Physical mapping of NBS-coding resistance genes to the <Emphasis Type="Italic">Me</Emphasis>-gene cluster on chromosome P9 reveals markers tightly linked to the <Emphasis Type="Italic">N</Emphasis> gene for root-knot nematode resistance in pepper

Natural root-knot nematode resistance genes are unique resources to control this major pest in pepper (Capsicum annuum). Although four genes (Me1, Me3, Me7 and N) conferring broad-spectrum resistance were mapped to a cluster in a 28-cm interval on chromosome P9, limited markers targeting this region were available. In the present study, the Me-gene cluster was structurally annotated for resistance genes to develop markers targeting the N gene. As a result, the Me-gene cluster (4.07 Mb in size) was found to contain three resistance gene hotspots. In addition, a SSR maker tightly linked to the N gene (0.8 cM away) was developed for marker-assisted selection in pepper.     

The potential role of nitric oxide in substrate switching in eosinophil peroxidase

Eosinophil recruitment and enhanced nitric oxide (NO) production are characteristic features of asthma and other airway diseases. Eosinophil peroxidase (EPO), a highly cationic hemoprotein secreted by activation of eosinophils, is believed to play a central role in host defense against invading pathogens. The enzyme uses hydrogen peroxide (H2O2) and bromide (Br-), a preferred cosubstrate of EPO, to generate the cytotoxic oxidant hypobromous acid. The aim of this work was to determine whether NO can compete with plasma levels of Br- and steer the enzyme reaction from a 2e- oxidation to a 1e- oxidation pathway. Rapid kinetic measurements were utilized to measure the rate of EPO compounds I and II formation, duration, and decay at 412 and 432 nm, respectively, at 10 degrees C. An EPO-Fe(III) solution supplemented with increasing Br- concentrations was rapidly mixed with fixed amounts of H2O2 in the absence and in the presence of increasing NO concentrations. In the absence of NO, EPO-Fe(III) primarily converted to compound I and, upon H2O2 exhaustion, it decayed rapidly to the ferric form. NO caused a significant increase in the accumulation of EPO compound II, along with a proportional increase in its rate of formation and duration as determined by the time elapsed during catalysis. The time courses for these events have been incorporated into a comprehensive kinetic model. Computer simulations carried out supported the involvement of a conformational intermediate in the EPO compound II complex decay. Collectively, our results demonstrated that NO displays the potential capacity to promote substrate switching by modulating substrate selectivity of EPO.     

S100A13-lipid interactions-role in the non-classical release of the acidic fibroblast growth factor

S100A13 is a 98-amino acid, calcium binding protein. It is known to participate in the non-classical secretion of signal peptide-less proteins, such as the acidic fibroblast growth factor. In this study, we investigate the lipid binding properties of S10013 using a number of biophysical techniques, including multidimensional NMR spectroscopy. Isothermal titration calorimetry and steady state fluorescence experiments show that apoS100A13 exhibits preferential binding to small unilamelar vesicles of l-phosphatidyl serine (pS). In comparison, Ca2+-bound S100A13 is observed to bind weakly to unilamelar vesicles (SUVs) of pS. Equilibrium thermal unfolding and limited trypsin digestion analysis reveal that apoS100A13 is significantly destabilized upon binding to SUVs of pS. Results of the far UV circular dichroism and ANS (8-anilino-1-napthalene sufonate) binding experiments indicate a subtle conformational change resulting in the increase in the solvent-accessible hydrophobic surface in the protein. Availability of the solvent-exposed hydrophobic surface(s) in apoS10013 facilitates its interaction with the lipid vesicles. Our data suggest that Ca2+ binding dictates the membrane binding affinity of S100A13. Based on the results of this study, a model describing the sequence of molecular events that possibly can occur during the non-classical secretion of FGF-1 is presented.