hsr203J, a tobacco gene whose activation is rapid, highly localized and specific for incompatible plant/pathogen interactions

A novel plant defense gene, hsr203J, whose corresponding mRNA accumulates preferentially during the incompatible interaction of tobacco (Nicotiana tabacum L.) with a pathogenic bacterium, Pseudomonas solanacearum, has been isolated and sequenced. No sequence homology of the putative product of this gene has been found in data bases. Evidence is presented here that the hsr203J gene promoter, when fused to the GUS reporter gene, is selectively expressed in response to the hypersensitive response (HR)-inducing bacteria in tobacco protoplasts and that the sequences responsible for this response are contained within 1.4 kb of the 5′ noncoding region. The temporal and spatial patterns of hsr203J activation in leaves and roots inoculated with P. solanacearum indicate that the hsr 203J promoter exhibits a rapid (3–6 h post-inoculation) and high level of induction only in plant cells inoculated with the HR-inducing bacterial isolate. In addition, this gene promoter which does not respond to various stress conditions and is only very weakly induced during compatible interactions, is strongly dependent on hrp (hypersensitive response and pathogenicity) genes of P. solanacearum. These data indicate that the hsr 203J gene promoter exhibits new and original characteristics of activation with regard to the plant defense genes studied so far; its spatial and temporal program of activation together with its specific induction during the HR underline the importance of this gene as a molecular tool for studying the establishment and regulation of the HR.     

Quantitative disease resistance to the bacterial pathogen Xanthomonas campestris involves an Arabidopsis immune receptor pair and a gene of unknown function

Although quantitative disease resistance (QDR) is a durable and broad‐spectrum form of resistance in plants, the identification of the genes underlying QDR is still in its infancy. RKS1 (Resistance related KinaSe1) has been reported recently to confer QDR in Arabidopsis thaliana to most but not all races of the bacterial pathogen Xanthomonas campestris pv. campestris (Xcc). We therefore explored the genetic bases of QDR in A. thaliana to diverse races of X. campestris (Xc). A nested genome‐wide association mapping approach was used to finely map the genomic regions associated with QDR to Xcc12824 (race 2) and XccCFBP6943 (race 6). To identify the gene(s) implicated in QDR, insertional mutants (T‐DNA) were selected for the candidate genes and phenotyped in response to Xc. We identified two major QTLs that confer resistance specifically to Xcc12824 and XccCFBP6943. Although QDR to Xcc12824 is conferred by At5g22540 encoding for a protein of unknown function, QDR to XccCFBP6943 involves the well‐known immune receptor pair RRS1/RPS4. In addition to RKS1, this study reveals that three genes are involved in resistance to Xc with strikingly different ranges of specificity, suggesting that QDR to Xc involves a complex network integrating multiple response pathways triggered by distinct pathogen molecular determinants.     

α-Galactose based neoglycopeptides. Inhibition of verotoxin binding to globotriosylceramide

Solution and solid phase strategies for the synthesis of α-galactose based neoglycopeptide derivatives Figure 2, Figure 3, Figure 3, Scheme 3 and Scheme 4 were developed. Neoglycopeptides generated were tested for the inhibition of verotoxin binding to globotriosylceramide (Gb3) using ELISA. Among all of the compounds tested, only the lipid derivatives of neoglycopeptides, Figure 3 and Scheme 4 and Figure 3 and Scheme 4 were found to be inhibitors, IC₅₀=2.0 mM (Figure 3 and Scheme 4) and 0.2 mM (Figure 3 and Scheme 4). All of the inhibitors ( Figure 3 and Scheme 4) have a similar branching of the two α-galactosyl units at the N-terminal glycine residue of a short peptide and a lipid moiety attached at the C-terminal site. Both of these factors seem to be crucial for the inhibition. It is interesting to note that the inhibitors have only a portion of the natural trisaccharide ligand. The secondary groups either may contribute in sub-site oriented interactions with the protein receptors or may mimic the internal sugar units of the cell-surface ligand, Gb3.     

Comparison of the performance of the borax buffer-based HRP-enhanced reagent and the ‘Lumi-Phos 530’ chemiluminescence systems in the detection of biotinylated DNA

A comparison of two chemiluminescence methods, the borax buffer-based HRP-enhanced reagent and Lumi-Phos 530, applied to the detection of a biotinylated 30-mer DNA slot blotted onto a nylon membrane, is presented. A streptavidin–HRP and streptavidin–ALP mediated detection system was used. The HRP-enhanced system is up to 15-fold greater with respect to the signal/background ratios than the Lumi-Phos 530 system at 0.5 μg biotinylated DNA with at least a two-fold improvement in detection sensitivity for 0.5 ng biotinylated DNA.     

Behaviour of West Greenland caribou during a population decline

The major decline of the West Greenland caribou herd during the 1970s prompted a study in 1977–78 of caribou behaviour in relation to environmental factors associated with the decline. Quantification of caribou activity revealed behavioural responses to critically low standing crops of preferred winter forage. Caribou on poor winter range were mostly inactive with low feeding intensities and abnormal diurnal activity patterns. In addition, these animals exhibited very restricted movements, frequently occurred alone or in small groups, and were unable to maintain normal social bonds. In contrast, where fruticose lichen winter forage was available, caribou did not display these behavioural traits. After the initiation of new vegetative growth, feeding intensity increased and social tendency returned. Comparison with behavioural data from other Rangifer populations suggests that the observed responses to low forage quality are not restricted to Greenland but are a normal response of barren-ground caribou to winter ranges poor in lichen forage.     

Biochemical clustering of monomeric GTPases of the Ras superfamily

To date phylogeny has been used to compare entire families of proteins based on their nucleotide or amino acid sequence. Here we developed a novel analytical platform allowing a systematic comparison of protein families based on their biochemical properties. This approach was validated on the Rho subfamily of GTPases. We used two high throughput methods, referred to as AlphaScreen and FlashPlate, to measure nucleotide binding capacity, exchange, and hydrolysis activities of small monomeric GTPases. These two technologies have the characteristics to be very sensitive and to allow homogenous and high throughput assays. To analyze and integrate the data obtained, we developed an algorithm that allows the classification of GTPases according to their enzymatic activities. Integration and hierarchical clustering of these results revealed unexpected features of the small Rho GTPases when compared with primary sequence-based trees. Hence we propose a novel phylobiochemical classification of the Ras superfamily of GTPases.