Parasitic plants depend on the hormone ethylene to launch an attack

Parasitic plants rely on ethylene to successfully launch an attack, according to a new study from the Nara Institute of Science and Technology. The researchers found that a signal from the plant hormone ethylene initiates the invasion of the roots of a host plant. 

In order to become established, parasitic plants form a specialized structure known as a haustorium. This structure attaches to and penetrates the tissues of the host plant to absorb nutrients and water, as well as small materials including plant hormones and RNAs. The formation of the haustoria is regulated by signal molecules derived from the host plant.

“To understand the genetic programs for haustorium development, we identified mutants that displayed haustorial defects on host invasion,” said study lead author Songkui Cui. “Genome sequencing showed that these mutants have defective ethylene signaling, and it turned out that ethylene signaling genes are crucial for the parasitic plant to infect its host plant.”

Ethylene is a gaseous plant hormone that is involved in the ripening of fruit, aging of leaves, and the formation of root nodules. Ethylene can also provide resistance or susceptibility to viruses and invasive insects depending on the type of pathogen.

“Our results indicate that ethylene mediates host recognition in parasitic plants for host invasion,” explained project leader Satoko Yoshida. “This is the first time that the mediation of host invasion by parasitic plant genes has been identified via forward genetics. Our findings offer a new understanding of how a parasitic plant uses the ethylene molecule to tweak haustorium development and host invasion.”

The research was focused on a family of parasitic plants that includes destructive weeds. Prior to the study, the molecular basis for parasitism has been largely unexplored.

“Our results suggest that parasitic plants have taken over ethylene signaling for parasitism at multiple stages of their life cycle, such as germination, haustorium growth termination, and host invasion,” said Cui. “This knowledge could provide new ways to use ethylene and ethylene inhibitors to control a broader range of parasitic weeds, including those that don’t rely entirely on hosts to complete their life cycle, by manipulating haustorial function.”

The study is published in the journal Science Advances.

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By Chrissy Sexton, Earth.com Staff Writer