Zombie Plants: Pollinating Leafhoppers Transmit Deadly Disease, Researchers Say

Some pollinating insects may be turning the plants they feed on into zombies, researchers from Friedrich Schiller University Jena (Uni. Jena) reveal in a new study. Generally, pollination benefits both parties: hungry insects feed on flower nectar while spreading it's pollin, helping the plant to reproduce and aiding in its survival as a species. But in exchange for delicious plant juice, some leafhoppers may be transmitting deadly bacteria to flowering plants and turning them into the living dead.

Leafhoppers are one of the largest families of plant-feeding insects. In fact, there are more leafhopper species worldwide than all species of birds, mammals, reptiles, and amphibians combined. Leafhoppers are known to feed on a broad range of  fruit, vegetable, flower, and woody plants. When doing so, the insects suck the nectar from vascular plants. Often times, this leaves plants stippled, pale, or brown; and, in some cases, their roots become shriveled and die. In the recent study, researchers specifically examined what happens when leafhoppers feed on flowering plants and subsequently infects them. 

"The insects transmit bacteria – so-called phytoplasmas – which destroy the life cycle of the plants," Dr. Günter Theißen, professor from the Uni. Jena, explained in a news release. "These plants become the living dead. Eventually they only serve the spread of the bacteria."

Phytoplasmas are pathogenic bacteria that ultimately result in abnormal plant development. When infected, plants form vestigial leaf structures instead of blossoming. This prevents sexual reproduction and threatens the plants' survival. Also, when the plant becomes infected, all it can do is make the bacteria available for other leafhoppers to spread. Currently there is no way to prevent or cure infected plants, according to the release. After taking a closer look at this bacterial infection, researchers discovered the phytoplasma protein SAP54 is to blame for the zombie-like effect on plants.  

"This protein comes from the bacteria and bears a strong structural resemblance to proteins which form a regulatory complex inside the plant, which permits a normal development of the blossom," Florian Rümpler, a post-graduate student and lead author of the study, said in the release. "This prevents the formation of petals and flower organs."

Next, researchers modeled this interaction to show that SAP54 imitates the structure of MADS-domain-proteins, which are responsible for regulating blossom development. When this happens, the infected plants are tricked into binding with SAP54 proteins instead of their own, which ultimately leads to the destruction of MADS-domain-proteins.

So how do SAP54 proteins imitate MADS-domain-proteins so perfectly?

"It is conceivable that both proteins trace back to a common origin," Rümpler explained.

Though, after further study, researchers suggest that the evolution of the bacterial protein has led to its flawless adaption to its host.

"Although, we understand the infection process better now, we are not yet able to prevent it," Theißen added in a statement.

Researchers hope that their study will eventually be able to reduce the effects of the phytoplasma infecting flowering plants. Their findings were recently published in the journal Trends in Plant Science. 

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