Today, Vincent Hervé successfully defended his PhD, entitled “Bacterial-fungal interactions in wood decay: from wood physicochemical properties to taxonomic and functional diversity of Phanerochaete chrysosporium-associated bacterial communities”.
Congratulations Vincent for this brilliant defense!
Thiol-based redox homeostasis and signalling
FJ Cejudo, A Meyer, JP Reichheld, N Rouhier, JA Traverso
Plant Physiology 5, 266
Plants imperatively have to cope with adverse conditions owing to their lack of mobility and to the high amounts of reactive oxygen species (ROS) generated from both respiration and photosynthetic metabolism. Although thiol redox homeostasis in plants is mainly preserved by the cellular glutathione pool, specific strategies have been adopted by the plant kingdom during evolution to manage these “extra” pro-oxidative conditions. Unlike human or yeast, plants generally possess a higher number of genes coding for antioxidant proteins, including protein families responsible of dithiol/disulfide exchange reactions. During the last decades, redox-dependent post-translational modifications of proteins proved to be pivotal to many cellular functions. In particular, this is critically important under some situations of environmental constraints taking into account the alterations and fine adjustment of the cellular redox status occurring during and after any biotic or abiotic stresses. Indeed, thiol groups of cysteinyl residues are highly sensitive to oxidation which might critically perturb cellular homeostasis. Members of the thioredoxin superfamily are key proteins involved in the regulation of cysteine/protein redox state. They share two common and well-known features: (i) the presence of an active center containing at least one catalytic cysteine residue, and (ii) a highly conserved 3D-structure, the so-called thioredoxin fold, which consists of a four-stranded anti-parallel b-sheet surrounded by three a-helices. Key members of this super family are thioredoxins (TRX) and glutaredoxins (GRX). Representatives of both subgroups are distributed in most cellular compartments and contain at least one TRX motif in their structures. While TRXs are generally reduced by thioredoxin reductases (TR), the reduction ofGRXs depends on reduced glutathione (GSH).
Effector MiSSP7 of the mutualistic fungus Laccaria bicolor stabilizes the Populus JAZ6 protein and represses jasmonic acid (JA) responsive genes
JM Plett, Y Daguerre, S Wittulsky, A Vayssières, A Deveau, SJ Melton, …
Proceedings of the National Academy of Sciences, 201322671
Ectomycorrhizal fungi, such as Laccaria bicolor, support forest growth and sustainability by providing growth-limiting nutrients to their plant host through a mutualistic symbiotic relationship with host roots. We have previously shown that the effector protein MiSSP7 (Mycorrhiza-induced Small Secreted Protein 7) encoded byL. bicolor is necessary for the establishment of symbiosis with host trees, although the mechanistic reasoning behind this role was unknown. We demonstrate here that MiSSP7 interacts with the host protein PtJAZ6, a negative regulator of jasmonic acid (JA)-induced gene regulation in Populus. As with other characterized JASMONATE ZIM-DOMAIN (JAZ) proteins, PtJAZ6 interacts with PtCOI1 in the presence of the JA mimic coronatine, and PtJAZ6 is degraded in plant tissues after JA treatment. The association between MiSSP7 and PtJAZ6 is able to protect PtJAZ6 from this JA-induced degradation. Furthermore, MiSSP7 is able to block—or mitigate—the impact of JA on L. bicolor colonization of host roots. We show that the loss of MiSSP7 production by L. bicolor can be complemented by transgenically varying the transcription of PtJAZ6 or through inhibition of JA-induced gene regulation. We conclude that L. bicolor, in contrast to arbuscular mycorrhizal fungi and biotrophic pathogens, promotes mutualism by blocking JA action through the interaction of MiSSP7 with PtJAZ6.
| Name | GOBILLARD Célia |  |
| Team | Ecology of forest pathogenic fungi team | |
| Supervisors | P. Frey/A. Andrieux | |
| Subject | Study of a life history trait of Melampsora-larici-populina : Quantification of uredinia mycélium with qPCR method | |
| Type of study | BTS Internship (1st year) | |
| Period | May-July, 2014 |
| Name | TORRES BEJAR Marta |  |
| Team | Ecogenomics of interactions team | |
| Supervisor | S. Uroz | |
| Subject | Cell signaling in salt environment | |
| Type of study | PhD stay, coming from University of Granada, Spain. | |
| Period | May-July, 2014 |
| Name | LECARDONNEL Laure |  |
| Team | Ecology of forest pathogenic fungi team | |
| Supervisors | B. Marçais/C. Husson | |
| Subject | Assessment of Chalara impact in young ash regenerations; Link between foliar infection and twig dieback | |
| Type of study | Master 1 Internship | |
| Period | May-June, 2014 |
| Name | SCHELLENBERGER Romain |  |
| Team | Ecogenomics of interactions team | |
| Supervisors | S. Wittulsky/C.Veneault-Fourrey | |
| Subject | Jasmonic-acid in ECM development | |
| Type of study | Master 1 Internship | |
| Period | April-May, 2014 |
The armoured catfish, Panaque nigrolineatus, has specialized physiological adaptations to enable high levels of wood to be ingested in its diet. However, it is unclear what nutritional benefit is derived or the nature of any symbiosis that facilitates it. In the present study, we examined microbial communities associated with the foregut, midgut, hindgut, and auxiliary lobe of P. nigrolineatus using a metagenomic approach utilizing 454 pyrosequencing. Microbial community diversity altered in the different regions of the GI tract indicating different functional roles of key bacterial populations. To complement this genetic approach, scanning electron microscopy of the different regions of the gastrointestinal tract was performed to examine the microbial community present. Lignocellulose degradation within the gastrointestinal tract was supported by scanning electron microscopy observations, indicating structural alterations in the wood. Furthermore, the wood particles in the hindgut appeared to harbour assemblies suggestive of microbial cells. Additionally, wood collected from different regions of the GI tract was analyzed using Fourier-Transformed Infrared (FTIR) spectroscopy. This technique revealed changes to the wood associated with gut transit. These changes are consistent with the presence of a wood-digesting activity within the GI tract within the P. nigrolineatus gastrointestinal tract. Furthermore, using fixed GI tract tissue using catalyzed reporter deposition enhanced immunofluorescence revealed the highest densities of nitrogenase-containing cells attached to the woody digesta within the GI tract with fewer cells sparsely colonizing the intestinal mucous layer. These findings are consistent with a role for the P. nigrolineatus intestinal tract microbial community in providing a source of fixed nitrogen under nitrogen limiting conditions.
http://www.biochemj.org/bj/imps/abs/BJ20140390.htm
La campagne de recrutement des ATER 2014-2015 est lancée.
Elle se termine le 25 mai à minuit.
Les candidats doivent postuler sur GALAXIE par l’application ALTAIR
Ils recevront un identifiant et un mot de passe pour pouvoir déposer leur dossier de candidature sur l’application Esup-Dematec
The defense will be held the 28th May 2014 at 9H00 in Amphitheater 7, Faculté des Sciences, Boulevard des Aiguillettes, Vandoeuvre
Title: Bacterial-fungal interactions in wood decay: from wood physicochemical properties to taxonomic and functional diversity of Phanerochaete chrysosporium-associated bacterial communities
Wood decomposition is an important process in forest ecosystems in terms of their carbon and nutrient cycles. In temperate forests, saprotrophic basidiomycetes such as white-rot fungi are the main wood decomposers. While they have been less studied, bacterial communities also colonise decaying wood and coexist with these fungal communities. Although the impact of bacterial-fungal interactions on niche functioning has been highlighted in a wide range of environments, little is known about their role in wood decay. Based on microcosm experiments and using a culture-independent approach, we showed that the presence of the white-rot fungus Phanerochaete chrysosporium significantly modified the structure and diversity of the bacterial communities associated with the degradation of beech wood (Fagus sylvatica). Using a culture-dependent approach, it was confirmed that in the presence of the fungus the mycosphere effect resulted in increased bacterial abundance and modified the functional diversity of the fungal-associated bacterial communities. Lastly, a polyphasic approach simultaneously analysing wood physicochemical properties and extracellular enzyme activities was developed. This approach revealed that P. chrysosporium associated with a bacterial community isolated from its mycosphere was more efficient in degrading wood compared to the fungus on its own, highlighting for the first time synergistic bacterial-fungal interactions in decaying wood.
Keywords: wood decomposition, bacterial-fungal interactions, mycosphere effect, bacterial diversity, Phanerochaete chrysosporium, Fagus sylvatica, white rot.
Dans les écosystèmes forestiers, la décomposition du bois est un processus majeur, notamment impliqué dans le cycle du carbone et des nutriments. Les champignons basidiomycètes saprotrophes, incluant les pourritures blanches, sont les principaux agents de cette décomposition dans les forêts tempérées. Bien que peu étudiées, des communautés bactériennes sont également présentes dans le bois en décomposition et cohabitent avec ces communautés fongiques. L’impact des interactions bactéries-champignons sur le fonctionnement d’une niche écologique a été décrit dans de nombreuxenvironnements. Cependant, très peu de choses sont connues sur leur rôle dans le processus de décomposition du bois. A partir d’expériences en microcosme et en utilisantune approche non cultivable, il a été démontré que la présence du champignonPhanerochaete chrysosporiuminfluençait significativement la structureet la diversité des communautés bactériennes associées au processus de décomposition du hêtre (Fagus sylvatica). Par une approche cultivable, cet effet mycosphère aété confirmé, se traduisant par une augmentation de la concentration des communautés bactériennes en présence du champignonainsi que par une modification de la diversité fonctionnelle des communautés bactériennes associées au champignon. Enfin, une approche polyphasique a été développée,combinant l’analyse des propriétés physico-chimiques du bois et des activités enzymatiques extracellulaires. Ces derniers résultatsont révélé que l’association de P. chrysosporium avec une communauté bactérienne issue de la mycosphère de ce dernier aboutissait à une dégradation plus importante du matériau bois par rapport à la dégradation par le champignon seul, indiquant pour la première fois une interaction bactéries-champignon synergique dans le bois en décomposition.
Mots-clefs : décomposition du bois, interactions bactéries-champignons, effet mycosphère, diversité bactérienne, Phanerochaete chrysosporium, Fagus sylvatica, pourriture blanche.