Arbuscular Mycorrhizal Fungi and Plant Chemical Defence: Effects of Colonisation on Aboveground and Belowground Metabolomes

Elizabeth M Hill,Lynne A Robinson,Lynne A Robinson,Adam J Vanbergen,Sue E Hartley,Sue E Hartley,Ali Abdul-Sada,Angela Hodge

doi:10.1007/s10886-017-0921-1

Abstract

Arbuscular mycorrhizal fungal (AMF) colonisation of plant roots is one of the most ancient and widespread interactions in ecology, yet the systemic consequences for plant secondary chemistry remain unclear. We performed the first metabolomic investigation into the impact of AMF colonisation by Rhizophagus irregularis on the chemical defences, spanning above- and below-ground tissues, in its host-plant ragwort (Senecio jacobaea). We used a non-targeted metabolomics approach to profile, and where possible identify, compounds induced by AMF colonisation in both roots and shoots. Metabolomics analyses revealed that 33 compounds were significantly increased in the root tissue of AMF colonised plants, including seven blumenols, plant-derived compounds known to be associated with AMF colonisation. One of these was a novel structure conjugated with a malonyl-sugar and uronic acid moiety, hitherto an unreported combination. Such structural modifications of blumenols could be significant for their previously reported functional roles associated with the establishment and maintenance of AM colonisation. Pyrrolizidine alkaloids (PAs), key anti-herbivore defence compounds in ragwort, dominated the metabolomic profiles of root and shoot extracts. Analyses of the metabolomic profiles revealed an increase in four PAs in roots (but not shoots) of AMF colonised plants, with the potential to protect colonised plants from below-ground organisms.

Highlights

IntroductionThese effects (Johnson et al 2012, 2016; Wardle et al 2004)
Plant-mediated interactions between organisms above- and below-ground are increasingly recognised as a structuring force in ecology, though in many systems there is still a need for a more mechanistic understanding of the chemical basis of Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.these effects (Johnson et al 2012, 2016; Wardle et al 2004)
This study, the first to use a non-targeted metabolomic approach to assess the effect of arbuscular mycorrhizal fungi (AMF) colonisation on host plant secondary chemistry in both roots and shoots, showed that colonisation by AMF could increase the concentrations of 33 metabolites in roots by between two and many thousand fold

Summary

Introduction

These effects (Johnson et al 2012, 2016; Wardle et al 2004). Colonisation by AMF has been shown to increase plant resistance to below-ground antagonists such as parasitic plants (Li et al 2012) and plant parasitic nematodes (Rodriguez-Echeverria et al 2009), as well as to

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