Inferences of evolutionary relationships from a population survey of LTR-retrotransposons and telomeric-associated sequences in theSaccharomyces sensu stricto complex

Abstract

The Saccharomyces sensu stricto complex consists of six closely related species and one natural hybrid. Intra-and inter-species variability in repetitive elements can help elucidate the population structure and evolution of these close relatives. The chromosome positions of several telomeric associated sequences (TASs) and LTRretrotransposons have been determined, using PFGE, in 112 isolates. Most of the repetitive elements studied are found in multiple copies in each strain, although in some subpopulations these elements are present in low copy number or are absent. Hybridization patterns and copy numbers of the repetitive elements correlate with geographic distribution. These patterns may yield interesting clues as to the origins and evolution of some TASs and retrotransposons, e.g. we can infer that Y originated on the left end of chromosome XIV. There is strong evidence for horizontal transfer of Ty2 between S. cerevisiae and S. mikatae. Ty1 and Ty5 are either lost easily or frequently horizontally transferred. We have also found some gross chromosomal rearrangements in isolates within species and a few new natural hybrids between species, indicating that these processes occur in the wild and are not limited to conditions of human influence. DNA sequences have been deposited with the EMBL/GenBank database under Accession Nos AJ632279-AJ632293.

Telomere behavior in a hybrid yeast

“…The sequences adjacent to the repeats are also rapidly evolving both within and among Saccharomyces species [3]. For example, the subtelomeric repeat, called the Y′ element, is present in S. cerevisiae, but absent from S. bayanus [4]. Although the X element, another subtelomeric repeat, is present in both species, the primary sequences have diverged both within and between the two species [4].…”

“…For example, the subtelomeric repeat, called the Y′ element, is present in S. cerevisiae, but absent from S. bayanus [4]. Although the X element, another subtelomeric repeat, is present in both species, the primary sequences have diverged both within and between the two species [4]. Recent whole genome sequencing of Saccharomyces sensu stricto species, including S. paradoxus, S. mikatae, and S. bayanus, has revealed that in addition to the rapid evolution of X and Y′ elements, the gene families found within the subtelomeric regions also show significant differences in different species [5].…”

Molecular genetic study of introgression between Saccharomyces bayanus and S. cerevisiae

“…The formation of hybrids in the fermentation environment is not restricted to brewing process. Recently, a number of S. cerevisiae × S. bayanus hybrids have been found among industrial strains, including wine isolates (Masneuf et al, 1998;Naumov et al, 2000c;Le Jeune et al, 2004;Naumova et al, 2004;Liti et al, 2005).…”

Reconstruction of the genome origins and evolution of the hybrid lager yeast Saccharomyces pastorianus

“…As described in more detail below, S. pastorianus has been shown to be a hybrid organism, and it is likely that lager yeast arose by "instantaneous speciation" due to an interspecific hybridization event (Martini and Kurztman 1985;Martini and Martini 1987) that occurred during these selective growth conditions. Not only is this mechanism known to be common in angiosperm speciation (Hegarty and Hiscock 2005), but interspecific hybridization (or "allopolyploidy") among the closely related sensu stricto Saccharomyces yeast species is known to occur in both industrial and natural settings (Masneuf et al 1998;Groth et al 1999;de Barros Lopes et al 2002;Liti et al 2005;Gonzalez et al 2007Gonzalez et al , 2008Lopandic et al 2007), and indeed may also have been the mechanism leading to the original whole-genome duplication in the ancestor of the Saccharomyces clade (Scannell et al 2006).…”