High specificity in plant leaf metabolic responses to arbuscular mycorrhiza

Abstract

The chemical composition of plants (phytometabolome) is dynamic and modified by environmental factors. Understanding its modulation allows to improve crop quality and decode mechanisms underlying plant-pest interactions. Many studies that investigate metabolic responses to the environment focus on single model species and/or few target metabolites. However, comparative studies using environmental metabolomics are needed to evaluate commonalities of chemical responses to certain challenges. We assessed the specificity of foliar metabolic responses of five plant species to the widespread, ancient symbiosis with a generalist arbuscular mycorrhizal fungus. Here we show that plant species share a large 'core metabolome' but nevertheless the phytometabolomes are modulated highly species/taxon-specifically. Such a low conservation of responses across species highlights the importance to consider plant metabolic prerequisites and the long time of specific plant-fungus coevolution. Thus, the transferability of findings regarding phytometabolome modulation by an identical AM symbiont is severely limited even between closely related species.

Enhanced Secondary- and Hormone Metabolism in Leaves of Arbuscular Mycorrhizal Medicago truncatula

“…They enhance water uptake and mineral nutrition (mostly inorganic phosphate [P i ]) of the host plant, which, in return, provides photosynthates to the fungus through hyphal structures called arbuscules (Baier et al, 2010;Doidy et al, 2012). The major advantage to plants is enhanced biomass production in a P i -limiting environment (Rooney et al, 2009;Adolfsson et al, 2015), although some studies reported a lack of positive effects on biomass or P i status in AM plants (Smith et al, 2011;Schweiger et al, 2014b). Moreover, AM fungi provide nonnutritional benefits to the host, including resistance against pathogens and pests as well as tolerance to abiotic stress (Nadeem et al, 2014).…”

“…truncatula is a well-established model plant for legume genomics (Cook, 1999). It has been broadly used for studies of transcriptomic, proteomic, and metabolomic changes induced by AM symbiosis in either roots or leaves (Liu et al, 2007;Schliemann et al, 2008;Abdallah et al, 2014;Schweiger et al, 2014b;Daher et al, 2017). Previous microarray-based transcriptional analyses in leaves of M. truncatula during AM symbiosis revealed systemic induction of genes involved in plant defense (Liu et al, 2007).…”

Medicago truncatula Mtha1-2 mutants loose metabolic responses to mycorrhizal colonization

“…2 The changes seem to be speciesspecific, with Medicago truncatula showing a more pronounced metabolic answer than other dicots, probably due to a higher symbiotic capability. 3 The most prominent changes are visible in the catabolic and amino acid metabolism, probably due to the improved carbon sink strength and an improved P-and N-level. 4 However, not only P and N, but also S provided by the symbiotic uptake pathway leads to changes in the metabolic response.…”

What the transcriptome does not tell — proteomics and metabolomics are closer to the plants’ patho-phenotype

“…Recently, metabolite fingerprinting led to the identification of resistance genes for the oilseed rape pathogen Verticillium longisporum in Arabidopsis [50] and contributed to the understanding of how secreted effectors of the maize pathogen Ustilago maydis manipulate the specialized metabolism of its host [43,51]. Moreover the non-targeted approach was applied for deepening our knowledge about priming mechanisms in Arabidopsis [52] and even analyzing symbiosis with a generalist arbuscular mycorrhizal fungus in the non-model species Plantago, Veronica and Poa [53]. One major finding of recent research in metabolomics of plant-microbe interactions is, that the metabolomic response is far more complex than expected in that the numerous ways and combinations of how specialized metabolites are being modified, mainly by central metabolites, are still being discovered.…”