Biology subjects

Schornack, S.

Publications and source records attributed to Schornack, S..

25 records · Page 2Linked to original sources

bioRxiv2019

The genome of Peronospora belbahrii reveals high heterozygosity, a low number of canonical effectors and CT-rich promoters

Along with Plasmopara destructor, Peronosopora belbahrii has arguably been the economically most important newly emerging downy mildew pathogen of the past two decades. Originating from Africa, it has started devastating basil production throughout the world, most likely due to the distribution of infested seed material. Here we present the genome of this pathogen and results from comparisons of its genomic features to other oomycetes. The assembly of the nuclear genome was ca. 35.4 Mbp in length, with an N50 scaffold length of ca. 248 kbp and an L50 scaffold count of 46. The circular mitochondrial genome consisted of ca. 40.1 kbp. From the repeat-masked genome 9049 protein-coding genes were predicted, out of which 335 were predicted to have extracellular functions, representing the smallest secretome so far found in peronosporalean oomycetes. About 16 % of the genome consists of repetitive sequences, and based on simple sequence repeat regions, we provide a set of microsatellites that could be used for population genetic studies of Pe. belbahrii. Peronospora belbahrii has undergone a high degree of convergent evolution, reflecting its obligate biotrophic lifestyle. Features of its secretome, signalling networks, and promoters are presented, and some patterns are hypothesised to reflect the high degree of host specificity in Peronospora species. In addition, we suggest the presence of additional virulence factors apart from classical effector classes that are promising candidates for future functional studies.

genomics↗

bioRxiv2019

Centrin-anchored hydrodynamic shape changes underpin active nuclear rerouting in branched hyphae of an oomycete pathogen

Polyenergid fungi and oomycetes are phylogenetically distant but structurally similar. To address whether they share similar nuclear dynamics we carried out time-lapse imaging of fluorescently labelled Phytophthora palmivora nuclei. Nuclei underwent coordinated bi-directional movements during plant infection. Within hyphal networks growing in planta or in axenic culture nuclei are either dragged passively with the cytoplasm or actively become rerouted toward nuclei-depleted hyphal sections and often display a very stretched shape. Benomyl-induced depolymerization of microtubules reduced active movements and the occurrence of stretched nuclei. A centrosome protein localized at the leading end of stretched nuclei, suggesting that like fungi astral microtubule-guided movements contribute to nuclear distribution within oomycete hyphae. The remarkable hydrodynamic shape adaptations of Phytophthora nuclei contrast those in fungi and likely enable them to migrate over longer distances. Therefore, our work summarises mechanisms which enable a near equal nuclear distribution in an oomycete. We provide a basis for computational modelling of hydrodynamic nuclear deformation within branched tubular networks.

cell biology↗

bioRxiv2019

Mucoromycotina fine root endophyte fungi form nutritional mutualisms with vascular plants.

Fungi and plants have engaged in intimate symbioses that are globally widespread and have driven terrestrial biogeochemical processes since plant terrestrialisation >500 Mya. Recently, hitherto unknown nutritional mutualisms involving ancient lineages of fungi and non-vascular plants have been discovered. However, their extent and functional significance in vascular plants remains uncertain. Here, we provide first evidence of abundant carbon-for-nitrogen exchange between an early-diverging vascular plant (Lycopodiaceae) and Mucoromycotina (Endogonales) fine root endophyte regardless of changes in atmospheric CO2 concentration. Furthermore, we provide evidence that the same fungi also colonize neighbouring non-vascular and flowering plants. These findings fundamentally change our understanding of the evolution, physiology, interrelationships and ecology of underground plant-fungal symbioses in terrestrial ecosystems by revealing an unprecedented nutritional role of Mucoromycotina fungal symbionts in vascular plants.

plant biology↗

bioRxiv2018

Glycerol phosphate acyltransferase 6 controls filamentous pathogen interactions and cell wall properties of the tomato and Nicotiana benthamiana leaf epidermis

The leaf epidermal wall is covered by a cuticle, composed of cutin and waxes, which protects against dehydration and constitutes a barrier against pathogen attack. Cutin monomers are formed by the transfer of 16- or 18-carbon fatty acids to glycerol by glycerol-3-phosphate acyltransferase (GPAT) enzymes, which facilitates their transport to the plant surface. Here we address the dual functionality of pathogen-inducible Glycerol phosphate acyltransferase 6 (GPAT6) in controlling pathogen entry and dehydration in leaves. Silencing of Nicotiana benthamiana NbGPAT6a increased leaf susceptibility to the oomycetes Phytophthora infestans and P. palmivora, whereas stable overexpression of NbGPAT6a-GFP rendered leaves more resistant to infection. A loss-of-function mutation of the orthologous gene in tomato (Solanum lycopersicum), SlGPAT6, similarly resulted in increased susceptibility of leaves to Phytophthora infection concomitant with altered intracellular infection structure morphology. Conversely, Botrytis cinerea disease symptoms were reduced. Modulation of GPAT6 expression predominantly altered the outer cell wall of leaf epidermal cells. The impaired cell wall-cuticle continuum of tomato gpat6-a mutants resulted in increased water loss and these plants had fewer stomata. Our work highlights a hitherto unknown role for GPAT6-generated cutin monomers in controlling epidermal cell properties that are integral to leaf-microbe interactions and limit dehydration.

plant biology↗

bioRxiv2018

Enhanced resistance to bacterial and oomycete pathogens by short tandem target mimic RNAs in tomato

Nucleotide binding site leucine-rich repeat (NLR) proteins of the plant innate immune system are negatively regulated by the miR482/2118 family microRNAs (miRNAs) that are in a distinct 22nt class of miRNAs with a double mode of action. First they cleave the target RNA, as with the canonical 21nt miR-NAs, and second they trigger secondary siRNA production using the target RNA as a template. Here we address the extent to which the miR482/2118 family affects expression of NLR mR-NAs and disease resistance. First we show that structural differences of miR482/2118 family members in tomato (Solanum lycopersicum) are functionally significant. The predicted target of the miR482 subfamily is conserved motif in multiple NLR mRNAs whereas, for miR2118b, it is a novel non-coding RNA target formed by rearrangement of several different NLR genes. From RNA sequencing and degradome data in lines expressing short tandem target mimic (STTM) RNAs of miR482/2118 we confirm the different targets of these miRNAs. The effect on NLR mRNA accumulation is slight but, nevertheless, the tomato STTM lines display enhanced resistance to infection with the oomycete and bacterial pathogens. These data implicate an RNA cascade of miRNAs and secondary siRNAs in the regulation of NLR RNAs and show that the encoded NLR proteins have a role in quantitative disease resistance in addition to dominant gene resistance that has been well characterized elsewhere. We also illustrate the use of STTM RNA in a biotechnological approach for enhancing quantitative disease resistance in highly bred cultivars.

plant biology↗

bioRxiv2017

Phytophthora palmivora establishes tissue-specific intracellular infection structures in the earliest divergent land plant lineage

The expansion of plants onto land was a formative event that brought forth profound changes to the Earths geochemistry and biota. Filamentous eukaryotic microbes developed the ability to colonize plant tissues early during the evolution of land plants, as demonstrated by intimate symbiosis-like associations in >400 million-year-old fossils. However, the degree to which filamentous microbes establish pathogenic interactions with early divergent land plants is unclear. Here, we demonstrate that the broad host-range oomycete pathogen Phytophthora palmivora colonizes liverworts, the earliest divergent land plant lineage. We show that P. palmivora establishes a complex tissue-specific interaction with Marchantia polymorpha, where it completes a full infection cycle within air chambers of the dorsal photosynthetic layer. Remarkably, P. palmivora invaginates M. polymorpha cells with haustoria-like structures that accumulate host cellular trafficking machinery and the membrane-syntaxin MpSYP13B but not the related MpSYP13A. Our results indicate that the intracellular accommodation of filamentous microbes is an ancient plant trait that is successfully exploited by pathogens like P. palmivora.

plant biology↗

bioRxiv2017

Time-resolved dual root-microbe transcriptomics reveals early induced Nicotiana benthamiana genes and conserved infection-promoting Phytophthora palmivora effectors

BackgroundPlant-pathogenic oomycetes are responsible for economically important losses on crops worldwide. Phytophthora palmivora, a broad-host-range tropical relative of the potato late blight pathogen, causes rotting diseases in many important tropical crops including papaya, cocoa, oil palm, black pepper, rubber, coconut, durian, mango, cassava and citrus.\n\nTranscriptomics have helped to identify repertoires of host-translocated microbial effector proteins which counteract defenses and reprogram the host in support of infection. As such, these studies have helped understanding of how pathogens cause diseases. Despite the importance of P. palmivora diseases, genetic resources to allow for disease resistance breeding and identification of microbial effectors are scarce.\n\nResultsWe employed the model plant N. benthamiana to study the P. palmivora root infections at the cellular and molecular level. Time-resolved dual transcriptomics revealed different pathogen and host transcriptome dynamics. De novo assembly of P. palmivora transcriptome and semi-automated prediction and annotation of the secretome enabled robust identification of conserved infection-promoting effectors. We show that one of them, REX3, suppresses plant secretion processes. In a survey for early transcriptionally activated plant genes we identified a N. benthamiana gene specifically induced at infected root tips that encodes a peptide with danger-associated molecular features.\n\nConclusionsThese results constitute a major advance in our understanding of P. palmivora diseases and establish extensive resources for P. palmivora pathogenomics, effector-aided resistance breeding and the generation of induced resistance to Phytophthora root infections. Furthermore, our approach to find infection relevant secreted genes is transferable to other pathogen-host interactions and not restricted to plants.

plant biology↗