In Nature this week, Umea University researchers report the draft assembly of the Norway spruce genome sequence, marking the first such milestone for any gymnosperm. Despite the size of its genome, the number of well-supported genes of the tree is similar to the much smaller genome of Arabidopsis thaliana, and they found no evidence of recent whole-genome duplication in the gymnosperm lineage. "Instead, the large genome size seems to result from the slow and steady accumulation of a diverse set of long-terminal repeat transposable elements, possibly owing to the lack of an efficient elimination mechanism," the investigators write. They also discovered that the expression of small RNAs, previously implicated in transposable element silencing, is tissue-specific and much lower than in other plants.
GenomeWeb Daily News has more on the spruce genome here.
Also in Nature, University of London investigators publish data contradicting the prevailing hypothesis that rare genetic variants account for much of the heritability of autoimmune disease. They looked for protein-coding regions of genes known to confer risk of autoimmune disorders in a large group of patients with specific autoimmune conditions, and discovered that rare coding-region variants at known loci have a negligible role in susceptibility to common autoimmune diseases.