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: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.
Project description:The biocontrol agent Pseudomonas chlororaphis PA23 protects canola (Brassica napus) against infection by the necrotrophic fungus Sclerotinia sclerotiorum. Production of PA23 secondary metabolites is governed by a complex regulatory pathway that includes the GacA/GacS two component system, the PhzI/PhzR quorum-sensing system, and a novel LysR-type transcriptional regulator, called PtrA. Through RNA-sequencing, transcriptomic profiles of PA23-WT, two quorum sensing-deficient strains, PA23-AHL and PA23-phzR, and regulatory mutants PA23-gacA, PA23-gacS and PA23-ptrA were generated allowing elucidation of the PhzRI, Gac and PtrA regulons of P. chlororaphis PA23.
Project description:Plant growth promoting bacteria (PGPB) are a growing subset of agricultural adjuncts which can be used to increase crop yield and plant productivity. Although, substantial research has been conducted on the metabolites and active molecules secreted by PGPBs; relatively little is known about their effects on the global transcriptome of the host plant. The present study was carried out to investigate changes in the gene expression landscape of early vegetative Brassica napus following treatment with Pseudomonas chlororaphis PA23. This PGPB was isolated from the soybean rhizosphere and has been extensively studied as a biocontrol agent. However, little is known about its effects on plant growth and development. Using a combination of RNA-sequencing and physiological analyses, we identified increased abundance of mRNA transcripts associated with photosynthesis and phytohormone response. Phenotypically we observed increased photosynthetic rates and larger root and shoot systems in B. napus following P. chlororaphis PA23 treatment. Lastly, we identified auxin production by P. chlororaphis PA23 which likely contributes to changes in gene expression and observed phenotypic differences in root and shoot structures. Together, the results of our study suggest that PA23 is a potent plant growth promoting agent with the potential for field applications as an agricultural adjunct.
Project description:We profiled the gene regulatory landscape of Brassica napus reproductive development using RNA sequencing. Comparative analysis of this nascent allotetraploid across the plant lifecycle revealed the contribution of each subgenome to plant reproduction. Global mRNA profiling across reproductive development revealed lower accumulation of C subgenome transcripts relative to the A subgenome. Subgenome-specific transcriptional networks identified distinct transcription factor families enriched in each of the A and C subgenome in early seed development. Analysis of a tissue specific transcriptome of early seed development revealed transcription factors predicted to be regulators encoded by the A subgenome are expressed primarily in the seed coat whereas regulators encoded by the C subgenome were expressed primarily in the embryo. Whole genome transcription factor networks identified BZIP11 as an essential regulator of early B. napus seed development. Knockdown of BZIP11 using RNA interference resulted in knockdown of predicted target genes, and a reproductive-lethal phenotype. Our data indicate that subgenome bias are characteristic features of the B. napus seed throughout its development, and that such bias might not be universal across the embryo, endosperm, and seed coat of the developing seed. We also find that examining transcriptional networks spanning both the A and C genomes of the whole B. napus seed can identify valuable targets for seed development research. We suggest that-omics level approaches to studying gene regulation in B. napus can benefit from both broad and high-resolution analyses.
Project description:ErfA is a transcription factor of Pseudomonas aeruginosa. We here define the genome-wide binding sites of ErfA by DAP-seq in Pseudomonas aeruginosa PAO1 and IHMA87, Pseudomonas chlororaphis PA23, Pseudomonas protegens CHA0 and Pseudomonas putida KT2440.
Project description:The hemibiotrophic fungal pathogen Leptosphaeria maculans is the causal agent of blackleg disease in Brassica napus (canola, oilseed rape) and causes significant losses in crop yields worldwide. While genetic resistance has been used to mitigate the disease, little information about the genes and gene regulatory networks underlying blackleg resistance is currently available. High-throughput RNA sequencing and rigorous bioinformatics approaches revealed dynamic changes in the host transcriptome and identified plant defense pathways specific to the host-pathogen incompatible LepR1-AvrLepR1 interaction.
Project description:To characterize the molecular basis of cytotoxicity of different Pseudomonas species and strains, we analyzed the protein content of secretomes of three P. chlororaphis strains (CIP63, CIP75 and the reference strain PA23) and of six P. entomophila strains (L48 WT, or deleted for various virulence factors: the global activator GacA, the pore-forming toxin Mnl, the pore-forming toxin ExlA, and double mutants for these genes).