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This Week in PLOS: Jul 23, 2018

In PLOS Genetics, researchers from the University of Texas and Wayne State University explore potential ties between transcription levels and mutations involving the non-canonical DNA residue uracil in the budding yeast model organism Saccharomyces cerevisiae. Prior studies hinted that mutations related to uracil incorporation in the yeast genome might stem from repair-associated DNA synthesis that occur when damage arises during transcription, the team notes. With a mutation reporter system, the investigators saw a rise in mutations associated with uracil excision in highly transcribed parts of the genome — a pattern supported by their subsequent quantitative long amplicon real-time PCR experiments. "[O]ur results show that the DNA composition can be modified to include higher uracil content through the non-replicative, repair-associated DNA synthesis," they write.

A University of Missouri at Columbia-led team presents a transcriptomic analysis of the medicinal leech, Hirudo verbana, in PLOS One. The researchers produced a de novo transcriptome using samples from one adult leech, focusing on the central nervous system of the invertebrate model organism, used to study nervous system and developmental questions. With the help of an available sequence database, they annotated 39,047 contigs in the central nervous system transcriptome, uncovering more than 100 ion channel, receptor, or other suspected nervous system genes not reported previously. The study "lays a foundation for further molecular analyses in the leech preparation that has been a stalwart contributor to our understanding of the fundamentals of nervous system function and behavior," the authors write.

Researchers from Thailand and the US report on genetic heterogeneity in scrub typhus-causing Orientia tsutsugamushi bacteria found in dozens of trombiculid mite vectors for a paper in PLOS Neglected Tropical Diseases. Starting from 28 O. tsutsugamushi-positive mites isolated from rodents and other small mammals in Thailand, the team used targeted sequencing to genotype O. tsutsugamushi, exploring relationships between bacterial genetics, the mite vector species involved, and host mammal. The results point to high O. tsutsugamushi diversity within individual vector mites, for example, and up to three bacterial genotypes turned up in a single mite.