Newly discovered enzyme is 'firing pin' for plant immunity

September 17, 2018, UC Davis
The SIK1 protein links plant cell membrane receptors that detect pathogens (left) to enzymes that produce reactive oxygen that attacks and kills them (right). Credit: Coaker lab/Cell Host & Microbe

Just like humans, plants have an immune system that helps them fight off infections. Plant immunity has some important differences: they don't make antibodies and can't fight off the same bug more quickly months or years later. However, plant cells can identify pathogens and react to them, often by producing a burst of reactive oxygen which is toxic to bacteria or fungi. Cells around an infected site will go into programmed cell death to seal off the disease.

Gitta Coaker, professor in the Department of Plant Pathology at UC Davis and colleagues have now identified a key step in how plant cells respond to . They have identified a family of kinase enzymes that activate the enzymes that make reactive . The work is published Sept. 12 in the journal Cell Host & Microbe.

"It was known that can produce reactive oxygen, but not how different proteins coordinate activation of the reactive oxygen synthase," Coaker said.

Every plant cell can respond to pathogens, Coaker said, through receptors on the cell surface that react to things like bacterial proteins. Plants have a large repertoire of these innate immune receptors: the small laboratory plant Arabidopsis, for example, has about 600 receptors that could respond to different pathogens.

Plants also have receptors with similarity to "Toll-Like Receptors" or TLRs. These TLRs are similar to proteins found in insects and mammals that trigger responses to bacteria and other pathogens. TLRs were first discovered in plants by Professor Pamela Ronald of the UC Davis Department of Plant Pathology.

Key Step Connects Detection and Action

Coaker's laboratory has now isolated an enzyme, SIK1, in Arabidopsis that is the "firing pin" of . It connects the receptors that detect pathogens to the reactive oxygen that kills them.

"This particular kinase works with and stabilizes others that converge on the enzyme that makes reactive oxygen," Coaker said. "We think this is a key step."

When the researchers deleted SIK1, the plants were unable to make enough reactive oxygen and were more susceptible to infections.

Coaker's group is now looking for homologs of SIK1 in other plants, including crop plants. They want to know if the gene can be tuned up to boost resistance to pathogens in crops. That could lead to new treatments for plant diseases and breeding of crops that are more resistant to infections.

Explore further: How plants harness microbes to get nutrients

More information: Meixiang Zhang et al, The MAP4 Kinase SIK1 Ensures Robust Extracellular ROS Burst and Antibacterial Immunity in Plants, Cell Host & Microbe (2018). DOI: 10.1016/j.chom.2018.08.007

Related Stories

How plants harness microbes to get nutrients

September 17, 2018

A Rutgers-led team has discovered how plants harness microbes in soil to get nutrients, a process that could be exploited to boost crop growth, fight weeds and slash the use of polluting fertilizers and herbicides.

Cancer-fighting drugs also help plants fight disease

August 14, 2018

Cancer-fighting drugs used on humans can help plants fight disease as well. That discovery, by two Washington State University plant pathologists, could help scientists develop new pathways for plants to battle infection, ...

A novel battleground for plant-pathogen interactions

March 13, 2014

Scientists at The Sainsbury Laboratory in Norwich, with collaborators at Michigan State University and the University of Illinois, have unveiled a new way in which plants perceive pathogens to activate immunity.

Recommended for you

Observation of quantized heating in quantum matter

February 19, 2019

Shaking a physical system typically heats it up, in the sense that the system continuously absorbs energy. When considering a circular shaking pattern, the amount of energy that is absorbed can potentially depend on the orientation ...

Sound waves let quantum systems 'talk' to one another

February 18, 2019

Researchers at the University of Chicago and Argonne National Laboratory have invented an innovative way for different types of quantum technology to "talk" to each other using sound. The study, published Feb. 11 in Nature ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.