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This Week in Cell: Sep 25, 2014

A bacterial endosymbiont living in some cicada insects appears to have split into two species that remain metabolically dependent on one another, each carrying genome sequences that complement one another to form a single complete genome. An American and Canadian research team took a comparative genomic and microscopic look at the Tettigades cicadas and their endosymbiont Hodgkinia cicadicola. The analysis revealed two separate H. cicadicola chromosomes that were subsequently found to house distinct but inter-dependent gene sets that resembled findings following events such as speciation and whole genome duplication, the study's authors note. "We suggest that our results highlight the potential power of non-adaptive forces in shaping organismal complexity," they add.

Researchers from the US and Switzerland sequenced the germline genome of the single-celled ciliate Oxytricha trifallax in an effort to understand the characteristic genome disassembly and rearrangement that the organism undergoes during development. When the team compared the Oxytricha germline genome — found in its micronucleus — to sequences from the organism's transcriptionally active somatic macronucleus, it uncovered more than 3,500 genes that are scrambled in the somatic genome, along with genes that get post-translationally modified as the genome is rearranged. Another 800 or more genes appear to be germline restricted, the investigators report, noting that the new genome "provides a draft of a scrambled genome and a powerful model for studies of genome rearrangement."

An RNA modification called pseudouridylation appears to occur quite frequently across messenger RNAs and non-coding, small nucleolar RNAs transcribed in human and yeast cells, according to a transcriptome mapping study by investigators in the US and Puerto Rico. Using a sequencing method specifically designed to quantify pseudouridine levels in conjunction with strand-specific RNA sequencing, the team assessed yeast cells from both wild type and deletion mutant strains, as well as human cells from HEK293 and fibroblast cell lines. Together, the sequence data highlighted hundreds of RNA sites that are prone to pseudouridylation and provided clues to the molecular machinery that controls this process.