Meiosis is a type of cell division which is essential for halving the number of chromosomes to make gametes needed for sexual reproduction in animals, plants and fungi. A further feature of meiosis, and one of the main driving forces behind the success of sex, is that it affords the organism a chance to shuffle its genome, using well distributed recombination events (“crossovers“) to make a new meld of its parents’ genotypes. Although crossovers benefit from being randomly placed, their number and approximate position needs to be tightly regulated. In a new research article by Marina Jahns, Mathilde Grelon and colleagues, they investigate how this is done. They identified a novel regulatory pathway controlling crossover localisation in Arabidopsis plants, which may also be conserved in mammals. This pathway involves post-translational modification via neddylation (covalent attachment of the ubiquitin-related protein Nedd8).
Despite the public health significance of Avian influenza viruses (pivotal to the origination of human pandemic strains) much is not understood about their ecology and evolution in wild birds. The host pool in birds supports a very large range of strains, but once in humans the genetic diversity is much reduced. Benjamin Roche, Pejman Rohani and colleagues present comparative analyses of human and avian viruses and use computational models to try to explain these differences. They conclude that the combination of the short lifespan of wild birds, and greater durability of viruses in aquatic environments, is key to maintaining the high levels of flu virus diversity observed in wild birds.
The archaea and the bacteria – the two deepest branches of the tree of life. They share many features in common, but their cell membranes are profoundly different. It seems therefore that the membranes must have evolved after the two diverged from their last universal common ancestor (“LUCA”). But if that ancestor did not have a membrane, how could it harvest energy, and why did the archaeal and bacterial progeny produce such different membrane structures? Victor Sojo, Andrew Pomiankowski, and Nick Lane developed a mathematical model of primordial membrane bioenergetics, showing that a leaky membrane of simple lipids could be a precursor of both types of modern membrane. Read more in the accompanying synopsis.