Biology subjects

Symeonidi, E.

Publications and source records attributed to Symeonidi, E..

8 recordsLinked to original sources

bioRxiv2026

Biosynthetic gene clusters in Pseudomonas viridiflava have a fitness cost during Arabidopsis thaliana infection

Specialized or secondary metabolites mediate biotic interactions, including virulence and defense. In plant-pathogenic Pseudomonas, certain specialized metabolites can enhance colonization of plant hosts, yet their broader contribution to plant-microbe interactions and the relative importance of different metabolites remain unclear. Specialized metabolites are products of enzymes encoded in biosynthetic gene clusters (BGCs), whose prediction from genome sequences has become routine but whose functional roles are rarely tested experimentally. Here, we characterize the BGC repertoire of 225 P. viridiflava isolates from Arabidopsis thaliana and assess BGC contributions to fitness in planta and disease severity. The BGC landscape of P. viridiflava was dominated by non-ribosomal peptide synthetase (NRPS) and NRPS-like BGCs, with one-third of families restricted to a single isolate. Transposon mutagenesis coupled with random barcode transposon sequencing (RB-TnSeq) revealed that the majority of BGCs reduce rather than increase fitness during A. thaliana infection, with the magnitude of the fitness cost varying across host genotypes. This cost could be due to exploitation of public goods by cheater mutant strains. In single-isolate plant infections, where public goods are not available, several BGC families were negatively associated with disease severity, which is positively correlated with bacterial growth in this pathosystem, further indicating that BGCs are generally not beneficial in planta. Our findings reveal extensive and largely uncharacterized biosynthetic potential in populations of P. viridiflava and indicate that candidate metabolites are likely not adaptive for direct interactions with the plant, but perhaps for microbe-microbe interactions either in planta or in other ecological niches. IMPORTANCEBacteria living on plant leaves produce a vast array of chemical compounds, called secondary or specialized metabolites, that can mediate their interaction with the plant host or other microorganisms. Some of these compounds are known to directly influence how bacteria interact with plants, but it has been unclear whether this is a general rule. We studied a large collection of closely related leaf-dwelling bacteria that varied in their ability to cause disease, focusing on leaf-associated Pseudomonas viridiflava--a plant pathogen. We found that very few of the gene clusters responsible for making specialized metabolites improved the ability of the bacteria to colonize Arabidopsis thaliana. On the contrary, carrying these gene clusters often reduced bacterial growth and disease severity in plants. Specialized metabolites may instead primarily be important for interacting with other microbes, different host species, or under environmental conditions we did not test. These are questions that remain for future research.

microbiology↗

bioRxiv2025

Functional memory of drought affects leaf chemical defenses and microbial interactions in aspen

Drought is an increasingly important driver of tree mortality, but its long-term impacts on trait expression remain poorly understood. Leaves are a key interface at which trees respond to abiotic stress, and foliar traits such as chemical defenses and microbial communities may play an important role in determining post-drought resilience. Here, we tested whether prior-year drought leaves a persistent imprint on leaf traits in Populus tremuloides. Using a three-year common garden experiment with controlled water limitation, we measured two major classes of defensive phenolics--salicinoid phenolic glycosides (SPGs) and condensed tannins (CTs)--alongside foliar fungal community composition. SPG concentrations increased and CTs declined in response to prior-year drought, with these effects persisting across growing seasons. While overall fungal community composition remained relatively stable, we detected shifts in the relative abundance of individual amplicon sequence variants (ASVs), particularly within potentially pathogenic lineages, associated with drought history. These findings provide evidence that drought leaves a legacy in leaf chemistry and microbial colonization, with potential consequences for how trees tolerate future abiotic and biotic stress. Our results highlight the importance of incorporating foliar trait legacies into models of forest resilience under climate change. Significance StatementTrees are known to exhibit long-term responses to drought, but whether such legacy effects extend to annually renewed tissues like leaves remains unclear. Our findings reveal that prior-year drought alters both chemical defenses and microbial associations in newly formed leaves, demonstrating a form of physiological memory. This work uncovers a novel mechanism by which trees integrate past environmental stress into future interactions, with implications for understanding forest resilience under climate change.

plant biology↗

bioRxiv2025

Persistent trade-offs balance competition and colonization across centuries

Microbial competition drives rapid adaptation, often forcing organisms to specialize in new ecological niches. Adaptations that improve competitive ability can reduce performance in other environments creating trade-offs. Whether such trade-offs persist in nature--or are eroded as lineages adapt through compensatory changes--remains largely unknown. Here we show that a trade-off between competitive ability and host colonization has been stably maintained in natural Pseudomonas populations for centuries. Wild plant-pathogenic Pseudomonas compete using tailocins--phage-derived molecular weapons that bind to specific cell-surface receptors. Genomic surveys and functional assays reveal that the most broadly lethal tailocins remain rare--while the tailocins production increases competitive killing, it also compromises plant colonization. We determine that the polymorphisms behind this trade-off are not transient -- historical genomes spanning two centuries show that the trade-off has been maintained for at least 10-10 generations. Our results demonstrate that, in natural populations, a trade-off between competition and pathogenicity is fundamental and not easily overcome. SignificanceWhen a microbe colonizes a host, it must both establish infection and outcompete other organisms. Short-term experiments show that gains in competitive ability can reduce colonization, creating trade-offs, but whether microbes resolve these conflicts over long evolutionary timescales is unknown. We show that a trade-off between competitive killing and host colonization has been stably maintained for centuries in natural Pseudomonas populations infecting Arabidopsis thaliana. Tailocins--phage-derived weapons--provide strong competitive advantages, yet their production reduces colonization success, explaining why the most broadly lethal variants remain rare. Genomic surveys and historical genomes spanning two centuries reveal that the polymorphisms underlying this trade-off have persisted across 10-10 generations. Understanding such long-lived constraints can inform antimicrobial strategies that exploit evolutionary trade-offs.

evolutionary biology↗

bioRxiv2020

Unique and distinct identities and functions of leaf phloem cells revealed by single cell transcriptomics

AO_SCPLOWBSTRACTC_SCPLOWThe leaf vasculature plays a key role in solute translocation. Veins consist of at least seven distinct cell types, with specific roles in transport, metabolism, and signaling. Little is known about the vascular cells in leaves, in particular the phloem parenchyma (PP). PP effluxes sucrose into the apoplasm as a basis for phloem loading; yet PP has only been characterized microscopically. Here, we enriched vascular cells from Arabidopsis leaves to generate a single-cell transcriptome atlas of leaf vasculature. We identified [≥]19 cell clusters, encompassing epidermis, guard cells, hydathodes, mesophyll, and all vascular cell types, and used metabolic pathway analysis to define their roles. Clusters comprising PP cells were enriched for transporters, including SWEET11 and SWEET12 sucrose and UmamiT amino acid efflux carriers. PP development occurs independently from APL, a transcription factor required for phloem differentiation. PP cells have a unique pattern of amino acid metabolism activity distinct from companion cells (CC), explaining differential distribution/metabolism of amino acids in veins. The kinship relation of the vascular clusters is strikingly similar to the vein morphology, except for a clear separation of CC from the other vascular cells including PP. In summary, our scRNA-seq analysis provides a wide range of information into the leaf vasculature and the role and relationship of the leaf cell types.

plant biology↗

bioRxiv2020

CRISPR-finder: A high throughput and cost effective method for identifying successfully edited A. thaliana individuals

Background Genome editing with the CRISPR/Cas9 system allows the user to mutate a targeted region of the genome using an endonuclease (Cas9) and an artificial single-guide RNA (sgRNA). Both because of variable efficiency with which such mutations arise and because the repair process produces a spectrum of mutations, one needs to ascertain the genome sequence at the targeted locus for many individuals that have been subjected to CRISPR/Cas9 mutagenesis. This process can be laborious, expensive and inefficient with conventional methods such as the T7E1 assay or Sanger sequencing. An alternative comprises methods for amplicon sequencing, but most available protocols do not include a facile way for high throughput generation of the samples for sequencing.Results In this study we provide a full pipeline based on amplicon sequencing, CRISPR-finder. We provide a complete protocol for the generation of amplicons up until the identification of the exact mutations in the targeted region. CRISPR-finder can be used to process thousands of individuals in a single sequencing run. For example, we were able to analyze in one sequencing reaction over 900 Arabidopsis thaliana individuals whose genomes had been targeted with the CRISPR/Cas9 system.Conclusions In order to validate the potential of CRISPR-finder, we targeted the ISOCHORISMATE SYNTHASE 1 gene in A. thaliana using the CRISPR/Cas9 system. We successfully identified a mutant line in which the production of salicylic acid was impaired compared to the wild type, as expected. These features establish CRISPR-finder as a high-throughput, cost-effective and -efficient genotyping method of individuals whose genomes have been targeted using the CRISPR/Cas9 system.Competing Interest StatementThe authors have declared no competing interest.View Full Text

plant biology↗

bioRxiv2019

The relationship between microbial biomass and disease in the Arabidopsis thaliana phyllosphere

A central goal in microbiome research is to learn what distinguishes a healthy from a dysbiotic microbial community. Shifts in diversity and taxonomic composition are important indicators of dysbiosis, but a full understanding also requires knowledge of absolute microbial population sizes. In addition to the number of microbial cells, information on taxonomic composition can provide important insight into microbiome function and disease state. Here we use shotgun metagenomics to simultaneously assess microbiome composition and microbial load in the phyllosphere of wild populations of the plant Arabidopsis thaliana. We find that wild plants vary substantially in the load of colonizing microbes, and that high loads are typically associated with the proliferation of single taxa, with only a few putatively pathogenic taxa achieving high abundances in the field. Our results suggest (i) that the inside of a plant leaf is on average sparsely colonized with an estimated two bacterial genomes per plant genome and an order of magnitude fewer eukaryotic microbial genomes, and (ii) that higher levels of microbial cells often indicate successful colonization by pathogens. Lastly, our results show that load is a significant explanatory variable for loss of estimated Shannon diversity in phyllosphere microbiomes, implying that reduced diversity may be a significant predictor of microbial dysbiosis in a plant leaf.

plant biology↗

bioRxiv2019

The BIR2/BIR3-interacting Phospholipase D gamma 1 negatively regulates immunity in Arabidopsis

Plants have evolved effective strategies to defend themselves against pathogen invasion. Starting from the plasma membrane with the recognition of microbe-associated molecular patterns (MAMPs) via pattern recognition receptors, internal cellular signaling pathways are induced to ultimately fend off the attack. Phospholipase D (PLD) hydrolyzes membrane phospholipids to produce phosphatidic acid (PA), which has been proposed to play a second messenger role in immunity. The Arabidopsis PLD family consists of 12 members and for some a specific function in resistance towards a subset of pathogens has been shown. We demonstrate here that Arabidopsis PLD{gamma}1, but not its close homologs PLD{gamma}2 and PLD{gamma}3, is specifically involved in plant immunity. Genetic inactivation of PLD{gamma}1 resulted in increased resistance towards the virulent bacterium Pseudomonas syringae pv. tomato DC3000 and the necrotrophic fungus Botrytis cinerea. As pld{gamma}1 mutant plants responded with elevated levels of reactive oxygen species to MAMP-treatment, a negative regulatory function for this PLD isoform is proposed. Importantly, PA levels in pld{gamma}1 mutants were not affected compared to stressed wild-type plants, suggesting that alterations in PA levels are unlikely the cause for the enhanced immunity in the pld{gamma}1 line. Instead, the plasma-membrane-attached PLD{gamma}1 protein colocalized and associated with the receptor-like kinases BIR2 and BIR3, which are known negative regulators of pattern-triggered immunity. Moreover, complex formation of PLD{gamma}1 and BIR2 was further promoted upon MAMP-treatment. Hence, we propose that PLD{gamma}1 acts as a negative regulator of plant immune responses in complex with immunity-related proteins BIR2 and BIR3.\n\nOne-sentence summaryA phospholipase D is a novel negative regulator of plant immunity and forms complexes with regulatory receptor-like kinases.

plant biology↗

bioRxiv2017

A rainfall-manipulation experiment with 517 Arabidopsis thaliana accessions

The gold standard for studying natural selection and adaptation in the wild is to quantify lifetime fitness of individuals from natural populations that have been grown together in a common garden, or that have been reciprocally transplanted. By combining fitness values with species traits and genome sequences, one can infer selection coefficients at the genetic level. Here we present a rainfall-manipulation experiment with 517 whole-genome sequenced natural accessions of the plant Arabidopsis thaliana spanning the global distribution of the species. The experiments were conducted in two field stations in contrasting climates, in the Mediterranean and in Central Europe, where we built rainout shelters and simulated high and low rainfall. Using custom image analysis we quantified fitness- and phenology-related traits for 23,154 pots, which contained about 14,500 plants growing independently, and over 310,000 plants growing in small populations (max. 30 plants). This large field experiment dataset, which associates fitness and ecologically-relevant traits with genomes, will provide an important resource to test eco-evolutionary genetic theories and to understand the potential evolutionary impacts of future climates on an important plant model species.

evolutionary biology↗