Gaseous 3-pentanol primes plant immunity against a bacterial speck pathogen, Pseudomonas syringae pv. tomato via salicylic acid and jasmonic acid-dependent signaling pathways in Arabidopsis.

Choong-Min Ryu,Hye K. Choi,Geun C. Song

doi:10.3389/fpls.2015.00821

Abstract

3-Pentanol is an active organic compound produced by plants and is a component of emitted insect sex pheromones. A previous study reported that drench application of 3-pentanol elicited plant immunity against microbial pathogens and an insect pest in crop plants. Here, we evaluated whether 3-pentanol and the derivatives 1-pentanol and 2-pentanol induced plant systemic resistance using the in vitro I-plate system. Exposure of Arabidopsis seedlings to 10 μM and 100 nM 3-pentanol evaporate elicited an immune response to Pseudomonas syringae pv. tomato DC3000. We performed quantitative real-time PCR to investigate the 3-pentanol-mediated Arabidopsis immune responses by determining Pathogenesis-Related (PR) gene expression levels associated with defense signaling through salicylic acid (SA), jasmonic acid (JA), and ethylene signaling pathways. The results show that exposure to 3-pentanol and subsequent pathogen challenge upregulated PDF1.2 and PR1 expression. Selected Arabidopsis mutants confirmed that the 3-pentanol-mediated immune response involved SA and JA signaling pathways and the NPR1 gene. Taken together, this study indicates that gaseous 3-pentanol triggers induced resistance in Arabidopsis by priming SA and JA signaling pathways. To our knowledge, this is the first report that a volatile compound of an insect sex pheromone triggers plant systemic resistance against a bacterial pathogen.

Highlights

Plants protect themselves against diverse microbial pathogens and insects using a variety of defense mechanisms (Agrios, 2004)
The signaling pathways involved in major plant defense mechanisms, such as those that mediate the effects of salicylic acid (SA), jasmonic acid (JA), and ethylene (ET), have been intensively studied using only 2,3-butanediol and tridecane volatile organic compound (VOC) within the Arabidopsis thaliana-Pectobacterium carotovorum/Pseudomonas syringae pathosystem (Ryu et al, 2004; Han et al, 2006; Kwon et al, 2010; Rudrappa et al, 2010; Lee et al, 2012;)
The number of bacterial cells in leaf collected 3 and 7 days after inoculation was reduced significantly in plants exposed to 100 nM, 10 μM, and 1 mM 3pentanol, whereas bacterial growth was not significantly different in plants exposed to 1 nM 3-pentanol and control plants

Summary

Introduction

Plants protect themselves against diverse microbial pathogens and insects using a variety of defense mechanisms (Agrios, 2004). Among these mechanisms, induced resistance represents a unique machinery against a broad spectrum of plant pathogens (Mysore and Ryu, 2004; Eyles et al, 2010). Volatile organic compounds (VOCs) have been reported to induce plant immunity when applied to plants (Farag et al, 2013; Chung et al, 2015; Kanchiswamy et al, 2015a). There have been no reports to our knowledge of the defense signaling induced by insect-produced VOCs

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Results

Conclusion