Rapid genome evolution can occur in predictable patterns, an international team of scientists has found whilst researching young plant species. The discovery – published online in Current Biology (19 January 2012) – provides new evidence for predetermined pathways in evolution.
The work was carried out at the University of Florida and Iowa State University and involved scientists from Queen Mary, University of London, Massey University in New Zealand, and Universidade Federal de Juiz de Fora in Brazil; it was funded by the US National Science Foundation.
The scientists were studying a new species in the daisy family called Tragopogon miscellus, which originated naturally about 80 years ago in northwest USA, as a hybrid between two Tragopogon species that had been introduced from their native ranges in Europe. Tragopogon miscellus formed through the combined processes of hybridisation and genome doubling.
Tragopogonmiscellus has two versions of every gene, one from each parent species. The researchers found that many genes had lost one parental version within just 40 generations of evolution and patterns of gene loss were not random. Five different natural populations of independent origin showed similar patterns of gene loss, meaning evolution repeated itself.
When researchers compared the functions of genes lost to patterns resulting from an ancient genome-doubling event (thought to be 35 million years ago) in the same plant family, they found a similar pattern. “We were surprised at the speed at which patterns seemed to form in which genes show loss versus retention,” says lead author, Dr Richard Buggs, from Queen Mary’s School of Biological and Chemical Sciences.
The data seem to fit a hypothesis made by Professor Michael Freeling of University of California, Berkeley. This proposes that genes whose products interact closely with other gene products are more likely to be maintained in duplicate after genome doubling event formation. This can predetermine some aspects of genome evolution.
Many crops species underwent hybridisation and chromosome doubling during their domestication. A recently arisen natural polyploid such as Tragopogon miscellus can give unique insights into the early stages of this process.