The role of ethylene in rhizobacteria-induced systemic resistance (ISR)

Abstract

To protect themselves from disease, plants have evolved sophisticated defense mechanisms in which the signal molecules salicylic acid (SA), jasmonic acid (JA) and ethylene (ET) often play crucial role. Elucidation of signaling pathways controlling disease resistance is a major objective in research on plant-pathogen interactions. The capacity of a plant to develop a broad spectrum, systemic acquired resistance (SAR) after primary infection with a necrotizing pathogen is well known and its signal transduction pathway extensively studied. Plants of which the roots have been colonized by specific strains of nonpathogenic fluorescent Pseudomonas spp. develop a phenotypically similar form of protection that is called rhizobacteria-mediated induced systemic resistance( ISR). In contrast to pathogen induced SAR, which is regulated by SA, rhizobacteria mediated ISR is controlled by a signaling pathway in which ET and JA play key roles.In the past decade, the model plant species Arabidopsis thaliana was explored to study the molecular basis of rhizobacteria mediated ISR. Here we review the current knowledge of the signal transduction steps involved in the ISR pathway that leads from recognition of the rhizobacteria in the roots to systemic expression of broad-spectrum disease resistance in above-ground foliar tissues.