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Crop Biotech Update

John Innes Centre Research Group Identifies Microbial Molecule that Turns Plants into Zombies

September 22, 2021
Phytoplasma effector SAP05 induces witches’ broom in Arabidopsis. Photo Source: Weijie Huang, JIC

Researchers from the Hogenhout group at the John Innes Centre and their collaborators have identified a manipulation molecule produced by Phytoplasma bacteria to hijack plant development. Inside a plant, this protein causes the breakdown of key growth regulators, triggering abnormal growth.

Phytoplasma are microbes that are notorious for their ability to reprogram their host plants' development. This group of bacteria is often responsible for the excessive number of branches in trees grown close together called ‘witches' brooms'. These bushy outgrowths are the result of the plant being stuck in a vegetative "zombie" state, unable to reproduce, and therefore progress to a ‘forever young' status. Phytoplasma bacteria also cause devastating crop diseases in grain and leaf crops such as lettuce, carrots, and cereals.

The research shows that the bacterial protein SAP05 manipulates plants by taking advantage of some of its own molecular machinery. This machinery, called the proteasome, breaks down proteins that are no longer needed inside plant cells. SAP05 then hijacks this process, causing plant proteins that are important in regulating growth and development to effectively be thrown in a molecular recycling center. Without these proteins, the plant's development is reprogrammed to favor the bacteria, triggering the growth of multiple vegetative shoots and tissues and putting the pause on plant aging.

The team uncovered in detail the role of SAP05 and found that the protein binds directly to both the plant developmental proteins and the proteasome. The research also allowed the team to pinpoint two amino acids in the proteasome that are needed to interact with SAP05. If the plant proteins are switched to have the two amino acids, they are no longer degraded by SAP05, preventing the ‘witches' broom' abnormal growth.

For more details, read the article on the John Innes Centre website.

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