Do volatile compounds produced by Fusarium oxysporum and Verticillium dahliae affect stress tolerance in plants?

Ningxiao Li,Seogchan Kang

doi:10.1080/21501203.2018.1448009

Abstract

ABSTRACTVolatile compounds (VCs) produced by diverse microbes seem to affect plant growth, development and/or stress tolerance. We investigated how VCs released by soilborne fungi Fusarium oxysporum and Verticillium dahliae affect Arabidopsis thaliana responses to abiotic and biotic stresses. Under salt stress, VCs from both fungi helped its growth and increased chlorophyll content. However, in contrast to wild-type A. thaliana (Col-0), V. dahliae VCs failed to increase leaf surface area in auxin signalling mutants aux1-7, tir1-1 and axr1-3. Compared to wild-type Col-0, the degree of lateral root density enhanced by V. dahliae VCs in these mutants was also reduced. Consistent with the involvement of auxin signalling in fungal VC-mediated salt torelance, A. thaliana line carrying DR5::GUS displayed increased auxin accumulation in root apex upon exposure to V. dahliae VCs, and 1-naphthylphthalamic acid, an auxin transport inhibitor, adversely affected V. dahliae VC-mediated salt tolerance. F. oxysporum VCs induced the expression of PR1 but not PDF1.2 in A. thaliana lines containing PR1::GUS and PFD1.2::GUS. When challenged with Pseudomonas syringae after the exposure to F. oxysporum VCs, A. thaliana showed reduced disease symptoms. However, the number of bacterial cells in F. oxysporum VC-treated plants was not significantly different from that in control plants.

Highlights

Even though plants have evolved multiple mechanisms to mitigate the effect of various biotic and abiotic stresses (Fujita et al 2006; Harrison 2012; Huang et al 2012), high levels of stress adversely affect plant growth and development, resulting in reduced crop productivity and health
Volatile compounds (VCs) emitted by both F. oxysporum and V. dahliae increased salt tolerance in A. thaliana
To investigate how VCs produced by these fungi affect plant growth under salt stress, we employed two strains each of F. oxysporum (NRRL26379 and NRRL38335) and V. dahliae (PD322 and PD413)

Summary

Introduction

Even though plants have evolved multiple mechanisms to mitigate the effect of various biotic and abiotic stresses (Fujita et al 2006; Harrison 2012; Huang et al 2012), high levels of stress adversely affect plant growth and development, resulting in reduced crop productivity and health. Increasing salinity in certain arable lands, due to irrigation, draught or a combination of both, is one of the most serious abiotic threats to global crop production, because most crops are sensitive to high levels of NaCl (Xiong and Zhu 2002). Volatile compounds (VCs) produced by some plant growth promoting rhizobacteria (PGPR) have been shown to alleviate plant salt stress (Zhang et al 2008, 2010; Vaishnav et al 2015, 2016; Ledger et al 2016). VCs produced by Bacillus amyloliquefaciens GB03 conferred increased salt tolerance in A. thaliana presumably via tissue-specific regulation of HKT1, a high-affinity K+ transporter, and induced accumulation

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