of developmental and molecular responses to [phosphate] starvation."