Acclimatation de l’espèce aquatique invasive, Ludwigia grandiflora, au milieu terrestre : Approches physiologique et épigénétique

Abstract: In the context of the expansion of invasive species, their survival is conditioned by their ability to adapt. In France, Ludwigia grandiflora has invaded aquatic biotopes and its recent deployment in wet meadows has led to the emergence of two morphotypes, one aquatic and the other called “terrestrial”. The aim of this thesis was to get a better understanding of water primrose acclimation capacities to terrestrial environment through exploring genetic and epigenetic sources of flexibility. The responses of two morphotypes to different water stresses were evaluated by observing physiological traits. The epigenetic pathway was addressed by the use of a hypomethylant drug. This work showed that L. grandiflora adapts its development and metabolism according to environmental conditions.The terrestrial morphotype shows higher trait values than those of the aquatic morphotype, regardless of the condition. However, phenotypic plasticity is higher in the aquatic morphotype. Finally, our results suggest the involvement of DNA methylation and phenotypic plasticity in the response of water primrose to environmental change. Since the terrestrial morphotype has higher capacities than the aquatic morphotype, its management must become a priority. The acquisition of genomic resources in L. grandiflora will make it possible to search for genetic and epigenetic markers of acclimation to the terrestrial environment.Dans un contexte d’expansion des espèces invasives, leur survie et succès sont conditionnés par leur capacité à s’adapter. En France, Ludwigia grandiflora (jussie) a envahi bon nombre de biotopes aquatiques et son déploiement récent dans les prairies humides a conduit à l’apparition de deux morphotypes, l’un aquatique et l’autre dit « terrestre ». L’objectif de cette thèse visait à mieux comprendre les capacités d’acclimatation de la jussie au milieu terrestre en explorant les sources de flexibilité que sont les mécanismes génétiques et épigénétiques. Les réponses des morphotypes aquatique et terrestre à différentes contraintes hydriques ont été évaluées via l’observation des traits morphologiques et développementaux, des dosages de métabolites et de phytohormones. La piste épigénétique a été abordée par l’utilisation d’une drogue hypométhylante, la zébularine. Ces travaux ont montré que L. grandiflora adapte son développement et son métabolisme avec des valeurs de biomasses élevées etLe morphotype terrestre présente des valeurs de traits plus importants que ceux du morphotype aquatique, quelle que soit la condition. Cependant, la plasticité phénotypique est plus importante chez le morphotype aquatique. Enfin, l’épigénétique via la méthylation de l’ADN semble impliquée dans la transition du morphotype aquatique vers le milieu terrestre. Nos résultats suggèrent une implication de la méthylation de l’ADN et de la plasticité phénotypique dans la réponse de la jussie au changement de milieu. Le morphotype terrestre ayant des capacités supérieures au morphotype aquatique, s

Acclimation of the invasive aquatic species, Ludwigia grandiflora, to terrestrial environment : Physiological and epigenetic approaches by Julien Genitoni

Dans un contexte d’expansion des espèces invasives, leur survie et succès sont conditionnés par leur capacité à s’adapter. En France, Ludwigia grandiflora (jussie) a envahi bon nombre de biotopes aquatiques et son déploiement récent dans les prairies humides a conduit à l’apparition de deux morphotypes, l’un aquatique et l’autre dit « terrestre ». L’objectif de cette thèse visait à mieux comprendre les capacités d’acclimatation de la jussie au milieu terrestre en explorant les sources de flexibilité que sont les mécanismes génétiques et épigénétiques. Les réponses des morphotypes aquatique et terrestre à différentes contraintes hydriques ont été évaluées via l’observation des traits morphologiques et développementaux, des dosages de métabolites et de phytohormones. La piste épigénétique a été abordée par l’utilisation d’une drogue hypométhylante, la zébularine. Ces travaux ont montré que L. grandiflora adapte son développement et son métabolisme avec des valeurs de biomasses élevées etLe morphotype terrestre présente des valeurs de traits plus importants que ceux du morphotype aquatique, quelle que soit la condition. Cependant, la plasticité phénotypique est plus importante chez le morphotype aquatique. Enfin, l’épigénétique via la méthylation de l’ADN semble impliquée dans la transition du morphotype aquatique vers le milieu terrestre. Nos résultats suggèrent une implication de la méthylation de l’ADN et de la plasticité phénotypique dans la réponse de la jussie au changement de milieu. Le morphotype terrestre ayant des capacités supérieures au morphotype aquatique, saAbstract: In the context of the expansion of invasive species, their survival is conditioned by their ability to adapt. In France, Ludwigia grandiflora has invaded aquatic biotopes and its recent deployment in wet meadows has led to the emergence of two morphotypes, one aquatic and the other called “terrestrial”. The aim of this thesis was to get a better understanding of water primrose acclimation capacities to terrestrial environment through exploring genetic and epigenetic sources of flexibility. The responses of two morphotypes to different water stresses were evaluated by observing physiological traits. The epigenetic pathway was addressed by the use of a hypomethylant drug. This work showed that L. grandiflora adapts its development and metabolism according to environmental conditions.The terrestrial morphotype shows higher trait values than those of the aquatic morphotype, regardless of the condition. However, phenotypic plasticity is higher in the aquatic morphotype. Finally, our results suggest the involvement of DNA methylation and phenotypic plasticity in the response of water primrose to environmental change. Since the terrestrial morphotype has higher capacities than the aquatic morphotype, its management must become a priority. The acquisition of genomic resources in L. grandiflora will make it possible to search for genetic and epigenetic markers of acclimation to the terrestrial environment

Etude de la plasticité de la plante aquatique invasive [i]Ludwigia grandiflora[/i] en milieu terrestre

Session 1 : Scénarios et Potentiel InvasifNational audienc

Aquatic and terrestrial morphotypes of the aquatic invasive plant, Ludwigia grandiflora, show distinct morphological and metabolomic responses

International audienceIn the context of expansion of invasive species, survival of invasive plants is conditioned by their ability to adapt. In France, the water primrose , an aquatic invasive species, invades yet wet meadows, leading to a depreciation of their fodder value. Understanding its potential adaption is necessary to its management, strong differences between both morphotypes were expected. So morphological and metabolic responses to terrestrial environment were analyzed for aquatic and terrestrial morphotypes. All morphological and biomass variables were greater in the terrestrial morphotype than the aquatic morphotype, independent of conditions. In terrestrial condition, both morphotypes showed a high production of sugars in root tissues, especially in the terrestrial morphotype and both morphotypes produced a low level of amino acids in shoot tissues. All results demonstrate that the terrestrial condition seems a stressful situation for both morphotypes, which activates glycolysis and fermentation pathways to improve their survival under hypoxic stress. But, only the terrestrial morphotype has been able to adjust its metabolism and maintain efficient growth. In the future, a differential transcriptomic analysis will be carried out to confirm this result

Biological Invasion: The Influence of the Hidden Side of the (Epi)Genome

International audienceUnderstanding the mechanisms underlying biological invasions and rapid adaptation to global change remains a fundamental challenge, particularly in small populations lacking in genetic variation. Two under‐studied mechanisms that could facilitate adaptive evolution and adaptive plasticity are the increased genetic variation due to transposable elements, and associated or independent modification of gene expression through epigenetic changes.2.Here we focus on the potential role of these genetic and non‐genetic mechanisms for facilitating invasion success. Because novel or stressful environments are known to induce both epigenetic changes and transposable element activity, these mechanisms may play an underappreciated role in generating phenotypic and genetic variation for selection to act on. We review how these mechanisms operate, the evidence for how they respond to novel or stressful environments, and how these mechanisms can contribute to the success of biological invasions by facilitating adaptive evolution and phenotypic plasticity.3.Because genetic and phenotypic variations due to transposable elements and epigenetic changes are often well regulated or “hidden” in the native environment, the independent and combined contribution of these mechanisms may only become important when populations colonize novel environments. A focus on the mechanisms that generate and control the expression of this variation in new environments may provide insights into biological invasions that would otherwise not be obvious.4.Global changes and human activities impact on ecosystems and allow new opportunities for biological invasions. Invasive species succeed by adapting rapidly to new environments. The degree to which rapid responses to environmental change could be mediated by the epigenome – the regulatory system that integrates how environmental and genomic variation jointly shape phenotypic variation ‐ requires greater attention if we want to understand the mechanisms by which populations successfully colonize and adapt to new environments

Does plasticity of the aquatic invasive plant, L. grandiflora, to terrestrial environment involve an epigenetic component?

International audienc

Hypomethylation of the aquatic invasive plant, Ludwigia grandiflora subsp. hexapetala mimics the adaptive transition into the terrestrial morphotype

International audienceOngoing global changes affect ecosystems and open up new opportunities for biological invasion. The ability of invasive species to rapidly adapt to new environments represents a relevant model for studying short‐term adaptation mechanisms. The aquatic invasive plant, Ludwigia grandiflora subsp. hexapetala, is classified as harmful in European rivers. In French wet meadows, this species has shown a rapid transition from aquatic to terrestrial environments with emergence of two distinct morphotypes in 5 years. To understand the heritable mechanisms involved in adjustment to such a new environment, we investigate both genetic and epigenetic as possible sources of flexibility involved in this fast terrestrial transition. We found a low overall genetic differentiation between the two morphotypes arguing against the possibility that terrestrial morphotype emerged from a new adaptive genetic capacity. Artificial hypomethylation was induced on both morphotypes to assess the epigenetic hypothesis. We analyzed global DNA methylation, morphological changes, phytohormones and metabolite profiles of both morphotype responses in both aquatic and terrestrial conditions in shoot and root tissues. Hypomethylation significantly affected morphological variables, phytohormone levels and the amount of some metabolites. The effects of hypomethylation depended on morphotypes, conditions and plant tissues, which highlighted differences among the morphotypes and their plasticity. Using a correlative integrative approach, we showed that hypomethylation of the aquatic morphotype mimicked the characteristics of the terrestrial morphotype. Our data suggest that DNA methylation rather than a new adaptive genetic capacity is playing a key role in L. grandiflora subsp. hexapetala plasticity during its rapid aquatic to terrestrial transition