Loline alkaloids: Currencies of mutualism

Schardl, Christopher L.; Grossman, Robert B.; Nagabhyru, Padmaja; Faulkner, Jerome R.; Mallik, Uma Prasad

doi:10.1016/j.phytochem.2007.01.010

Cited by 258 publications

(148 citation statements)

References 78 publications

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“…by Argentine Stem Weevil, is an unquestionable benefit of endophyte infection to plant fitness, in both natural and commercial (agricultural) contexts. Usually, this fitness benefit is ascribed to the production of antiherbivorous alkaloids (Siegel et al 1990;Rowan and Latch 1994;Bush et al 1997;Schardl et al 2007). However, the widespread changes seen in metabolic profiles, and especially the shift to higher carbon/ nitrogenous metabolite ratios, and potential stimulation of defense compounds make it arguable that effects on insect herbivores might be causally related to metabolic factors other than the alkaloids alone (Brown et al 2002;Douglas 2006;Douglas et al 2006), or at least that other factors can modulate alkaloid impacts.. We exposed the same plant material used in the studies discussed above (Rasmussen et al 2007(Rasmussen et al , 2008b) to a suite of insects (aphid spp., thrips, mites) and assessed the impacts on the insect populations (Rasmussen et al 2008a).…”

Section: Effects Of N Lolii Endophytes On Insect Herbivoresmentioning

confidence: 99%

Metabolomics analysis of the Lolium perenne–Neotyphodium lolii symbiosis: more than just alkaloids?

2009

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Above ground plant parts of Lolium perenne often harbour endophytic Neotyphodium lolii fungi. These occur both naturally and commercially, as variant strains are introduced to modify the grass metabolic profile. They reside in the apoplastic spaces and rarely cause visible symptoms of infection. The vast majority of literature has focussed on the biosynthesis, accumulation, and ecological relevance of a limited number of alkaloids produced by N. lolii which have been shown to negatively affect insect pests and vertebrate herbivores. Much less is known about the effects of other metabolites in these interactions or the role of resource supply on metabolic profiles, nor critically on the metabolic consequences of differences in the amount (concentration) of endophyte present. Here, we provide a synthesis of some of our recently published studies on effects of resource supply (nitrogen, carbohydrates) on concentrations of endophytes and endophyte specific metabolites in the L. perenne-N. lolii association. We present results of both quantitative PCR and targeted metabolomics studies, using contrasting endophyte strains in two perennial ryegrass cultivars. We also present and discuss a hypothetical schematic representation of possible links between plant and fungal metabolic networks. A multiple regression analysis of numerical insect responses and metabolic profiles indicates that effects of endophyte infection on insect population sizes could be predicted by concentrations of a range of metabolites other than alkaloids and depended on insect species, fungal strain, and nitrogen supply.

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Section: Effects Of N Lolii Endophytes On Insect Herbivoresmentioning

confidence: 99%

Metabolomics analysis of the Lolium perenne–Neotyphodium lolii symbiosis: more than just alkaloids?

2009

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“…The indole-diterpene lolitrem B and ergot alkaloid ergovaline have significant detrimental effects on the health and production of stock animals that graze infected pastures (7,8). The lolines are insecticidal (9), and peramine is a potent deterrent of feeding by insects, including the agriculturally important invertebrate pest Listronotus bonariensis (Argentine stem weevil) (10)(11)(12).…”

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confidence: 99%

Disparate Independent Genetic Events Disrupt the Secondary Metabolism Gene perA in Certain Symbiotic Epichloë Species

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Schardl

et al. 2015

Appl Environ Microbiol

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Peramine is an insect-feeding deterrent produced by Epichloë species in symbiotic association with C 3 grasses. The perA gene responsible for peramine synthesis encodes a two-module nonribosomal peptide synthetase. Alleles of perA are found in most Epichloë species; however, peramine is not produced by many perA-containing Epichloë isolates. The genetic basis of these peramine-negative chemotypes is often unknown. Using PCR and DNA sequencing, we analyzed the perA genes from 72 Epichloë isolates and identified causative mutations of perA null alleles. We found nonfunctional perA-⌬R* alleles, which contain a transposon-associated deletion of the perA region encoding the C-terminal reductase domain, are widespread within the Epichloë genus and represent a prevalent mutation found in nonhybrid species. Disparate phylogenies of adjacent A2 and T2 domains indicated that the deletion of the reductase domain (R*) likely occurred once and early in the evolution of the genus, and subsequently there have been several recombinations between those domains. A number of novel point, deletion, and insertion mutations responsible for abolishing peramine production in full-length perA alleles were also identified. The regions encoding the first and second adenylation domains (A1 and A2, respectively) were common sites for such mutations. Using this information, a method was developed to predict peramine chemotypes by combining PCR product size polymorphism analysis with sequencing of the perA adenylation domains. Fungal secondary metabolites are a diverse group of important but often nonessential organic compounds with a wide range of properties that are likely to be advantageous for the producing organism or in some cases essential for pathogenicity or developmental stages (1-3). These low-molecular-weight compounds tend to only be produced under certain environmental or growth conditions. The biosynthetic pathways for production of any particular class of secondary metabolites are common to many fungi, but production of a specific secondary metabolite is often unique to a small phylogenetic group of species (4). Epichloë species are fungal endophytes of C 3 grasses that are known to produce several bioactive alkaloids that provide bioprotective properties to the host plant (5). These secondary metabolites include the indolediterpenes, ergot alkaloids, lolines, and peramine ( Fig. 1) (6, 7). The indole-diterpene lolitrem B and ergot alkaloid ergovaline have significant detrimental effects on the health and production of stock animals that graze infected pastures (7,8). The lolines are insecticidal (9), and peramine is a potent deterrent of feeding by insects, including the agriculturally important invertebrate pest Listronotus bonariensis (Argentine stem weevil) (10-12).Peramine synthesis is catalyzed by the two-module nonribosomal peptide synthetase (NRPS), peramine synthetase (PerA), encoded by the 8.3-kb gene perA (12). The first module of PerA contains an adenylation (A1) domain responsible for selection and activation of t...

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“…The pyrrolizidine class of fungal natural products [50] has been associated to the grass-Epichloe¨/Neotyphodium symbiosis, but only recently the proof of their fungal origin was brought by Schardl and coworkers [51]. Indeed, lolines (12-18) (Fig.…”

Section: Studies In Natural Products Chemistrymentioning

confidence: 99%