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This Week in PNAS: Dec 25, 2013

Researchers from Yale University and elsewhere report in the Proceedings of the National Academy of Sciences this week that Hydra contain two PIWI proteins that are expressed in Hydra stem/progenitor cells, though not in differentiated cells. By sequencing piRNAs that bind to either Hywi or Hyli and mapping them to the Hydra transcriptome, they further found that piRNAs, especially ones expressed in interstitial lineage, are enriched for transposon transcripts. "These data strongly suggest that the PIWI–piRNA pathway has ancient and conserved stem cell functions beyond the germline and sets the stage for a mechanistic understanding of the pathway in adult somatic stem cells," the researchers add.

Also in PNAS, a research team led by the University of California, Riverside's Julia Bailey-Serres report on their mapping of ribosomes to mRNA in Arabidopsis thaliana seedlings under both control and low-oxygen conditions. The group found that, in the low-oxygen scenario, fewer ribosomes lined up at start codons, as compared to the control conditions, though hypoxia-associated genes saw an uptick in the number of polysome complexes. "The results demonstrate nearly 100-fold variation in the efficiency of translation of individual mRNAs under both conditions and provide unique insights into posttranscriptional and translational regulation modulated by low-energy stress in Arabidopsis thaliana," Bailey-Serres and her colleagues note.

Linnaeus University's Anders Forsman writes that genotypic and phenotypic diversity in founder populations is linked to better success in the establishment of those new populations. Through a series of meta-analyses, Forsman examined the effect of diversity on population establishment. "The recognition of the key role of founder genotypic and heritable phenotypic diversity for successful establishment has important implications for different areas and calls for some changes in policy and management," he notes. For instance, he says that conservation efforts should take such diversity into consideration when introducing new organisms into the population.