Role of Microbial Bioagents as Elicitors in Plant Defense Regulation

Plants are constantly challenged by an array of potential pathogens like fungi, bacteria, viruses, insects, nematodes, etc., which lead to a significant loss to plant yield. Plants commonly overcome these phytopathogens by showing resistance through plant defense mechanisms. Several general microbe elicitors allow plants to mitigate the harmful effects of pathogenic microbes by enhancing the capability of plants to identify anonymous pathogenic agents and act as surveillance systems for plants. Elicitors are small drug-like compounds released by pathogens that are composed of molecules like oligosaccharides, lipids, peptides, and proteins, and they activate various kinds of defense responses in plants. They deliver information to plants through perception and identification of signaling molecules by cell surface-localized receptors, which is followed by the triggering of signal transmission pathways that commonly induces the synthesis of active oxygen species (AOS), phytoalexin production, production of defense enzymes, and the aggregation of pathogenesis-related (PR) proteins. This article chiefly highlights the role of microbial elicitors in improving plant defense mechanisms as well as their modes of action that have been used to boost up the plant immune system.