To discover which components of plant defense responses make significant contributions to limiting pathogen attack, we screened a mutagenized population of Arabidopsis thaliana for individuals that exhibit increased susceptibility to the moderately virulent bacterial pathogen Pseudomonas syringae pv. maculicola ES4326 (Psm ES4326). The 12 enhanced disease susceptibility (eds) mutants isolated i...

Proteolytic processing is required for the activation of most caspases. However, recent reports have suggested that the activation of the mammalian initiator caspase caspase-9 occurs during dimerization rather than after processing. Previously, we reported that, in normal living Drosophila S2 cells, the initiator caspase Dronc is continuously processed to a 40 kDa form we called Pr1 and that, d...

Salicylic acid (SA) has been shown to act as a signal molecule that is produced by many plants subsequent to the recognition of potentially pathogenic microbes. Increases in levels of SA often trigger the activation of plant defenses and can result in increased resistance to subsequent challenge by pathogens. We observed that the polyketide 6-methylsalicylic acid (6-MeSA), a compound that appar...

p-Fluorophenylalanine (FPA) causes a 100-fold increase in alkaline phosphatase in Escherichia coli B, strain PR1 at 30 C in minimal medium that contains excess inorganic phosphate (1.92 x 10(-3)m). Little increase in alkaline phosphatase synthesis occurs under these conditions at 22 C. [This strain is known to have a mutation in a regulator gene (R(2)) that, in the absence of FPA, permits derep...

The Arabidopsis (Arabidopsis thaliana) WRKY7 gene is induced by pathogen infection and salicylic acid (SA) treatment and may therefore play a role in plant defense responses. Here, we show that WRKY7 is localized in the nucleus, recognizes DNA molecules with the W-box (TTGAC) elements, and functions as a transcriptional repressor in plant cells. To study its biological functions directly, we ha...

The broad objective of the research presented here is to develop a noncatalytic plasmid maintenance system for the stabilization of multicopy expression plasmids encoding foreign antigens in a Salmonella typhi live-vector vaccine strain such as CVD 908-htrA. We have enhanced the maintenance of expression plasmids at two independent levels. First, we removed dependence upon balanced-lethal maint...

The capacity of H(2)O(2), the most stable of the reactive oxygen species (ROI), to diffuse freely across biological membranes and to signal gene expression suggests that H(2)O(2) could function as a short-lived second messenger diffusing from cell to cell. We tested this hypothesis in tobacco plants treated with a glycoprotein elicitor. Applied at 50 nM, it induces H(2)O(2) accumulation and the...

An Arabidopsis PR1::luciferase (LUC) transgenic line was transformed with activation T-DNA tags and the resulting population screened for dominant gain-of-function mutants exhibiting constitutive LUC activity. LUC imaging identified activated disease resistance 2 (adr2), which exhibited slowly spreading lesions in the absence of pathogen challenge. Molecular, genetic and histochemical analysis ...

In plant-pathogen interaction, the plant hormone ABA can serve as a crucial modulator of plant responses to biotic as well as abiotic stress. Recent studies have identified pyrabactin resistance (PYR) 1/PYR1-like (PYL)/regulatory component of ABA receptor (RCAR) proteins as an ABA receptor that interacts with the protein phosphatase type 2C (PP2C) family. Here, we examined the functional involv...