Insights into plant beneficial microorganism-triggered induced systemic resistance

Plants have inherent capabilities to modulate their resistance against both biotic and abiotic stresses. Plant–microorganism interactions in the rhizosphere play vital role in such responses. The interactions of non-pathogenic or beneficial bacteria such as plant beneficial microbial strains with plants in the soil are governed mostly by Plant growth regulators such as salicylic acid (SA), jasmonic acid (JA), and ethylene (ET), which are involved in the regulation of basal resistance against various pathogens. Plant growth regulators are well known to induce systemic resistance (ISR), similar to the pathogen-activated systemic acquired resistance (SAR) that provides basal resistance to plants against pathogens as well as herbivores. ISR response mediated through JA/ET is independent of the SA-mediated response of SAR. Different components of plant beneficial microbial strains involved in induced systemic resistance have been identified and characterized recently using different plant–pathogen model systems. Here, we provide an update on ISR and the role of non-expressor of pathogenesis-related gene 1 (NPR1) and other elicitors of bacterial origin in their interaction with plants, with an emphasis on the underlying factors involved in systemic resistance.