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Newly acquired plasmids are frequently lost due to fitness costs. Here, Zhang et al. show that the evolution of satellite plasmids with gene deletions can reduce fitness costs by driving down the copy number of full plasmids and thus favor maintenance of the full plasmid and its novel accessory genes.
Why transposable elements (TEs) accumulate in polyploids and the evolutionary implications remain unclear. Here, the authors show that following whole genome duplication, relaxed purifying selection is the main driver of TE over-accumulation, which provides variants for rapid local adaptation.
The contribution of transposable elements (TEs) to the creation of heritable mutations is unknown. Here the authors show in Arabidopsis that TEs accumulate exponentially once mobilized and that COPIA retrotransposons preferentially integrate in environmental response genes in a H2A.Z-dependent manner.
Wolbachia bacteria live within the cells of many insects, including the mosquito Culex pipiens. Here, the authors analyse new and existing Wolbachia metagenomes from C. pipiens mosquitoes and find evidence of a plasmid, which may facilitate genetic manipulation of these bacteria for vector control applications.
Transposable element (TE) bursts shape genome evolution but their origin remains unclear. Here, the authors show that a burst is restricted to only a few domesticated rice accessions and is associated with the acquisition of two TE variants, Ping16A and Ping16A_Stow, not the loss of TE silencing.
Large-scale patterns of genomic repeat element evolution have been studied mainly in birds and mammals. Here, the authors analyze the genomes of over 60 squamate reptiles and show high variation in repeat elements compared to mammals and birds, and particularly high microsatellite seeding in snakes.
It is unclear if experimental evolution is a good model for natural processes. Here, Clerissi et al. find parallels between the evolution of symbiosis in rhizobia after horizontal transfer of a plasmid over 10 million years ago and experimentally evolved symbionts.
Retrotransposons are abundant in eukaryotic genomes. Here, Sanchez et al. show evidence of high-frequency recombination between members of an LTR retrotransposon family during transposition bursts in Arabidopsis.
Teratorn is a large mobile genetic element originally identified in the small teleost fish medaka. Here, the authors show that Teratorn is derived from the fusion of a piggyBac superfamily DNA transposon and an alloherpesvirus and that it is widely found across teleost fish.
Helitron elements are proposed rolling-circle transposons in eukaryotic genomes, but experimental evidence for their transposition has been lacking. Here, Grabundzija et al. reconstruct an active Helitron from bats which they name Helraiser, and characterize its mechanism of transposition in cell-free reactions and in human cell cultures in vitro.
Horizontal gene transfer is important for bacterial evolution but the molecular basis of its fitness costs remain unclear. Here the authors show that fitness costs produced by a plasmid in P. aeruginosaare alleviated by mutations in recently acquired genes encoded in mobile genetic elements.
Horizontal gene transfer occurs in most bacteria, yet it is unclear whether it happens in clonal species. Here, Everitt et al. show widespread within-species recombination, driven by mobile elements, in the genome of the pathogen Staphylococcus aureus, but no recombination between closely related strains.
Horizontal gene transfer of mobile genetic elements contributes to bacterial evolution and emergence of new pathogens. Here the authors demonstrate that the highly diverse structure of wall teichoic acid polymers governs horizontal gene transfer among Gram-positive pathogens, even across long phylogenetic distances.