Many wild and cultivated plants arise through the combination of two different species. The genome of these so-called polyploid species often consists of a quadruple set of chromosomes — a double set for each parental species — and thus has about twice as many genes as the original species. About 50 years ago, evolutionary biologists postulated that this process drives evolution, leading to new species. Due to the size and complexity of such genomes, however, proving this theory on a genetic level has been difficult.
Arabidopsis kamchatica arose through the natural hybridization of the two parental species A. halleri and A. lyrata between 65,000 and 145,000 years ago. With 450 million base pairs, its genome is somewhat small for a polyploid plant, but still very complex. Using state-of-the-art sequencing methods and technology as well as bioinformatics tools, the researchers were able to determine the genetic sequence of the plant individuals.
Due to the large amount of genetic information, A. kamchatica is better equipped to adapt to new environmental conditions. “With these results, we have demonstrated on a molecular-genetic level that genome duplications can positively affect the adaptability of organisms,” says plant scientist Timothy Paape. The multiple gene copies enable the plant to assume advantageous mutations while keeping an original copy of important genes. Paper. (open access) – Timothy Paape, Roman V. Briskine, Gwyneth Halstead-Nussloch, Heidi E. L. Lischer, Rie Shimizu-Inatsugi, Masaomi Hatakeyama, Kenta Tanaka, Tomoaki Nishiyama, Renat Sabirov, Jun Sese, Kentaro K. Shimizu. Patterns of polymorphism and selection in the subgenomes of the allopolyploid Arabidopsis kamchatica. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-06108-1
The researchers believe that the resulting huge genome enables the plant to be widespread more widespread. The article doesn’t say whether kamchatka can breed back into the parent groups, which would be helpful for assessing what is really happening here. Is polyploidy a frequent resort for tough plants?
The vid below is a good introduction to colonies of essentially the same plant that have diploid, polyploid, even octoploid members. See especially the kiwi fruit:
Notably, no one is claiming that most of the huge numbers of base pairs are “junk DNA.” Are we past that phase now? Let’s hope so.
See also: Polyploidy: Genetic fundamentalism is still looking for a job?
New species originated via polyploidy?
Genome doubling (polyploidy) a key factor in evolution?