Agricultural parasite avoids evolutionary arms race, shuts down genes of host plants

A parasitic plant has found a way to circumvent an evolutionary arms race with the host plants from which it steals nutrients, allowing the parasite to thrive on a variety of agriculturally important plants. The parasite dodder, an agricultural pest found on every continent, sends genetic material into its host to shut down host defense genes.

According to a new study by researchers at Penn State, dodder targets host genes that are evolutionarily conserved and sends many slightly different versions of its genetic weaponry to ensure effectiveness. This strategy, described in a paper appearing online in the journal eLife on December 17, 2019, restricts the host's ability to respond.

Instead of making its own energy through photosynthesis, dodder wraps itself around a host plant, using special structures to siphon off water and nutrients. Dodder can parasitize a variety of species, including some of agricultural importance like tomatoes, and its dense vine-like structure can interfere with harvesting machinery. The research team, led by Penn State Professor of Biology Michael Axtell, previously determined that dodder sends microRNAs -- short segments of nucleic acids whose sequence matches a segment of a host gene -- into its host. Binding to the host's protein-coding messenger RNAs prevents host proteins from being made.

"It seems that dodder creates several iterations of its microRNA in order to account for the natural variation within the host's targeted genes," said Johnson. "This shotgun strategy likely also helps the parasite be successful against a wide variety of host species." Next the researchers hope to explore the evolutionary origins of these microRNAs, as well as the cellular and molecular mechanisms of their delivery from parasite to host.