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This Week in PNAS: Nov 4, 2014

Editor's Note: Some of the articles described below are not yet available at the PNAS site, but they are scheduled to be posted some time this week.

In the early, online edition of the Proceedings of the National Academy of Sciences, researchers from China and the US describe genomic approaches they used to assess speciation and host adaptations by Metarhizium fungi. The team started by producing new long-read sequences to bolster the genome of the fungal species M. robertsii. That augmented genome sequence served as a reference for genomic analyses on six more Metarhizium species known for an array of lifestyle patterns. "Genomic analyses of seven Metarhizium species revealed a directional speciation continuum from specialists with narrow host ranges to transitional species and then generalists that paralleled insect evolution," the study's authors say.

For another PNAS study, investigators at centers in China and the US performed de novo genome sequencing and assembly on so-called "AA" diploid genomes from five Oyza sativa-related rice species selected from sites around the world as part of an effort better understand rice adaptation. The team saw significant levels of structural variation in the new genomes — which represented O. nivara from Asia, O. glaberrima and O. barthii from Africa, South America's O. glumaepatula, and O. meridionalis from Australia. These included expansions and contractions of gene and non-coding RNA families that contributed to lineage-specific traits, along with sequences showing signs of positive selection in genes related to processes such as reproduction, development, and disease resistance.

Finally, a Chinese and American team tracked down genes and microRNAs involved in metastatic reactivation of breast cancer in a mouse model of the disease. After injecting complementary DNAs and miRNAs from metastatic cells into mice with dormant lesions in their lungs, the researchers watched for instances of cancer reactivation, using sequencing to track down culprits contributing to this shift. The forward genetic screening approach "enables the identification and rapid biological validation of single genetic entities that are necessary to maintain dormancy or to induce reactivation," according to the authors. "This technology should facilitate the elucidation of the molecular underpinnings of these processes."