Enhancing Plant Defense Mechanisms and Managing Plant-Parasitic Nematodes through Ascaroside Signaling

Abstract

Nematodes, like insects, produce specific pheromones known as ascarosides, which regulate key behaviors, growth, and development. First identified in Caenorhabditis elegans, ascarosides are secreted in species-specific blends and concentrations across all nematode species. Studies have shown that certain ascarosides act as plant elicitors, inducing physiological responses that trigger plant defense mechanisms and inhibit pathogen proliferation. Notably, ascr#1, ascr#5, and ascr#18 have been shown to increase the production of defense-related compounds such as reactive oxygen species, salicylic acid, and jasmonic acid. These ascarosides also promote callose formation in some plant species, aiding in pathogen suppression. Additionally, plants can metabolize ascr#18 and release ascr#9 through their roots, suggesting a potential role for ascr#9 in managing plant-parasitic nematodes. While ascarosides can be chemically synthesized, entomopathogenic nematodes (EPNs) offer an alternative source of these pheromones. Liquid culture mass production of EPNs in fermenters produces billions of nematodes, but the remaining liquid medium is often discarded. This by-product could serve as a valuable alternative source for obtaining ascarosides. This review provides a comprehensive overview of the role of ascarosides in triggering plant defense responses, methods for their production, and their potential applications in managing plant-parasitic nematodes.