Gray mold is a fungal disease that affects more than 1,400 different plant species, including many fruits and vegetables. It causes billions of dollars in crop losses every year, and there is no effective cure for it. This disease can infect plants at any stage of growth, and it thrives in humid and cool conditions.
If you see fuzzy gray or brown spots on leaves, stems, flowers, and fruits, that's gray mold. If you have ever seen a rotten strawberry, you may have seen this prominent issue.
Gray mold is caused by a fungus called Botrytis cinerea, which has evolved to overcome the plant's immune system. The fungus secretes small molecules called RNA that can silence the genes involved in plant defense.
These RNA molecules are delivered to the plant cells inside lipid bubbles, also known as extracellular vesicles. These bubbles protect the RNA from degradation and help them enter the plant cells.
Researchers from the University of California, Riverside have discovered a way to disrupt this delivery system and weaken the fungus's ability to infect plants.
They found that a protein called tetraspanin is essential for the fungus to produce and secrete lipid bubbles.
By knocking out the gene that encodes tetraspanin, they reduced the fungus's ability to produce and deliver RNA weapons.
How tetraspanin works
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Tetraspanin is a protein that is embedded in the membrane of the lipid bubbles. It helps to shape and stabilize the bubbles and also to fuse them with other membranes. It is found in many organisms, including fungi, bacteria, and mammals, as per Phys.org.
It plays a role in various biological processes, such as cell adhesion, migration, signaling, and communication.
The researchers found that tetraspanin is highly expressed in Botrytis cinerea during infection. They used gene editing techniques to create mutant strains of the fungus that lacked tetraspanin. They then tested these strains on tomato plants and found that they were less virulent than the wild-type strain.
The mutant strains produced fewer lipid bubbles and fewer RNA molecules, and they were less able to suppress the plant's immune response.
Moreover, the researchers found that tetraspanin interacts with another protein called Vps4, which is involved in the formation and release of lipid bubbles.
By knocking out both tetraspanin and Vps4, they further reduced the fungus's ability to produce and deliver RNA weapons.
The researchers suggested that targeting tetraspanin or Vps4 could lead to a new generation of eco-friendly fungicides that can inhibit gray mold disease, as per UCR News.
These fungicides would be based on RNA molecules that can interfere with the expression of these proteins in the fungus.
Unlike conventional fungicides, which are often toxic to humans, animals, and the environment, RNA fungicides would be safe and biodegradable.
"Everything has RNA in it, and it is easily digested by humans and animals. RNA can be degraded quickly in the environment and wouldn't leave any toxic residues," said Hailing Jin, UCR professor of microbiology and plant pathology, who led the research project.
The researchers also hope that their findings can be applied to other fungal pathogens that use similar mechanisms to infect plants or animals.
For example, Magnaporthe oryzae, which causes rice blast disease, also secretes RNA molecules inside lipid bubbles to suppress host immunity. By blocking the production or delivery of these bubbles, it may be possible to control this devastating disease as well.
