Estimation of fungal diversity and identification of major abiotic drivers influencing fungal richness and communities in northern temperate and boreal Quebec forests

Fungi play important roles in forest ecosystems and understanding fungal diversity is crucial to address essential questions about species conservation and ecosystems management. Changes in fungal diversity can have severe impacts on ecosystem functionality. Unfortunately, little is known about fungal diversity in northern temperate and boreal forests, and we have yet to understand how abiotic variables shape fungal richness and composition. Our objectives were to make an overview of the fungal richness and the community composition in the region and identify their major abiotic drivers. We sampled 262 stands across the northern temperate and boreal Quebec forest located in the region of Abitibi-Témiscamingue, Mauricie, and Haute-Mauricie. At each site, we characterized fungal composition using Illumina sequencing, as well as several potential abiotic drivers (e.g., humus thickness, soil pH, vegetation cover, etc.). We tested effects of abiotic drivers on species richness using generalized linear models, while difference in fungal composition between stands was analyzed with permutational multivariate analysis of variance and beta-diversity partitioning analyses. Fungi from the order Agaricales, Helotiales, and Russulales were the most frequent and sites from the north of Abitibi-Témiscamingue showed the highest OTUs (Operational Taxonomic Unit) richness. Stand age and moss cover were the best predictors of fungal richness. On the other hand, the strongest drivers of fungal community structure were soil pH, average cumulative precipitation, and stand age, although much of community variance was left unexplained in our models. Overall, our regional metacommunity was characterized by high turnover rate, even when rare OTUs were removed. This may indicate strong environmental filtering by several unmeasured abiotic filters, or stronger than expected dispersal limitations in soil fungal communities. Our results show how difficult it can be to predict fungal community assembly even with high replication and efforts to include several biologically relevant explanatory variables

Boreal forest multifunctionality is promoted by low soil organic matter content and high regional bacterial biodiversity in Northeastern Canada

Boreal forests provide important ecosystem services, most notably being the mitigation of increasing atmospheric CO2 emissions. Microbial biodiversity, particularly the local diversity of fungi, has been shown to promote multiple functions of the boreal forests of Northeastern China. However, this microbial biodiversity-multifunctionality relationship has yet to be explored in Northeastern Canada, where historical environment have shaped a different regional pool of microbial diversity. This study focuses on the relationship between the soil microbiome and ecosystem multifunctionality, as well as the influence of pH and redox potential (Eh) on the regulation of such relationship. Structural equation modelling (SEM) was used to explore the different causal relationships existing in the studied ecosystems. In a managed part of the Canadian boreal forest, 156 forest polygons were sampled to (1) estimate the α- and β-diversity of fungal and bacterial communities and (2) measure 12 ecosystem functions mainly related to soil nutrient storage and cycling. Both bacteria and fungi influenced ecosystem multifunctionality, but on their own respective functions. Bacterial β-diversity was the most important factor increasing primary productivity and soil microbial biomass, while reducing soil emitted atmospheric CO2. Environmental characteristics, particularly low levels of organic matter in soil, were shown to have the strongest positive impact on boreal ecosystem multifunctionality. Overall, our results were consistent with those obtained in Northeastern China; however, some differences need to be further explored especially considering the history of forest management in Northeastern Canada

Role of the small G protein Arf6 on cardiac function

Les petites protéines G sont des régulateurs bien caractérisés de l’endocytose et du transport endocytaire de plusieurs protéines membranaires. Ces dernières sont impliquées dans la transmission de signaux extracellulaires vers l’intérieur de la cellule, lui permettant de réagir à son environnement de façon appropriée. Dans les cardiomyocytes, les cellules contractiles du cœur, les protéines membranaires sont importantes afin de contrôler la vitesse et la force de contraction. Une altération de leur localisation membranaire est souvent associée au développement de pathologies contractiles (p. ex. l’insuffisance cardiaque) ou de troubles du rythme (p. ex. les arythmies). Bien que le rôle de plusieurs protéines G ait été identifié dans le cœur, la fonction précise de la petite protéine G Arf6 dans les cardiomyocytes n’a jamais été adressée. Dans ce projet, nous avons mis en lumière pour la première fois le rôle d’ADAP1, une Arf6 GAP (GTPase-activating protein), sur l’hypertrophie des cardiomyocytes en culture. Nous avons démontré un mécanisme impliquant une altération de l’expression membranaire de l’intégrine β1, une protéine essentielle à l’attachement des cardiomyocytes à la matrice extracellulaire et à leur étalement lors de l’hypertrophie. À l’aide d’un modèle unique de souris transgénique, nous avons démontré pour la première fois un rôle cardiaque pour Arf6. En effet, l’absence d’Arf6 spécifiquement dans les cardiomyocytes réduit la fonction contractile et altère certains paramètres de l’activité électrique du cœur. Une approche protéomique a permis de confirmer qu’Arf6 régule la localisation membranaire de plusieurs protéines susceptibles d’altérer la fonction ou la localisation de récepteurs, canaux ioniques et connexines, qui sont tous importants pour la contractilité des cardiomyocytes et la propagation du potentiel d’action dans le cœur. Ainsi, ce projet a permis de confirmer, pour la première fois, que la protéine Arf6 a un rôle important dans le cœur en régulant le trafic de protéines transmembranaires impliquées dans la fonction contractile et électrique du cœur.Abstract : Small G proteins are well-known regulators of endocytosis and endocytic transport of many membrane proteins. These membrane proteins are involved in the transmission of extracellular signals inside the cell, allowing the cell to react appropriately to its environment. In cardiomyocytes, which are the heart contractile cells, membrane proteins are important to control the speed and force of contraction. An alteration in their membrane expression is often associated with the development of contractile pathologies (e.g. heart failure) or rhythm problems (e.g. arrhythmias). While the role of many small G proteins have been characterized in the heart, the precise function of Arf6 in cardiomyocytes has never been addressed. In this project, we identified for the first time a role for ADAP1, an Arf6 GAP, on cardiomyocyte hypertrophy. We identified a mechanism involving an alteration of the membrane expression of β1-integrin, an essential protein for the attachment of cardiomyocytes to the extracellular matrix and for their spreading during hypertrophy. Using a unique mouse transgenic model, we identified, for the first time, a cardiac function for Arf6. In fact, the genetic depletion of Arf6 specifically in cardiomyocytes reduces the contractile function and alters some parameters of the heart’s electrical activity. A proteomic approach allowed us to confirm that Arf6 regulates the membrane expression of many proteins that can alter the function or localization of receptors, ion channels or connexins, all important for cardiomyocyte contractility and action potential propagation in the heart. In sum, this project allowed us to identify, for the first time, a role for Arf6 in the heart by regulating the traffic of membrane proteins involved in contractile and electrical function

Estimation of Fungal Diversity and Identification of Major Abiotic Drivers Influencing Fungal Richness and Communities in Northern Temperate and Boreal Quebec Forests

Fungi play important roles in forest ecosystems and understanding fungal diversity is crucial to address essential questions about species conservation and ecosystems management. Changes in fungal diversity can have severe impacts on ecosystem functionality. Unfortunately, little is known about fungal diversity in northern temperate and boreal forests, and we have yet to understand how abiotic variables shape fungal richness and composition. Our objectives were to make an overview of the fungal richness and the community composition in the region and identify their major abiotic drivers. We sampled 262 stands across the northern temperate and boreal Quebec forest located in the region of Abitibi-Témiscamingue, Mauricie, and Haute-Mauricie. At each site, we characterized fungal composition using Illumina sequencing, as well as several potential abiotic drivers (e.g., humus thickness, soil pH, vegetation cover, etc.). We tested effects of abiotic drivers on species richness using generalized linear models, while difference in fungal composition between stands was analyzed with permutational multivariate analysis of variance and beta-diversity partitioning analyses. Fungi from the order Agaricales, Helotiales, and Russulales were the most frequent and sites from the north of Abitibi-Témiscamingue showed the highest OTUs (Operational Taxonomic Unit) richness. Stand age and moss cover were the best predictors of fungal richness. On the other hand, the strongest drivers of fungal community structure were soil pH, average cumulative precipitation, and stand age, although much of community variance was left unexplained in our models. Overall, our regional metacommunity was characterized by high turnover rate, even when rare OTUs were removed. This may indicate strong environmental filtering by several unmeasured abiotic filters, or stronger than expected dispersal limitations in soil fungal communities. Our results show how difficult it can be to predict fungal community assembly even with high replication and efforts to include several biologically relevant explanatory variables

Monitoring TRPC7 Conformational Changes by BRET Following GPCR Activation

Transient receptor potential canonical (TRPC) channels are membrane proteins involved in regulating Ca2+ homeostasis, and whose functions are modulated by G protein-coupled receptors (GPCR). In this study, we developed bioluminescent resonance energy transfer (BRET) biosensors to better study channel conformational changes following receptor activation. For this study, two intramolecular biosensors, GFP10-TRPC7-RLucII and RLucII-TRPC7-GFP10, were constructed and were assessed following the activation of various GPCRs. We first transiently expressed receptors and the biosensors in HEK293 cells, and BRET levels were measured following agonist stimulation of GPCRs. The activation of GPCRs that engage Gαq led to a Gαq-dependent BRET response of the functional TRPC7 biosensor. Focusing on the Angiotensin II type-1 receptor (AT1R), GFP10-TRPC7-RLucII was tested in rat neonatal cardiac fibroblasts, expressing endogenous AT1R and TRPC7. We detected similar BRET responses in these cells, thus validating the use of the biosensor in physiological conditions. Taken together, our results suggest that activation of Gαq-coupled receptors induce conformational changes in a novel and functional TRPC7 BRET biosensor