Les associations symbiotiques entre différentes espèces de champignon du genre Epichloë et des plantes fourragères sont à l’origine de la production de mycotoxines responsables, dans certains pays, de toxicoses du bétail et de pertes économiques. Le développement de d’E. coenophiala dans la fétuque, qui est associé à la production d’ergovaline, est responsable de « fescue foot disease » alors que la présence d’E. festucae var. lolii dans le ray-grass anglais, qui est accompagnée d’une production de lolitrem B, est responsable du « ryegrass staggers » et de la production d’ergovaline, dont les effets toxiques associés à la présence de lolitrème B sont mal documentés. Mon travail de thèse a consisté à explorer les effets de la distribution de différents fourrages de fétuque et ray-grass endophytés toxinogènes produits dans des conditions agricoles françaises, sur la santé et la production animale et les mécanismes d’action de l’ergovaline et du lolitrème B. / The symbiotic associations between different varieties of fungi of the Epichloë 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 E. coenophiala in tall fescue, which is associated with the production of ergovaline, is responsible for « fescue foot disease » while the presence of E. festucae var. lolii in ryegrass, which is accompanied by the production of lolitrem B, is responsible for the « ryegrass staggers ». and the production of ergovaline, whose the toxic effects associated in the presence of lolitrem B are poorly documented. My thesis was to explore the effects of the distribution of different toxic forages of endophyte-infected tall fescue or ryegrass produced in French agricultural conditions on health and animal production and the mechanisms of action of ergovaline and lolitrem B.

Les associations symbiotiques Epichloë- graminées fourragères les plus étudiées concernent le ray grass anglais (Lolium perenne) avec Epichloë festucae var. lolii et la fétuque élevée (L. arundinaceum) avec E. coenophiala. Ces champignons peuvent synthétiser des alcaloïdes toxiques pour le bétail tels que l’ergovaline et le lolitrème B. Mon travail de thèse a consisté à explorer les facteurs en lien avec la production de mycotoxines dans les graminées. Pour cela différentes études ont été conduites sur la fétuque et le ray grass afin de révéler i) la présence de souches endophytées toxinogènes dans le Sud Ouest de la France et ii) l’influence des conditions climatiques françaises sur la synthèse d’ergovaline et de lolitrème B dans des variétés fourragères connues pour être responsables de cas de toxicité sur d’autres continents. / The most studied symbiotic associations Epichloë- cool seasons grasses concern perennial ryegrass (Lolium perenne) with Epichloë festucae var. lolii and tall fescue (L. arundinaceum) with E. coenophiala. These fungi can synthesize alkaloids that could be toxic to livestock such as ergovaline and lolitrem B. My thesis work was to explore the factors related to the production of mycotoxins in grasses. Different studies have been conducted on tall fescue and perennial ryegrass to reveal i) the presence of endophyte-infected toxigenic strains in the South West of France and ii) the influence of environmental conditions of Saint-Affrique (Aveyron) on the synthesis of ergovaline and lolitrem B in forage varieties known to be responsible for toxicity on other continents.

LOL is a novel secondary metabolite gene cluster associated with the production of loline alkaloids (saturated 1-aminopyrrolizidine alkaloids with an oxygen bridge) exclusively in closely related grass-endophyte species in the genera Epichloë and Neotyphodium. In this study I characterize the LOL cluster in E. festucae, including the presentation of sequence corresponding to 10 individual lol genes as well as defining the boundaries of the cluster and evaluation of the genomic DNA region flanking LOL in E. festucae. In addition to characterizing the LOL cluster in E. festucae, I present LOL sequence from two additional species, Neotyphodium coenophialum and Neotyphodium sp. PauTG-1. Together with two recently published LOL clusters from N. uncinatum, these data allow for a powerful phylogenetic comparison of five clusters from four closely related species. There is a high degree of microsynteny (conserved gene order and orientation) among the five LOL clusters, allowing us to predict potential transcriptional co-regulatory binding motifs in lol promoter regions. The relatedness of LOL clusters is especially interesting in light of the history of interspecific hybridizations that generated the asexual, Neotyphodium lineages. In fact, three of the clusters appear to have been introduced to different Neotyphodium species by the same ancestral Epichloë species, for which present day isolates are no longer able to produce lolines. To address the evolutionary origins of the cluster we have investigated the phylogenetic relationships of particular lol ORFs to their paralogous primary metabolism genes (and gene families) from endophytes, other fungi and even other kingdoms. I present extensive evidence that at least two individual lol genes have evolved from primary metabolism genes within the fungal ancestors of endophytes, rather than being introduced via horizontal gene transfer. I also present complementation studies in Neurospora crassa exploring the functional divergence of one lol gene from its primary metabolism paralog. While it is clear that these insecticidal compounds should convey a selective advantage to the fungus and its host, thus explaining preservation of the trait, this analysis provides an exploration into the evolutionary origin and maintenance of the genes that comprise the LOL and the cluster itself.

LOL is a novel secondary metabolite gene cluster associated with the production of loline alkaloids (saturated 1-aminopyrrolizidine alkaloids with an oxygen bridge) exclusively in closely related grass-endophyte species in the genera Epichloë and Neotyphodium. In this study I characterize the LOL cluster in E. festucae, including the presentation of sequence corresponding to 10 individual lol genes as well as defining the boundaries of the cluster and evaluation of the genomic DNA region flanking LOL in E. festucae. In addition to characterizing the LOL cluster in E. festucae, I present LOL sequence from two additional species, Neotyphodium coenophialum and Neotyphodium sp. PauTG-1. Together with two recently published LOL clusters from N. uncinatum, these data allow for a powerful phylogenetic comparison of five clusters from four closely related species. There is a high degree of microsynteny (conserved gene order and orientation) among the five LOL clusters, allowing us to predict potential transcriptional co-regulatory binding motifs in lol promoter regions. The relatedness of LOL clusters is especially interesting in light of the history of interspecific hybridizations that generated the asexual, Neotyphodium lineages. In fact, three of the clusters appear to have been introduced to different Neotyphodium species by the same ancestral Epichloë species, for which present day isolates are no longer able to produce lolines. To address the evolutionary origins of the cluster we have investigated the phylogenetic relationships of particular lol ORFs to their paralogous primary metabolism genes (and gene families) from endophytes, other fungi and even other kingdoms. I present extensive evidence that at least two individual lol genes have evolved from primary metabolism genes within the fungal ancestors of endophytes, rather than being introduced via horizontal gene transfer. I also present complementation studies in Neurospora crassa exploring the functional divergence of one lol gene from its primary metabolism paralog. While it is clear that these insecticidal compounds should convey a selective advantage to the fungus and its host, thus explaining preservation of the trait, this analysis provides an exploration into the evolutionary origin and maintenance of the genes that comprise the LOL and the cluster itself.