Modified yeast inhibits fungal growth in plants

Saccharomyces cerevisiae, SEM image. Credit: Mogana Das Murtey and Patchamuthu Ramasamy / CC BY-SA 3.0

About 70-80% of crop losses due to microbial diseases are caused by fungi. Fungicides are key weapons in the arsenal of agriculture, but they present environmental risks. Over time, fungi also develop resistance to fungicides, leading growers on an endless quest for new and improved ways to control fungal diseases.

The latest development takes advantage of a natural defense of plants against fungi. In an article published in Biotechnology and bioengineering, engineers and plant pathologists at UC Riverside describe a way to design a protein that prevents fungi from breaking down cell walls, as well as a way to produce this protein in quantity for external application as a natural fungicide. The work could lead to a new way to control plant diseases that would reduce reliance on conventional fungicides.

To enter plant tissue, fungi produce enzymes that use catalytic reactions to break down hard cell walls. Among these are polygalacturonases, or PGs, but plants are not helpless in the face of this attack. Plants produce proteins called PG inhibitor proteins, or PGIPs, which slow down catalysis.

A group of researchers at UC Riverside have located the segment of DNA that tells the plant how to make IFMPs in common green beans. They inserted complete and partial segments into the genomes of baker’s yeast for the yeast to produce IFMPs. The team used yeast instead of plants because yeast doesn’t have its own IFMP to muddle the experience and grows faster than plants.

After confirming that the yeast reproduced with the new DNA, the researchers introduced it to cultures of Botrytis cinerea, a fungus that causes gray rot in peaches and other crops; and Aspergillus niger, which causes black mold on grapes and other fruits and vegetables.

Yeast which had both complete and partial DNA segments encoding the production of PGIP successfully retarded fungal growth. The result indicates that the yeast produced enough PGIP to make the method a potential candidate for large-scale production.

“These results reaffirm the potential of using IFMPs as exogenous applied agents to inhibit fungal infections,” said Yanran Li, assistant professor of chemical and environmental engineering at the Marlan and Rosemary Bourns College of Engineering, who worked on the project. with plant pathologist Alexander Putman in the Department of Microbiology and Plant Pathology. “IFMPs only inhibit the infection process, but are unlikely to be fatal to fungi. Therefore, application of this natural peptide derived from plant proteins to crops is likely to have minimal impact on the ecology of plant microbes. “

Li also said that IFMPs likely biodegrade into naturally occurring amino acids, meaning fewer potential effects for consumers and the environment compared to synthetic small-molecule fungicides.

“The generation of transgenic plants takes time and the application of such transgenic crops in the agricultural industry requires a long period of approval. On the other hand, modified IFMPs which are derived from natural proteins are applicable as an accelerated product for FDA approval, if they can be used exogenously in a fungicide-like manner, ”Li said.

By tweaking the yeast in a slightly different way, the researchers were able to make it exude IFMPs for external application. Previous studies have shown that freeze-drying natural microbes on apples, then reconstituting them in solution and spraying them on the crops, significantly reduces fungal disease and losses during transport. The authors suggest that yeast expressing PGIP could be used in the same way. However, they warn that because plants also form beneficial relationships with certain fungi, future research will need to ensure that plants only repel harmful fungi.

Li will continue to design IFMPs for increased efficacy and a broader spectrum against various pathogenic fungi. Meanwhile, Li and Putman will continue to assess the potential of using modified IFMPs to suppress preharvest and postharvest diseases induced by fungi.

Widely applicable new tool provides insight into fungicide resistance

More information:
Tiffany Chiu et al, Exploring the Engineering Potential of Polygalacturonase Inhibiting Protein as an Environmentally Friendly, User-Friendly and Non-toxic Pest Control Agent, Biotechnology and bioengineering (2021). DOI: 10.1002 / bit.27845

Provided by the University of California – Riverside

Quote: Modified Yeast Inhibits Fungal Growth in Plants (2021, July 15) retrieved July 15, 2021 from

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