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The objective of this work was to assess the impact of various NaCl concentrations on Lactobacillus rhamnosus OXY viability after freeze-drying. Osmotic stress was applied during the exponential growth phase of bacterial culture. At salt concentrations between 0.2–0.5 M, a high biomass concentration and a significant increase in cell viability after lyophilisation was observed. An analysis of two-dimensional protein gels indicated the presence of shock proteins, for example, GroEL, ClpB, DnaK, TF, which provide resistance during freeze-drying and subsequent storage. On the basis of these results, it is recommended that lactic acid bacteria cultures be sub-lethally treated with 0.5 M NaCl before freeze-drying.

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Sharka ( Plum pox virus , PPV), is one of the most serious viral diseases affecting apricot production in those areas that are affected. The development and cultivation of new resistant cultivars could be the definitive solution to the disease. In this process of development and introduction of new resistant cultivars, the availability of a reliable method is of great interest for the evaluation of resistance. The development of molecular (genomic or proteomic) markers linkage to this trait could greatly accelerate this evaluation process in apricot. In this work, a double strategy for the development of molecular markers linkage to PPV resistance in apricot is presented: search for genomic (DNA) markers and study the protein expression through 2D electrophoresis (proteomic markers). The search of DNA markers linkage to the resistance is focused on the application of SSR (simple sequence repeat) markers located in the linkage group I, in which PPV resistance has been located by different authors. On the other hand, studies of activity of antioxidant enzymes and protein expression by 2D electrophoresis have been performed in resistant and susceptible apricot cultivars.

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Commercial sodium caseinate isolate (SCI) was hydrolysed with either protease Subtilisina carlsberg - Alcalase 2.4 FG (purchased from Novo Nordisk), pronase from Streptomyces griseus, and papain EC 3.4.22.2 (both from Sigma) in a two-step process to determine the changes in the immunoreactivity of a-, ß- and ?-casein. Enzymatic hydrolysis of SCI was performed by pH-stat method. Hydrolysates were analysed using IEF, SDS-PAGE, 2D electrophoresis, FPLC-gel permeation chromatography. Immunoreactive properties of peptide fractions separated from the hydrolysates by FPLC were determined using dot-immunobinding and ELISA methods. The two-step process was observed to be effective in reduction of casein fractions immunoreactivity, however, allergenic epitopes were still present in all peptide fractions.

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Acta Phytopathologica et Entomologica Hungarica
Authors: J. Hernández, P. Díaz-Vivancos, M. Rubio, E. Olmos, M. Clemente, A. Ros-Barceló, and P. Martínez-Gómez

The effect of Plum pox virus (PPV) infection on the response of some antioxidant enzymes was studied in Prunus species showing different susceptibility to PPV. PPV infection produced changes in the antioxidant systems from the Prunus species at subcellular level. In general, in PPV susceptible plants, the infection produced a decrease in some antioxidant enzymes, mainly in chloroplasts. However, in peach cv GF305 (PPV-susceptible) also an increase in class I APX in the three compartments studied as well as an increase in POX took place. In contrast, the PPV-resistant plants showed a general increase of antioxidant enzymes in soluble, chloroplast and apoplastic fractions. Long-term PPV infection produced an oxidative stress only in susceptible plants, as observed by the increase in leaf lipid peroxidation, protein oxidation and electrolyte leakage as well as in apoplastic H 2 O 2 . This H 2 O 2 increase was much higher in the PPV-susceptible than in the PPV-resistant plants. In peach, the increase in apoplastic H 2 O 2 correlated with the rise in NADH-POX and PPO activities. However, in apricot leaves, no increases in apoplastic NADH-POX were observed, and the increases in apoplastic H 2 O 2 correlated with increase in PPO activity in both cv. Real Fino (100%) and cv. SEO (40%), where a rise in SOD was detected, too. The specific inhibitor of NADPH oxidase, diphenylene iodonium (DPI), had only small effects on NADH oxidation, whereas it was inhibited almost completely by 1 mM KCN. Therefore, most of the NADH oxidation in the apoplastic space of Prunus species is due to NADH-POX and not NAD(P)H oxidase. In previous studies and by means of 2D electrophoresis, we showed that PPV infection produced the induction of a thaumatin-like protein as well as the decrease of mandelonitrile lyase (MDL) in peach apoplast. Mandelonitrile lyase catalyses the breakdown of mandelonitrile into benzaldehyde and cyanide. Benzaldehyde can be oxidised easily in vivo to produce benzoic acid, the precursor of salicylic acid. It was suggested that decreased MDL activity may result in a decreased SA biosynthesis in PPV-infected peach plants. It is also possible that a decline in antioxidant enzymes and an increase in ROS could be necessary for the establishment of infection and the replication and spread of some plant viruses, in agreement with results described by other authors. Results suggest that the higher antioxidant capacity showed by resistant SEO plants in comparison to PPV-susceptible plants could be associated, among other factors with their resistance to PPV.

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