Poacic Acid, an ecofriendly Antifungal

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Generating biofuels and bio-based chemicals from plants need a potential feedstock of sugar and the components which provide the same, are termed lignocellulosics. The process of converting plant materials to biofuels is aided by fermentation, but before this process can occur, the plant cell wall containing polysaccharides must be hydrolyzed to sugar monomers. Apart from the sugar monomers, small acids, furans and a few other compounds which affect microbial growth and inhibit fermentation are generated, thereby posing a challenge to the efficient microbial bioconverstion. Exploiting this little advantage of the inhibitors produced in the process, Piotrowski and his colleagues have been successful in discovering poacic acid, primarily found in its namesake grass Poaceae. It is produced in grass during the hydrolysis of diferulate, known to be lignocellulosic fermentation inhibitors.

With this study, the authors have addressed the threat posed to agricultural sustainability due to the increased resistance to antifungal agents. Variation of the fungal pathogens due to climatic changes also augments the need to discover new fungicides.

The study proved that poacic acid not only has a biological activity against yeast (Sacchromyces cerevisiae)- which is used as the golden standard to test the antifungal activity; but also other economically important fungal oomycete pathogens.

Chemical genomics was one of the approaches used by the team, wherein they deleted genes encoding specific pathways essential for the fungi’s sustenance, generating mutant strains and checked how they reacted to poacic acid. This study confirmed that the synthesis of ß-1, 3-glucan, which forms the cell wall of the fungi was damaged, thereby inhibiting the enzyme important for synthesis and the pathway involved. The study highlighted the uniqueness of this new compound due to its specificity in localizing to the cell surface, targeting ß-1,3-glucan and its potential in causing rapid cell leakage.

Yeast treated with poacic acid also showed a difference in morphology, these cells had variations in their growth pattern, the daughter cell size was smaller than the parent bud, which was confirmed by the uneven cell wall staining.

They also investigated the effect of this novel compound on soybean leaves affected by S.sclerotorium, an oomycete causing them to rot. Lesion development was markedly reduced in poacic acid treated leaves and similar effects were seen fungi causing blight in tomato and potato crops.

With this study published in PNAS, the authors are positive that this natural plant-derived fungicide can play a promising role in eradicating fungicide resistance due to its broad mechanism of action. They speculate that poacic acid could also be used in combination with other fungicides having the capability to disrupt cell wall integrity. The goal to make poacic acid commercially available has a long way to go, but it is indeed a boon in disguise for the farmers and a step closer in creating a safer environment.

Plant-derived antifungal agent poacic acid targets ß-1, 3-glucan