Oomycetes are filamentous parasitic microorganisms that infect plants and animals. They can decimate crops, causing such diseases as downy mildew, one of the most important and devastating diseases of grapevine. The real problem is that no targeted solution to combat these organisms exists. Treating the diseases they cause relies on massive use of environmentally toxic plant protection products.

A protein that was already there
But a solution may lie just over the horizon. Researchers from the Institut Sophia-Agrobiotech (1) have recently detected an oomycete-fighting action of a protein that is widespread in the animal kingdom, produced especially by people.

This substance was revealed by a small invertebrate, Biomphalaria glabrata, the freshwater snail found in tropical ponds, marshes and even sewer pipes, which are teeming with pathogenic organisms. “To ensure their survival, these molluscs lay their eggs in masses and cover them with a protective gel. While studying the gel’s composition, we observed that a single protein, BgLBP/BPI1, accounted for 60% of all proteins in the protective film,” explains Christine Coustau, research director at CNRS and co-author of the paper published in the journal PLOS Pathogens. “We were already aware of this protein’s antibacterial properties, but the high concentration attracted our attention. We wanted to see if it played an even bigger role.”

Double duty: a preventive and curative effect
The researchers’ intuition was spot on. Despite being very different, neither the plant pathogen Phytophthora nor fish pathogen Saprolegnia oomycete cells were unable to survive when exposed to BgLBP/BPI11 in vitro. During in vivoexperiments, the eggs laid by the snails in which production of the protein was inhibited were attacked by the oomycetes, contrary to the eggs with a normal quantity of the protein. In fact, the protein targets the oomycete’s zoospores, the pathogen’s means of propagation. By doing so, it is thought that the protein can both directly cure the disease and prevent it from spreading.

An eco-friendly solution
This protein could be a very effective weapon for protecting crops and aquaculture from oomycetes. “For the time being, our methods to combat these organisms are limited to highly toxic chemical products which, unfortunately, affect more than just the pathogens,” says Coustau. “With the new European standards, these types of non-targeted products are increasingly being banned. The snail protein could offer an alternative.” And what’s more, not only does the protein specifically target oomycetes, but it is also biodegradable, a significant environmental advantage. Quite naturally, this protein has piqued the interest of the phytosanitary industry.

Patent pending
Given the considerable economic interests of this discovery, INRA has filed a patent that covers the use of proteins from the same group as that produced by the freshwater snails against oomycete diseases. 

REFERENCE

Baron O L, van West P, Industri B, Ponchet M, Dubreuil G, Gourbal, B, Reichhart J-L, Coustau C. 2013. Parental Transfer of the Antimicrobial Protein LBP/BPI Protects Biomphalaria glabrata Eggs against Oomycete Infections. PLoS Pathog 9 (12): e1003792. doi:10.1371/journal. ppat.1003792