The rhizobacterial elicitor acetoin induces systemic resistance inArabidopsis thaliana

Abstract

The majority of plant growth promoting rhizobacteria (PGPR) confer plant immunity against a wide range of foliar diseases by activating plant defences that reduce a plant's susceptibility to pathogen attack. Here we show that Arabidopsis thaliana (Col-0) plants exposed to Bacillus subtilis strain FB17 (hereafter FB17), results in reduced disease severity against Pseudomonas syringae pv. tomato DC3000 (hereafter DC3000) compared to plants without FB17 treatment. Exogenous application of the B. subtilis derived elicitor, acetoin (3-hydroxy-2-butanone), was found to trigger induced systemic resistance (ISR) and protect plants against DC3000 pathogenesis. Moreover, B. subtilis acetoin biosynthetic mutants that emitted reduced levels of acetoin conferred reduced protection to A. thaliana against pathogen infection. Further analysis using FB17 and defense-compromised mutants of A. thaliana indicated that resistance to DC3000 occurs via NPR1 and requires salicylic acid (SA)/ethylene (ET) whereas jasmonic acid (JA) is not essential. This study provides new insight into the role of rhizo-bacterial volatile components as elicitors of defense responses in plants.

Phaeobacter gallaeciensis genomes from globally opposite locations reveal high similarity of adaptation to surface life

“…In both as well as three genes that are part of the biosynthetic pathway for acetoin and 2,3-butanediol, indicating the possible production of these compounds by the strain. These compounds can act as nutrient source as well as plant growth-promoting molecules (Ryu et al, 2003;Rudrappa et al, 2010), which might facilitate the interaction with algal hosts. Genes for the complete multi-peptide urease (ureA-G; PGA2_c31970-c32030) and three genes probably coding for surface antigens (PGA2_c18820-PGA2_c18840) are also unique in strain 2.10.…”

Microbe-Associated Molecular Patterns-Triggered Root Responses Mediate Beneficial Rhizobacterial Recruitment in Arabidopsis

“…Among these PGPR strains, FB17 rhizoinoculated onto the roots of Arabidopsis plants reduced disease severity, thus inhibiting the proliferation of foliar pathogen Pst DC3000 through induction of JA/ET-mediated ISR and SAmediated SAR (Rudrappa et al, 2010). The magnitude of colonization on the root by beneficial microbes is limited by several factors that include root surface biochemistry and composition of root exudates (Rudrappa et al, 2008a;Doornbos et al, 2011;Chen et al, 2012).…”

“…This recent data validates the specificity and preference of B. subtilis for MA. Our previous studies showed that aerial plant pathogenesis involved the induction of MA in root secretions that effectively recruited beneficial rhizobacteria (Rudrappa et al, 2008a(Rudrappa et al, , 2010. We also showed that the pathogenic phyllosphere pathogen, Pst DC3000, induced root ALMT1 expression (Rudrappa et al, 2008b).…”

“…There is a tempting possibility that FB17 may down-regulate the root defense response in the initial phases of rootmicrobe interaction for the establishment of the biofilm community. It is also known that FB17 specifically induces the expression of PR1 and PDF1.2 in Arabidopsis leaves but not in the roots (Rudrappa et al, 2010). Similarly, B. subtilis strain AR156, when applied to Arabidopsis roots, resulted in the expression of four defense-related genes (PR1, PR2, PR5, and PDF1.2) in the leaves but not in the roots (Niu et al, 2011).…”

“…As a mutualist, FB17 confers beneficial traits such as increased abiotic stress tolerance and disease resistance to plants (Rudrappa et al, 2008b(Rudrappa et al, , 2010Zhang et al, 2008; for review, see Choudhary and Johri, 2009). Herein, we show that foliar applied MAMPs and COR elicited FB17 colonization in Arabidopsis roots through activation of root ALMT1 expression and those FLS2-and COI1-dependent graft-transmissible long-distance signals recruited FB17 belowground.…”