Biology subjects

Hacquard, S.

Publications and source records attributed to Hacquard, S..

15 recordsLinked to original sources

bioRxiv2026

Fungal community composition links rhizosphere microbiome organization to plant phenotype in response to moderate warming

BackgroundGlobal warming increasingly challenges plant performance and ecosystem function, and plant responses to elevated temperature are shaped not only by intrinsic plasticity, but also by interactions with rhizosphere microbial communities. However, it remains unclear how warming-induced microbiome reorganization relates to plant performance, whether microbiome community composition predicts plant phenotypic responses to elevated temperature better than simple host-microbiome origin matching, and which bacterial or fungal community features contribute most strongly to this prediction. ResultsWe implemented a full factorial design manipulating plant genotype (P), microbial inoculum (M), and temperature (T) using natural Arabidopsis thaliana ecotypes and their corresponding rhizosphere microbiomes from contrasting climatic regions. By integrating high-throughput plant phenotyping, microbial community profiling, microbiome-phenotype coupling analyses, and predictive modeling, we found that elevated temperature induced a coherent thermomorphogenic shift in plant architecture, while plant phenotypic variation remained determined primarily by genotype over the 14-day vegetative growth period covered in this study. Overall, cold-origin genotypes showed larger temperature-induced trait shifts than warm-origin genotypes. Rhizosphere microbial communities were structured predominantly by inoculum origin, but were also affected by warming. Evidence for a increased thermomorphogenic growth when genotypes were combined with inoculum from their home site was limited. Instead, microbiome-phenotype associations were better captured by community composition than by matching status, with fungal community variation showing stronger and more consistent associations with plant phenotype than bacterial variation and providing more robust predictions of plant phenotypes across models. ConclusionsWarming reorganized plant-rhizosphere systems within persistent host- and inoculum-associated baselines. Plant phenotypic variation during vegetative development under elevated temperature was linked more closely to microbiome composition, especially in fungi, than to simple host-microbiome matching of origins. These findings provide a framework for identifying microbiome features associated with plant performance under climate warming.

plant biology↗

bioRxiv2026

Bacteria rewire fungal antimicrobial gene expression in microbial arms races

Microbial communities are shaped by antagonistic interactions, yet how competitors evade antimicrobial strategies in a community context remains unclear. Fungi deploy antimicrobial proteins (AMPs) to suppress bacterial niche competitors, but how bacteria counteract these defences is unknown. Here we show that soil microbiota suppress fungal AMP expression, revealing a previously unrecognized mode of intermicrobial interference. In the soil-borne pathogen Verticillium dahliae, AMP genes are highly conserved yet broadly repressed in the presence of natural microbial communities. This repression extends across diverse fungi, suggesting a widespread phenomenon. Correlation analyses of AMP expression and community compositions linked the bacterial genera Leptothrix and Devosia to repression of the V. dahliae AMPs VdL1 and VdD1, respectively. Both AMPs antagonize these bacterial taxa, and microbiota-mediated repression of VdL1 reduces its contribution to fungal soil colonization. Together, our findings reveal that bacteria can evade fungal antagonism by suppressing AMP deployment, highlighting community-level control of microbial competition.

microbiology↗

bioRxiv2025

Genetic factors driving multi-host infection in a core member of the root mycobiota

Core members of the fungal root microbiota include pathogens capable of colonizing multiple hosts, yet the underlying genetic determinants remain unknown. We report that Plectosphaerella cucumerina is a core member of the Arabidopsis thaliana root microbiota displaying high pathogenic potential and multi-host colonization capabilities. Establishment of a Plectosphaerella reference culture collection, followed by whole-genome sequencing of 72 strains reveals subtle phenotypic and genotypic variation that associate with fungal phylogeny, but not host plant identity. Transcriptome profiling of a model P. cucumerina isolate in roots of multiple hosts identifies core and host-specific fungal processes linked to carbon catabolism and root cell wall deconstruction of the hosts. A fungal gene encoding a candidate {beta}-1,3-glucanase (GH64) was identified as a key genetic factor driving infection and disease in plants that diverged 110 million years ago. The gene is enriched in plant-colonizing fungi and consistently functions as a disease determinant in the root pathogen Colletotrichum incanum. We conclude that diverse and tunable fungal repertoires of carbohydrate-active enzymes act as disease determinants and drive multi-host compatibility belowground.

microbiology↗

bioRxiv2025

Differential contributions of an antimicrobial effector from Verticillium dahliae to virulence and tomato microbiota assembly across natural soils

Throughout their life cycle plants associate with diverse and complex microbial communities, known as their microbiota. These microbiota contribute to plant performance and health, in part by providing a microbial barrier against invading plant pathogens. To colonize plant hosts, pathogens not only have to overcome host immune responses, but also breach the microbial barrier, for which they secrete so-called effector proteins. Accordingly, the soil-borne fungal plant pathogen Verticillium dahliae secretes the antimicrobial effector Ave1 to suppress antagonistic microbes and facilitate host colonization. Notably, many pathogens, including V. dahliae, have life stages outside their host plants, for instance in soil, where they encounter diverse microbial communities. Yet, how antimicrobial effectors support establishment across these environments remains poorly understood. To address this, we established a collection of natural soil samples with diverse physicochemical properties and microbiota compositions. Using this collection, we show for three plant species, barley, tomato and cotton, that root-associated bacterial and fungal communities are primarily shaped by the type of soil, whereas the phyllosphere microbiota is mainly determined by plant species. On tomato, we furthermore show that Ave1 differentially contributes to virulence on diverse soils, as Ave1 altered the tomato microbiota on all soils tested, but the taxa affected by these shifts varied depending on the specific soils. Our findings suggest that while Ave1-mediated microbiota manipulation occurs across soils, its impact on fungal virulence is influenced by the specific composition of the soil-derived microbiota assembled by the host.

plant biology↗

bioRxiv2024

Plant phenotypic differentiation outweighs genetic variation in shaping the lettuce leaf microbiota

Lettuce is a widely consumed raw vegetable, making it crucial to understand and predict its leaf-associated microbial communities for the benefit of both plant and human health. While environmental factors are known to strongly influence plant leaf microbiomes, the role of plant-specific determinants in shaping microbial diversity remains unclear. In this study, we investigated the impact of three key plant factors -genetic distance, morphology and leaf micro- and macronutrient content- on the composition and diversity of lettuce leaf bacterial communities. Using 131 fully-sequenced Lactuca sativa genotypes, we analyzed their leaf-associated bacterial communities via 16S rRNA amplicon sequencing. Our findings revealed that morphological classification, as defined by breeders, exerts a greater influence on bacterial community diversity than genetic distance or variations in leaf nutrient levels. Together with shoot traits they explained 13.9% of the observed bacterial diversity. Further analysis of 10 specific leaf morphological traits showed that heart formation, head height, and venation types significantly shaped bacterial richness and evenness, mainly acting on non-hub members. The strong association between leaf morphology and bacterial community structure suggests that phenotypic traits play a disproportionately large, yet understudied, role in leaf microbiota establishment offering new potential for manipulation by breeders.

plant biology↗

bioRxiv2024

Pseudomonas intra-genus competition determines protective function of SynComs in Arabidopsis thaliana

The plant root microbiota is crucial for nutrient acquisition, development, and disease suppression. Although commensal bacteria display host preference, their beneficial impact on their cognate host and mechanisms of species selection by the plant are still unclear. We use bacterial culture collections derived from the two model species Arabidopsis thaliana (At) and Lotus japonicus (Lj) to design synthetic communities (SynComs) and test their protective function upon exposure of At Col-0 to the detrimental root-colonizing Pseudomonas isolate R401. Lj-derived SynComs were fully protective, whereas At-derived SynComs displayed full protective activity only towards a R401 mutant impaired in the production of inhibitory exometabolites. The protective phenotypes were associated with a reduced titer of the R401 opportunistic pathogen. In vitro antagonist assays, in planta and in vitro bacterial community profiling, as well as strain-swapping and strain-dropout experiments revealed that competition among commensal Pseudomonas strains and R401 determines the success of the opportunist, independent of the original host or the phylogeny of the commensals. Furthermore, we determine the carbon utilization potential of these isolates, which may explain the competition with the detrimental strain and the role of host-secreted compounds. Our results provide evidence that intra-genus interactions within SynComs modulate plant health and disease, and that an individual beneficial strain can be sufficient to outcompete an opportunistic relative. This has implications for the successful development of beneficial microbial consortia for agriculture.

plant biology↗

bioRxiv2022

Tryptophan specialized metabolism and ER body-resident myrosinases modulate root microbiota assembly

Indole glucosinolates (IGs) are tryptophan (Trp)-derived sulfur-containing specialized metabolites that play a crucial role in plant-microbe interactions in plants of the order Brassicales, including Arabidopsis thaliana. Despite the growing body of evidence implicating IG biosynthetic pathways in root-microbiota interactions, how myrosinases, the enzymes that convert inert IGs into bioactive intermediate/terminal products, contribute to this process remains unknown. Here, we describe the roles of the PYK10 and BGLU21 myrosinases in root-microbiota assembly partly via metabolites secreted from roots into the rhizosphere. PYK10 and BGLU21 localize to the endoplasmic reticulum (ER) body, an ER-derived organelle observed in plants of the family Brassicaceae. We investigated the root microbiota structure of mutants defective in the Trp metabolic (cyp79b2b3 and myb34/51/122) and ER body (nai1 and pyk10bglu21) pathways and found that these factors together contribute to the assembly of root microbiota. Microbial community composition in soils as well as in bacterial synthetic communities (SynComs) treated with root exudates axenically collected from pyk10bglu21 and cyp79b2b3 differed significantly from those treated with exudates derived from wild-type plants, pointing to a direct role of root-exuded compounds. We also show that growth of the pyk10bglu21 and cyp79b2b3 mutants was severely inhibited by fungal endophytes isolated from healthy A. thaliana plants. Overall, our findings demonstrate that root ER body-resident myrosinases influencing the secretion of Trp-derived specialized metabolites represent a lineage-specific innovation that evolved in Brassicaceae to regulate root microbiota structure. SignificanceER bodies were first identified in roots of Brassicaceae plants more than 50 years ago, but their physiological functions have remained uncharacterized. A series of previous studies have suggested their possible role in root-microbe interactions. Here, we provide clear experimental evidence showing a role for ER bodies in root-microbiota interactions, which overlaps with that of root-exuded Trp-derived metabolites. Our findings delineate a plant lineage-specific innovation involving intracellular compartments and metabolic enzymes that evolved to regulate plant-microbe interactions at the root-soil interface.

plant biology↗

bioRxiv2021

Genetic determinants of endophytism in the Arabidopsis root mycobiome

Roots of Arabidopsis thaliana do not engage in symbiotic associations with mycorrhizal fungi but host taxonomically diverse fungal communities that influence health and disease states. We sequenced the genomes of 41 fungal isolates representative of the A. thaliana root mycobiota for comparative analysis with 79 other plant-associated fungi. We report that root mycobiota members evolved from ancestors with diverse lifestyles and retained large repertoires of plant cell wall-degrading enzymes (PCWDEs) and effector-like small secreted proteins. We identified a set of 84 gene families predicting best endophytism, including families encoding PCWDEs acting on xylan (GH10) and cellulose (AA9). These genes also belong to a core transcriptional response induced by phylogenetically-distant mycobiota members in A. thaliana roots. Recolonization experiments with individual fungi indicated that strains with detrimental effects in mono-association with the host not only colonize roots more aggressively than those with beneficial activities but also dominate in natural root samples. We identified and validated the pectin degrading enzyme family PL1_7 as a key component linking aggressiveness of endophytic colonization to plant health.

microbiology↗

bioRxiv2021

Differential impact of plant secondary metabolites on the soil microbiota

Plant metabolites can shape the microbial community composition in the soil. Two indole metabolites, benzoxazolinone (BOA) and gramine, produced by different Gramineae species, and quercetin, a flavonoid synthesized by many dicot species, were studied for their impacts on the community structure of soil bacteria. The three plant metabolites were directly added to agricultural soil over a period of 28 days. Alterations in bacterial composition were monitored by next generation sequencing of 16S rRNA gene PCR products and phospholipid fatty acid analysis. Treatment of the soil with the plant metabolites altered the composition of bacterial taxa on the phylum and genus levels. Alpha diversity was significantly altered by BOA or quercetin, but not by gramine. BOA treatment caused an increase in the relative abundances of only four genera, three of them belonging to the Actinobacteriota. Gramine or quercetin treatment resulted in the increase in relative abundance of 13 or 14 genera, respectively, most of them belonging to the Proteobacteria. The relative abundance of 22 genera was decreased after BOA treatment, 16 of which were also decreased by gramine or quercetin. Isolation and characterization of cultivable bacterial indicated an enrichment in specific Arthrobacter or Pseudomonas strains. Therefore, the effects of the treatments on soil bacteria were characteristic for each metabolite, with BOA exerting a broad-spectrum inhibitory effect, with only few genera able to proliferate, while gramine and quercetin caused the proliferation of many potentially beneficial strains. As a consequence, benzoxazolinone or gramine biosynthesis which have evolved in different barley species, is accompanied with the association with distinct bacterial communities in the soil, presumably after mutual adaptation during evolution.

microbiology↗

bioRxiv2021

Reference-based error correction of amplicon sequencing data from synthetic communities

SummarySynthetic microbial communities (SynComs) constitute an emerging and powerful tool in biological, biomedical, and biotechnological research. Despite recent advances in algorithms for the analysis of culture-independent amplicon sequencing data from microbial communities, there is a lack of tools specifically designed for analysing SynCom data, where reference sequences for each strain are available. Here we present Rbec, a tool designed for the analysis of SynCom data that accurately corrects PCR and sequencing errors in amplicon sequences and identifies intra-strain polymorphic variation. Extensive evaluation using mock bacterial and fungal communities show that our tool outperforms current methods for samples of varying complexity, diversity, and sequencing depth. Furthermore, Rbec also allows accurate detection of contaminants in SynCom experiments. Availability and implementationRbec is freely available as an open-source multi-platform R package. Release versions can be obtained via Bioconductor. The developer version is maintained and can be downloaded at: https://github.com/PengfanZhang/Rbec. Contactgarridoo@mpipz.mpg.de

bioinformatics↗

bioRxiv2020

Microbiota-root-shoot axis modulation by MYC2 favours Arabidopsis growth over defence under suboptimal light

Bidirectional root-shoot signalling is likely key in orchestrating stress responses and ensuring plant survival. Here we show that Arabidopsis thaliana responses to microbial root commensals and light are interconnected along a microbiota-root-shoot axis. Microbiota and light manipulation experiments in a gnotobiotic system reveal that low photosynthetically active radiation (LP) perceived by leaves induce long-distance modulation of root bacterial, but not fungal or oomycetal communities. Reciprocally, bacterial root commensals and particularly Pseudomomas isolates are necessary for rescuing plant growth under LP. RNA-Seq, combined with leaf inoculation experiments with biotrophic and necrotrophic microbial pathogens indicate that microbiota-induced growth under LP coincides with transcriptional repression of immune responses, thereby increasing susceptibility to both pathogens. Inspection of a set of A. thaliana mutants demonstrates that orchestration of this light-dependent growth-defence trade-off requires the transcriptional regulator MYC2. Our work indicates that aboveground stress responses in plants can be governed by signals from microbial root commensals.

plant biology↗

bioRxiv2020

Obtaining deeper insights into microbiome diversity using a simple method to block host and non-targets in amplicon sequencing

Microbiome profiling is revolutionizing our understanding of biological mechanisms such as metaorganismal (host+microbiome) assembly, functions and adaptation. Amplicon sequencing of multiple conserved, phylogenetically informative loci is an instrumental tool for characterization of the highly diverse microbiomes of natural systems. Investigations in many study systems are hindered by loss of essential sequencing depth due to amplification of non-target DNA from hosts or overabundant microorganisms. This issue requires urgent attention to address ecologically relevant problems using high throughput, high resolution microbial profiling. Here, we introduce a simple, low cost and highly flexible method using standard oligonucleotides ("blocking oligos") to block amplification of non-targets and an R package to aid in their design. They can be dropped into practically any two-step amplicon sequencing library preparation pipeline. We apply them in leaves, a system presenting exceptional challenges with host and non-target microbial amplification. Blocking oligos designed for use in eight target loci reduce undesirable amplification of host and non-target microbial DNA by up to 90%. In addition, 16S and 18S "universal" plant blocking oligos efficiently block most plant hosts, leading to increased microbial alpha diversity discovery without biasing beta diversity measurements. By blocking only chloroplast 16S amplification, we show that blocking oligos do not compromise quantitative microbial load information inherent to plant-associated amplicon sequencing data. Using these tools, we generated a near-complete survey of the Arabidopsis thaliana leaf microbiome based on diversity data from eight loci and discuss complementarity of commonly used amplicon sequencing regions for describing leaf microbiota. The blocking oligo approach has potential to make new questions in a variety of study systems more tractable by making amplicon sequencing more targeted, leading to deeper, systems-based insights into microbial discovery.

microbiology↗

bioRxiv2019

Root microbiota assembly and adaptive differentiation among European Arabidopsis populations

Factors that drive continental-scale variation in root microbiota and plant adaptation are poorly understood. We monitored root-associated microbial communities in Arabidopsis thaliana and co-occurring grasses at 17 European sites across three years. Analysis of 5,625 microbial community profiles demonstrated strong geographic structuring of the soil biome, but not of the root microbiota. Remarkable similarity in bacterial community composition in roots of A. thaliana and grasses was explained by the presence of a few diverse and geographically widespread taxa that disproportionately colonize roots across sites. In a reciprocal transplant between two A. thaliana populations in Sweden and Italy, we uncoupled soil from location effects and tested their respective contributions to root microbiota variation and plant adaptation. The composition of the root microbiota was affected by location and soil origin, and to a lesser degree by host genotype. The filamentous eukaryotes were particularly strongly affected by location. Strong local adaptation between the two A. thaliana populations was observed, with difference in soil properties and microbes of little importance for the observed magnitude of adaptive differentiation. Our results suggest that, across large spatial scales, climate is more important than are soil conditions for plant adaptation and variation in root-associated filamentous eukaryotic communities.

microbiology↗

bioRxiv2018

Microbial interkingdom interactions in roots promote Arabidopsis survival

Roots of healthy plants are inhabited by soil-derived bacteria, fungi, and oomycetes that have evolved independently in distinct kingdoms of life. How these microorganisms interact and to what extent those interactions affect plant health are poorly understood. We examined root-associated microbial communities from three Arabidopsis thaliana populations and detected mostly negative correlations between bacteria and filamentous microbial eukaryotes. We established microbial culture collections for reconstitution experiments using germ-free A. thaliana. In plants inoculated with mono- or multi-kingdom synthetic microbial consortia, we observed a profound impact of the bacterial root microbiota on fungal and oomycetal community structure and diversity. We demonstrate that the bacterial microbiota is essential for plant survival and protection against root-derived filamentous eukaryotes. Deconvolution of 2,862 binary bacterial-fungal interactions ex situ, combined with community perturbation experiments in planta, indicate that biocontrol activity of bacterial root commensals is a redundant trait that maintains microbial interkingdom balance for plant health.

microbiology↗

bioRxiv2017

The rust fungus Melampsora larici-populina expresses a conserved genetic program and distinct sets of secreted protein genes during infection of its two host plants, larch and poplar

Mechanims required for broad spectrum or specific host colonization of plant parasites are poorly understood. As a perfect illustration, heteroecious rust fungi require two alternate host plants to complete their life cycle. Melampsora larici-populina infects two taxonomically unrelated plants, larch on which sexual reproduction is achieved and poplar on which clonal multiplication occurs leading to severe epidemics in plantations. High-depth RNA sequencing was applied to three key developmental stages of M. larici-populina infection on larch: basidia, pycnia and aecia. Comparative transcriptomics of infection on poplar and larch hosts was performed using available expression data. Secreted protein was the only significantly over-represented category among differentially expressed M. larici-populina genes in basidia, pycnia and aecia compared together, highlighting their probable involvement in the infection process. Comparison of fungal transcriptomes in larch and poplar revealed a majority of rust genes commonly expressed on the two hosts and a fraction exhibiting a host-specific expression. More particularly, gene families encoding small secreted proteins presented striking expression profiles that highlight probable candidate effectors specialized on each host. Our results bring valuable new information about the biological cycle of rust fungi and identify genes that may contribute to host specificity.

microbiology↗