Biology subjects

Strelkov, S.

Publications and source records attributed to Strelkov, S..

4 recordsLinked to original sources

bioRxiv2026

Global population genomics and pangenome of the clubroot pathogen link clonal expansion and effector diversification to resistance breakdown in canola

Clubroot disease, caused by the obligate biotrophic protist Plasmodiophora brassicae, threatens Brassica crops worldwide. Novel pathogen virulence frequently breaks resistance in agricultural crops, and yet explanations for isolate evolution remain unknown. We combined whole genome sequencing of 192 isolates from 24 countries with a pangenome analysis of 55 high-quality complete or nearly complete genome assemblies and performed functional effector analyses to investigate potential mechanisms of virulence emergence. Three major phylogenetic clusters were identified, including two highly clonal lineages with contrasting virulence profiles, and a genetically diverse population retaining signatures of recombination. Our findings support a model in which genome-wide purifying selection maintained core genome integrity, while effector genes evolved under less constraint. Despite a compact closed pangenome, we identified chromosome 17 as a major hotspot of single nucleotide and structural variations, transposable elements and expansion of ankyrin repeat effectors. Within the variable chromosome 17, PbAnk2 alleles from virulent and avirulent isolates encoded proteins with distinct predicted structures. PbAnk2 interacted with the Arabidopsis co-chaperone DJC31 in yeast two-hybrid and BiFC assays, whereas co-immunoprecipitation did not detect an interaction for the allele found in isolates that break CRa-mediated resistance, suggesting that allelic variation may alter PbAnk2's association with DJC31. These findings reveal the clonal expansion of virulent isolates and connect it to effector diversification that led to resistance breakdown and establish a genomic framework for pathogen surveillance and durable clubroot resistance.

genomics↗

bioRxiv2023

A Hydroponic-Based Bioassay to Facilitate Plasmodiophora brassicae Phenotyping

Clubroot, caused by the obligate parasite Plasmodiophora brassicae, is one of the most devastating diseases affecting the canola/oilseed rape (Brassica napus) industry worldwide. Currently, the planting of clubroot-resistant (CR) cultivars is the most effective strategy used to restrict the spread and the economic losses linked to the disease. However, virulent P. brassicae isolates have been able to infect many of the currently available CR cultivars, and the options to manage the disease are becoming limited. Another challenge has been achieving consistency in evaluating host reactions to P. brassicae infection, with most bioassays conducted in soil and/or potting medium, which requires significant space and can be labour intensive. Visual scoring of clubroot symptom development can also be influenced by user bias. Here, we have developed a hydroponic bioassay using well-characterized P. brassicae single-spore isolates representative of clubroot virulence in Canada, as well as field isolates from three Canadian provinces, in combination with canola inbred homozygous lines carrying resistance genetics representative of CR cultivars available to growers in Canada. To improve the efficiency and consistency of disease assessment, symptom severity scores were compared with clubroot evaluations based on the scanned root area. According to the results, this bioassay offers a reliable, less expensive, and reproducible option to evaluate P. brassicae virulence, as well as a means to identify which canola resistance profile(s) may be effective against particular isolates. This bioassay will contribute to the breeding of new CR canola cultivars and the identification of virulence genes in P. brassicae that could trigger resistance and have been very elusive to this day.

microbiology↗

bioRxiv2022

Dissecting the Pyrenophora tritici-repentis (tan spot of wheat) pangenome

We sequenced the genome of a global collection (40 isolates) of the fungus Pyrenophora tritici-repentis (Ptr), a major foliar pathogen of wheat and model for the evolution of necrotrophic pathogens. Ptr exhibited an open-pangenome, with 43% of genes in the core set and 57% defined as accessory (present in only a subset of isolates), of which 56% were singleton genes (present in only one isolate). A clear distinction between pathogenic and non-pathogenic genomes was observed in size, gene content, and phylogenetic relatedness. Chromosomal rearrangements and structural organization, specifically around the effector coding genes, were explored further using the annotated genomes of two isolates sequenced by PacBio RS II and Illumina HiSeq. The Ptr genome exhibited major chromosomal rearrangements, including chromosomal fusion, translocation, and segment duplications. An intraspecies translocation of ToxA, the necrosis-inducing effector-coding gene, was facilitated within Ptr via a 143 kb Starship transposon (dubbed Horizon). Additionally, ToxB, the gene encoding the chlorosis-inducing effector, was clustered as three copies on a 294 kb transposable element in a ToxB-producing isolate. ToxB and its carrying transposon were missing from the ToxB non-coding reference isolate, but the homolog toxb and the transposon were both present in another non-coding isolate. The Ptr genome also appears to exhibit a one-compartment organization, but may still possess a two-speed genome that is facilitated by copy-number variation as reported in other fungal pathosystems. IMPORTANCEPtr is one of the most destructive wheat pathogens worldwide. Its genome is a mosaic of present and absent effectors, and serves as a model for examining the evolutionary processes behind the acquisition of virulence in necrotrophs and disease emergence. In this work, we took advantage of a diverse collection of pathogenic Ptr isolates with different global origins and applied short- and long-read sequencing technologies to dissect the Ptr genome. This study provides comprehensive insights into the Ptr genome and highlights its structural organization as an open pangenome with one-compartment. In addition, we identified the potential involvement of transposable elements in genome expansion and the movement of virulence factors. The ability of effector-coding genes to shuffle across chromosomes on large transposons was illustrated by the intraspecies translocation of ToxA and the multi-copy ToxB. In terms of gene contents, the Ptr genome exhibits a large percentage of orphan genes, particularly in non-pathogenic or weakly-virulent isolates.

genomics↗

bioRxiv2017

CCFold: Rapid And Accurate Prediction Of Coiled-Coil Structures And Application To Modelling Intermediate Filaments

Accurate molecular structure of the protein dimer representing the elementary building block of intermediate filaments (IFs) is essential towards the understanding of the filament assembly, rationalizing their mechanical properties and explaining the effect of disease-related IF mutations. The dimer contains a [~]300-residue long -helical coiled coil which is not assessable to either direct experimental structure determination or modelling using standard approaches. At the same time, coiled coils are well-represented in structural databases. Here we present CCFold, a generally applicable threading-based algorithm which produces coiled-coil models from protein sequence only. The algorithm is based on a statistical analysis of experimentally determined structures and can handle any hydrophobic repeat patterns in addition to the most common heptads. We demonstrate that CCFold outperforms general-purpose computational folding in terms of accuracy, while being faster by orders of magnitude. By combining the CCFold algorithm and Rosetta folding we generate representative dimer models for all IF protein classes. The source code is freely available at https://github.com/biocryst/IF

bioinformatics↗