Scientists from Norway (UiT, The Arctic University of Norway), Germany (RWTH Aachen, Research Center Jülich, Helmholz Center, Technical University in Munich) and Austria (University of Vienna) have sequenced the genome of the parasitic flowering plant Cuscuta campestris. The work was led by parasitic plant researcher Prof. Kirsten Krause (UiT), and by genome expert Prof. Björn Usadel (RWTH) and was recently published in the high ranking journal Nature Communications (DOI: 10.1038/s41467-018-04344-z).
Along with numerous other plants species, C. campestris survives by infecting other plants and by stealing the nutrients that these produce by using the energy of the sunlight. Parasitic plants threaten crops production in many countries across the globe due to the damage they inflict on their victims. Like many other parasites, C. campestris is optimally adapted to its ecological niche. Most noticeably, it possesses specialized feeding organs that are absent in other plants. On the other hand it lacks some organs that other plants usually have, such as true leaves and roots.
The C. campestris genome sequence is the first one of a parasitic plant that has been released. It provides insight into the unique genomic footprint that the parasitic lifestyle has left in these unusual plants. One remarkable result is the finding that during its evolution, the parasite has taken up genome fragments from its hosts and incorporated them into its own genome – sometimes in smaller portions and sometimes in bigger chunks. This process, known as horizontal gene transfer (HGT), has equipped Cuscuta with new genetic material which may have given Cuscuta an advantage in their struggle to remain undiscovered by the host. From their careful analysis in the future we will be able to learn whether the parasite has selected genes that were beneficial for its survival, be it to conceal it from the host or be it to widen its repertoire of biomass-degrading enzymes.
Another finding is that more than 1700 genes that are otherwise highly conserved among land plants, are missing in the genome of the parasite. Many losses occur in functional clusters give evidence for the consequences of the independence of the parasites from, for example, photosynthesis.
With the insight that this genome gives researchers, they will be able to understand how this parasite can be so harmful to its host plants. Along with this understanding, it will be possible to develop new approaches to help farmers overcome this devastating weed.