Phytochemistry and Diversity: Adaptation or Random Variation? M.R. Berenbaum, A.R. Zanger. Diversity, Redundancy and Multiplicity in Chemical Defense Systems of Aspen R.L. Lindroth, S.Y. Hwang. Diversity and Dynamics of Crucifer Defenses against Adults and Larvae of Cabbage Butterflies J.A.A. Renwick. Defensive Chemicals in Grass-Fungal Endophyte Associations M.R. Siegel, L.P. Bush. Multiple Defenses and Signals in Plant Defense against Pathogens and Herbivores R. Hammerschmidt, J.C. Schultz. Phytochemistry of the Meliceae: So Many Terpenoids, So Few Insecticides M.B. Isman, et al. The Role of Mixtures and Variation in the Production of Terpenoids in Conifer-Insect-Pathogen Interactions R.G. Cates. Relationships between the Defense Systems of Plants and Insects: The Cyanogenic System of the Moth Zygaena trifolii A. Nahrstedt. Polyphenol Oxidase as a Component of the Inducible Defense Response in Tomato against Herbivores C.P. Constabel, et al. The Role of Benzoic Acid Derivatives in Systemic Acquired Resistance S. Uknes, et al. Natural Products, Complexity, and Evolution B.B. Jarvis, J.D. Miller. An Explanation of Secondary Product Redundancy R.D. Firn, C.G. Jones. Index.

/pdf/phytochemical-diversity-and-redundancy-in-ecological-4uecpg2uui.pdf

Phytochemical diversity and redundancy in ecological interactions

The ability of organisms to form long term intimate and diverse relationships with each other (symbiosis) is now recognized as a common ecological phenomenon. Symbiosis, as a general term, does not imply detriment or benefit, but rather that the outcome (net effect) of species interaction exists within a symbiotic continuum or “species interaction grid” that includes agonism (predation and disease) and mutualism (benefits for both species).1,2 The continuum also includes pleotropic symbiosis, where net effects of species interaction vary spatially or temporally in relative agonism or mutualism.3 Grasses systematically infected with specific clavicipitaceous fungi are examples of species interactions that span the symbiotic continuum, profoundly affecting the ecological fitness of the hosts.4–8

Defensive chemicals in grass-fungal endophyte associations.

While the discovery that fungal endophytes were present in some pooid grass species was made at the turn of the 20th century (White et al. 1993), knowledge of their widespread distribution (Leuchtmann 1992; Chap. 12, Vol. V, Part B) and the ecological and evolutionary consequences for host and fungi (Clay 1994; Leuchtmann 1994; Schardl et al. 1994; Tsai et al. 1994; Chap. 14, Vol. V, Part B), as well as their impact on livestock production (Prestidge 1993; Strickland et al. 1993), is of more recent origin. The association of grasses with endophytes of the genus Epichloe has been shown to affect the growth and/or reproduction not only of mammalian herbivores, but also of insect herbivores (Latch 1993; Popay and Rowan 1994) and, to lesser extents, nematodes, (Latch 1993), plants (Petroski et al. 1990), and fungi (Guo et al. 1992; Gwinn and Gavin 1992). In many cases, the toxicity has been associated with specific secondary metabolites produced by grass/endophyte associations (symbiota). Additionally, endophyte compatibility and toxin production is under the influence of both host and fungal genomes (Leuchtmann 1992; Christensen et al. 1993; Leuchtmann and Clay 1993; Agee and Hill 1994; Roylance et al. 1994; Welty et al. 1994; Christensen 1995) as well as the environment (Agee and Hill 1994; Arechavaleta et al. 1992; Bacon 1993). These constraints upon toxin biosynthesis result in a wide spectrum of biological activity for symbiota and offer the opportunity for manipulation of the endophytes for improvement of the grasses when used in forage, turf, and soil conservation (Schardl 1994; Siegel and Bush 1994).

Toxin Production in Grass/Endophyte Associations

objectif de cette revue bibliographique est de faire un rappel des conditions historiques des survenues de ces affections, et une analyse des etudes cherchant a les reproduire experimentalement. Les mecanismes d’action toxiques supposes de l’ergovaline et du lolitrem B, ainsi que leurs toxicocinetiques et risques de persistance a l’etat residuel dans les productions animales et d’origine animale sont ensuite presentes. Mots-cles : Neotyphodium, endophytes, alcaloides ergotiques, lolitrem B, ergovaline, fescue foot, ryegrass staggers SUMMARY Toxicity of mycotoxins produced by endophytic fungi of the genus Neotyphodium The symbiotic associations between different varieties of fungi of the Neotyphodium kind and forages are responsible for the production of mycotoxins which are responsible of toxicoses in livestock and economic losses in some countries. The development of N. coenophialum in tall fescue, which is associated with the production of ergovaline, is responsible for « fescue foot disease » while the presence of N. lolii in ryegrass, which is accompanied by the production of lolitrem B, is responsible for the « ryegrass staggers ». The aim of this literature review is to recall the historical conditions on which these diseases occurred, followed by an analysis of studies seeking to experimentally reproduce the diseases. The supposed mechanisms of the toxic actions for ergovaline and lolitrem B, their toxicokinetics and the risk of persistence in the residual state in animal productions and animal origin are later presented.

Toxicité des mycotoxines produites par des champignons endophytes du genre Neotyphodium

https://www.biorxiv.org/content/biorxiv/early/2022/10/14/2022.09.08.507134.full.pdf

28 minutes later: investigating the role of aflatrem-like compounds in Ophiocordyceps parasite manipulation of zombie ants

The gamma-aminobutyric acid (GABA) receptor is the major inhibitory receptor in vertebrate and invertebrate brains. Activation of this GABA A receptor, which traverses the membrane, results in its opening of an anionic channel that is part of the receptor protein and permeation of Cl- along its concentration gradient. Thus, Cl influxes producing membrane hyperpolarization.6,11 This GABA A receptor is inhibited competitively by bicuculline and allosterically by picrotoxinin and t-butylbicyclophosphorothionate (TBPS), which bind to another site that is closely associated with the Cl- channel component of the receptor protein. The GABAA receptor is studied biochemically by the characteristics and specificity or its binding of [35S]TBPS and also by monitoring its function in vitro, i.e. 36C1 influx that is induced by binding of GABA to the receptor in membrane vesicles, is inhibited by competitive and noncompetitive inhibitors and is potentiated by certain modulators. GABA A receptors also have a site that binds benzodiazepines and another that binds depressant barbiturates.14 Benzodiasepines are mostly potentiators of GABA receptor function (e.g., diazepam) increasing the receptor’s affinity for GABA and facilitating the frequency of opening of its Cl- channel, but a few benzodiazepines are inhibitors of diazepam action. There are also benzodiazepine modulators of receptor function, acting as convulsants or proconvulsants and thus are called inverse agonists (e.g., ethyl β-carboline-3-carboxylate).

The GABA Receptor and the Action of Tremorgenic Mycotoxins

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The GABA Receptor and the Action of Tremorgenic Mycotoxins