Induced Systemic Resistance against Botrytis cinerea by Bacillus cereus AR156 through a JA/ET- and NPR1-Dependent Signaling Pathway and Activates PAMP-Triggered Immunity in Arabidopsis

Abstract

Induced resistance response is a potent and cost effective plant defense against pathogen attack. The effectiveness and underlying mechanisms of the suppressive ability by <i>Bacillus cereus</i> AR156 to <i>Pseudomonas syringae</i> pv. <i>tomato</i> DC3000 (<i>Pst</i> DC3000) in <i>Arabidopsis</i> has been investigated previously; however, the strength of induced systemic resistance (ISR) activity against <i>Botrytis cinerea</i> remains unknown. Here, we show that root-drench application of AR156 significantly reduces disease incidence through activation of ISR. This protection is accompanied with multilayered ISR defense response activated via enhanced accumulation of PR1 protein expression in a timely manner, hydrogen peroxide accumulation and callose deposition, which is significantly more intense in plants with both AR156 pretreatment and <i>B. cinerea</i> inoculation than that in plants with pathogen inoculation only. Moreover, AR156 can trigger ISR in <i>sid2-2</i> and <i>NahG</i> mutants, but not in <i>jar1, ein2</i> and <i>npr1</i> mutant plants. Our results indicate that AR156-induced ISR depends on JA/ET-signaling pathway and <i>NPR1</i>, but not SA. Also, AR156-treated plants are able to rapidly activate MAPK signaling and <i>FRK1</i>/<i>WRKY53</i> gene expression, both of which are involved in pathogen associated molecular pattern (PAMP)-triggered immunity (PTI). The results indicate that AR156 can induce ISR by the JA/ET-signaling pathways in an <i>NPR1</i>-dependent manner and involves multiple PTI components.