Plant Elicitor Peptides: Mechanism of Action and Its Applications in Agriculture

In agriculture, to protect crops from insect and pests and for increasing crop yield and quality, the agrochemicals have been used, which implies ecological contamination and potential health risks. A novel line of research in the use of alternative of agrochemicals has been proposed, such as elicitors which are eco-friendly and has less potential health risks. Elicitors, either chemicals or bio-factors, can stimulate plant secondary-metabolite synthesis and amplify the protective mechanisms against invading organisms both locally and systemically. These compounds include both exogenous substances, released by pathogens and endogenous elicitors, i.e., compounds secreted from plants. Some of the classes of endogenous elicitors are cell wall fragments, peptides, and phytohormones. Plant elicitor peptides (Peps) are widely distributed across the plant kingdom and play a role in signaling that contribute to broad-spectrum defense against biotic and abiotic factors. Certain ProPep genes are upregulated in response to insect oral secretions and pathogen invasion, and mature Peps attach with plant elicitor peptide receptors (PEPRs) to trigger calcium signaling, accumulation of reactive species, synthesis of defensive phytohormone, transcriptional reprogramming, and production of defensive proteins. Bioactive Peps are the long sequence of 23–36 amino acids, which are generated from the carboxyl termini of longer pro-peptide precursors (PROPEPs), and typically contain a glycine enriched motif: (S/G)(S)Gxx(G/P)xx(N). Peptides, recognized as important physiological regulator, have found applications in various fields including cosmetics, medicine, plant nutrition, and protection. Nowadays, application of plant elicitor peptides has become a popular research subject area in plant protection as immune inducer, plant growth regulator, insecticides, and herbicides for their excellent activity and ideal environmental compatibility.