Origin and genome evolution of Cardamine occulta

For the first time, whole-genome cytogenomic maps were established for octoploid plants.

Cardamine occulta (Brassicaceae) is an octoploid weedy species (2n = 8x = 64) originating from Eastern Asia. It has been introduced to other continents including Europe and is considered to be an invasive species. Mandáková et al. reconstructed comparative genome structure, origin and evolutionary history in C. occulta and related species.

For the first time, whole-genome cytogenomic maps were established for octoploid plants. In Post-polyploid evolution in Asian Cardamine, polyploids have not been associated with descending dysploidy and intergenomic rearrangements. The combination of different parental (sub)genomes adapted to distinct habitats provides an evolutionary advantage to newly formed polyploids that can occupy new ecological niches.

Schematic diagram representing niche separation among the six studied Cardamine species along the hydrological gradient (a horizontal arrow separated by vertical broken lines) in natural and human-made habitats (vertically arranged and separated by a horizontal broken line). Black, blue and red rectangles represent habitat ranges of the parental diploids, autopolyploids and allopolyploids, respectively. Source Mandáková et al. (2019).

Commenting on the paper, Michael Chester said: “The results for the four Cardamine polyploids match a picture obtained for other meiotically stable polyploids; they are a chromosomal sum of their parental species with a few structural alterations. The key point is that the octoploids, for which there is little cytological or genomic information, do not appear materially different to the tetraploids.”

Chester concludes: “In my view this area of research is crying out for more collaboration between the plant breeding industry and academia, especially given that so many domesticated crops are polyploids.”

Further reading

Chester, M. (2019). The makings of higher-order polyploids. A commentary on: “The story of promiscuous crucifers: origin and genome evolution of an invasive species, Cardamine occulta (Brassicaceae), and its relatives.” Annals of Botany, 124(2), vi–vii. https://doi.org/10.1093/aob/mcz109

Mandáková, T., Zozomová-Lihová, J., Kudoh, H., Zhao, Y., Lysak, M. A., & Marhold, K. (2019). The story of promiscuous crucifers: origin and genome evolution of an invasive species, Cardamine occulta (Brassicaceae), and its relatives. Annals of Botany. https://doi.org/10.1093/aob/mcz019