Phenylacetic Acid Is ISR Determinant Produced by Bacillus fortis IAGS162, Which Involves Extensive Re-modulation in Metabolomics of Tomato to Protect against Fusarium Wilt.

Waheed Akram,Tehmina Anjum,Basharat Ali

doi:10.3389/fpls.2016.00498

Waheed Akram, Tehmina Anjum + Show 1 more

Open Access

https://doi.org/10.3389/fpls.2016.00498

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Abstract

Bacillus fortis IAGS162 has been previously shown to induce systemic resistance in tomato plants against Fusarium wilt disease. In the first phase of current study, the ISR determinant was isolated from extracellular metabolites of this bacterium. ISR bioassays combined with solvent extraction, column chromatography and GC/MS analysis proved that phenylacetic acid (PAA) was the potential ISR determinant that significantly ameliorated Fusarium wilt disease of tomato at concentrations of 0.1 and 1 mM. In the second phase, the biochemical basis of the induced systemic resistance (ISR) under influence of PAA was elucidated by performing non-targeted whole metabolomics through GC/MS analysis. Tomato plants were treated with PAA and fungal pathogen in various combinations. Exposure to PAA and subsequent pathogen challenge extensively re-modulated tomato metabolic networks along with defense related pathways. In addition, various phenylpropanoid precursors were significantly up-regulated in treatments receiving PAA. This work suggests that ISR elicitor released from B. fortis IAGS162 contributes to resistance against fungal pathogens through dynamic reprogramming of plant pathways that are functionally correlated with defense responses.

Highlights

During the long history of coevolution between host plants and pathogens, plants have developed their own strategies to combat with pathogens
We previously proved that B. fortis IAGS162 is a beneficial rhizospheric bacterium capable of managing fusarium wilt disease of tomato by Induced systemic resistance (ISR) phenomenon in tomato plants (Akram et al, 2013)
These results suggested that Cell free culture filtrate (CFCF) from B. fortis IAGS162 could be mainly responsible for the suppression of fusarium wilt disease and carry the potential ISR determinant/s

Summary

Introduction

During the long history of coevolution between host plants and pathogens, plants have developed their own strategies to combat with pathogens. In case of plant-pathogen interactions, plants can produce immune signals from the ISR Determinant/s of B. fortis IAGS162 infection sites (Ausubel, 2005; Jones and Dangl, 2006) These immune signals activate batteries of defense responses (Chisholm et al, 2006; Dodds and Rathjen, 2010). ISR is accompanied with augmented expression of defense related genes, increased accumulation of secondary metabolites, and defense associated proteins (van Loon et al, 1998; Conrath, 2006; van Hulten et al, 2006; Zamioudis and Pieterse, 2012) These induced defense mechanisms are dependent on jasmonic acid (JA) and ethylene (ET) signaling in the plants (van Loon et al, 1998; Conrath et al, 2006). SAR is dependent on salicylic acid (SA) signaling pathway (Park et al, 2008) while ISR typically relies on the JA and ET signaling pathways (Pieterse et al, 2002)

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