Mitochondrial introgression suggests extensive ancestral hybridization events amongSaccharomycesspecies

1.AbstractHorizontal Gene Transfer (HGT) in eukaryotic plastids and mitochondrial genomes is common, and plays an important role in organism evolution. In yeasts, recent mitochondrial HGT has been suggested betweenS. cerevisiaeandS. paradoxus. However, few strains have been explored due to the lack of accurate mitochondrial genome annotations. Mitochondrial genome sequences are important to understand how frequent these introgressions occur and their role in cytonuclear incompatibilities and fitness. In fact, most of the Bateson-Dobzhansky-Muller genetic incompatibilities described in yeasts are driven by cytonuclear incompatibilities. In this study, we have explored the mitochondrial inheritance of several worldwide distributedSaccharomycesspecies isolated from different sources and geographic origins. We demonstrated the existence of several recombination points in the mitochondrial regionCOX2-ORF1, likely mediated by the transfer of two different types ofORF1(F-SceIII), encoding a freestanding homing endonuclease, or mostly facilitated by A+T tandem repeats and regions of integration of GC clusters. These introgressions were shown to occur at intra- as well as at interspecific levels. This suggest a complex model ofSaccharomycesevolution which involve several ancestral hybridization events in wild environments.

Radio observations of Galactic Center massive stars

High-resolution multi-frequency observations made with the VLA have revealed the presence of stellar winds in two of the three known massive stellar clusters at the Galactic Center (GC). At a distance of only 8.0 kpc, we are able to resolve radio sources associated with individual near-infrared sources known to be losing mass at high rates. Herein, I discuss the spectral and spatial properties of the radio sources and their near-infrared counterparts, their inferred mass-loss rates, variability and the prospects for detecting stellar winds sources in the Central Cluster, near the supermassive blackhole SgrA*. Such massive clusters as these three GC clusters have a profound impact on the interstellar medium, as evidenced by radio and X-ray observations of the surrounding regions.