The surface of plant leaves, or the phyllosphere, harbors hyperdiverse microbial communities. These communities mediate foliar functional traits, influence plant fitness, and contribute to several ...ecosystem functions, including nutrient and water cycling. In this review, we briefly recall the history of phyllosphere research and present the features of this microbial habitat. Adopting a recent framework for evolutionary community ecology, we then review evidence for each of the four major processes shaping phyllosphere microbial communities: dispersal, evolutionary diversification, selection, and drift. We show how these processes are influenced by the host plant, the surrounding atmospheric conditions, and microbial interactions. Rapidly growing evidence indicates that phyllosphere microbial communities are altered by global change, with potential cascading effects on plant performance, plant evolution, and ecosystem functioning. We propose future avenues for phyllosphere research aimed at improving plant adaptation and ecosystem resilience to environmental changes.
Pest regulation is an important ecosystem service provided by biodiversity, as plants growing in species‐rich communities often experience associational resistance to herbivores. However, little is ...known about the respective influence of the quantity and identity of associated species on herbivory in focal plants. Using a meta‐analysis to compare insect herbivory in pure and mixed forests, we specifically tested the effects of the relative abundance of focal tree species and of phylogenetic distance between focal and associated tree species on the magnitude of associational resistance. Overall, insect herbivory was significantly lower in mixed forests, but the outcome varied greatly depending on the phylogenetic relatedness among tree species and the degree of herbivore feeding specialization. Specialist herbivore damage or abundance was positively related to relative abundance of their host trees, regardless of the phylogenetic distance between host and associated tree species. By contrast, tree diversity triggered associational resistance to generalist herbivores only when tree mixtures included tree species phylogenetically distant to the focal species. Synthesis and applications. Our study demonstrates that the establishment of mixed forests per se is not sufficient to convey associational resistance to herbivores if the identity of tree species associated in mixtures is not taken into account. As a general rule, mixing phylogenetically more distinct tree species, such as mixtures of conifers and broadleaved trees, results in more effective reduction in herbivore damage.
Little is known about the potential effect of climate warming on phyllosphere fungi, despite their important impact on the dynamics and diversity of plant communities. The structure of phyllosphere ...fungal assemblages along elevation gradients may provide information about this potential effect, because elevation gradients correspond to temperature gradients over short geographic distances.
We thus investigated variations in the composition of fungal assemblages inhabiting the phyllosphere of European beech (Fagus sylvatica) at four sites over a gradient of 1000 m of elevation in the French Pyrénées Mountains, by using tag-encoded 454 pyrosequencing.
Our results show that the composition of fungal assemblages varied significantly between elevation sites, in terms of both the relative abundance and the presence–absence of species, and that the variations in assemblage composition were well correlated with variations in the average temperatures.
Our results therefore suggest that climate warming might alter both the incidence and the abundance of phyllosphere fungal species, including potential pathogens. For example, Mycosphaerella punctiformis, a causal agent of leaf spots, showed decreasing abundance with elevation and might therefore shift to higher elevations in response to warming.
VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome is a newly described entity linked to somatic mutation of UBA1, encompassing inflammatory disorders and hematological ...malignancies. Patients experiments symptoms related to inflammatory manifestations on the skin, joints, lungs. Most patients are refractory to usual anti-inflammatory or immunosuppressive treatments. Half of them will develop hematological diseases, mostly myelodysplastic syndromes. VEXAS patients with hematological malignancies have a poor outcome and no curative option has been described so far. Because in the first reported cohort of VEXAS patients the UBA1 mutation was only found in hematopoietic stem cells but not in fibroblasts, we hypothesized that bone marrow transplantation would provide a cure for the disease. Here we report the case of a VEXAS patient who successfully received an allogeneic hematopoietic stem cell transplantation as a curative option.
The evolution of resistance to pesticides and drugs by pests and pathogens is a textbook example of adaptation to environmental changes and a major issue in both public health and agronomy. ...Surprisingly, there is little consensus on how to combine selection pressures (i.e., molecules used in the treatment of pests or pathogens) over space and time to delay or prevent this evolutionary process. By reviewing theoretical models and experimental studies, we show that higher levels of heterogeneity of selection are associated with longer-term sustainability of pest or pathogen control. The combination of molecules usually outcompetes other resistance management strategies, such as Responsive alternation, Periodic application, or Mosaic, because it ensures ‘multiple intragenerational killing’. A strategic deployment over space and/or time of several combinations can ensure ‘multiple intergenerational killing’, further delaying the evolution of resistance.
Plant-inhabiting microorganisms interact directly with each other, forming complex microbial interaction networks. These interactions can either prevent or facilitate the establishment of new ...microbial species, such as a pathogen infecting the plant. Here, our aim was to identify the most likely interactions between Erysiphe alphitoides, the causal agent of oak powdery mildew, and other foliar microorganisms of pedunculate oak (Quercus robur L.). We combined metabarcoding techniques and a Bayesian method of network inference to decipher these interactions. Our results indicate that infection with E. alphitoides is accompanied by significant changes in the composition of the foliar fungal and bacterial communities. They also highlight 13 fungal operational taxonomic units (OTUs) and 13 bacterial OTUs likely to interact directly with E. alphitoides. Half of these OTUs, including the fungal endophytes Mycosphaerella punctiformis and Monochaetia kansensis, could be antagonists of E. alphitoides according to the inferred microbial network. Further studies will be required to validate these potential interactions experimentally. Overall, we showed that a combination of metabarcoding and network inference, by highlighting potential antagonists of pathogen species, could potentially improve the biological control of plant diseases.
The diversity of fungi along environmental gradients has been little explored in contrast to plants and animals. Consequently, environmental factors influencing the composition of fungal assemblages ...are poorly understood. The aim of this study was to determine whether the diversity and composition of leaf and root-associated fungal assemblages vary with elevation and to investigate potential explanatory variables. High-throughput sequencing of the Internal Transcribed Spacer 1 region was used to explore fungal assemblages along three elevation gradients, located in French mountainous regions. Beech forest was selected as a study system to minimise the host effect. The variation in species richness and specific composition was investigated for ascomycetes and basidiomycetes assemblages with a particular focus on root-associated ectomycorrhizal fungi. The richness of fungal communities associated with leaves or roots did not significantly relate to any of the tested environmental drivers, i.e. elevation, mean temperature, precipitation or edaphic variables such as soil pH or the ratio carbon∶nitrogen. Nevertheless, the ascomycete species richness peaked at mid-temperature, illustrating a mid-domain effect model. We found that leaf and root-associated fungal assemblages did not follow similar patterns of composition with elevation. While the composition of the leaf-associated fungal assemblage correlated primarily with the mean annual temperature, the composition of root-associated fungal assemblage was explained equally by soil pH and by temperature. The ectomycorrhizal composition was also related to these variables. Our results therefore suggest that above and below-ground fungal assemblages are not controlled by the same main environmental variables. This may be due to the larger amplitude of climatic variables in the tree foliage compared to the soil environment.
As more and more network-structured data sets are available, the statistical analysis of valued graphs has become common place. Looking for a latent structure is one of the many strategies used to ...better understand the behavior of a network. Several methods already exist for the binary case. We present a model-based strategy to uncover groups of nodes in valued graphs. This framework can be used for a wide span of parametric random graphs models and allows to include covariates. Variational tools allow us to achieve approximate maximum likelihood estimation of the parameters of these models. We provide a simulation study showing that our estimation method performs well over a broad range of situations. We apply this method to analyze host-parasite interaction networks in forest ecosystems.
Key message
The datasets describe bacterial and fungal communities of European beech (
Fagus sylvatica
) leaves collected along a vertical gradient in a gallery forest throughout the growing season. ...They also describe communities in the surrounding environment of beech trees. Dataset access is at
https://doi.org/10.7910/DVN/FFHAQU
, and associated metadata are available at
https://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/f17fe848-fc3e-4297-be11-9871b35a1be4
. Both can be used to uncover the dynamics and assembly processes of phyllosphere microbial communities in forest ecosystems.
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