Plants possess inducible systemic defense responses when locally infected by pathogens. Bacterial infection results in the increased accumulation of mobile metabolite azelaic acid, a nine-carbon dicarboxylic vascular sap Arabidopsis that confers local and resistance against pathogen Pseudomonas syringae. Azelaic acid primes plants to accumulate salicylic (SA), known signal, upon infection. Mutation AZELAIC ACID INDUCED 1 (AZI1) gene, which is induced specific loss immunity triggered or...

Escherichia coli responds to superoxide-generating agents by inducing approximately 40 proteins. We have identified a genetic locus, soxR (superoxide response), that positively regulates 9 of these proteins during superoxide stress. Induction under control is at the transcriptional level, as shown with lac fusions five paraquat-inducible promoters. Members regulon include least three demonstrable antioxidant roles: Mn-containing dismutase (which destroys radicals), endonuclease IV repairs...

Plants cope with pathogen attacks by using mechanisms of resistance that rely both on preformed protective defenses and inducible defenses. The latter are the most well studied, progress is being made in determining which induced responses responsible for limiting growth. Many plant-pathogen interactions accompanied plant cell death. Recent evidence suggests this death often programmed results from an active process part host. review considers roles possible response to pathogens.

Type III secreted “effector” proteins of bacterial pathogens play central roles in virulence, yet are notoriously difficult to identify. We used an vivo genetic screen identify 13 effectors by the type apparatus (called Hrp, for “hypersensitive response and pathogenicity”) plant pathogen Pseudomonas syringae . Although sharing little overall homology, amino-terminal regions these had strikingly similar amino acid compositions. This feature facilitated bioinformatic prediction 38 P....

We isolated a dominant gain-of-function Arabidopsis mutant, accelerated cell death 6 (acd6), with elevated defenses, patches of dead and enlarged cells, reduced stature, increased resistance to Pseudomonas syringae. The acd6-conferred phenotypes are suppressed by removing key signaling molecule, salicylic acid (SA), using the nahG transgene, which encodes SA hydroxylase. This suppression includes that not induced application wild-type plants, indicating acts second signal cause many...

The balance between the bioactive sphingolipid ceramide and its phosphorylated derivative has been proposed to modulate amount of programmed cell death (PCD) in eukaryotes. We characterized first kinase (CERK) mutant any organism. Arabidopsis CERK mutant, called accelerated 5 , accumulates substrates shows enhanced disease symptoms during pathogen attack apoptotic-like dependent on defense signaling late development. ACD5 protein high specificity for ceramides vitro. Strikingly, C2 induces,...

accelerated cell death 2 ( acd2 ) mutants of Arabidopsis have spontaneous spreading lesions and constitutive activation defenses in the absence pathogen infection. Lesion formation plants can be triggered by bacterial toxin coronatine through a light-dependent process. Coronatine-triggered lesion also requires protein translation, indicating that occurs an active We cloned ACD2 gene; its predicted product shows significant extensive similarity to red chlorophyll catabolite reductase, which...

Mutants of Arabidopsis thaliana which exhibit accelerated cell death in response to pathogens were isolated and characterized gain insight into how symptom severity disease resistance are modulated. This paper describes mutants that fall one two complementation groups identified. A novel feature these is they unable control the rate extent after exposure a variety stimuli induce senescence responses. Thus, ( acd1 ) show rapid, spreading necrotic responses both virulent avirulent Pseudomonas...

Summary Plant cells undergoing programmed cell death (PCD) at late stages typically show chromatin condensation and endonucleolytic cleavage prior to obvious membrane or organelle ultrastructural changes. To investigate possible early PCD‐associated events, we used microscopic observations flow cytometry quantitate mitochondrial potential (ΔΨ m ) changes during PCD the single population levels using Arabidopsis protoplasts. A ΔΨ loss was commonly induced plant important for execution, as...

Escherichia coli treated with nontoxic levels of the superoxide-generating redox-cycling agents menadione and paraquat showed dramatic changes in protein composition as monitored by two-dimensional gel analysis. The distribution proteins synthesized after treatment these overlapped significantly that seen hydrogen peroxide treatment, it included all oxyR regulon. also elicited synthesis at least 33 other were not peroxide, including three heat shock proteins, Mn-containing superoxide...

Abstract The Arabidopsis thaliana chloroplast protein ACCELERATED CELL DEATH2 (ACD2) modulates the amount of programmed cell death (PCD) triggered by Pseudomonas syringae and protoporphyrin IX (PPIX) treatment. In vitro, ACD2 can reduce red chlorophyll catabolite, a derivative. We find that shields root protoplasts lack from light- PPIX-induced PCD. Thus, catabolism is not obligatory for anti-PCD function. Upon P. infection, levels localization change in cells undergoing PCD their close...

Abstract Salicylic acid (SA) is required for resistance to many diseases in higher plants. SA-dependent cell death and defense-related responses have been correlated with disease resistance. The accelerated 5 mutant of Arabidopsis provides additional genetic evidence that SA regulates responses. However, acd5, these events are uncoupled from acd5 plants more susceptible Pseudomonas syringae early development show spontaneous accumulation, death, markers later development. In plants,...

The bacterial plant pathogen Pseudomonas syringae injects a large repertoire of effector proteins into cells using type III secretion apparatus. Effectors can trigger or suppress defences in host-dependent fashion. Host are often accompanied by programmed cell death, while interference with is sometimes associated death suppression. We previously predicted the sequenced bean P. pv. (Psy) B728a bioinformatics. Here we show that PsyB728a also pathogenic on model species Nicotiana benthamiana...

The Arabidopsis thaliana agd2-like defense response protein1 (ald1) mutant was previously found to be hypersusceptible the virulent bacterial pathogen Pseudomonas syringae and had reduced accumulation of signal salicylic acid (SA). ALD1 shown possess aminotransferase activity in vitro, suggesting it generates an amino acid-derived signal. We now find a key component that acts multiple contexts partially requires PHYTOALEXIN DEFICIENT4 (PAD4) regulatory gene for its expression infection. ald1...

Plant heat shock protein Hsp70 is the major target of HopI1, a virulence effector pathogenic Pseudomonas syringae. essential for function HopI1. HopI1 directly binds through its C-terminal J domain and stimulates ATP hydrolysis activity in vitro. In plants, forms large complexes association with induces recruits cytosolic to chloroplasts, site localization. Deletion central P/Q-rich repeat region disrupts but not interactions or chloroplasts. Thus, must only bind domain, likely actively...

In Arabidopsis thaliana, responses to pathogen-associated molecular patterns (PAMPs) are mediated by cell surface pattern recognition receptors (PRRs) and include the accumulation of reactive oxygen species, callose deposition in wall, generation signal molecule salicylic acid (SA). SA acts a positive feedback loop with ACCELERATED CELL DEATH6 (ACD6), membrane protein that contributes immunity. This work shows PRRs associate part ACD6/SA loop. ACD6 positively regulates abundance several...

Priming is a major mechanism behind the immunological 'memory' observed during two key plant systemic defences: acquired resistance (SAR) and induced (ISR). Lipid-derived azelaic acid (AZA) mobile priming signal. Here, we show that lipid transfer protein (LTP)-like AZI1 its closest paralog EARLI1 are necessary for SAR, ISR movement uptake of AZA in Arabidopsis. Imaging fractionation studies indicate localize to expected places exchange/movement occur. These ER/plasmodesmata, chloroplast...

A central mechanism of virulence extracellular bacterial pathogens is the injection into host cells effector proteins that modify cellular functions. HopW1 an injected by type III secretion system increases growth plant pathogen Pseudomonas syringae on Columbia accession Arabidopsis. When delivered P. cells, causes a reduction in filamentous actin (F-actin) network and inhibition endocytosis, known actin-dependent process. directly produced plants, forms complexes with actin, disrupts...

Arabidopsis thaliana plants that lack ceramide kinase, encoded by ACCELERATED CELL DEATH5 (ACD5), display spontaneous programmed cell death late in development and accumulate substrates of ACD5. Here, we compared accumulation kinetics, defense responses, ultrastructural features, sites reactive oxygen species (ROS) production wild-type acd5 during and/or Botrytis cinerea infection. Quantitative sphingolipid profiling indicated paralleled the appearance death, it was accompanied autophagy...

Summary Salicylic acid (SA) plays a key role in activating defenses and cell death during plant–pathogen interactions. In response to some pathogens, SA also limits the extent of death, indicating that it acts positively or negatively depending on host–pathogen interaction. addition, we previously showed affects growth Arabidopsis defense‐related mutants accelerated 6–1 ( acd6–1 ) aberrant 2 agd2 . Using , two other mutants, lesion simulating disease 6 lsd6 ), suppressor SA‐insensitivity...