TheMedicago truncatulahypermycorrhizal B9 mutant displays an altered response to phosphate and is more susceptible toAphanomyces euteiches

Inorganic phosphate (Pi) plays a key role in the development of arbuscular mycorrhizal (AM) symbiosis, which is favoured when Pi is limiting in the environment. We have characterized the Medicago truncatula hypermycorrhizal B9 mutant for its response to limiting (P/10) and replete (P2) Pi. On P2, mycorrhization was significantly higher in B9 plants than in wild-type (WT). The B9 mutant displayed hallmarks of Pi-limited plants, including higher levels of anthocyanins and lower concentrations of Pi in shoots than WT plants. Transcriptome analyses of roots of WT and B9 plants cultivated on P2 or on P/10 confirmed the Pi-limited profile of the mutant on P2 and highlighted its altered response t…

Polyamines and related enzymes in rice seeds differing in germination potential

In ungerminated rice seeds, (Japonica rice variety, CV Tapei 309), the content of free amines (putrescine, spermidine, spermine, tyramine) was higher in seed lots having a low germination frequency compared to those with high germination potential. Conversely, amine conjugates (di-feruloylputrescine, di-feruloylspermidine, diferuloyldiaminopropane and feruloyltyramine) decreased with loss of viability. Thus, these compounds appeared to constitute biochemical markers of seed viability. In seeds with high germination potential, conjugates decreased drastically during germination, with an early and rapid increase in free amines (putrescine, spermidine, tyramine). Arginine decarboxylase (ADC) a…

Mycorhization et viticulture

Prod 2017-372 SPE IPM INRA UB; National audience

Stimulation of root and somatic embryo production in Euconymus europaeus L. by an inhibitor of polyamine biosynthesis

In vitro formation of roots and somatic embryos is obtained from cotyledon explants of a Spindle tree (Euonymus europaeus L.) cultured on two different media: a medium inducing callus formation and the production of roots, and a medium inducing callus formation, root and somatic embryo production. We studied the effects of α-difluoromethylornithine (DFMO), a specific, irreversible inhibitor of ornithine decarboxylase (ODC) on root and somatic embryo production, growth and titers of putrescine in Euonymus explants and explant-derived calli. Early changes in putrescine levels were detected in both cultures before the visible emergence of roots or somatic embryos. DFMO rapidly inhibited putres…

Influence of phytosterols on the structural and dynamic properties of plant plasma membrane

National audience; The complex mixture of sterols, namely phytosterols, found in the plasma membrane (PM) of plant cells is an intriguing characteristic. In the present work, we characterized the sterol composition of tobacco BY-2 cell PM, and we adapted a sterol manipulation method to this plant material. Methyl-b-cyclodextrin was found to induce a drastic reduction of the PM total free sterol content, with a low specificity for the different phytosterols, and without effect on steryl-conjugates. The consequences of phytosterols depletion were investigated by means of fluorescence spectroscopy and biochemical detergent resistant membrane (DRM) fraction purification methods. Data obtained w…

Sugar exchanges in arbuscular mycorrhiza: RiMST5 and RiMST6, two novel Rhizophagus irregularis monosaccharide transporters, are involved in both sugar uptake from the soil and from the plant partner

SPE IPM INRA UB CT1; International audience; Arbuscular mycorrhizal (AM) fungi are associated with about 80% of land plants. AM fungi provide inorganic nutrients to plants and in return up to 20% of the plant-fixed CO2 is transferred to the fungal symbionts. Since AM fungi are obligate biotrophs, unraveling how sugars are provided to the fungus partner is a key for understanding the functioning of the symbiosis. In this study, we identified two new monosaccharide transporters from Rhizophagus irregularis (RiMST5 and RiMST6) that we characterized as functional high affinity monosaccharide transporters. RiMST6 was characterized as a glucose specific, high affinity H(+) co-transporter. We prov…

Mycorhization et viticulture : État des lieux et services écosystémiques rendus au vignoble

Prod 2017-371 SPE IPM INRA UB; National audience

Control of in vitro somatic embryogenesis of the spindle tree ( Euonymus europaeus L.) by the sugar type and the osmotic potential of the culture medium

 In vitro somatic embryogenesis was achieved from zygotic embryo explants of a woody angiosperm species, the spindle tree, cultivated on various culture media differing in their sugar type and concentration, or in the applied osmotic potential. The highest frequency of somatic embryogenesis was obtained with a 350 mM sucrose, or a 89 mM glucose concentration in the culture medium. Experiments with culture media differing only in osmotic potential indicated that a minimal threshold osmotic potential is required to stimulate the emergence of somatic embryos. Elevated concentrations of glucose have an inhibitory effect, independent of their osmotic effect, while elevated concentrations of sucr…

The arbuscular mycorrhizal transportome, what next!

International audience; Understanding how arbuscular mycorrhizal (AM) symbioses establish and function is one of the most important current challenges in microbial ecology. Despite the fact that the AM symbiosis requires some complex and fine molecular tuning among symbionts in order to take place, both partners benefit from each other in a number of ways. For instance, the availability, uptake and exchange of nutrients in this biotrophic interaction are key factors driving plant growth and modulating biomass allocation. This underground trade is regulated by both plant and fungal transport components [1], as for instance the long distance transport of photosynthates from leaves towards col…

Identification of sugar transporters in arbuscular mycorrhiza, from basic to applied science

Our study focuses on sugar transporters from both plant and fungal partners at the symbiotic interface to better understand biotrophic exchange systems. Thereby, a collection of putative contigs and ESTs of hexose transporters from Medicago truncatula and Fragaria x ananassa will be processed. The full length sequences will be cloned for functional complementation and uptake experiments in transport deficient yeast mutants. This work also investigates the influence of different mycorrhizal fungi on (1) the expression level of sugar transporters and (2) the economically relevant part of F. x ananassa by analyzing its impact on the plant and the fruit. To this aim, combination of phenological…

Plasma membrane sterol complexation, generated by filipin, triggers signaling responses in tobacco cells

International audience; The effects of changes in plasma membrane (PM) sterol lateral organization and availability on the control of signaling pathways have been reported in various animal systems, but rarely assessed in plant cells. In the present study, the pentaene macrolide antibiotic filipin III, commonly used in animal systems as a sterol sequestrating agent, was applied to tobacco cells. We show that filipin can be used at a non-lethal concentration that still allows an homogeneous labeling of the plasma membrane and the formation of filipin-sterol complexes at the ultrastructural level. This filipin concentration triggers a rapid and transient NADPH oxidase-dependent production of …

BioVine project - Increase plant health through mycorrhizal fungi

National audience; Organic vineyards still rely on large external inputs to control harmful organisms. BIOVINE will develop natural solutions based on plant diversity to control pests and reduce pesticide dependence. The capacity of plants of increasing the ecosystem resistance to pests and invasive species is a well-known ecosystem service. However, monocultures like vineyards do not exploit the potential of plant diversity. BIOVINE aims to develop new viticultural systems based on increased plant diversity within (e.g. cover crops) and/or around vineyards by planting selected plant species for the control of arthropods, soil-borne pests (oomycetes, fungi, nematodes), and foliar pathogens.…

Is co-inoculation with plant growth promoting bacteria and arbuscular mycorrhizal fungi increasing strawberry production yields ?

Polyamine metabolism during seedling development in rice

The main free amines identified during growth and development of rice seedlings were agmatine, putrescine, spermidine, diaminopropane and tyramine. Amine composition differed according to tissue and stages of development. Conjugated amines were only found in roots. We present evidence that arginine decarboxylase (ADC) regulates putrescine during the development of rice seedlings. When ADC action was blocked by DFMA (α-DL-difluoromethylarginine, a specific irreversible inhibitor of ADC), polyamine titers and seedling development were diminished; when agmatine or putrescine was added, normal polyamine titers and growth were restored. The effects of DFMA were concentration dependent. DFMO (α-D…

Somatic embryogenesis and plant regeneration in a woody species: the European Spindle Tree (Euonymus europaeus L.).

Somatic embryogenesis and subsequent plant regeneration of Euonymus europaeus L (European Spindle Tree) were obtained from square pieces of mature zygotic embryos with an intervening callus phase. Callus and somatic embryos were induced using a Murashige and Skoog's semi-solid basal medium supplemented with several combinations of auxins and cytokinins. The greatest number of somatic embryos was obtained with a continuous exposure to 22.8 μM indoleacetic acid and 0.046 μM kinetin. The frequency of somatic embryogenesis from zygotic embryos depends on the cold conservation time of seeds. The embryos frequently germinated on the same medium. Further development of somatic embryos into plantle…

Combined phosphate and nitrogen limitation generates a nutrient stress transcriptome favorable for arbuscular mycorrhizal symbiosis in M edicago truncatula

International audience; Arbuscular mycorrhizal (AM) symbiosis is stimulated by phosphorus (P) limitation and contributes to P and nitrogen (N) acquisition. However, the effects of combined P and N limitation on AM formation are largely unknown. Medicago truncatula plants were cultivated in the presence or absence of Rhizophagus irregularis (formerly Glomus intraradices) in P-limited (LP), N-limited (LN) or combined P- and N-limited (LPN) conditions, and compared with plants grown in sufficient P and N. The highest AM formation was observed in LPN, linked to systemic signaling by the plant nutrient status. Plant free phosphate concentrations were higher in LPN than in LP, as a result of cros…

Sugar exchanges in arbuscular mycorrhiza : Characterization and role of two new monosaccharide transporters from the model fungus Rhizophagus irregularis

Services écosystémiques rendus par la symbiose mycorhizienne à arbuscule au vignoble

National audience; Qu’appelle-t-on symbiose mycorhizienne ?Le sol est un milieu vivant puisque dans quelques grammes de terre fine se trouvent environ 200 milliards de bactéries, 100 km de filaments de champignons et 200 000 insectes, vers et protozoaires (figure 1). Cette vie souterraine va partager son habitat (le sol) avec les ceps de vigne. Ce fameux « vivre ensemble » est alors défini par le terme « symbiose » (du grec syn : ensemble ; et bios : vivre). Cette définition ne fait pas de distinction vis-à-vis des modalités d’interaction qui peuvent s’établir entre les deux organismes impliqués. Ainsi, des interactions neutres, ou encore du véritable parasitisme, pour lequel un partenaire …

Étude de l’impact des pratiques culturales sur le fonctionnement de la symbiose mycorhizienne à arbuscule dans un système agroforestier

International audience; Au milieu du 20ème siècle, l’utilisation massive d’intrants chimiques a fortement réduit la biodiversité, la fertilité du sol, a augmentée l’érosion hydrique et la compaction du sol. La mise en place de nouveaux itinéraires de culture dans lesquels l’arbre a un rôle prépondérant pourrait devenir un élément clé d’une agriculture plus durable. Les systèmes agroforestiers participent à la conservation du potentiel agricole des terres via une couverture végétale annuelle et une diversification de la production. Dans la symbiose mycorhizienne à arbuscule, le champignon apporte des éléments nutritifs nécessaires au développement de la plante, et reçoit en retour des ressou…

Identification of sugar transporters in arbuscular mycorrhiza

Our study focuses on sugar transporters from both plant and fungal partners at the symbiotic interface to better understand biotrophic exchange systems. Thereby, a collection of putative contigs and ESTs of hexose transporters from Medicago truncatula and Fragaria x ananassa will be processed. The full length sequences will be cloned for functional complementation and uptake experiments in transport deficient yeast mutants. This work also investigates the influence of different mycorrhizal fungi on (1) the expression level of sugar transporters and (2) the economically relevant part of F. x ananassa by analyzing its impact on the plant and the fruit. To this aim, combination of phenological…

Étude des échanges trophiques au cours de la symbiose mycorhizienne à arbuscule dans un système agroforestier

Les systèmes agroforestiers participent à la conservation du potentiel agricole des terres via une couverture végétale annuelle, une diversification de la production et une conservation de la vie des sols. Dans les sols, les champignons mycorhiziens apportent des éléments nutritifs nécessaires au développement de la plante, et reçoivent en retour des ressources carbonées. L’objectif de ma thèse est d’intégrer le processus de mycorhization dans un système noyer - maïs, et de mieux comprendre les mécanismes qui régissent les échanges trophiques dans ce modèle agroforestier. Cette première année a permis de déterminer les conditions de cultures favorables à l’acclimatation des noyers, et de me…

The Medicago truncatula hypermycorrhizal B9 mutant displays an altered response to phosphate and is more susceptible to Aphanomyces euteiches.

SPE IPM; National audience; Inorganic phosphate (Pi) plays a key role in the development of arbuscular mycorrhizal (AM) symbiosis, which is favoured when Pi is limiting in the environment. We have characterized the Medicago truncatula hypermycorrhizal B9 mutant for its response to limiting (P/10) and replete (P2) Pi. On P2, mycorrhization was significantly higher in B9 plants than in wild-type (WT). The B9 mutant displayed hallmarks of Pi-limited plants, including higher levels of anthocyanins and lower concentrations of Pi in shoots than WT plants. Transcriptome analyses of roots of WT and B9 plants cultivated on P2 or on P/10 confirmed the Pi-limited profile of the mutant on P2 and highli…

Environmental and Biochemical Factors Controlling the in Vitro Emergence of Somatic Embryos in European Spindle Tree (Euonymus europaeus L)

The European spindle tree (Euonymus europaeus L. Celastraceae) is a shrubby tree widely distributed in temperate regions of western European countries from the northern part of France to St. Petersburg and the western part of Russia. The Celastraceae comprises 55 genera, including at least 850 known species of trees and shrubs which are found in tropical and temperate regions. Various secondary metabolites are elaborated in the family including steroids, triterpenoids, sesquiterpene, peptide ore alkaloids. The spindle tree is commonly found in quickset hedges and small broad-leaved forests when the soil is deep, moist, clayey and chalky. The leaves are relatively small (3–4 cm long) simple …

Le microbiote de la vigne : de nouveaux paradigmes et une perspective pour la vigne de demain

Prod 2018-253a SPE EA BIOmE IPM INRA UB; National audience

Identification de transporteurs de sucres marqueurs de la mycorhize à arbuscules

Mycorhization en viticulture : état des lieux et étude de l’intérêt au vignoble

SPEIPMUBINRA; Mycorhization en viticulture : état des lieux et étude de l’intérêt au vignoble. 13. Journée Technique du CIVB (Conseil Interprofessionnel du Vin de Bordeaux)

Starvation-induced expression of autophagy-related genes in Arabidopsis

Background information. Autophagy is a catabolic process for degradation of cytoplasmic components in the vacuolar apparatus. A genome-wide survey recently showed evolutionary conservation among autophagy genes in yeast, mammals and plants. To elucidate the molecular and subcellular machinery responsible for the sequestration and subsequent digestion of intracellular material in plants, we utilized a combination of morphological and molecular methods (confocal laser-scanning microscopy, transmission electron microscopy and real-time PCR respectively). Results. Autophagy in Arabidopsis thaliana suspension-cultured cells was induced by carbon starvation, which triggered an immediate arrest of…