Wasn’t suppose to happen in the old days, right? But it turns out to be surprisingly common.
The common baker’s yeast (Saccharomyces cerevisiae) is used to make bread, wine and beer, and is the laboratory workhorse for a substantial proportion of research into molecular and cell biology. It was also the first non-bacterial living thing to have its genome sequenced, back in 1996. However, when the sequence of that genome emerged it appeared that the scientists were seeing double – the organism seemed to have two very different versions of many of its genes. How could this have happened?
Researchers from the Centre for Genomic Regulation (CRG) Barcelona, Spain, writing in the Open Access journal PLOS Biology in a paper publishing 7th August, have now proposed a new theory to explain this phenomenon; the answer involves an ancient mating event between two distinct species, and may have implications for our own genomes.
Since the initial observation, scientists had assumed that about 100 million years ago the entire genome had somehow been duplicated, and that subsequently and although some genes had been lost, the yeast kept two copies of many genes and used them to acquire new functions that helped it to survive.
Such “whole genome duplications” are now known to be surprisingly widespread; for instance, we know that whole genome duplications were important in the early evolution of vertebrates (our own genomes bear the hallmarks of two separate ancient whole genome duplication events) and that it is a very common phenomenon in plants, especially cultivated ones such as wheat. More.
See also: New call for an Extended Evolutionary Synthesis (The main problem the extended evolutionary synthesis creates for Darwinism (Modern Synthesis) is that evolution happens in many different ways, not just their way.)
Here’s the abstract:
Whole-genome duplications have shaped the genomes of several vertebrate, plant, and fungal lineages. Earlier studies have focused on establishing when these events occurred and on elucidating their functional and evolutionary consequences, but we still lack sufficient understanding of how genome duplications first originated. We used phylogenomics to study the ancient genome duplication occurred in the yeast Saccharomyces cerevisiae lineage and found compelling evidence for the existence of a contemporaneous interspecies hybridization. We propose that the genome doubling was a direct consequence of this hybridization and that it served to provide stability to the recently formed allopolyploid. This scenario provides a mechanism for the origin of this ancient duplication and the lineage that originated from it and brings a new perspective to the interpretation of the origin and consequences of whole-genome duplications. Open access – Marcet-Houben M, Gabaldón T (2015) Beyond the Whole-Genome Duplication: Phylogenetic Evidence for an Ancient Interspecies Hybridization in the Baker’s Yeast Lineage. PLoS Biol 13(8): e1002220. doi:10.1371/journal.pbio.1002220
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