Biology subjects

Schornack, S.

Publications and source records attributed to Schornack, S..

At least 19 recordsLinked to original sources

bioRxiv2026

Structural modeling uncovers diverse predicted transcriptional and post-transcriptional modulators among type III effectors of symbiotic Rhizobia

Rhizobia are soil bacteria that establish nitrogen-fixing symbioses with legumes. While many rhizobia use a Type III Secretion System to deliver "Nodulation Outer Protein" (Nop) effectors, some uniquely use these proteins to initiate nodule organogenesis, bypassing classical signalling. The molecular functions of these effectors remain largely unknown due to extreme sequence divergence. Using AlphaFold2-mediated structural proteomics, we identified a modular architecture in rhizobial effectors composed of 22 distinct structural units. We reveal that many Nop effectors are cryptic transcriptional or post-transcriptional regulators, harbouring unrecognised nucleic acid-binding modules and RNA-dependent RNA polymerase domains. Crucially, these modules are conserved in specific plant pathogens, such as gall-inducing Pantoea, where our predicted structural units align with experimentally validated DNA-binding domains. Furthermore, we discovered the BPN (B3 and PUA-like nucleic acid binding) domain as a structural mimic of plant B3-domain transcription factors, pointing to a direct mechanism for hijacking legume development. Our findings strongly suggest that rhizobia employ a modular domain-fusion strategy to act as direct genetic modulators, uncovering a conserved mechanism used by both symbionts and pathogens to hijack host developmental programmes.

microbiology↗

bioRxiv2026

Exploring the large-scale properties of a protein secondary structure genotype-to-phenotype map

We perform a large-scale computational characterization of the map of protein primary to secondary structure using an AVR3a class protein effector domain from the plant pathogen P. palmivora as a case study. We formulate a modified site-scanning approach for exploring the neutral component of secondary structure phenotypes based on predictions from the machine-learning algorithm Porter 5 and apply it to the AVR3a phenotype. We predict a set of sensitive sites within the effector domain that are generally located at or near the boundaries of structured regions, with restrictions on the possible amino acid residues at these sites dictated by the secondary structure type that they participate in within the WT. We characterize a set of mutated phenotypes derived through the exploration of the neutral component of the WT effector domain, selecting them so that they span a range including both very rarely and very commonly seen secondary structures, and that they include both secondary structures nearly identical to the WT and ones far removed from it. We find that all these diverse phenotypes have an estimated robustness of the same order as that of the WT, and that the robustness scales logarithmically phenotype frequency, as seen in other genotype-to-phenotype maps. Furthermore, we observe that the dependence of the estimated phenotype frequency on the Kolmogorov complexity indicates simplicity bias in the protein secondary structure map.

biophysics↗

bioRxiv2026

Engineering quantitative root disease resistance in barley by targeting conserved SCAR susceptibility genes without compromising seed yield or mycorrhizal symbiosis

Durable resistance to soil-borne pathogens remains elusive in cereals, partly because susceptibility (S) genes that facilitate root infection have not been identified in monocots. In the model legume Medicago truncatula, the SCAR/WAVE complex member MtAPI functions as a root S-gene for microbial invasion. Whether SCAR gene associated susceptibility function is conserved in monocots, and whether SCAR gene inactivation can enhance root resistance in cereals, remains unknown. Here, we identify and characterize three SCAR genes in barley: HvSCAR-A, HvSCAR-B, and HvSCAR-C. Cross-species complementation assays indicate that HvSCAR-B and HvSCAR-C are functionally similar to MtAPI. While hscar-b and hvscar-c single mutants exhibited no major growth defects, hvscar-a mutants showed strongly reduced seed production, and a hvscar-b/c double mutant displayed shorter root hairs. Notably, the hvscar-b/c double mutant exhibited increased resistance to the hemibiotrophic pathogen Phytophthora palmivora but greater colonization by the symbiotic arbuscular mycorrhizal fungus Funneliformis mosseae, underscoring a complex role in plant root - microbe interactions. Our findings reveal a conserved susceptibility function of SCAR genes in monocots and identify api monocot homologs as promising targets for engineering disease resistance in cereals. This study offers new insights into SCAR protein functional diversification and its potential for improving root health in crop plants.

plant biology↗

bioRxiv2026

MycorrhizaFinder: an efficient machine learning tool to quantify endomycorrhizal colonisation of real-world roots

AbstractO_ST_ABSBackground and aimsC_ST_ABSRoot colonisation by endomycorrhizal fungi has long been one of the most widely used metrics in mycorrhizal studies. However, due to the significant time required to assess colonisation using traditional microscope techniques, studies of colonisation at large scales are impractical. AI-powered approaches may increase output and facilitate ecosystem assessments. MethodsWe trained an AI-powered tool (MycorrhizaFinder) on field roots from diverse grasslands and heathlands hosting common Northern European plants with a range of arbuscular (AM) and ericoid mycorrhizal (ErM) fungal structures, and dark septate endophytes (DSE), also common in field-sourced roots. We incorporated a user-customized confidence threshold to encourage the user to engage with inevitable morphological ambiguities, in e.g. ErM and DSE. A Macro F1 statistic was used to assess the tools development. ResultsWe provide a sample workflow from root processing and microscope slide scanning to semi-automated model training and performance evaluation. Without human supervision, our automated baseline Macro F1 is 66% for arbuscular and at 57% for ericoid mycorrhizal colonisation assessment. ConclusionMycorrhizaFinder is user friendly, requires no programming skills and offers flexibility for advanced agronomists or ecologists who wish to train the tool using their own labelled mycorrhizal root datasets, including images acquired from different instruments or staining protocols. This adaptability allows users to customize the model for specific ecosystems or experimental designs. Leveraged with molecular identification and/or functional assessment of fungi, MycorrhizaFinder could support scalable and repeatable monitoring across ecosystems to assess mycorrhizal status and track land-use changes over time.

ecology↗

bioRxiv2026

Deep learning enables quantitative subcellular analysis of plant-microbe interfaces

Specialized host-microbe interfaces are central to cellular interactions in plants. Intracellular structures such as haustoria formed by filamentous pathogens mediate nutrient exchange and effector delivery to host cells. Despite their biological importance, the lack of quantitative frameworks has largely confined the study of these interfaces to qualitative observations, limiting our ability to compare infection strategies, cellular responses, and spatial organization across cells and tissues. Here, we present HFinder, a deep learning-based framework for automated detection, segmentation, and quantitative analysis of plant-microbe interfaces in confocal images. Using an object-centric deep learning approach, HFinder enables robust identification of haustoria, microbial hyphae, and host organelles across diverse imaging conditions and pathosystems. We demonstrate that this framework supports quantitative analyses of subcellular processes at host-microbe interfaces, including effector secretion, perturbation of host cellular processes, and immune receptor accumulation at haustoria. HFinder provides a practical and scalable solution for the systematic digitalization of plant infection imaging data and establishes a general framework for quantitative studies of cellular dynamics at host-microbe contact zones.

cell biology↗

bioRxiv2025

Microscopical and molecular characterization of the infection cycle of Phytophthora betacei during disease development on tree tomato (Solanum betaceum).

Phytophthora betacei is a recently described oomycete plant pathogen closely related to Phytophthora infestans sensu stricto. This plant pathogen naturally infects tree tomato (Solanum betaceum) but has not been reported on tomatoes and potatoes, the primary hosts of P. infestans. The aim of this study was to characterize the infection cycle of P. betacei using microscopy and molecular approaches. Several strains were inoculated in susceptible tree tomato plants and disease progression was monitored via six epidemiological parameters. Although different P. betacei strains displayed a highly variable disease phenotype, the most aggressive one was chosen for further plant inoculations. Samples at different time points of the infection cycle were analyzed at the cellular level via light and scanning electron microscopy (SEM) and at the molecular level via qRT-PCR of infection-stage-specific markers. The infection cycle of P. betacei differed from that of P. infestans in having a longer biotrophic stage, larger lesions, and higher sporulation capacity. Additionally, P. betacei transcriptomic profiles were monitored along the infection cycle via RNAseq and evidenced a changing expression landscape that supports an elongated hemibiotrophic transition and a clear distinction from what is being expressed in the mycelium or the sporangia. This study provides novel insights into the interaction between P. betacei and S. betaceum.

plant biology↗

bioRxiv2025

Mutualist-pathogen co-colonisation modulates phosphoinositide signatures at host intracellular interfaces

The host membrane that surrounds intracellular microbes forms a critical interface influencing whether interactions result in mutualism or pathogenesis. While phosphoinositide identities differ between pathogen and mutualist interface membranes, it is unclear if these are modulated during co-colonisation. To address this, we generated Nicotiana benthamiana plants expressing biosensors for PI4P and PI(4,5)P2 and imaged root colonisation by the pathogenic oomycete Phytophthora palmivora and the mutualistic fungus Funneliformis mosseae. Binary host-microbe interactions revealed distinct patterns: PI(4,5)P2 was tip-enriched at mutualist structures but evenly distributed around pathogen structures, while PI4P was absent from pathogen-associated membranes but present at mutualist interfaces. Strikingly, co-colonisation altered host membrane identity, triggering PI4P recruitment at pathogen haustoria, and enhanced resistance to P. palmivora. These findings reveal that phosphoinositide signatures distinguish pathogenic and mutualistic interfaces and are dynamically remodelled during co-colonisation, likely influencing interaction outcomes. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=105 SRC="FIGDIR/small/661106v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@9c0024org.highwire.dtl.DTLVardef@1cd5b98org.highwire.dtl.DTLVardef@138938dorg.highwire.dtl.DTLVardef@15f2633_HPS_FORMAT_FIGEXP M_FIG C_FIG

plant biology↗

bioRxiv2025

An ancient plant symbiotic fungus with distinct features identified through advanced fluorescence and Raman imaging

Mycorrhizal associations between fungi and plants are a fundamental aspect of terrestrial ecosystems. The occurrence of mycorrhizae is now well established in c. 85% of extant plants, yet the geological record of these associations is sparse. Fossil evidence from early Paleozoic terrestrial environments provides rare insights into these ancient symbioses, but imaging micro-scale fossil fungi in surrounding plant tissues is challenging. We employed brightfield microscopy, confocal laser scanning microscopy (CLSM), fluorescence lifetime imaging microscopy (FLIM), and Raman spectroscopy to investigate a newly identified endomycorrhizal fungus within a 407-million-year-old plant from the Windyfield Chert. An exquisite preservation and our advanced imaging approach enabled the description of the fungal structures to unprecedented detail. The fungus, Rugosomyces lavoisieriae gen. nov., & sp. nov., exhibits structural features resembling modern Glomeromycotina arbuscular mycorrhizal fungi. Combining CLSM with FLIM provides extra information by separating features based upon fluorescence lifetime. Raman spectroscopy indicates that fungal arbuscules and plant water-conducting cells have undergone geological alterations, resulting in a similar chemical composition. These findings enhance our understanding of ancient plant-fungal symbioses and demonstrate the potential of advanced imaging techniques in paleobotanical research. Significance statementMost living plants form mycorrhizal associations with fungi, but how this ancient evolutionary relationship developed is poorly understood. Exceptional fossil materials preserve direct evidence of endomycorrhizae, but imaging micro-scale fossil fungi inside plant cells is challenging. Here we use confocal microscopy combined with fluorescence lifetime imaging and Raman spectroscopy to study a new endomycorrhizal fungus inside a 400-million-year-old plant. We document structures resembling modern Glomeromycotina. We show that the residual organic matter of the fungus and the plant cell walls has a very short fluorescence lifetime, which provides a new means of imaging these fossils. Raman spectroscopy indicates that both arbuscules and water-conducting cells were geologically altered by their diagenetic history and that they now have a similar chemical composition.

plant biology↗

bioRxiv2025

An approach to enhance symbiotic nitrogen fixation

Through symbiosis with nitrogen-fixing bacteria, cultivated legumes provide themselves and subsequent crops with nitrogen, making genetic improvements of symbiotic efficiency particularly attractive. Here, we identify the symbiosis-specific GBP1 gene which negatively regulates nitrogen fixation by attenuating bacterial nitrogenase activity in Medicago truncatula nodules. GBP1 inactivation increases nitrogen fixation without affecting nodule development and numbers, providing inroads for engineering legumes with increased productivity for sustainable nitrogen provision.

plant biology↗

bioRxiv2024

An environment-responsive SCLA-type GRAS protein controls reproductive strategy in Marchantia polymorpha

By controlling their reproductive strategies, plants strike a balance between generating genetic diversity or maintaining stability, promoting long-term survival in a range of environmental conditions. The liverwort Marchantia polymorpha propagates clonally through vegetative gemmae or via sexually generated spores, but our understanding of the genetic pathways underpinning reproductive decision-making is limited. GRAS transcriptional regulators are highly conserved proteins across land plants, with diverse functionality in stress and development. Here, we discover a central role for the SCLA-type transcription regulator MpGRAS7 in both stress signalling and reproduction in Marchantia. MpGRAS7 is highly expressed in gemma cups and gametangiophores and is activated in response to Far Red (FR) light and abscisic acid (ABA) environmental cues. Genetic dissection further suggests MpGRAS7 is required to maintain gemma dormancy, gemma cup frequency, and FR-induced gametangiophore development. The sequence conservation and expression patterns of MpGRAS7 orthologs in flowering plants hints towards the broader function of SCLA-type GRAS proteins in stress-regulated developmental transitions in plants.

plant biology↗

bioRxiv2024

A molecular basis for plant SCAR/WAVE functional divergence

Dynamic actin cytoskeleton reorganisation enables plant developmental processes requiring polarised transport such as root hair and leaf trichome formation. The SCAR/WAVE complex plays a crucial role in regulating these dynamics through ARP2/3-mediated actin branching. SCAR/WAVE genes occur as small families across a wide range of plant species but whether and how they fulfil different functions remains unclear. We utilise a systematic chimaera approach to define the differential functionality of two closely related Medicago truncatula SCAR proteins in plant development. We show that SCAR/WAVE contribution to Medicago truncatula root hair or Arabidopsis thaliana trichome formation is dependent on two central intrinsically disordered regions (IDRs). Differential functionalities of Medicago truncatula SCAR proteins were furthermore associated with the presence/absence of a 42-amino acid sequence within the IDR that impacted protein stability. Through uncovering a molecular basis for functional differences, we advance our understanding of plant SCAR/WAVE complexes. One Sentence SummaryIntrinsically disordered regions in SCAR/WAVE proteins drive diverse functions in root hair and leaf trichome development.

plant biology↗

bioRxiv2024

An oomycete effector co-opts a host RabGAP protein to remodel pathogen interface and subvert defense-related secretion

Pathogens have evolved sophisticated mechanisms to manipulate host cell membrane dynamics, a crucial adaptation to survive in hostile environments shaped by innate immune responses. Plant- derived membrane interfaces, engulfing invasive hyphal projections of fungal and oomycete pathogens, are prominent junctures dictating infection outcomes. Understanding how pathogens transform these host-pathogen interfaces to their advantage remains a key biological question. Here, we identified a conserved effector, secreted by plant pathogenic oomycetes, that co-opts a host Rab GTPase-activating protein (RabGAP), TBC1D15L, to remodel the host-pathogen interface. The effector, PiE354, hijacks TBC1D15L as a susceptibility factor to usurp its GAP activity on Rab8a--a key Rab GTPase crucial for defense-related secretion. By hijacking TBC1D15L, PiE354 purges Rab8a from the plasma membrane, diverting Rab8a-mediated immune trafficking away from the pathogen interface. This mechanism signifies an uncanny evolutionary adaptation of a pathogen effector in co- opting a host regulatory component to subvert defense-related secretion, thereby providing unprecedented mechanistic insights into the reprogramming of host membrane dynamics by pathogens.

plant biology↗

bioRxiv2023

The Marchantia pangenome reveals ancient mechanisms of plant adaptation to the environment

Plant adaptation to a terrestrial life 450 million years ago played a major role in the evolution of life on Earth. This shift from an aquatic environment has been mostly studied by focusing on flowering plants. Here, we gathered a collection of 133 accessions of the non-vascular plants Marchantia polymorpha and studied its intraspecific diversity using selection signature analyses, genome-environment association study and a gene-centered pangenome. We identified adaptive features shared with flowering plants, such as peroxidases or nucleotide-binding and leucine-rich repeat (NLR), which likely played a role in the adaptation of the first land plants to the terrestrial habitat. The M. polymorpha pangenome also harbored lineage-specific accessory genes absent from seed plants. We conclude that different land plants lineages still share many elements from the genetic toolkit evolved by their most recent common ancestor to adapt to the terrestrial habitat, refined by lineage specific polymorphisms and gene family evolutions.

plant biology↗

bioRxiv2022

A pathogen effector FOLD diversified in symbiotic fungi

Pathogenic fungi use secreted effector proteins to suppress immunity and support their infection, but effectors have also been reported from fungi that engage in nutritional symbioses with plants. Sequence based effector comparisons between pathogens and symbiotic arbuscular mycorrhizal (AM) fungi are hampered by the huge diversity of effector sequences even within closely related microbes. Here we used a systematic protein structure modelling approach to classify the secretome of the AM fungus Rhizophagus irregularis. We identified secreted proteins with high structural similarity to Fusarium oxysporum f. sp. lycopersici dual domain (FOLD) effectors, which occur in low numbers in fungal pathogen genomes. Contrastingly, genes encoding FOLD proteins from AM fungi (MycFOLDs) are found in enlarged and diversified gene families. Our structure-model comparison suggests that MycFOLDs are similar to carbohydrate binding motifs. Different MycFOLD genes are expressed during colonisation of different hosts and MycFOLD-17 transcripts accumulate in plant intracellular arbuscules. The exclusive presence of MycFOLDs across unrelated plant-colonising fungi, their inducible expression, lineage specific sequence diversification, and transcripts in arbuscules support the hypothesis that FOLD proteins act as effectors during plant colonisation by symbiotic and pathogenic fungi.

microbiology↗

bioRxiv2021

Transcriptional activity and epigenetic regulation of transposable elements in the symbiotic fungus Rhizophagus irregularis

Arbuscular mycorrhizal (AM) fungi form mutualistic relationships with most land plant species and have long been considered as ancient asexuals. Long-term clonal evolution would be remarkable for a eukaryotic lineage and suggests the importance of alternative mechanisms to promote genetic variability facilitating adaptation. Here, we assessed the potential of transposable elements (TEs) for generating genomic diversity. The dynamic expression of TEs during Rhizophagus irregularis spore development suggests ongoing TE activity. We find Mutator-like elements located near genes belonging to highly expanded gene families. Characterising the epigenomic status of R. irregularis provides evidence of DNA methylation and small RNA production occurring at TE loci. Our results support a potential role for TEs in shaping the genome, and roles for DNA methylation and small RNA-mediated silencing in regulating TEs. A well-controlled balance between TE activity and repression may therefore contribute to genome evolution in AM fungi.

genomics↗

bioRxiv2021

Artificial intelligence enables the identification and quantification of arbuscular mycorrhizal fungi in plant roots

Soil fungi establish mutualistic interactions with the roots of most vascular land plants. Arbuscular mycorrhizal (AM) fungi are among the most extensively characterised mycobionts to date. Current approaches to quantifying the extent of root colonisation and the abundance of hyphal structures in mutant roots rely on staining and human scoring involving simple, yet repetitive tasks prone to variations between experimenters. We developed AMFinder which allows for automatic computer vision-based identification and quantification of AM fungal colonisation and intraradical hyphal structures on ink-stained root images using convolutional neural networks. AMFinder delivered high-confidence predictions on image datasets of roots of multiple plant hosts (Nicotiana benthamiana, Medicago truncatula, Lotus japonicus, Oryza sativa) and captured the altered colonisation in ram1-1, str and smax1 mutants. A streamlined protocol for sample preparation and imaging allowed us to quantify mycobionts from the genera Rhizophagus, Claroideoglomus, Rhizoglomus and Funneliformis via flatbed scanning or digital microscopy including dynamic increases in colonisation in whole root systems over time. AMFinder adapts to a wide array of experimental conditions. It enables accurate, reproducible analyses of plant root systems and will support better documentation of AM fungal colonisation analyses. AMFinder can be accessed here: https://github.com/SchornacklabSLCU/amfinder.git

plant biology↗

bioRxiv2020

Host-interactor screens of Phytophthora infestans RXLR proteins reveal vesicle trafficking as a major effector-targeted process

Pathogens modulate plant cell structure and function by secreting effectors into host tissues. Effectors typically function by associating with host molecules and modulating their activities. This study aimed to identify the host processes targeted by the RXLR class of host-translocated effectors of the potato blight pathogen Phytophthora infestans. To this end, we performed an in planta protein-protein interaction screen by transiently expressing P. infestans RXLR effectors in Nicotiana benthamiana leaves followed by co-immunoprecipitation (co-IP) and liquid chromatography tandem mass spectrometry (LC-MS/MS). This screen generated an effector-host protein interactome matrix of 59 P. infestans RXLR effectors x 586 N. benthamiana proteins. Classification of the host interactors into putative functional categories revealed over 35 biological processes possibly targeted by P. infestans. We further characterized the PexRD12/31 family of RXLR-WY effectors, which associate and co-localize with components of the vesicle trafficking machinery. One member of this family, PexRD31, increased the number of FYVE positive vesicles in N. benthamiana cells. FYVE positive vesicles also accumulated in leaf cells near P. infestans hyphae, indicating that the pathogen may enhance endosomal trafficking during infection. We anticipate that the interactome dataset we generated will serve as a useful community resource for functional studies of P. infestans effectors and of effector-targeted host processes.

plant biology↗

bioRxiv2020

The Irish potato famine pathogen subverts host vesicle trafficking to channel starvation-induced autophagy to the pathogen interface

Eukaryotic cells deploy autophagy to eliminate invading microbes. In turn, pathogens have evolved effector proteins to counteract antimicrobial autophagy. How and why adapted pathogens co-opt autophagy for their own benefit is poorly understood. The Irish famine pathogen Phythophthora infestans secretes the effector protein PexRD54 that selectively activates an unknown plant autophagy pathway, while antagonizing antimicrobial autophagy. Here we show that PexRD54 induces autophagosome formation by bridging small GTPase Rab8a-decorated vesicles with autophagic compartments labelled by the core autophagy protein ATG8CL. Rab8a is required for pathogen-triggered and starvation-induced but not antimicrobial autophagy, revealing that specific trafficking pathways underpin selective autophagy. We discovered that Rab8a contributes to basal immunity against P. infestans, but PexRD54 diverts a sub-population of Rab8a vesicles to lipid droplets that associate with autophagosomes. These are then diverted towards pathogen feeding structures that are accommodated within the host cells. We propose that PexRD54 mimics starvation-induced autophagy by channeling host endomembrane trafficking towards the pathogen interface possibly to acquire nutrients. This work reveals that effectors can interconnect independent host compartments to stimulate complex cellular processes that benefit the pathogen. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/000117v1_ufig1.gif" ALT="Figure 1"> View larger version (83K): org.highwire.dtl.DTLVardef@bfc9fforg.highwire.dtl.DTLVardef@166b5f8org.highwire.dtl.DTLVardef@34d581org.highwire.dtl.DTLVardef@ad397f_HPS_FORMAT_FIGEXP M_FIG C_FIG

plant biology↗