Parasitic plants may form weapons out of genes stolen from hosts
Sneaky parasitic weeds may be able to steal genes from the plants they are attacking and then use those genes against the host plant, according to a team of scientists.
|Orobanche cumana (right) is parasitizing a sunflower (left) |
[Credit: Christopher Clarke, Penn State]
"These parasitic plants that we study from the broomrape family include some of the the world's most devastating agricultural weeds," said dePamphilis. "The HGT discovery is really part of our effort to try to better understand how parasitic plants work and how we can better control them. Our hope is that we can use this information to find the best strategies to generate, or breed, resistant host plants."
The researchers, who released their findings in the current issue of Proceedings of the National Academy of Sciences, suggest that the transfer could boost the parasitic plant's ability to invade their hosts and overcome defenses the host creates to try to ward off attacks. HGT may also help reduce the risk of infection for the parasites.
|Striga asiatica is shown on sorghum in Malawi-Tanzania |
[Credit: Mike Timko]
"Parasitic plants seem to have a far greater rate of horizontal gene transfer than non-parasitic plants and we think this is because of their very intimate connection they have with their host," said dePamphilis.
The roots of the parasite contact and enter the host, and then begin extracting water, sugars, mineral nutrients and even nucleic acids, including DNA and RNA, he added.
"So, they are stealing genes from their host plants, incorporating them into the genome and then turning those genes back around, very often, as a weapon against the host," said dePamphilis.
|Triphysaria eriantha field with wild grasses and other host plants in California |
[Credit: Huiting Zhang]
To detect HGT in the plants, the researchers used data generated by their collaborative research effort funded by the U.S. National Science Foundation -- the Parasitic Plant Genome Project -- to generate evolutionary histories for thousands of genes in the parasitic plants, said dePamphilis.
The researchers focused on transcriptomes -- expressed gene sequences -- of three parasitic plants:, Triphysaria versicolor, also called yellowbeak owl's-clover; Striga hermonthica, or giant witchweed; and Phelipanche aegyptiaca, called Egyptian broomrape, as well as the nonparasitic plant Lindenbergia philippensis, and genome sequences from 22 other nonparasitic plants. Because the researchers considered mRNA, which can move between hosts and their parasites, as a possible source of the transfers, they tested and re-tested the data to rule out the experimental host as the source of the genetic material. Instead, they found that the foreign sequences had been derived from entire genes of past host plants and incorporated into the parasitic plants genomes.
Future research may investigate the mechanism of horizontal gene transfer to help engineer improved plant defenses against parasitic attacks, dePamphilis said.
Source: Penn State University [October 24, 2016]