Characteristics, Roles and Applications of Proteinaceous Elicitors from Pathogens in Plant Immunity

Abstract

In interactions between pathogens and plants, pathogens secrete many molecules that facilitate plant infection, and some of these compounds are recognized by plant pattern recognition receptors (PRRs), which induce immune responses. Molecules in both pathogens and plants that trigger immune responses in plants are termed elicitors. On the basis of their chemical content, elicitors can be classified into carbohydrates, lipopeptides, proteinaceous compounds and other types. Although many studies have focused on the involvement of elicitors in plants, especially on pathophysiological changes induced by elicitors in plants and the mechanisms mediating these changes, there is a lack of up-to-date reviews on the characteristics and functions of proteinaceous elicitors. In this mini-review, we provide an overview of the up-to-date knowledge on several important families of pathogenic proteinaceous elicitors (i.e., harpins, necrosis- and ethylene-inducing peptide 1 (nep1)-like proteins (NLPs) and elicitins), focusing mainly on their structures, characteristics and effects on plants, specifically on their roles in plant immune responses. A solid understanding of elicitors may be helpful to decrease the use of agrochemicals in agriculture and gardening, generate more resistant germplasms and increase crop yields.

Systemic resistance induced in tomato plants by Beauveria bassiana‐derived proteins against tomato yellow leaf curl virus and aphid Myzus persicae

“…Although plants have acquired an array of defensive mechanisms against viral, bacterial or fungal pathogens, microbe-mediated induced resistance in plants have been of great interest in recent years as a novel microbiological tool in disease and insect pest management. [30][31][32][33][34] In this in-vitro study, B. bassiana strains BB252, BB72 and ARSEF-2860 were evaluated against TYLCV and aphid M. persicae. In the first two bioassays, different concentrations of conidial and filtrate suspensions of BB252 and BB72 strains were evaluated for their effect on TYLCV disease severity index.…”

“…Some studies have suggested the activation of plant defense genes via signals generated by elicitor-receptor interactions at plant cell plasma membranes resulting in defense reactions such as the biosynthesis of phytoalexins and phenolic compounds and the activation of plant defense-related enzymes. 34,46,47…”

“…However, it has been a challenging threat to tomato production through the world. Although plants have acquired an array of defensive mechanisms against viral, bacterial or fungal pathogens, microbe‐mediated induced resistance in plants have been of great interest in recent years as a novel microbiological tool in disease and insect pest management 30–34 …”

“…However, insight into the physiological and molecular pathways behind this enhanced expression of plant immune marker genes and plant defense against pests is required. Some studies have suggested the activation of plant defense genes via signals generated by elicitor‐receptor interactions at plant cell plasma membranes resulting in defense reactions such as the biosynthesis of phytoalexins and phenolic compounds and the activation of plant defense‐related enzymes 34,46,47 …”