Impact of Arbuscular Mycorrhizal Symbiosis on Plant Response to Biotic Stress: The Role of Plant Defence Mechanisms

DOI: 10.1007/978-90-481-9489-6_9 In book: Arbuscular Mycorrhizas: Physiology and Function, pp.193-207


Arbuscular mycorrhizal associations imply a remarkable reprogramming­ of functions in both plant and fungal symbionts. The
consequent alterations on plant physiology have a clear impact on the plant response to biotic stresses. In this chapter we
discuss the effects of the mycorrhizal symbiosis on plant susceptibility/resistance to potential deleterious organisms, including
root and shoot pathogens, root parasitic plants and phytophagous insects, highlighting the mechanisms that may be operating
in each particular case. Special attention is given to the modulation of plant defence responses in mycorrhizal systems, as
it may affect all interactions. Finally we focus on the priming of jasmonate regulated plant defence mechanisms that seem
to mediate the induction of resistance by arbuscular mycorrhizas.

KeywordsBiotic stress-Bioprotection-Induced resistance-Priming-Plant defence-Biocontrol-Defence signalling-Jasmonates-Pathogens-Insects

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    • "Endophytes also seem to affect the interaction between their hosts and other beneficial fungal microorganisms such as arbuscular mycorrhizal fungi (AMF) (Novas et al. 2005; Omacini et al. 2006). Benefits from the symbiosis with AMF, such as: improved soil structure , increased nutrient uptake and water usage efficiency , enhanced resistance to environmental stresses and protection against pathogens are well known (Borowicz 2001; Marulanda et al. 2003; Smith and Read 2008; Pozo et al. 2010). Mycorrhiza colonization is recognized to be significantly reduced by high phosphorus levels in soil (Nagy et al. 2009; Balzergue et al. 2011). "
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    ABSTRACT: Background and aims Plants often establish multiple simultaneous symbiotic associations with different microorganisms ; however, the way in which each sym-biont affects the other symbionts and the effects of these multiple interactions on plant performance are not well understood. The aim of this study was to evaluate how two different asexual Epichloë species modulate the establishment of arbuscular mycorrhizal fungi (AMF) in a wild forage grass under different soil fertilization levels. Methods We performed a completely randomized 12-month-long field experiment to evaluate the effect of two B. auleticus-endophyte ecotypes and two soil fertilization levels on the colonization of AMF, in seedlings and adult plants. Plant biomass and reproductive tillers production were also measured. Results The symbiosis, measured as the total extent of AM fungal colonization and frequency of arbuscules was significantly higher in Epichloë-infected plants and was not affected by fertilization either in seedlings or in adult plants. Plant biomass was increased by fertilization but no differences were observed due to the endophytic status. However, E+ plants produced more panicles than their E− counterparts. Conclusions Our findings strongly support the hypothesis of positive association between Epichloë endo-phytes and AMF in wild grasses, making this model important for agronomic improvement.
    Plant and Soil 05/2015; DOI:10.1007/s11104-015-2522-5 · 2.95 Impact Factor
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    • "Finally, it has been postulated that priming is related to sensitisation of the hormone-inducible defence response, possibly through an increased accumulation of signalling proteins that function in the response pathways of these hormones, which would require a secondary post-translational activation upon pathogen attack (Pastor et al. 2013). At the molecular level, several reports have shown that some jasmonic acid (JA)-responsive genes show higher expression in leaves of mycorrhizal plants following a pathogen challenge, compared with non-colonised plants (Pozo et al. 2010; Gallou et al. 2011; Campos-Soriano et al. 2012). In addition, Campos-Soriano et al. (2012) have presented evidence suggesting that mycorrhiza colonisation induces JA biosynthesis and signalling pathways before a pathogen challenge. "
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    ABSTRACT: The arbuscular mycorrhizal (AM) symbiosis is an intimate association between specific soil-borne fungi and the roots of most land plants. AM colonisation elicits an enhanced defence resistance against pathogens, known as mycorrhizal-induced resistance (MIR). This mechanism locally and systemically sensitises plant tissues to boost their basal defence response. Although a role for oxylipins in MIR has been proposed, it has not yet been experimentally confirmed. In this study, when the common bean (Phaseolus vulgaris L.) lipoxygenase PvLOX2 was silenced in roots of composite plants, leaves of silenced plants lost their capacity to exhibit MIR against the foliar pathogen Sclerotinia sclerotiorum, even though they were colonised normally. PvLOX6, a LOX gene family member, is involved in JA biosynthesis in the common bean. Downregulation of PvLOX2 and PvLOX6 in leaves of PvLOX2 root-silenced plants coincides with the loss of MIR, suggesting that these genes could be involved in the onset and spreading of the mycorrhiza-induced defence response.
    Functional Plant Biology 08/2014; 42(1). DOI:10.1071/FP14101 · 3.15 Impact Factor
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    • "Such a symbiosis is characterized by reciprocal nutrient exchanges between the two symbionts: the fungus depends on a carbon supply from the plant to accomplish its life cycle, and in turn delivers mineral nutrients, especially phosphate and nitrogen, to its host [2]. The establishment of this symbiosis involves major changes in the physiology of the host plant causing a global cell reprogramming [3] and a modulation of plant responses to biotic and abiotic stresses [4] [5]. "
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    ABSTRACT: a b s t r a c t Cadmium is a serious environmental pollution threats to the planet. Its accumulation in plants affects many cellular functions, resulting in growth and development inhibition, whose mechanisms are not fully understood. However, some fungi forming arbuscular mycorrhizal symbiosis with the majority of plant species have the capacity to buffer the deleterious effect of this heavy metal. In the present work we investigated the capacity of Rhizophagus irregularis (syn. Glomus irregularis) to alleviate cadmium stress in Medicago truncatula. In spite of a reduction in all mycorrhizal parameters, plants colonized for 21 days by R. irregularis and treated by 2 mg kg À1 cadmium displayed less growth inhibition in comparison to plants grown without cadmium. Cadmium strongly increased the accumulation of some isoflavonoids and their derivates: formononetin, malonylononin, medicarpin 3-O-fl-(6 0 -malonylglucoside), medicarpin and coumestrol. Interestingly, in plants colonized by R. irregularis we noticed a strong reduction of the cadmium-induced accumulation of root isoflavonoids, a part for medicarpin and coumestrol. Moreover, transcripts of chalcone reductase, a protein that we reported previously as being down-regulated in R. irregularis-colonized M. truncatula roots, revealed a similar expression pattern with a strong increase in response to cadmium and a reduced expression in cadmium-treated mycorrhizal roots. Ó 2012 Published by Elsevier Masson SAS.
    Plant Physiology and Biochemistry 09/2012; 60. DOI:10.1016/j.plaphy.2012.08.014 · 2.76 Impact Factor
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