AM plants acquire Pi via two pathways; the direct uptake pathway via plant roots and the AM pathway via external fungal hyphae and colonised cortical cells. It has been assumed that these two pathways are additive and therefore in non-responsive plants the AM pathway is often considered to be non-functional. However, data from ³²P uptake studies indicates that the AM pathway is functional in many non-responsive symbioses and in some instances supplies the majority of plant P. In recent years the high-affinity Pi transporters involved in both direct and AM Pi uptake pathways have been identified. They are expressed at the root epidermis and the symbiotic interface of colonised cortical cells and respond to the P and AM status of the plant. The overall objective of the work described in this thesis was to characterise Pi uptake via the AM pathway in barley, a non-responsive AM host, using an approach which integrated physiological measurements of plant responsiveness and AM contribution with investigations of gene expression and functional characterisation of the plant Pi transporters. A preliminary survey of field-grown barley demonstrated the persistence of AM colonisation under commercial cropping regimes in southern Australia and highlighted the relevance of AM studies to commercial agriculture. Under glasshouse conditions AM colonisation of barley induced depressions in growth and P uptake compared to NM controls. Growth depressions were unrelated to percent colonisation by two AM fungal species and could not readily be explained by fungal C demand; the strong correlation between growth and P content suggested that P was the limiting factor in these experiments. However, a compartmented pot system incorporating ³²P-labelling demonstrated that the AM pathway is functional in colonised barley and, in the interaction with G. intraradices, contributed 48% of total P. This suggested that P flux via the direct uptake pathway is decreased in AM barley. The expression of three Pi transporters, HvPT1, HvPT2 and HvPT8 was investigated in colonised roots. HvPT1 and HvPT2 have previously been localised to the root epidermis and root hairs and are involved in Pi uptake via the direct pathway whilst HvPT8 is an AM-inducible Pi transporter which was localised by in-situ hybridisation to colonised cortical cells. Using promoter::GFP gene fusions the localisation of HvPT8 to arbuscule-containing cortical cells was confirmed in living roots from transgenic barley. Quantitative real-time PCR analysis of the expression of these three Pi transporters indicated that HvPT1 and HvPT2 were expressed constantly, under all conditions regardless of AM colonisation status and indicated that decreased P flux via the direct pathway is not related to expression of these transporters. HvPT8 was induced in AM colonised roots. However, the level of expression was not related to flux via the AM pathway or arbuscular colonisation. The HvPT8 transporter was further characterised by constitutive over-expression in transgenic barley. ³²P uptake assays in excised roots demonstrated increased Pi uptake from low P solution compared to wild-type roots and confirmed that HvPT8 is a functional Pi transporter with high-affinity transport properties. This is the first report of characterisation of an AM-inducible Pi transporter in planta. When these transgenic plants were grown in solution culture there was no increase in growth or P uptake relative to wild-type or transgenic controls and growth in soil and AM colonisation were also unaffected in these transgenic lines. The data presented in this thesis highlights the importance of combined physiological and molecular approaches to characterising plant AM interactions. The persistence of AM colonisation in barley in the field indicates the importance of improving our understanding of symbiotic function in non-responsive plants. Future efforts should be directed towards understanding the signals which regulate P flux via both the direct and AM pathways with the ultimate aim of enhancing AM responsiveness of non-responsive species. Making the direct and AM pathways additive in nonresponsive species should be a key aim of future research. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1313311 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008

AM plants acquire Pi via two pathways; the direct uptake pathway via plant roots and the AM pathway via external fungal hyphae and colonised cortical cells. It has been assumed that these two pathways are additive and therefore in non-responsive plants the AM pathway is often considered to be non-functional. However, data from ³²P uptake studies indicates that the AM pathway is functional in many non-responsive symbioses and in some instances supplies the majority of plant P. In recent years the high-affinity Pi transporters involved in both direct and AM Pi uptake pathways have been identified. They are expressed at the root epidermis and the symbiotic interface of colonised cortical cells and respond to the P and AM status of the plant. The overall objective of the work described in this thesis was to characterise Pi uptake via the AM pathway in barley, a non-responsive AM host, using an approach which integrated physiological measurements of plant responsiveness and AM contribution with investigations of gene expression and functional characterisation of the plant Pi transporters. A preliminary survey of field-grown barley demonstrated the persistence of AM colonisation under commercial cropping regimes in southern Australia and highlighted the relevance of AM studies to commercial agriculture. Under glasshouse conditions AM colonisation of barley induced depressions in growth and P uptake compared to NM controls. Growth depressions were unrelated to percent colonisation by two AM fungal species and could not readily be explained by fungal C demand; the strong correlation between growth and P content suggested that P was the limiting factor in these experiments. However, a compartmented pot system incorporating ³²P-labelling demonstrated that the AM pathway is functional in colonised barley and, in the interaction with G. intraradices, contributed 48% of total P. This suggested that P flux via the direct uptake pathway is decreased in AM barley. The expression of three Pi transporters, HvPT1, HvPT2 and HvPT8 was investigated in colonised roots. HvPT1 and HvPT2 have previously been localised to the root epidermis and root hairs and are involved in Pi uptake via the direct pathway whilst HvPT8 is an AM-inducible Pi transporter which was localised by in-situ hybridisation to colonised cortical cells. Using promoter::GFP gene fusions the localisation of HvPT8 to arbuscule-containing cortical cells was confirmed in living roots from transgenic barley. Quantitative real-time PCR analysis of the expression of these three Pi transporters indicated that HvPT1 and HvPT2 were expressed constantly, under all conditions regardless of AM colonisation status and indicated that decreased P flux via the direct pathway is not related to expression of these transporters. HvPT8 was induced in AM colonised roots. However, the level of expression was not related to flux via the AM pathway or arbuscular colonisation. The HvPT8 transporter was further characterised by constitutive over-expression in transgenic barley. ³²P uptake assays in excised roots demonstrated increased Pi uptake from low P solution compared to wild-type roots and confirmed that HvPT8 is a functional Pi transporter with high-affinity transport properties. This is the first report of characterisation of an AM-inducible Pi transporter in planta. When these transgenic plants were grown in solution culture there was no increase in growth or P uptake relative to wild-type or transgenic controls and growth in soil and AM colonisation were also unaffected in these transgenic lines. The data presented in this thesis highlights the importance of combined physiological and molecular approaches to characterising plant AM interactions. The persistence of AM colonisation in barley in the field indicates the importance of improving our understanding of symbiotic function in non-responsive plants. Future efforts should be directed towards understanding the signals which regulate P flux via both the direct and AM pathways with the ultimate aim of enhancing AM responsiveness of non-responsive species. Making the direct and AM pathways additive in nonresponsive species should be a key aim of future research. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1313311 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008

[Truncated abstract] Nitrogen fixation is a feature of the symbiotic association between legumes and rhizobia, which occurs within the symbiosomes of root nodules and involves the conversion of atmospheric N2 to ammonia to be used by the plant in exchange for carbon compounds. Exchange of other nutrients is controlled by plant-synthesised proteins on the symbiosome membrane. Iron is a component of symbiotically important proteins, so is essential for nitrogen fixation. Low soil iron leads to decreased plant yields, whilst in other environments plants may accumulate iron to toxic levels. Knowledge of iron acquisition, transport and storage mechanisms is important to elucidate the role of iron transporters in the maintenance of iron homeostasis in the plant. This study provides evidence that iron has a profound effect in the Bradyrhizobium japonicum-Glycine max symbiosis on the development of the nodule, and on the development of the symbiotic soybean plant itself. cDNAs encoding four putative iron transporters in soybean; GmDmt1, GmYSL1, GmCCC1;1 and GmCCC1;2, were identified, isolated and characterised in this study. GmDmt1 is localised to the symbiosome membrane. Expression of GmDmt1 occurs in nodules, roots and leaves and increases in response to iron starvation. GmDmt1 rescues growth and enhances 55Fe(II) uptake in the iron transport deficient yeast strain fet3fet4, with uptake following Michaelis-Menten kinetics, resembling the situation in isolated symbiosomes. Competition experiments using fet3fet4 indicated that GmDmt1 is able to transport other divalent cations, including zinc, copper and manganese, and is also able to complement a zinc transport deficient yeast mutant. ... These results suggest the divalent metal transporter GmDmt1, the putative iron chelate transporter GmYSL1 and the putative vacuolar iron transporters GmCCC1;1 and GmCCC1;2 act together to maintain iron homeostasis in symbiotic soybeans. The possible interactions and regulation of these proteins and their roles in the acquisition, transport and utilisation of iron in symbiotic soybeans are discussed.

Thesis (MScBosb)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2008. / Härtill 3 uppsatser.

Thesis (M.S.)--Michigan State University. Dept. of Biochemistry and Molecular Biology, 2008. / "Advisor, Todd A. Ciche"--Acknowledgements. Title from PDF t.p. (viewed on Aug. 5, 2009) Includes bibliographical references. Also issued in print.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2010. / Härtill 3 uppsatser.

La définition de l’individu biologique pose problème tant à la philosophie qu’à la biologie. Enparticulier, comment prendre en compte une hiérarchie d’entités diverses, depuis la cellulejusqu’aux communautés ou associations ? De nombreuses analyses s’efforcent de considérerdes degrés d’individualité divers, mais soit elles laissent de côté certains composants del’individualité, les composants abiotiques par exemple, soit elles persistent à considérerl’organisme comme l’individualité typique. Afin de dépasser ces différents biais, noussoutenons qu’une approche pertinente est celle de la biologie du développement. En effet, ledéveloppement, en tant qu’il est l’étude des mécanismes et processus par lesquels l’individu seforme, apparaît comme un outil privilégié pour examiner les facteurs causaux qui rendent raisonde l’individualité biologique, et les hiérarchiser. À travers le concept d’individu endéveloppement, nous nous attachons à définir le développement d’une part et à élaborer uneanalyse critique des études qui ont été menées à son sujet d’autre part. En redéfinissant ledéveloppement à l’aune des interactions – avec les facteurs environnementaux et diversesentités – qui le composent, nous soutenons que la microbiologie est une voie privilégiée à partirde laquelle une refonte du concept d’individu est possible. Nous appliquons enfin lesconséquences de nos analyses à un cas d’étude précis, celui des symbioses aux bactériesWolbachia, et soulignons la nécessité de faire des communautés le niveau d’individualitétypique ainsi que de repenser les modèles du développement individuel / Defining the biological individual raises questions both for philosophers and biologists. Inparticular, how is it possible to take into account a hierarchy of entities, from the cells to the communities and associations? Many analyses try to consider degrees of individuality, but some of them leave some components out – like abiotic components for instance – whereas otherskeep defining the organism as the typical individual. We think that these views imply biases inthe definition of the individual, that can be solved by the study of the developmental biology.Indeed, development is defined as the study of all the processes involved in the individual’sconstitution. As such, development represents a relevant tool from which the analysis and theselecting of the necessary causes and factors of the individual’s formation can be done. Usingthe concept of “developmental individual”, we first define what development is, and thenformulate a critical analysis of the different conceptions of development. We offer a definitionof the developmental individual based on the different interactions that compose it, and definethe field of microbiology as a relevant way to redesign the concept of the individual. We finallyapply those analyses to a case-study: Wolbachia symbiosis, and show that both the individualand the models used in developmental biology have to be considered from the level of thecommunities.

Dans les sols, les champignons ectomycorhiziens (ECM) forment une symbiose très répandue avec les racines des arbres et contribuent ainsi à leur croissance et à leur santé. Des études antérieures ont montré que certaines bactéries pouvaient influencer positivement la symbiose entre les ECM et les arbres, appelées BAM pour Bactéries Auxiliaires de la Mycorhization. Les mécanismes de l’effet auxiliaire des BAM sont encore peu connus. En amont de cette thèse, il avait été montré in vitro que la BAM Pseudomonas fluorescens BBc6 formait des structures similaires à des biofilms sur les hyphes de l'ECM Laccaria bicolor. Dans ce contexte, afin d'enrichir les connaissances concernant les interactions entre les ECM et les BAM, cette thèse a porté sur l'interaction physique entre ces deux organismes. L'étude a en partie été réalisée via une méthode d'analyse par microscopie confocale, développée durant cette thèse. Les résultats obtenus ont montré que cette bactérie formait des biofilms localisés préférentiellement sur la région apicale des colonies de l'ECM ce qui pourrait indiquer une interaction trophique. L'existence d'une telle interaction a d'ailleurs par la suite été confirmée. Les résultats ont également montré que l'interaction physique entre Laccaria bicolor et BBc6 n'est pas spécifique puisque l'ensemble des treize autres souches bactériennes testées a formé des biofilms sur les hyphes de Laccaria bicolor. En revanche, BBc6 s'est montrée incapable de former des biofilms sur certains champignons appartenant aux Ascomycètes, suggérant des mécanismes d'inhibition. De plus, l'étude de la matrice des biofilms formés par BBc6 a révélé la présence de réseaux de filaments constitués d'ADN qui semblent structurer ces biofilms et qui ont aussi été observés chez l'ensemble des souches bactériennes testées. Ces résultats révèlent un rôle structural de la molécule d'ADN qui, bien qu'il semble répandu, n'a que peu été reporté jusqu'à présent. Enfin, il a été montré que des mutants de BBc6 qui ont perdu leur effet auxiliaire forment des biofilms différents de la souche sauvage sur une surface abiotique suggérant un lien potentiel entre l'effet auxiliaire et la formation de biofilms / In soil ecosystems, ectomycorrhizal fungi (ECM) form a widespread symbiosis with roots of trees, contributing to tree growth and health. It has been shown that some bacteria, called mycorrhization helper bacteria (MHB), stimulate mycorrhizal symbiosis. The mechanisms of this helper effect are poorly understood. Previous studies have shown that the MHB Pseudomonas fluorescens BBc6 formed biofilm-like structures around the hyphae of the ECM Laccaria bicolor during their in vitro interaction. In this context, in order to increase knowledge concerning MHB/ECM interactions, the work presented here focuses on the physical interaction between these two organisms. To this purpose, a method of analysis based on confocal microscopy was developed. The results showed that the bacteria formed biofilms preferentially localized on the apical region of the ECM colonies, which could indicate a trophic interaction. Such an interaction has been subsequently confirmed. The results also showed that the physical interaction between L. bicolor and BBc6 is not specific since all thirteen other bacterial strains tested formed biofilms on the hyphae of L. bicolor. On the other hand, BBc6 was unable to form biofilms on some fungi belonging to Ascomycetes, suggesting the existence of inhibition mechanisms. Moreover, the study of the BBc6 biofilm matrix revealed networks of DNA-containing filaments which seem to structure these biofilms and which have also been observed in all the bacterial strains tested. These results reveal a structural role of the DNA molecule, a role that has been rarely reported so far despite its probable high occurrence. Finally, it has been shown that BBc6 mutants having lost their helper effect presented a modified phenotype concerning their biofilm formation on abiotic surface, suggesting a potential link between the helper effect and the biofilms formation

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Devido à liberação de substâncias tóxicas, os cnidários apresentam poucas associações com outras espécies, entretanto as associações mais conhecidas são frequentemente descritas como obrigatórias ou comensais facultativas. Um dos grupos deste filo, Ceriantharia, é representando por membros genericamente conhecidos por ceriantários ou anêmonas-de-tubo cuja característica mais marcante é a presença de uma secreção celular única (pticocisto) que auxilia na construção de um tubo, sintetizado pelo próprio animal, que fica inserido no substrato e abriga o animal. Embora existam estudos quanto ao histórico, taxonomia e posição sistemática, análises moleculares e morfológicas e ciclo de vida, estudos a respeito de associações interespecíficas ocorrendo em tubos de ceriantários são escassos. Logo, pouco se conhece sobre essas associações bem como os métodos que as espécies utilizam para se ancorarem aos tubos desses animais. Sendo assim, esse estudo elencou espécies que ocorrem em tubos de Ceriantharia, abordando principalmente os métodos de ancoragem e hábitos alimentares envolvidos nas relações observadas. Os tubos de 8 espécies de ceriantários foram analisados, fornecendo dados quanto a associações de Annelida, Crustacea e Mollusca aos tubos. / The phylum Cnidaria is characterized by animals that carry stinging cells named cnidocytes in their tissues. Due to the release of toxic substances, cnidarians have few associations with other species, however mostly known associations are often described as mandatory or optional commensalism. One of the groups in this phylum, Ceriantharia, is represented by members generally known as ceriantharians or tube-dwelling anemones whose most remarkable feature is the presence of a peculiar cell secretion (ptychocyst) that supports the construction of a tube, synthetized by the animal itself, and inserted into the substrate, lodging the animal. Although there are some studies concerning the history, taxonomy and systematic position, molecular and morphological analyzes and life-cycle, studies regarding interspecific associations occurring with ceriantharian tubes are scarce. Thus, little is known about these associations as well as the methods that the species use in order to anchor on these tubes. Thereby, this study listed species occurring in ceriantharian tubes mainly discussing the anchoring methods and feeding habits involved in the associations observed. The tubes of 8 Ceriantharia species were analyzed, yielding data about interactions with Annelida, Crustacea and Mollusca to the tubes. / 2016/00689-7 / 2017/07870-1