Salicylic Acid in Plant Disease Resistance

Abstract

Salicylic acid (SA) plays an important role in plant defense. Its role in plant disease resistance is well documented for dicotyledonous plants, where it is required for basal resistance against pathogens as well as for the inducible defense mechanism, systemic acquired resistance (SAR), which confers resistance against a broad-spectrum of pathogens. The activation of SAR is associated with the heightened level of expression of the pathogenesis-related proteins, some of which possess antimicrobial activity. Studies in the model plant Arabidopsis thaliana have provided important insights into the mechanism of SA signaling in plant defense. The NPR1 protein is an important component of SA signaling in Arabidopsis. Homologues of NPR1 are present in other plant species. NPR1 is also required for plant defense mechanisms that do not require SA. Hence, NPR1 provides an important link between different defense mechanisms. Similarly, cross talk between SA and other defense signaling pathways results in the fine-tuning of plant defense response. Recent discoveries have implicated an important role for lipids in SA signaling. We discuss the progress made in understanding SA biosynthesis and signaling, its cross talk with other mechanisms in plant defense and the practical utility in targeting this defense mechanism for enhancing disease resistance.