Relevant bibliographies by topics / Mutualiste

Academic literature on the topic 'Mutualiste'

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Published: 23 September 2022
Last updated: 28 September 2022

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Journal articles on the topic "Mutualiste"

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Sachs, Joel L., Ryan G. Skophammer, Nidhanjali Bansal, and Jason E. Stajich. "Evolutionary origins and diversification of proteobacterial mutualists." Proceedings of the Royal Society B: Biological Sciences 281, no. 1775 (January 22, 2014): 20132146. http://dx.doi.org/10.1098/rspb.2013.2146.

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Mutualistic bacteria infect most eukaryotic species in nearly every biome. Nonetheless, two dilemmas remain unresolved about bacterial–eukaryote mutualisms: how do mutualist phenotypes originate in bacterial lineages and to what degree do mutualists traits drive or hinder bacterial diversification? Here, we reconstructed the phylogeny of the hyperdiverse phylum Proteobacteria to investigate the origins and evolutionary diversification of mutualistic bacterial phenotypes. Our ancestral state reconstructions (ASRs) inferred a range of 34–39 independent origins of mutualist phenotypes in Proteobacteria, revealing the surprising frequency with which host-beneficial traits have evolved in this phylum. We found proteobacterial mutualists to be more often derived from parasitic than from free-living ancestors, consistent with the untested paradigm that bacterial mutualists most often evolve from pathogens. Strikingly, we inferred that mutualists exhibit a negative net diversification rate (speciation minus extinction), which suggests that mutualism evolves primarily via transitions from other states rather than diversification within mutualist taxa. Moreover, our ASRs infer that proteobacterial mutualist lineages exhibit a paucity of reversals to parasitism or to free-living status. This evolutionary conservatism of mutualism is contrary to long-standing theory, which predicts that selection should often favour mutants in microbial mutualist populations that exploit or abandon more slowly evolving eukaryotic hosts.
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Riberolles, Brigitte. "Le bilan mutualiste de la mutualité sociale agricole." Revue internationale de l'économie sociale: Recma, no. 294 (2004): 27. http://dx.doi.org/10.7202/1022020ar.

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Vidal, Mayra C., Sheng Pei Wang, David M. Rivers, David M. Althoff, and Kari A. Segraves. "Species richness and redundancy promote persistence of exploited mutualisms in yeast." Science 370, no. 6514 (October 15, 2020): 346–50. http://dx.doi.org/10.1126/science.abb6703.

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Mutualisms, or reciprocally beneficial interspecific interactions, constitute the foundation of many ecological communities and agricultural systems. Mutualisms come in different forms, from pairwise interactions to extremely diverse communities, and they are continually challenged with exploitation by nonmutualistic community members (exploiters). Thus, understanding how mutualisms persist remains an essential question in ecology. Theory suggests that high species richness and functional redundancy could promote mutualism persistence in complex mutualistic communities. Using a yeast system (Saccharomyces cerevisiae), we experimentally show that communities with the greatest mutualist richness and functional redundancy are nearly two times more likely to survive exploitation than are simple communities. Persistence increased because diverse communities were better able to mitigate the negative effects of competition with exploiters. Thus, large mutualistic networks may be inherently buffered from exploitation.
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Lautman, Albert, and Camille Brouard. "La gouvernance mutualiste." Regards N�52, no. 2 (2017): 163. http://dx.doi.org/10.3917/regar.052.0163.

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Koga, Ryuichi, Minoru Moriyama, Naoko Onodera-Tanifuji, Yoshiko Ishii, Hiroki Takai, Masaki Mizutani, Kohei Oguchi, et al. "Single mutation makes Escherichia coli an insect mutualist." Nature Microbiology 7, no. 8 (August 4, 2022): 1141–50. http://dx.doi.org/10.1038/s41564-022-01179-9.

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AbstractMicroorganisms often live in symbiosis with their hosts, and some are considered mutualists, where all species involved benefit from the interaction. How free-living microorganisms have evolved to become mutualists is unclear. Here we report an experimental system in which non-symbiotic Escherichia coli evolves into an insect mutualist. The stinkbug Plautia stali is typically associated with its essential gut symbiont, Pantoea sp., which colonizes a specialized symbiotic organ. When sterilized newborn nymphs were infected with E. coli rather than Pantoea sp., only a few insects survived, in which E. coli exhibited specific localization to the symbiotic organ and vertical transmission to the offspring. Through transgenerational maintenance with P. stali, several hypermutating E. coli lines independently evolved to support the host’s high adult emergence and improved body colour; these were called ‘mutualistic’ E. coli. These mutants exhibited slower bacterial growth, smaller size, loss of flagellar motility and lack of an extracellular matrix. Transcriptomic and genomic analyses of ‘mutualistic’ E. coli lines revealed independent mutations that disrupted the carbon catabolite repression global transcriptional regulator system. Each mutation reproduced the mutualistic phenotypes when introduced into wild-type E. coli, confirming that single carbon catabolite repression mutations can make E. coli an insect mutualist. These findings provide an experimental system for future work on host–microbe symbioses and may explain why microbial mutualisms are omnipresent in nature.
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Labbé, Pierrick. "D'une société de secours mutuel locale à une société fraternelle nationale : la transformation du projet social de l’Union Saint-Joseph d’Ottawa (1863-1905)." Mens 11, no. 1 (March 3, 2014): 37–75. http://dx.doi.org/10.7202/1023337ar.

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Cet article examine la transformation de la mutualité canadienne-française à la fin du xixe siècle en analysant le cas de l’Union Saint-Joseph d’Ottawa. Elle fut l’une des rares sociétés de secours mutuel de première génération à adapter sa structure et son projet social pour se conformer au courant mutualiste émergent et, ainsi, se transformer en une société fraternelle. L’exemple nous montre que la lutte pour la survivance dans les milieux de migration facilitait cette transition du modèle mutualiste et justifiait la redéfinition des objectifs par une petite élite au nom d’un idéal national. Le besoin d’assurer des bases institutionnelles solides pour les Canadiens français de l’Ontario légitimait cette transformation de l’Union Saint-Joseph, qui devint une grande société fraternelle vouée à la défense des intérêts économiques des Canadiens français, grâce à l’établissement de succursales dans plus de six cents communautés canadiennes-françaises du Canada et des États-Unis.
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Segraves, Kari A., David M. Althoff, and Olle Pellmyr. "Limiting cheaters in mutualism: evidence from hybridization between mutualist and cheater yucca moths." Proceedings of the Royal Society B: Biological Sciences 272, no. 1577 (August 31, 2005): 2195–201. http://dx.doi.org/10.1098/rspb.2005.3201.

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Mutualisms are balanced antagonistic interactions where both species gain a net benefit. Because mutualisms generate resources, they can be exploited by individuals that reap the benefits of the interaction without paying any cost. The presence of such ‘cheaters’ may have important consequences, yet we are only beginning to understand how cheaters evolve from mutualists and how their evolution may be curtailed within mutualistic lineages. The yucca–yucca moth pollination mutualism is an excellent model in this context as there have been two origins of cheating from within the yucca moth lineage. We used nuclear and mitochondrial DNA markers to examine genetic structure in a moth population where a cheater species is parapatric with a resident pollinator. The results revealed extensive hybridization between pollinators and cheaters. Hybrids were genetically intermediate to parental populations, even though all individuals in this population had a pollinator phenotype. The results suggest that mutualisms can be stable in the face of introgression of cheater genes and that the ability of cheaters to invade a given mutualism may be more limited than previously appreciated.
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Wooding, Amy L., Michael J. Wingfield, Brett P. Hurley, Jeffrey R. Garnas, Peter de Groot, and Bernard Slippers. "Lack of fidelity revealed in an insect–fungal mutualism after invasion." Biology Letters 9, no. 4 (August 23, 2013): 20130342. http://dx.doi.org/10.1098/rsbl.2013.0342.

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Symbiont fidelity is an important mechanism in the evolution and stability of mutualisms. Strict fidelity has been assumed for the obligate mutualism between Sirex woodwasps and their mutualistic Amylostereum fungi. This assumption has been challenged in North America where the European woodwasp, Sirex noctilio , and its fungal mutualist, Amylostereum areolatum , have recently been introduced. We investigate the specificity of the mutualism between Sirex and Amylostereum species in Canada, where S. noctilio co-infests Pinus with native Sirex nigricornis and its mutualist, Amylostereum chailletii . Using phylogenetic and culture methods, we show that extensive, reciprocal exchange of fungal species and strains is occurring, with 75.3 per cent of S. nigricornis carrying A. areolatum and 3.5 per cent of S. noctilio carrying A. chailletii . These findings show that the apparent specificity of the mutualism between Sirex spp. and their associated Amylostereum spp. is not the result of specific biological mechanisms that maintain symbiont fidelity. Rather, partner switching may be common when shifting geographical distributions driven by ecological or anthropogenic forces bring host and mutualist pairs into sympatry. Such novel associations have potentially profound consequences for fitness and virulence. Symbiont sharing, if it occurs commonly, may represent an important but overlooked mechanism of community change linked to biological invasions.
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Fricke, Evan C., Joshua J. Tewksbury, Elizabeth M. Wandrag, and Haldre S. Rogers. "Mutualistic strategies minimize coextinction in plant–disperser networks." Proceedings of the Royal Society B: Biological Sciences 284, no. 1854 (May 10, 2017): 20162302. http://dx.doi.org/10.1098/rspb.2016.2302.

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The global decline of mutualists such as pollinators and seed dispersers may cause negative direct and indirect impacts on biodiversity. Mutualistic network models used to understand the stability of mutualistic systems indicate that species with low partner diversity are most vulnerable to coextinction following mutualism disruption. However, existing models have not considered how species vary in their dependence on mutualistic interactions for reproduction or survival, overlooking the potential influence of this variation on species' coextinction vulnerability and on network stability. Using global databases and field experiments focused on the seed dispersal mutualism, we found that plants and animals that depend heavily on mutualistic interactions have higher partner diversity. Under simulated network disruption, this empirical relationship strongly reduced coextinction because the species most likely to lose mutualists depend least on their mutualists. The pattern also reduced the importance of network structure for stability; nested network structure had little effect on coextinction after simulations incorporated the empirically derived relationship between partner diversity and mutualistic dependence. Our results highlight a previously unknown source of stability in mutualistic networks and suggest that differences among species in their mutualistic strategy, rather than network structure, primarily accounts for stability in mutualistic communities.
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Simonsen, Anna K., and John R. Stinchcombe. "Standing genetic variation in host preference for mutualist microbial symbionts." Proceedings of the Royal Society B: Biological Sciences 281, no. 1797 (December 22, 2014): 20142036. http://dx.doi.org/10.1098/rspb.2014.2036.

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Many models of mutualisms show that mutualisms are unstable if hosts lack mechanisms enabling preferential associations with mutualistic symbiotic partners over exploitative partners. Despite the theoretical importance of mutualism-stabilizing mechanisms, we have little empirical evidence to infer their evolutionary dynamics in response to exploitation by non-beneficial partners. Using a model mutualism—the interaction between legumes and nitrogen-fixing soil symbionts—we tested for quantitative genetic variation in plant responses to mutualistic and exploitative symbiotic rhizobia in controlled greenhouse conditions. We found significant broad-sense heritability in a legume host's preferential association with mutualistic over exploitative symbionts and selection to reduce frequency of associations with exploitative partners. We failed to detect evidence that selection will favour the loss of mutualism-stabilizing mechanisms in the absence of exploitation, as we found no evidence for a fitness cost to the host trait or indirect selection on genetically correlated traits. Our results show that genetic variation in the ability to preferentially reduce associations with an exploitative partner exists within mutualisms and is under selection, indicating that micro-evolutionary responses in mutualism-stabilizing traits in the face of rapidly evolving mutualistic and exploitative symbiotic bacteria can occur in natural host populations.
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Dissertations / Theses on the topic "Mutualiste"

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Combes, Victor. "Management mutualiste : la fin d'un oxymore ?" Thesis, Paris, HESAM, 2022. http://www.theses.fr/2022HESAC005.

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Les organisations mutualistes font partie de l’Economie Sociale et Solidaire, qui porte l’ambition d’une alternative face au modèle capitaliste dominant, malgré des pratiques hétérogènes et une banalisation galopante. Le management mutualiste, encore peu conceptualisé, est l’objet d’une thèse CIFRE au sein d’un groupe mutualiste français. Dans le cadre d’un positionnement épistémologique interprétativiste, notre travail empirique, sous-tendu par trois méthodes de collecte de données, s’est focalisé sur le suivi et l’analyse des effets d’un dispositif fondé sur le codéveloppement et proposé aux managers de ce groupe mutualiste. Il révèle un isomorphisme managérial en décalage avec la dynamique de l’alter souhaitée et prônée par les organisations mutualistes. Ce travail fait émerger : un apport conceptuel autour de l’intelligence relationnelle, des recommandations autour d’un management mutualiste, et la proposition d’un nouveau dispositif au service d’une culture mutualiste repensée
Mutualist organizations are part of the Social and Solidarity Economy, which carries the ambition of an alternative to the dominant capitalist model, despite heterogeneous practices and galloping trivialization. Mutualist management, still little conceptualized, is the subject of a CIFRE thesis within a French mutualist group. Within the framework of an interpretative epistemological position, our empirical work, underpinned by three data collection methods, focused on the monitoring and analysis of the effects of a system based on co-development and proposed to managers from this mutualist group. It reveals a managerial isomorphism that is out of step with the dynamics of the alter desired and advocated by mutual organizations. This work brings out: a conceptual contribution around relational intelligence, recommendations around a mutualist management, and the proposal of a new device for a redesigned mutualist culture
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Lapoutte, Alexandrine. "Gouvernance et légitimité : le modèle mutualiste." Thesis, Brest, 2013. http://www.theses.fr/2013BRES0071/document.

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Ce travail porte sur la gouvernance mutualiste. A partir d’un cadre d’analyse fondé sur la légitimité, nous avons cherché à comprendre comment s’exprime la légitimité en contexte mutualiste aujourd’hui. La proposition faite est qu’il existe nécessairement un gap entre la légitimité construite par les dirigeants et la légitimité perçue par les parties prenantes. Les dirigeants déploient alors des stratégies de légitimation par une communication mutualiste. Le modèle mutualiste deviendrait un outil de gestion des parties prenantes. Dans une phase de recherche quantitative auprès des parties prenantes impliquées, nous identifions un socle commun partagé ainsi qu’un gap mutualiste, qui porte sur la perception que l’entreprise maîtrise son projet et contribue au territoire. Une typologie des parties prenantes est dressée autour d’un clivage horizontal. L’analyse qualitative de discours révèle des systèmes de références sensiblement différents selon les entreprises. Nous distinguons trois approches dans la gestion de la légitimité en contexte mutualiste : communicationnelle, politique et managériale
This work concerns the mutualist governance. From a frame of analysis based on legitimacy theory, we tried to understand how appears legitimacy in mutual organisation context today. The proposal is that it exists inevitably a gap between the legitimacy built by managers and the legitimacy perceived by the stakeholders. Managers display then strategies of legitimization by a communication based on mutualist references. The mutualist model would become a management tool. In a phase of quantitative research with the involved stakeholders, we identify a common base shared between stakeholders, as well as a mutualist gap, which concerns the perception that the company masters its projet and contributes to the territory. A typology of the stakeholders is drawn up around a horizontal split. The qualitative analysis of speech reveals different patterns, based on communication, politics and management
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Baumard, Nicolas. "Une théorie naturaliste et mutualiste de la morale." Paris, EHESS, 2008. http://www.theses.fr/2008EHES0033.

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Ce travail cherche à répondre à la question : pourquoi sommes-nous moraux ? Il s'appuie sur deux approches. La première, naturaliste, reprend la tradition du sens moral (Shaftesbury, Hutcheson, et Adam Smith) et cherche à expliquer la morale à l'aide des outils des sciences naturelles (en particulier la théorie de l'évolution et la psychologie cognitive). La seconde, mutualiste, correspond à la tradition du contrat social (Hobbes, Rousseau ou Rawls) et considère les rapports moraux comme des rapports mutuellement avantageux. Ce travail se démarque donc à la fois des théories non naturalistes (comme les théories culturalistes ou les théories du choix rationnel) et des théories naturalistes non mutualistes (comme les théories de la sélection de groupe ou les théories basées sur les sentiments). Il montre comment, dans un grand nombre de situations morales (justice, assistance mutuelle, dilemme moral, jeux économiques, faute sans victime, limites de la communauté morale), les jugements comme les comportements s'expliquent mieux dans un cadre naturaliste et mutualiste
Why are we moral? This work relies on two approaches. The naturalist approach comes from the tradition of moral sense (Shaftesbury, Hutcheson, Adam Smith) and aims at explaining morality with the help of tools coming from natural sciences (evolutionary theory, cognitive psychology). The mutualist approach comes from the social contract tradition (Hobbes, Rousseau and Rawls) et see moral relationships as mutually advantageous interactions. Thus, this work distances oneself from non naturalist theories of morality ( culturalist theories, rational choice theories) and fron non mutualist theories (group selection or altruistic theories, sentimentalist or continuiste theories). This works shows that numerous moral situations (justice, solidarity, moral dilemmas, economic games, crimes without victim) are better explained in a naturalist and mutualist framework
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Storelli, Gilles. "Caractérisation de l’interaction mutualiste liant Drosophila melanogaster à son symbionte Lactobacillus plantarum." Thesis, Lyon, École normale supérieure, 2015. http://www.theses.fr/2015ENSL1041.

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Le microbiote a un impact majeur sur la physiologie de son hôte, cependant notre compréhension des mécanismes régulant la relation hôte/microbiote reste limitée. Nous utilisons un hôte modèle simple, la Drosophile, afin de répondre à ces questions. Durant mon doctorat, je me suis attaché à une étape particulière du cycle de vie de la Drosophile, sa phase larvaire. Celle-ci constitue sa phase de croissance et est influencée par le contexte nutritionnel. Le microbiote influence également cette étape: l’association avec la bactérie Lactobacillus plantarum tempère les effets de la carence alimentaire en soutenant un taux de croissance élevé et une maturation rapide, en modulant chez l’hôte l’activité de l’hormone Ecdysone et de l’insuline. En retour, L.plantarum bénéficie de l’association, les larvesassurant sa persistance dans la niche (la niche étant le substrat nutritif, les larves et les bactéries associées). Pour caractériser les mécanismes mis en jeu dans ce mutualisme nous avons décrit les réponses transcriptomiques et métaboliques de la larve et avons également étudié les perturbations métaboliques de la niche. Nos résultats mettent en avant l’optimisation de l’extraction des acides aminés du substrat comme facteur clef du mutualisme. L.plantarum active l’expression des protéases intestinales de l’hôte via la voie IMD/NF-κB, et bénéficierait en retour d’une quantité d’acides aminés plus importante assurant sa persistance. Ainsi, nos travaux contribuent à l’effort de compréhension desmécanismes régulant l’interaction hôte/microbiote et pourraient conduire à de nombreuses applications thérapeutiques, notamment dans le cadre de déséquilibres nutritionnels
Symbiotic bacterial populations (also called the “microbiota”) have a dramatic impact on their host’s physiology. However, our understanding of the mechanisms shaping host/microbes mutualism remains limited. We took advantage of Drosophila tractability to characterize the host’s and the microbial factors engaged in mutualism. During my PhD, I focused on the impact of the microbiota during the Drosophila larval phase, which constitutes its juvenile growth period. Drosophila larval phase is influenced by nutrition, but also by symbiotic microbes: specific association with the bacterium Lactobacillus plantarum buffers the deleterious effects of nutrient scarcity on the host’s juvenile growth, by sustaining greater growth rates and hastening maturation. L.plantarum mediate these effects by modulating the activity of the steroid hormone Ecdysone and the Insulin/Insulin-like Signaling pathway in its host. In return, L.plantarum benefits from Drosophila presence, as larvae ensure its long-term persistence in the niche (the niche being the nutritive substrate, the larvae and the bacteria dwelling on it). To characterize the mechanisms engaged in this mutualistic relationship, we described the host’s transcriptomic and metabolic responses to L.plantarum presence and characterized the metabolic perturbations occurring in the niche. Our results put forward the optimization of amino-acids extraction from the nutritive substrate as a cornerstone of mutualism. L.plantarum activates the expression of the host’s digestive proteases via IMD/NF-κB signaling and would benefit in return from an enhanced AA availability, which would help sustaining its long-term persistence. Altogether, our studies contribute to the understanding of the mechanisms regulating host/microbiota interaction and could lead to numerous therapeutic applications, notably aiming at counteracting the deleterious effects of nutritional imbalances
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Alburaki, Salam. "L'influence du statut mutualiste et coopératif sur la gouvernance d'entreprise : cas du secteur financier." Bordeaux 4, 2009. http://www.theses.fr/2009BOR40042.

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Les valeurs coopératives s'impriment dans la gouvernance des banques mutuelles. Le sociétaire est la pierre angulaire autour duquel tourne le système de gouvernance de ces banques affectées par la proximité, la responsabilité et la solidarité comme mode d'action et d'enracinement dans leur territoire et leur société locale. Le principe de base étant "un homme-une voix", la gouvernance coopérative est caractérisée par son aspect démocratique où le vote est le processus par lequel le sociétariat s'exprime. C'est une gouvernance souple et consensuelle. L'étude de deux cas de banques régionales en Aquitaine a démontré l'effet positif des valeurs coopératives dans la construction d'une relation de confiance mutuelle entre banque et client-sociétaire et l'effet positif de ces valeurs sur la performance, qui dépasse son aspect financier pour s'étendre à des aspects économique et social. Le modèle coopératif affiche, malgré les crises successives, une vitalité et une capacité d'adaptation qui assure sa pérennité
Values affect mutual Banks corporate governance. Member is the angular stone of governance system of these banks, for whose proximity, responsability and solidarity are guides for action and entrenchment in their territory and local society. Basic principal is "one voice-one vote", so mutual governance is characterised by its democratic aspect where voting is main process of claiming by membership. Mutual governance is soft and consensual. Case study of tow regional banks in Aquitaine reveals a positive effect of cooperative values on building trust relationship between mutual bank and client-member, and a positive effect of values on performance, beyond its financial aspect to cover economic and social aspects. Mutual banking presents, although successive crises, vitality and adaptation whose guaranted is continuity
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Lorenzi, Ange. "Analyse fonctionnelle d’une symbiose mutualiste : mécanismes de production du polydnavirus associé au parasitoïde ichneumonide Hyposoter didymator." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTG047.

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Les PDVs sont des virus à ADN associés à des dizaines de milliers d'espèces d'hyménoptères parasitoïdes. Ils sont divisés en deux taxa, les Bracovirus (BVs) et les Ichnovirus (IVs) associés respectivement aux sous-familles des Braconidae et Ichneumonidae. Les PDVs sont produits dans un tissu spécialisé du tractus génital (le calyx) de la femelle parasitoïde. Ils sont ensuite injectés lors de la ponte dans une chenille hôte, altérant les fonctions physiologiques et assurant un environnement favorable au développement de la progéniture du parasitoïde. Le génome des PDVs est intégré au génome des guêpes et est constitué de deux composants fonctionnels, avec d'une part des séquences impliquées dans la virulence chez l'hôte qui sont les seules à être encapsidées, et d'autre part des régions portant des clusters de gènes responsables de la production des particules virales. Ces gènes organisés en clusters arborent des caractéristiques de gènes viraux et sont exprimés spécifiquement dans le tissu réplicatif, le calyx. Ils dérivent de l’ancêtre viral des IVs actuels, mais ne présentent aucune homologie de séquence avec des gènes viraux connus ; en conséquence, la nature du virus ancêtre et la fonction des gènes qui en proviennent restent inconnues.Les régions portant ces groupes de gènes ont été nommées "Ichnovirus Structural Protein Encoding Regions (IVSPERs)". Cette thèse s'inscrit dans une démarche fondamentale visant à étudier la fonction des gènes IVSPERs afin de confirmer leur implication dans la production des particules virales d’IVs et de vérifier s’ils ont conservé ou non une fonction similaire à celle de leur ancêtre viral. Le modèle étudié a été celui de l'Ichnovirus associé à la guêpe parasitoïde Hyposoter didymator (HdIV).Pour répondre à la question de la fonction des gènes IVSPERs au cours de la production de HdIV, nous avons eu recours à la technologie de l'ARN interférence (ARNi) couplée à des approches de microscopie électronique. Nos travaux nous ont ainsi permis d’identifier des gènes IVSPERs impliqués dans différentes étapes clés du cycle de réplication des IVs. D’une part, nous avons mis en lumière au moins 6 protéines structurales intervenant dans l'assemblage et le trafic des particules virales dans les cellules du calyx. D’autre part, nous avons identifié un set de gènes IVSPERs qui jouent sur les niveaux de transcription des autres gènes viraux et qui pourraient vraisemblablement être impliqués dans la machinerie réplicative des IVs.L’ensemble des résultats obtenus ont permis de montrer l'efficacité de la technique de l'ARNi dans le but d'étudier la fonction des gènes viraux associés à ces guêpes parasitoïdes. D'autre part, les résultats présentés dans cette thèse constitue la première validation fonctionnelle de gènes impliqués dans la morphogénèse des IVs, mettant en évidence que ces protéines ont des fonctions similaires à celles de protéines virales "classiques", attestant de l'origine virale plus que probable des gènes contenus dans les clusters IVSPERs
PDVs are DNA viruses associated with tens of thousands of parasitoid hymenopteran species. They are divided into two taxa, the Bracoviruses (BVs) and the Ichnoviruses (IVs) associated respectively with the subfamilies of Braconidae and Ichneumonidae. PDVs are produced in a specialized tissue of the genital tract (calyx) of the female parasitoid. They are then injected during oviposition in a host caterpillar, altering its physiological functions and ensuring a favorable environment for the development of parasitoid offspring. The PDV genome is integrated into the genome of the wasps and consists of two functional components: firstly, sequences involved in virulence in the host that are the only ones to be packaged, and secondly regions with clusters of genes that are responsible for the production of viral particles. These clustered genes display viral gene characteristics and are specifically expressed in the replicative tissue, the calyx. They derive from the viral ancestor of current IVs, but show no sequence homology with known viral genes; as a result, the nature of the ancestral virus and the function of the genes that derivee from it remain unknown.Regions bearing these gene clusters have been named "Ichnovirus Structural Protein Encoding Re-gions (IVSPERs)". This thesis is part of a fundamental approach aimed at studying the function of IVSPERs genes in order to confirm their involvement in the production of IV particles and to verify whether they have retained or not a function similar to that of their viral ancestor. The model stud-ied was that of the Ichnovirus associated with the parasitoid wasp Hyposoter didymator (HdIV).To answer the question of IVSPERs gene function during HdIV production, we used RNA interference technology (RNAi) coupled with electron microscopy approaches. Our work has allowed us to identify IVSPER genes involved in different key steps of the IV replication cycle. On the one hand, we have highlighted at least 6 structural proteins involved in the assembly and trafficking of viral particles in calyx cells. On the other hand, we have identified a set of IVSPER genes that affect transcription levels of other viral genes and that could possibly be involved in the IVs replicative machinery.All the results obtained during this thesis made it possible to show the efficiency of the RNAi tech-nique to study the function of the viral genes associated with parasitoid wasps. On the other hand, the results presented here constitute the first functional validation of genes involved in the morphogenesis of IVs, highlighting that these proteins have functions similar to those of "classical" viral proteins, attesting to the more than likely viral origin of the genes contained in IVSPERs
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RABOTEAU, DOMINIQUE. "L'echelon local de la mutualite sociale agricole ou le mutualisme au quotidien." Angers, 1993. http://www.theses.fr/1993ANGE0008.

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La mutualite sociale agricole est un organisme prive charge de la gestion du service public que constitue l'application de la legislation sociale aux exploitants et aux salaries agricoles. Elle est sans doute l'un des organismes de protection les plus originaux tant par sa structure que par son activite; son histoire et son developpement est bati sur une philosophie le mutualisme, dont l'impact en milieu agricole a ete considerable. Le souci de concretion, les notions de solidarite et de participation a conduit la msa a adopter une organisation decentralisee dont l'echelon local est sans doute le plus important car c'est de lui qu'emane la plus large part du dynamisme et de la force de l'institution. L'histoire et les realisation de cet echelon local sont relates tout au long de ce document mais aussi les difficultes de maintenir un tel systeme et les possibilites de redynamisation
The "mutualite agricole" social affairs branch (m. S. A. Group), is a private organization, which ensures that legislation providing social protection is adequately applied to farm employees ans farmers. The "m. S. A. Group" can be considered unquestionably as the most original social welfare association as mush in the structures as in the activites. The growth and history of the "m. S. A. Group" are both based on a philosophy called mutualism which has a significant influence over the whole farming community. One of the major concern of the "m. S. S. Group" has been to put both abstract notions of solidarity and participation in concrete form. As a consequence, the group had been induced to adopt a tree fold decentralized structure. Out of these three operating stages, the volume of the local network operations appears to be the most significant since it makes a handsome contribution to the vitality and the strength of the institution. The history ans realizations of the local network are related along this document, but also the difficulties to maintain such a system and his future possibilities
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Durand, Lucile. "Étude de la diversité des peuplements épibiontes associés au tractus digestif de la crevette hydrothermale Rimicaris exoculata : une possible association mutualiste." Brest, 2010. http://www.theses.fr/2010BRES2004.

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Dans les écosystèmes hydrothermaux profonds, la chimiosynthèse microbienne est à la base des réseaux trophiques. Les symbioses entre des invertébrés et des micro-organismes sont fréquentes et peuvent être de différente nature et jouer différents rôles. La crevette Rimicaris exoculata est une espèce endémique des sites hydrothermaux de la Ride medio-Atlantique (MAR) et représente l’espèce majoritaire de la macrofaune de certains d’entre eux. Elle présente deux zones de colonisation microbienne, au niveau du céphalothorax et du tube digestif, mais leur rôle n’est pas encore établi. Ce travail a mis en évidence par approche moléculaire la présence de différentes communautés microbiennes dont une partie serait résidente, spécifique à R. Exoculata et représentée par des Deferribacteres, des Mollicutes et des Epsilonproteobacteria. Les approches microscopiques montrent la dominance d’épibiontes filamenteux étroitement associés à l’épithélium intestinal dont la croissance et l’installation semblent être contrôlées par l’hôte. Les approches moléculaires ont montré que: (1) les épibiontes du site hydrothermal Rainbow présentent une originalité taxinomique supposant une histoire évolutive ancienne tandis que les sites hydrothermaux Logatche et Ashadzé semblent avoir été colonisés plus récemment, (2) les épibiontes, non retrouvés dans le milieux extérieur et monophylétiques le long de la MAR pourraient être transmis verticalement et (3) il s’agirait d’une association mutualiste à caractère obligatoire. Ce travail de recherche a donc permis de poser les bases dans la compréhension du modèle symbiotique digestif R. Exoculata
In the deep-sea hydrothermal vents ecosystems, the driving energy comes from the microbial chemosynthesis. Symbioses between invertebrates and micro-organisms are common. They could be associations such as parasitism, commensalism or mutualism or even obligate symbioses and they could play distinct roles. The caridean shrimp Rimicaris exoculata is an endemic species of the Mid-Atlantic Ridge (MAR) hydrothermal sites. It is the main specie of the megafauna of some MAR sites. This crustacean harbors two microbial colonization regions, in the gill chamber and in the gut, but their roles are still unknown. Using various approaches, this work showed that there were distinct microbial communities among which a part would be resident and specific to R. Exoculata. This community is composed of Deferribacteres, Mollicutes and Epsilonproteobacteria. The microscopic approaches revealed the dominance of a single filamentous morphotype closely associated with the gut epithelium. Its settlement and growth seemed to be managed by the host. The molecular approaches showed that: (1) the Rainbow site epibionts harbored a phylogenetic particularity suggesting an ancient evolutionnary history whereas the Logatchev and Ashadzé seemed to have been colonized more recently by the association host-epibionts, (2) the epibionts, not retrieved in the surrounding environment and clustering i a monophyletic group along the MAR, could be vertically-transmitted, and (3) the association between R. Exoculata and the epibionts could be mutualistic and obligate. So, this research study gave the bases to understand the R. Exoculata symbiotic model
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Kawaye, Saadallah. "Les adénocarcinomes de l'ovaire : pronostic, moyens thérapeutiques : à propos de 104 cas suivis et traités à la Clinique mutualiste de la Digonnière, Saint-Étienne." Saint-Etienne, 1994. http://www.theses.fr/1994STET6210.

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Santos, Dina Maria Serrano. "Do mutualismo ao mercado. A banca mutualista em Portugal. Estudo de caso: o Crédito Agrícola Mútuo." Master's thesis, Faculdade de Ciêncais Sociais e Humanas, Universidade Nova de Lisboa, 2012. http://hdl.handle.net/10362/7355.

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Dissertação apresentada para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Sociologia, na especialidade de Sociologia Económica e das Organizações
Num mercado onde dominam os grandes grupos financeiros e onde existem estratégias agressivas de concorrência, o Crédito Agrícola, enquanto sistema cooperativo e mutualista bancário criado em 1911, tem conseguido não só sobreviver como obter sucesso. Este trabalho descreve o percurso do Crédito Agrícola desde a sua génese como projecto político, claramente alternativo à banca comercial, e a criação da legislação que o concebe de forma institucional até aos nossos dias, e procura compreender o seu crescimento e a sua readequação ao mercado e às instituições envolventes, também elas a sofrer uma enorme evolução. O capital social concretizado na sua origem, as alterações tecnológicas e organizacionais, a contenção e gestão do risco, a formação dos colaboradores e a standardização de procedimentos, são os principais factores analisados ao longo deste trabalho. As conclusões revelam a coalescência de círculos sociais diversos e de organizações de interesse na sua origem e em momentos chave de transformação institucional; um processo recente de isomorfismo institucional, a nível interno e externo, tendente a aproximar a instituição de crédito mutualista aos padrões de legitimidade vigentes no mercado financeiro; e evidenciam um trabalho simbólico de justificação discursiva visando resolver tensões valorativas causadas por esse isomorfismo, tornando os valores mercantis comensuráveis com os valores identitários da instituição mutualista.
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Books on the topic "Mutualiste"

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Toucas-Truyen, Patricia. L' identité mutualiste. Rennes: ENSP, 2001.

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Galland, Bruno. Promotion du mouvement mutualiste au Rwanda. Kigali: Centre de formation et de recherche coopératives, IWACU, 1989.

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Mentré, Paul. Les institutions d'épargne en Europe et en France: Le secteur public et mutualiste. Paris: Association d'économie financière, 2003.

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Dreyfus, Michel. Liberté, égalité, mutualité: Mutualisme et syndicalisme, 1852-1967. Paris: Editions de l'Atelier/Editions ouvrières, 2001.

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Carson, Kevin A. Studies in mutualist political economy. [S.l.]: K.A. Carson, 2007.

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Kato, Makoto, and Atsushi Kawakita, eds. Obligate Pollination Mutualism. Tokyo: Springer Japan, 2017. http://dx.doi.org/10.1007/978-4-431-56532-1.

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Quevedo, Hugo Orlando. Pioneras del mutualismo riojano. Córdoba, Argentina: Marcos Lerner Editora Córdoba, 1998.

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Lacrosse, Eugène Michel. Mutualité et sécurité sociale. Paris: Pensée universelle, 1994.

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Valencia, Gonzalo Pérez. Mutualismo y economía social. Medellín, Colombia: Corporación Educativa Mutualista, 1992.

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New, Tim R. Mutualisms and Insect Conservation. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-58292-4.

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Book chapters on the topic "Mutualiste"

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Callaway, Ragan M., and Jacob E. Lucero. "Soil biota and non-native plant invasions." In Plant invasions: the role of biotic interactions, 45–66. Wallingford: CABI, 2020. http://dx.doi.org/10.1079/9781789242171.0045.

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Abstract The trajectory of plant invasions - for better or for worse - can be tied to interactions between plants and the soil community. Here, we highlight five broad ways in which belowground interactions can influence the trajectory of biological invasions by non-native plant species. First, many non-native plant species in their non-native ranges can interact very differently with the resident soil community than do native species. Second, non-native plant species often interact very differently with the soil community in their non-native ranges than in their native ranges, which can result in enemy release from antagonistic interactions. Third, non-native plant species can cultivate a soil community that disproportionately harms native competitors in invaded communities. Fourth, antagonistic soil biota in invaded communities can reduce the performance of non-native plant species, resulting in meaningful biotic resistance against invasion. Fifth, besides or in addition to antagonistic interactions with soil biota, soil mutualisms can promote the success of invasive plant species (i) when mutualists co-invade with non-native plant species that require obligate specialist mutualists, (ii) when mutualists enhance the performance of non-native plant species in their non-native ranges, and (iii) when biotic interactions in the invaded community suppress the soil mutualists of native plant species. We conclude that management practices aimed at manipulating plant - soil interactions have considerable potential to help control plant invasions, but further work is needed to understand the spatial, temporal, taxonomic and biogeographic drivers of context dependence in interactions among plants and soil biota.
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Starey, Nigel. "Mutuality." In Health and Social Care in the Digital World, 121–36. First edition. | Boca Raton : CRC Press, 2020.: CRC Press, 2020. http://dx.doi.org/10.1201/9781003031079-8.

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Rusch, Antje. "Mutualism." In Encyclopedia of Estuaries, 449. Dordrecht: Springer Netherlands, 2015. http://dx.doi.org/10.1007/978-94-017-8801-4_285.

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Ghosh, Author-Paushali, Divya Singh, and Anuj Kumar Singh. "Mutualism." In Encyclopedia of Animal Cognition and Behavior, 1–4. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-319-47829-6_1377-1.

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Coppin, Alan, and John Barratt. "Mutuality." In Timeless Management, 135–73. London: Palgrave Macmillan UK, 2002. http://dx.doi.org/10.1057/9781403907158_6.

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Reitner, Joachim, and Volker Thiel. "Mutualism." In Encyclopedia of Geobiology, 675. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-1-4020-9212-1_239.

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Gooch, Jan W. "Mutualism." In Encyclopedic Dictionary of Polymers, 909. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_14276.

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Hangay, George, Susan V. Gruner, F. W. Howard, John L. Capinera, Eugene J. Gerberg, Susan E. Halbert, John B. Heppner, et al. "Mutualism." In Encyclopedia of Entomology, 2516. Dordrecht: Springer Netherlands, 2008. http://dx.doi.org/10.1007/978-1-4020-6359-6_4739.

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Mehlhorn, Heinz. "Mutualism." In Encyclopedia of Parasitology, 1715. Berlin, Heidelberg: Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-43978-4_2039.

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Mehlhorn, Heinz. "Mutualism." In Encyclopedia of Parasitology, 1. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-642-27769-6_2039-2.

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Conference papers on the topic "Mutualiste"

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Sinha, Soumya, and Ravinder Kumar. "Dynamics of a simple food chain with a mutualist(Facultative mutualism)." In 2016 IEEE Region 10 Humanitarian Technology Conference (R10-HTC). IEEE, 2016. http://dx.doi.org/10.1109/r10-htc.2016.7906829.

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Baharin, Hanif, Ralf Mühlberger, and Andrew Loch. "Mutuality." In the 10th International Conference NZ Chapter of the ACM's Special Interest Group. New York, New York, USA: ACM Press, 2009. http://dx.doi.org/10.1145/1577782.1577784.

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Araújo, João Taveira, Miguel Rio, and George Pavlou. "A mutualistic resource pooling architecture." In the Re-Architecting the Internet Workshop. New York, New York, USA: ACM Press, 2010. http://dx.doi.org/10.1145/1921233.1921237.

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Zhang, Qianqian, Ying-Chang Liang, Hong-Chuan Yang, and H. Vincent Poor. "Mutualistic Mechanism in Symbiotic Radios." In GLOBECOM 2021 - 2021 IEEE Global Communications Conference. IEEE, 2021. http://dx.doi.org/10.1109/globecom46510.2021.9685738.

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Burke, Gaelen. "The role of novel viruses as parasite mutualists." In 2016 International Congress of Entomology. Entomological Society of America, 2016. http://dx.doi.org/10.1603/ice.2016.92685.

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Maurya, Abhai. "Indian and Russian Literary Mutuality." In 2015 International Conference on Arts, Design and Contemporary Education. Paris, France: Atlantis Press, 2015. http://dx.doi.org/10.2991/icadce-15.2015.5.

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Marjakangas, Emma-Liina, Nerea Abrego, Vidar Grøtan, Renato A. F. de Lima, Carolina Bello, Ricardo Bovendorp, Laurence Culot, et al. "Mutualistic interactions along a fragmentation gradient." In 5th European Congress of Conservation Biology. Jyväskylä: Jyvaskyla University Open Science Centre, 2018. http://dx.doi.org/10.17011/conference/eccb2018/107407.

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Yoshimura, Masataka. "Fundamental Concepts for Collaboratively Obtaining Optimum Product Designs." In ASME 2010 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/detc2010-28376.

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Fundamental concepts for obtaining optimum product designs from higher view points are presented. These fundamental concepts are: (1) concepts that aim to achieve designs that are in harmony with natural and human environments; (2) collaborations based on mutuality, where the collaborating individuals are free from inhibiting hierarchies; and (3) methodologies that enable discovery of effective solutions by examining the deepest, most fundamental levels of design problems. Product designs that minimize stress on natural environments and maximize benefit to people are increasingly important, given limited natural resources and an increasing world population. The achievement of such product designs generally requires collaborative scenarios based on mutuality and equality of the participants, and the implementation of characteristics-based hierarchical optimization methodologies. Practical methodologies based on these fundamental concepts are discussed here and examples are provided.
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O'Donnell, Kerry. "Evolution of theFusarium–Euwallaceaambrosia beetle mutualism." In 2016 International Congress of Entomology. Entomological Society of America, 2016. http://dx.doi.org/10.1603/ice.2016.104886.

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Gopalsamy, K., and Pingzhou Liu. "On a Discrete Model of Mutualism." In Proceedings of the Third International Conference on Difference Equations. Taylor & Francis Group, 6000 Broken Sound Parkway NW, Suite 300, Boca Raton, FL 33487-2742: CRC Press, 2017. http://dx.doi.org/10.4324/9780203745854-14.

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Reports on the topic "Mutualiste"

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Rodriguez, Russell, and Stanley Freeman. Characterization of fungal symbiotic lifestyle expression in Colletotrichum and generating non-pathogenic mutants that confer disease resistance, drought tolerance, and growth enhancement to plant hosts. United States Department of Agriculture, February 2005. http://dx.doi.org/10.32747/2005.7587215.bard.

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Fungal plant pathogens are responsible for extensive annual crop and revenue losses throughout the world. To better understand why fungi cause diseases, we performed gene-disruption mutagenesis on several pathogenic Colletotrichum species and demonstrated that pathogenic isolates can be converted to symbionts (mutualism, commensalism, parasitism) expressing non-pathogenic lifestyles. The objectives of this proposal were to: 1- generate crop-specific mutants by gene disruption that express mutualistic lifestyles, 2- assess the ability of the mutualists to confer disease resistance, drought tolerance, and growth enhancement to host plants, 3- compare fslm1 sequences and their genomic locations in the different species, and 4- document the colonization process of each Colletotrichum species.It was demonstrated that wildtype pathogenic Colletotrichum isolates, can be converted by mutation from expressing a pathogenic lifestyle to symbionts expressing non-pathogenic lifestyles. In the US, mutants of Colletotrichum were isolated by homologous gene disruption using a vector containing a disrupted FSlm1 sequence while in Israel, C. acutatum mutants were selected by restriction enzyme mediated integration (REMI) transformation. One group (US) of non-pathogenic mutants conferred disease protection against pathogenic species of Colletotrichum, Fusarium, and Phytophthora; drought tolerance; and growth enhancement to host plants. These mutants were defined as mutualists and disease resistance correlated to a decrease in the time required for hosts to activate defense systems when exposed to virulent fungi. The second group (Israel) of non-pathogenic mutants did not confer disease resistance and were classified as commensals. In addition, we demonstrated that wildtype pathogenic Colletotrichum species can express non-pathogenic lifestyles, including mutualism, on plants they colonize asymptomatically. The expected long term contribution of this research to agriculture in the US and Israel is threefold. Host-specific mutualists will be utilized in the various crops to confer (1) disease resistance to reduce dependence on chemical fungicides; (2) drought tolerance to reduce water consumption for irrigation; (3) growth enhancement to increase yields.
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Rodriguez, Russell J., and Stanley Freeman. Gene Expression Patterns in Plants Colonized with Pathogenic and Non-pathogenic Gene Disruption Mutants of Colletotrichum. United States Department of Agriculture, February 2009. http://dx.doi.org/10.32747/2009.7592112.bard.

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Fungal plant pathogens are responsible for extensive annual crop and revenue losses throughout the world. To better understand why fungi cause diseases, we performed gene-disruption mutagenesis on several pathogenic Colletotrichum species and demonstrated that pathogenic isolates can be converted to symbionts expressing non-pathogenic lifestyles. One group of nonpathogenic mutants confer disease protection against pathogenic species of Col!etotrichum, Fusarium and Phytophthora; drought tolerance; and growth enhancement to host plants. These mutants have been defined as mutualists and disease resistance correlates to a decrease in the time required for hosts to activate defense systems when exposed to virulent fungi. A second group of non-pathogenic mutants did not confer disease resistance and were classified as commensals. In addition, we have demonstrated that wildtype pathogenic Colletotrichum species can express non-pathogenic lifestyles, including mutualism, on plants they colonize asymptomatically. We have been using wildtype and isogenic gene disruption mutants to characterize gene expression patterns in plants colonized with a pathogen, mutualist or commensal. The US group is contrasting genes expressed during colonization by mutuahstic and commensal mutants of C. magna and a pathogenic wildtype C. coccodes on tomato. The Israeli group is characterizing genes expressed during asymptomatic colonization of tomato by wildtype C. acutatum and a non-pathogenic mutant.To accomplish this we have been utilizing suppressive subtraction hybridization, microarray and sequencing strategies. The expected contribution of this research to agriculture in the US and Israel is: 1) understanding how pathogens colonize certain hosts asymptomatic ally will shed light on the ecology of plant pathogens which has been described as a fundamental deficiency in plant pathology; 2) identifying genes involved in symbiotically conferred disease resistance will help explain why and how pathogens cause disease, and may identify new candidate targets for developing genetically modified disease resistant crop plants.
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De Santis, Hugh. Mutualism: An American Strategy for the Next Century. Fort Belvoir, VA: Defense Technical Information Center, May 1999. http://dx.doi.org/10.21236/ada385926.

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Cordaro, Francesco, Marcel Fafchamps, Colin Mayer, Muhammad Meki, Simon Quinn, and Kate Roll. Microequity and Mutuality: Experimental Evidence on Credit with Performance-Contingent Repayment. Cambridge, MA: National Bureau of Economic Research, September 2022. http://dx.doi.org/10.3386/w30411.

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Sayavedra-Soto, Luis, and Daniel Arp. Interactions between ammonia and nitrite oxidizing bacteria in co-cultures: Is there evidence for mutualism, commensalism, or competition? Office of Scientific and Technical Information (OSTI), August 2017. http://dx.doi.org/10.2172/1375758.

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Valverde, Rodrigo A., Aviv Dombrovsky, and Noa Sela. Interactions between Bell pepper endornavirus and acute viruses in bell pepper and effect to the host. United States Department of Agriculture, January 2014. http://dx.doi.org/10.32747/2014.7598166.bard.

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Based on the type of relationship with the host, plant viruses can be grouped as acute or persistent. Acute viruses are well studied and cause disease. In contrast, persistent viruses do not appear to affect the phenotype of the host. The genus Endornavirus contains persistent viruses that infect plants without causing visible symptoms. Infections by endornaviruses have been reported in many economically important crops, such as avocado, barley, common bean, melon, pepper, and rice. However, little is known about the effect they have on their plant hosts. The long term objective of the proposed project is to elucidate the nature of the symbiotic interaction between Bell pepper endornavirus (BPEV) and its host. The specific objectives include: a) to evaluate the phenotype and fruit yield of endornavirus-free and endornavirus-infected bell pepper near-isogenic lines under greenhouse conditions; b) to conduct gene expression studies using endornavirus-free and endornavirus-infected bell pepper near-isogenic lines; and c) to study the interactions between acute viruses, Cucumber mosaic virus Potato virus Y, Pepper yellow leaf curl virus, and Tobacco etch virus and Bell pepper endornavirus. It is likely that BPEV in bell pepper is in a mutualistic relationship with the plant and provide protection to unknown biotic or abiotic agents. Nevertheless, it is also possible that the endornavirus could interact synergistically with acute viruses and indirectly or directly cause harmful effects. In any case, the information that will be obtained with this investigation is relevant to BARD’s mission since it is related to the protection of plants against biotic stresses.
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Freeman, Stanley, and Russell J. Rodriguez. The Interaction Between Nonpathogenic Mutants of Colletotrichum and Fusarium, and the Plant Host Defense System. United States Department of Agriculture, September 2000. http://dx.doi.org/10.32747/2000.7573069.bard.

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The intent of this proposal was to study the interaction between nonpathogenic mutants of Colletotrichum magna and Fusarium oxysporum, and the cucurbit host defense system. We had shown previously that a nonpathogenic endophytic mutant path- 1 of C. magna, caused no visible disease symptoms but protected watermelon seedlings from disease caused by the wildtype isolate and F. o. niveum. Objectives were: 1) Determine the microscopic, biochemical and molecular genetic interaction between "protected" (path- 1 colonized) cucurbit hosts and wildtype isolates of C. magna; 2) Isolate non-pathogenic mutants of F.o. melonis and test feasibility for protecting plants against fungal diseases. We found that path-1 caused no visible disease symptoms in cucurbit seedlings but conferred disease resistance against pathogenic isolates of C. magna, C. orbiculare, and F. oxysporum. Disease resistance conferred by path-1 correlated to a decrease in the time of activation of host defense systems after exposure of path-1 colonized plants to virulent pathogens. This was determined by monitoring the biochemical activity of PAL and peroxidase, and the deposition of lignin. It appears that path-1-conferred disease resistance is a multigenic phenomenon which should be more difficult for pathogen to overcome than single gene conferred resistance. Based on the benefits conferred by path-1, we have defined this mutant as expressing a mutualistic lifestyle. REMI (restriction enzyme-mediated integration) nonpathogenic mutants were also isolated using pHA1.3 plasmid linearized with Hind III and transformed into wildtype C. magna. The integrated vector and flanking genomic DNA sequences in REMI mutant R1 was re-isolated and cloned resulting in a product of approximately 11 kb designated pGMR1. Transformations of wildtype C. magna with pGMR1 resulted in the same non-pathogenic phenotype. A nonpathogenic mutant of F.o. melonis (pathogenic to melon) was isolated that colonized melon plants but elicited no disease symptoms in seedlings and conferred 25 - 50% disease protection against the virulent wildtype isolate. Subsequently, nonpathogenic mutant isolates of F.o. niveum (pathogenic to watermelon) were also isolated. Their protection capacity against the respective wildtype parent is currently under investigation. This research has provided information toward a better understanding of host-parasite interactions; specifically, endophytes, pathogens and their hosts. It will also allow us to assess the potential for utilizing nonpathogenic mutants as biological control agents against fungal pathogens and isolating molecular genetic factors of pathogenicity in Fusarium.
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