Global transcriptome of the fungal pathogen Sclerotinia sclerotiorum (strain 1980) during the colonization of 23 Accessions of Arabidopsis thaliana
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ABSTRACT: Quantitative disease resistance (QDR) is an almost universal and often broad-spectrum process in plants, serving to limit the damage caused by pathogen infections. It represents the primary form of plant immunity that reduces disease symptoms induced by numerous pathogens actively killing host cells during infection, including the necrotrophic pathogen Sclerotinia sclerotiorum. Investigating the evolutionary origins of QDR against necrotrophic fungi is crucial for comprehending how plant resistance evolves. To explore the diversity of local responses to S. sclerotiorum within a plant species level, we conducted a comprehensive analysis of the entire transcriptomes from 23 accessions of Arabidopsis thaliana, mainly distributed across Europe. More than half on the pan-transcriptome displayed local responses toS. sclerotiorum, including similar transcriptome patterns. Notably, core S. sclerotiorum-responsive genes exhibited a clear gene age pattern, dominated by older genes forming protein-protein networks that continuously acquiring new hubs. Comparative transcriptome analyses revealed QDR is associated with quantitative expression variations specific to accession subsets. By comparison of promoter sequences, we have shown evidence that accession subsets independently evolved and acquired specific cis-regulatory elements, confering Sclerotinia resistance. This scenario suggests multiple exaptation trajectories of novel QDR genes through species-level cis-regulation. This study sheds light on the regulation of QDR-associated genes within a species, contributing to our understanding of the molecular mechanisms of plant fungal resistance.
Project description:Plants deploy pattern recognition receptors to detect microbe- and damage-associated molecular patterns. Arabidopsis thaliana receptor-like protein RLP30 contributes to innate immunity to the necrotrophic fungus Sclerotinia sclerotiorum by recognizing SCLEROTINIA CULTURE FILTRATE ELICITOR 1 (SCFE1). Here we show that the S. sclerotiorum small cysteine-rich protein SCP1 accounts for elicitor activity of SCFE1. RLP30 recognizes SCP1 and its homologs from divergent fungi and oomycetes, as well as an SCP1-unrelated and conserved pattern from bacterial Pseudomonads. Stable expression of RLP30 in Nicotiana tabacum confers enhanced immunity to bacterial, fungal, and oomycete pathogens. Unlike Arabidopsis, which requires intact SCP1 for RLP30-mediated immunity, other Brassicaceae and Solanaceae respond to smaller immunogenic SCP1 epitopes. We conclude that Arabidopsis RLP30 recognizes immunogenic patterns from three microbial kingdoms and that mechanistically different SCP1 perception has evolved in other plant species, likely as a result of convergent evolution.
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:MicroRNAs are multifunctional non-coding short nucleotide molecules. Nevertheless, the role of miRNAs in the interactions between plants and necrotrophic pathogens is largely unknown. Here, we report the identification of the miRNA repertoire of the economically important oil crop oilseed rape (Brassica napus) and those involved in interacting with its most devastating necrotrophic pathogen Sclerotinia sclerotiorum. We identified 280 B. napus miRNA candidates, including 53 novel candidates and 227 canonical members or variants of known miRNA families, by high-throughput deep sequencing of small RNAs from both normal and S. sclerotiorum-inoculated leaves. Target genes of 15 novel candidates and 222 known miRNAs were further identified by sequencing of degradomes from the two types of samples. MicroRNA microarray analysis revealed that 68 miRNAs were differentially expressed between S. sclerotiorum-inoculated and uninoculated leaves. A set of these miRNAs target genes involved in plant defense to S. sclerotiorum and/or other pathogens such as NBS-LRR R genes and nitric oxygen and reactive oxygen species related genes. Additionally, three miRNAs target AGO1 and AGO2, key components of post-transcriptional gene silencing (PTGS). Expression of several viral PTGS suppressors reduced resistance to S. sclerotiorum. Arabidopsis mutants of AGO1 and AGO2 exhibited reduced resistance while transgenic lines over-expressing AGO1 displayed increased resistance to S. sclerotiorum in an AGO1 expression level-dependent manner. Moreover, transient over-expression of miRNAs targeting AGO1 and AGO2 decreased resistance to S. sclerotiorum in oilseed rape. Our results demonstrate that the interactions between B. napus and S. sclerotiorum are tightly regulated at miRNA level and probably involve PTGS.
Project description:MicroRNAs are multifunctional non-coding short nucleotide molecules. Nevertheless, the role of miRNAs in the interactions between plants and necrotrophic pathogens is largely unknown. Here, we report the identification of the miRNA repertoire of the economically important oil crop oilseed rape (Brassica napus) and those involved in interacting with its most devastating necrotrophic pathogen Sclerotinia sclerotiorum. We identified 280 B. napus miRNA candidates, including 53 novel candidates and 227 canonical members or variants of known miRNA families, by high-throughput deep sequencing of small RNAs from both normal and S. sclerotiorum-inoculated leaves. Target genes of 15 novel candidates and 222 known miRNAs were further identified by sequencing of degradomes from the two types of samples. MicroRNA microarray analysis revealed that 68 miRNAs were differentially expressed between S. sclerotiorum-inoculated and uninoculated leaves. A set of these miRNAs target genes involved in plant defense to S. sclerotiorum and/or other pathogens such as NBS-LRR R genes and nitric oxygen and reactive oxygen species related genes. Additionally, three miRNAs target AGO1 and AGO2, key components of post-transcriptional gene silencing (PTGS). Expression of several viral PTGS suppressors reduced resistance to S. sclerotiorum. Arabidopsis mutants of AGO1 and AGO2 exhibited reduced resistance while transgenic lines over-expressing AGO1 displayed increased resistance to S. sclerotiorum in an AGO1 expression level-dependent manner. Moreover, transient over-expression of miRNAs targeting AGO1 and AGO2 decreased resistance to S. sclerotiorum in oilseed rape. Our results demonstrate that the interactions between B. napus and S. sclerotiorum are tightly regulated at miRNA level and probably involve PTGS.
Project description:Sclerotinia sclerotiorum is a broad-host range necrotrophic pathogen which is the causative agent of Sclerotinia stem rot (SSR), and a major disease of soybean (Glycine max). A time course transcriptomic analysis was performed in both compatible and incompatible soybean lines to identify pathogenicity and developmental factors utilized by S. sclerotiorum to achieve pathogenic success.
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: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: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:Pennycress (Thlaspi arvense) is a winter oilseed domesticated recently to be incorporated as an intermediate crop between the existing cropping systems of the US Midwest. We show that a natural accession of pennycress, 2032, is more susceptible to the necrotrophic fungal pathogens Sclerotinia sclerotiorum and Alternaria japonica than the reference pennycress accession MN106. A previously identified marker associated with earliness in pennycress was found to be present in in a gene homologous to Arabidopsis Jumonji 14 (JMJ14). It has been reported that AtJMJ14 promotes disease resistance and represses flowering, and greenhouse studies of breeding populations confirmed this phenomenon in pennycress. Plants with the 2032 TaJMJ14 allele were more susceptible to fungi and flowered early. CRISPR-Cas9 editing was used to generate additional TaJMJ14 alleles. A 9 bp deletion in TaJMJ14 showed trends of early flowering and S. sclerotiorum susceptibility, whereas a complete loss-of-function allele led to infertility. We further investigated the transcriptomes of MN106 and 2032 plants in the early stages of S. sclerotiorum and A. japonica infection to identify potential resistance and susceptibility genes. Differences in the expression of pathogen-associated molecular pattern-triggered immunity (PTI)-associated genes led us to discover that 2032 plants have defects in elicitor-triggered oxidative bursts. The transcriptional responses unique to each accession lay a foundation for future gene-editing and breeding approaches to keep the beneficial early flowering phenotype conferred by 2032 but uncouple it from disease susceptibility.
Project description:Quantitative disease resistance (QDR) is a form of plant immunity conserved across species able to limit infections caused by a broad range of pathogens. QDR has a complex genetic determinism, the bases of which are not fully understood. The number of genes contributing to the QDR response and the extent to which molecular components of the QDR response vary across plant species remain elusive. The fungal pathogen Sclerotinia sclerotiorum, causal agent of white mold disease on hundreds of plant species, triggers QDR responses in host populations. To document the diversity of plant responses to S. sclerotiorum at the molecular level, we analyzed the complete transcriptome of six plant species spanning the Pentapetalae group inoculated by the same strain of S. sclerotiorum. We identified 48,910 genes differentially expressed (DEGs) upon infection across six species, enriched in 286 gene ontologies and 148 PFAM domains. DEGs represented ~32% of the plant genome, with an excess of down-regulated over up-regulated genes in all species. DEGs were enriched among orthologous gene groups conserved in all six species (core) compared to other orthologous groups and lineage-specific groups. Although 86.9% of core orthogroups included DEGs, only 5.5% included DEGs from all six species, revealing a high degree of regulatory divergence at the interspecific level. Focusing on a group of ABCG/PDR transporters with up-regulated members in all species, we propose that an ancestral function of AtPDR12 in acclimation to abiotic stress was exapted into QDR against S. sclerotiorum through reinforcement of pathogen responsiveness at the transcriptional level. Our results suggest that exaptation by cis-regulatory divergence contributed to the evolution of QDR and support an infinitesimal model of QDR determinism. It provides resources for functional studies on gene regulation and QDR molecular bases across the Pentapetalae clade.