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Defence Signalling (defence + signalling)
Selected AbstractsFine-Tuning Plant Defence Signalling: Salicylate versus JasmonatePLANT BIOLOGY, Issue 1 2006G. J. M. Beckers Abstract: Plant defences against pathogens and herbivorous insects form a comprehensive network of interacting signal transduction pathways. The signalling molecules salicylic acid (SA) and jasmonic acid (JA) play important roles in this network. SA is involved in signalling processes providing systemic acquired resistance (SAR), protecting the plant from further infection after an initial pathogen attack. SAR is long-lasting and provides broad spectrum resistance to biotrophic pathogens that feed on a living host cell. The regulatory protein NPR1 is a central positive regulator of SAR. SA-activated NPR1 localizes to the nucleus where it interacts with TGA transcription factors to induce the expression of a large set of pathogenesis-related proteins that contribute to the enhanced state of resistance. In a distinct signalling process, JA protects the plant from insect infestation and necrotrophic pathogens that kill the host cell before feeding. JA activates the regulatory protein COI1 that is part of the E3 ubiquitin ligase-containing complex SCFCOI1, which is thought to derepress JA-responsive genes involved in plant defence. Both synergistic and antagonistic interactions have been observed between SA- and JA-dependent defences. NPR1 has emerged as a critical modulator of cross-talk between the SA and JA signal and is thought to aid in fine tuning defence responses specific to the encountered attacker. Here we review SA- and JA-dependent signal transduction and summarize our current understanding of the molecular mechanisms of cross-talk between these defences. [source] Chemical genetics: catalysing pathway exploration and new target discoveryJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 11 2007Joshua I Armstrong Abstract Chemical genetics couples the availability of diverse chemistry with the strengths of molecular genetics to dissect signalling pathways in complex organisms. Plant biology laboratories have integrated this approach into their repertoire for probing hormone signalling, physiology and pesticide mode of action. These studies have led to the discovery of compounds that regulate development and the response to environmental stress. Chemical genetics facilitates our understanding of genetic signalling pathways and offers a new approach to pest management and plant health by enabling the direct chemical modulation of plant defence signalling. Copyright © 2007 Society of Chemical Industry [source] WRR4, a broad-spectrum TIR-NB-LRR gene from Arabidopsis thaliana that confers white rust resistance in transgenic oilseed brassica cropsMOLECULAR PLANT PATHOLOGY, Issue 2 2010MOHAMMAD HOSSEIN BORHAN SUMMARY White blister rust caused by Albugo candida (Pers.) Kuntze is a common and often devastating disease of oilseed and vegetable brassica crops worldwide. Physiological races of the parasite have been described, including races 2, 7 and 9 from Brassica juncea, B. rapa and B. oleracea, respectively, and race 4 from Capsella bursa-pastoris (the type host). A gene named WRR4 has been characterized recently from polygenic resistance in the wild brassica relative Arabidopsis thaliana (accession Columbia) that confers broad-spectrum white rust resistance (WRR) to all four of the above Al. candida races. This gene encodes a TIR-NB-LRR (Toll-like/interleukin-1 receptor-nucleotide binding-leucine-rich repeat) protein which, as with other known functional members in this subclass of intracellular receptor-like proteins, requires the expression of the lipase-like defence regulator, enhanced disease susceptibility 1 (EDS1). Thus, we used RNA interference-mediated suppression of EDS1 in a white rust-resistant breeding line of B. napus (transformed with a construct designed from the A. thaliana EDS1 gene) to determine whether defence signalling via EDS1 is functionally intact in this oilseed brassica. The eds1-suppressed lines were fully susceptible following inoculation with either race 2 or 7 isolates of Al. candida. We then transformed white rust-susceptible cultivars of B. juncea (susceptible to race 2) and B. napus (susceptible to race 7) with the WRR4 gene from A. thaliana. The WRR4-transformed lines were resistant to the corresponding Al. candida race for each host species. The combined data indicate that WRR4 could potentially provide a novel source of white rust resistance in oilseed and vegetable brassica crops. [source] Identification of differentially expressed root genes upon rhizomania diseaseMOLECULAR PLANT PATHOLOGY, Issue 6 2008LAURE SCHMIDLIN SUMMARY Rhizomania is one of the most devastating sugar beet diseases. It is caused by Beet necrotic yellow vein virus (BNYVV), which induces abnormal rootlet proliferation. To understand better the physiological and molecular basis of the disorder, transcriptome analysis was performed by restriction fragment differential display polymerase chain reaction (RFDD-PCR), which provided differential gene expression profiles between non-infected and infected sugar beet roots. Two distinct viral isolates were used to detect specific or general virus-induced genes. Differentially expressed genes were selected and identified by sequence analysis, followed by reverse Northern and reverse transcriptase PCR experiments. These latter analyses of different plants (Beta vulgaris and Beta macrocarpa) infected under distinct standardized conditions revealed specific and variable expressions. Candidate genes were linked to cell development, metabolism, defence signalling and oxidative stress. In addition, the expression of already characterized genes linked to defence response (pathogenesis-related protein genes), auxin signalling and cell elongation was also studied to further examine some aspects of the disease. Differential expression was retrieved in both B. vulgaris and B. macrocarpa. However, some candidate genes were found to be deregulated in only one plant species, suggesting differential response to BNYVV or specific responses to the BNYVV vector. [source] Post-translational modification of host proteins in pathogen-triggered defence signalling in plantsMOLECULAR PLANT PATHOLOGY, Issue 4 2008IRIS J. E. STULEMEIJER SUMMARY Microbial plant pathogens impose a continuous threat to global food production. Similar to animals, an innate immune system allows plants to recognize pathogens and swiftly activate defence. To activate a rapid response, receptor-mediated pathogen perception and subsequent downstream signalling depends on post-translational modification (PTM) of components essential for defence signalling. We discuss different types of PTMs that play a role in mounting plant immunity, which include phosphorylation, glycosylation, ubiquitination, sumoylation, nitrosylation, myristoylation, palmitoylation and glycosylphosphatidylinositol (GPI)-anchoring. PTMs are rapid, reversible, controlled and highly specific, and provide a tool to regulate protein stability, activity and localization. Here, we give an overview of PTMs that modify components essential for defence signalling at the site of signal perception, during secondary messenger production and during signalling in the cytoplasm. In addition, we discuss effectors from pathogens that suppress plant defence responses by interfering with host PTMs. [source] Induction of systemic resistance in Arabidopsis thaliana in response to a culture filtrate from a plant growth-promoting fungus, Phoma sp.PLANT BIOLOGY, Issue 1 2009GS8- Abstract The plant growth-promoting fungus (PGPF), Phoma sp. GS8-3, isolated from a zoysia grass rhizosphere, is capable of protecting cucumber plants against virulent pathogens. This fungus was investigated in terms of the underlying mechanisms and ability to elicit systemic resistance in Arabidopsis thaliana. Root treatment of Arabidopsis plants with a culture filtrate (CF) from Phoma sp. GS8-3 elicited systemic resistance against the bacterial speck pathogen Pseudomonas syringae pv. tomato DC3000 (Pst), with restricted disease development and inhibited pathogen proliferation. Pathway-specific mutant plants, such as jar1 (jasmonic acid insensitive) and ein2 (ethylene insensitive), and transgenic NahG plants (impaired in salicylate signalling) were protected after application of the CF, demonstrating that these pathways are dispensable (at least individually) in CF-mediated resistance. Similarly, NPR1 interference in npr1 mutants had no effect on CF-induced resistance. Gene expression studies revealed that CF treatment stimulated the systemic expression of both the SA-inducible PR-1 and JA/ET-inducible PDF1.2 genes. However, pathogenic challenge to CF-treated plants was associated with potentiated expression of the PR-1 gene and down-regulated expression of the PDF1.2 gene. The observed down-regulation of the PDF1.2 gene in CF-treated plants indicates that there may be cross-talk between SA- and JA/ET-dependent signalling pathways during the pathogenic infection process. In conclusion, our data suggest that CF of Phoma sp. GS8-3 induces resistance in Arabidopsis in a manner where SA and JA/ET may play a role in defence signalling. [source] ER quality control of immune receptors and regulators in plantsCELLULAR MICROBIOLOGY, Issue 6 2010Yusuke Saijo Summary Like in animals, cell surface and intracellular receptors mediate immune recognition of potential microbial intruders in plants. Membrane-localized pattern recognition receptors (PRRs) initiate immune responses upon perception of cognate microbe-associated molecular patterns (MAMPs). MAMP-triggered immunity provides a first line of defence that restricts the invasion and propagation of both adapted and non-adapted pathogens. The Leu-rich repeat (LRR) receptor protein kinases (RKs) define a major class of trans-membrane receptors in plants, of which some members are engaged in MAMP recognition and/or defence signalling. The endoplasmic reticulum (ER) quality control (QC) systems monitor N-glycosylation and folding states of the extracellular, ligand-binding LRR domains of LRR-RKs. Recent progress reveals a critical role of evolutionarily conserved ERQC components for different layers of plant immunity. N-glycosylation appears to play a role in ERQC fidelity rather than in ligand binding of LRR-RKs. Moreover, even closely related PRRs show receptor-specific requirements for N-glycosylation. These findings are reminiscent of the earlier defined function of the cytosolic chaperon complex for LRR domain-containing intracellular immune receptors. QC of the LRR domains might provide a basis not only for the maintenance but also for diversification of recognition specificities for immune receptors in plants. [source] Entering and breaking: virulence effector proteins of oomycete plant pathogensCELLULAR MICROBIOLOGY, Issue 1 2009Brett M. Tyler Summary Oomycete pathogens of plants and animals are related to marine algae and have evolved mechanisms to avoid or suppress host defences independently of other groups of pathogens, such as bacteria and fungi. They cause many destructive diseases affecting crops, forests and aquaculture. The development of genomic resources has led to a dramatic increase in our knowledge of the effectors used by these pathogens to suppress host defences. In particular, a huge, rapidly diverging superfamily of effectors with 100,600 members per genome has been identified. Proteins in this family use the N-terminal motifs RxLR and dEER to cross the host plasma cell membrane autonomously. Once inside the host cell, the proteins suppress host defence signalling. The importance of this effector family is underlined by the fact that plants have evolved intracellular defence receptors to detect the effectors and trigger a rapid counter-attack. The mechanisms by which the effector enter host cells, and by which they suppress host defences, remain to be elucidated. [source] | ||||||||||