Project description:Sclerotinia sclerotiorum, the causal agent of white mould, is a necrotrophic fungal pathogen responsible for extensive crop loss. Current control options rely heavily on the application of chemical fungicides that are becoming less effective and may lead to the development of fungal resistance. In the current study, we used a foliar spray application of boron to protect Brassica napus (canola) from S. sclerotiorum infection using whole plant infection assays. Application of boron to aerial surfaces of the canola plant reduced the number of S. sclerotiorum forming lesions by 87% compared to an untreated control. We used dual RNA sequencing to profile the effect of boron on both the host plant and fungal pathogen during the infection process. Differential gene expression analysis and gene ontology term enrichment further revealed the mode of action of a foliar boron spray at the mRNA level. A single foliar application of boron primed the plant defense response through the induction of genes associated with systemic acquired resistance while an application of boron followed by S. sclerotiorum infection induced genes associated with defense-response-related cellular signalling cascades. Additionally, in S. sclerotiorum inoculated on boron-treated B. napus, we uncovered gene activity in response to salicylic acid breakdown, consistent with salicylic-acid-dependent systemic acquired resistance induction within the host plant. Taken together, this study demonstrates that a foliar application of boron results in priming of the B. napus plant defense response, likely through systemic acquired resistance, thereby contributing to increased tolerance to S. sclerotiorum infection.
Project description:The host range of parasites is an important factor in assessing the dynamics of disease epidemics. The evolution of pathogens to accommodate new hosts may lead to host range expansion, a process the molecular bases of which are largely enigmatic. The fungus Sclerotinia sclerotiorum parasitizes more than 400 plant species from diverse eudicot families while its close relative, S. trifoliorum, is restricted to plants from the Fabaceae family. We analyzed S. sclerotiorum global transcriptome reprogramming on hosts from six botanical families and reveal a flexible, host-specific transcriptional program driven by core and host-response co-expression (SPREx) gene clusters. We generated a chromosome-level genome assembly for S. trifoliorum and found near-complete gene space conservation in broad and narrow host range Sclerotinia species. However, S. trifoliorum showed increased sensitivity to the Brassicaceae defense compound camalexin. Inter-specific transcriptome analyses revealed a lack of transcriptional response to camalexin in S. trifoliorum and provide evidence that cis-regulatory variation associates with the genetic accommodation of Brassicaceae in the Sclerotinia host range. Our work demonstrates adaptive plasticity of a broad host range pathogen with specific responses to different host plants and demonstrates the co-existence of signatures for generalist and polyspecialist life styles in the genome of a plant pathogen. We reason that this mechanism enables the emergence of new disease with no or limited gene flow between strains and species, and could underlie the emergence of new epidemics originating from wild plants in agricultural settings.
Project description:Sclerotinia sclerotiorum, a necrotrophic fungal pathogen with a broad host range, causes a devastating disease on soybean called Sclerotinia stem rot (SSR), can lead to losses as high as 50-60%. Resistance mechanisms against SSR are poorly understood. We used high throughput RNAseq approach to decipher the molecular mechanisms governing resistance to S. sclerotiorum in soybean. Transcripts of recombinant inbred lines (RILs) of soybean; susceptible (S) and resistant (R) were analyzed in a time course experiment. This study might provide an important step towards understanding resistance responses of soybean to S. sclerotiorum and identified novel mechanisms and targets.
Project description:Background: The biological control agent Pseudomonas chlororaphis PA23 is effective at protecting Brassica napus (canola) from the necrotrophic fungus Sclerotinia sclerotiorum via direct antagonism. Despite the growing importance of biocontrol bacteria in plant protection from fungal pathogens, little is known about how the host plant responds to bacterial priming on the leaf surface or about changes in gene activity genome-wide in the presence and absence of S. sclerotiorum. Results: PA23 priming of mature canola plants reduced the number of lesion forming petals by 90%. Global RNA sequencing of the host pathogen interface showed a reduction in the number of genes uniquely upregulated in response to S. sclerotiorum by 16-fold when pretreated with PA23. Upstream defense-related gene patterns suggest MAMP-triggered immunity via surface receptors detecting PA23 flagellin and peptidoglycans. Although systemic acquired resistance was induced in all treatment groups, a response centered around a glycerol-3-phosphate (G3P)-mediated pathway was exclusively observed in plants treated with PA23 alone. Activation of these defense mechanisms by PA23 involved mild reactive oxygen species production as well as pronounced thylakoid membrane structures and plastoglobule formation in leaf chloroplasts. Conclusion: Further to the direct antibiosis that it exhibits towards the pathogen S. sclerotiorum, PA23 primes defense responses in the plant through the induction of unique local and systemic defense regulatory networks. This study has shed light on the potential effects of biocontrol agents applied to the plant phyllosphere. Understanding these interactions will aid in the development of biocontrol systems as a viable alternative to chemical pesticides in the protection of important crop systems. Mature canola leaf tissue treated with combinations of PA23 or S. sclerotiorum ascospores (3 treatment groups) was compared to a water treated control (all treatments done in triplicate).
Project description:Known to infect more than 600 plant species worldwide, Sclerotinia sclerotiorum is a necrotrophic fungal pathogen, and the causative agent of white mold. With recent infection reports documented across North America, Cannabis sativa is known to be susceptible to Sclerotinia infection. Resulting from legal constraints associated with C. sativa, little is known about the Cannabis-Sclerotinia pathosystem, particularly in how the plant responds to pathogen attack at the cellular and molecular levels. Anatomical study revealed initial infection and degradation of the epidermis and cortical parenchyma, followed by widespread infection of the vascular phloem. Dual RNA sequencing provided a detailed transcriptomic profile of this pathosystem directly at the site of infection. Differential gene expression analysis revealed large-scale transcriptional shifts resulting from rapid infection. We identified the upregulation of 97 genes at 1 day post inoculation (dpi) and 6733 genes 5 dpi in C. sativa, while 3186 genes were identified in S. sclerotiorum 7 dpi. Gene ontology term enrichment identified processes associated with plant defense and signal transduction cascades during C. sativa infection while processes associated with redox control and sugar catabolism were enriched in S. sclerotiorum. Taken together, this study revealed transcriptional reprogramming in both the host plant and fungal pathogen associated with degradation of host cortical and vascular phloem tissues.
Project description:Cooperation is associated with major transitions in evolution such as the emergence of multicellularity. It is central to the evolution of many complex traits in nature, including growth and virulence in pathogenic bacteria. Whether cells of multicellular parasites function cooperatively during infection remains however largely unknown. Here, we show that hyphal cells of the fungal pathogen Sclerotinia sclerotiorum reprogram towards division of labor to facilitate the colonization of host plants. Using global transcriptome sequencing, we reveal that gene expression patterns diverge markedly in cells at the center and apex of hyphae during A. thaliana colonization compared to in vitro growth. We reconstructed a genome-scale metabolic model for S. sclerotiorum and used flux balance analysis to demonstrate metabolic heterogeneity supporting division of labor between hyphal cells. Accordingly, continuity between the central and apical compartments of invasive hyphae was required for optimal growth in planta. Using a multi-cell model of fungal hyphae, we show that this cooperative functioning enhances fungal growth predominantly during host colonization. Our work identifies cooperation in fungal hyphae as a mechanism emerging at the multicellular level to support host colonization and virulence.
Project description:To exploite S. sclerotiorum to identify differential fungal responses leading to either an endophytic or a pathogenic lifestyle during colonization of both asymptomatic host and symptomatic host We then performed gene expression profiling analysis using data obtained from RNA-seq of 9 different samples after 2 days.
Project description:Sclerotinia sclerotiorum is a pathogenic fungus that infects hundreds of crop species, causing extensive yield loss every year. Chemical fungicides are used to control this phytopathogen, but with concerns about increasing resistance and impacts on non-target species, there is a need to develop alternative control measures. In the present study, we engineered Brassica napus to constitutively express a hairpin (hp)RNA molecule to silence ABHYRDOLASE-3 in S. sclerotiorum. We demonstrate the potential for Host Induced Gene Silencing (HIGS) to protect B. napus from S. sclerotiorum using leaf, stem and whole plant infection assays. The interaction between the transgenic host plant and invading pathogen was further characterized at the molecular level using dual-RNA sequencing and at the anatomical level through microscopy to understand the processes and possible mechanisms leading to increased tolerance to this damaging necrotroph. We observed significant shifts in the expression of genes relating to plant defense as well as cellular differences in the form of structural barriers around the site of infection in the HIGS-protected plants. Our results provide proof-of-concept that HIGS is an effective means of limiting damage caused by S. sclerotiorum to the plant and demonstrates the utility of this biotechnology in the development of resistance against fungal pathogens.