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  • Author or Editor: A. Király x
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Similarities and differences in the immune systems of plants and animals are discussed in relation to non-specific and specific immunity (resistance), systemic acquired resistance (immune memory), transgenerational immune memory and gene silencing. Furthermore, we attempt to answer the question “what is inhibiting or killing pathogens during the immune (resistance) process”? Therefore, the possible roles of reactive oxygen species and antioxidants in pathogen inhibition are evaluated in different types of plant disease resistance.

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In plants, recognition of a pathogen as an invader may result in the formation of hypersensitive response (HR) lesions, i.e. localized programmed cell and tissue death associated with restriction of the pathogen to the infection site. A transient suppression of antioxidants is known to occur during relatively early stages of the HR. Here we show that the transient suppression of a catalase and an alternative oxidase gene during virusinduced local lesion formation (HR) has similar kinetics in different hosts regardless of the extent of leaf necrotization. Both Nicotiana edwardsonii var. Columbia and a paraquat tolerant N. tabacum biotype display significantly less and smaller necrotic lesions in response to inoculation by two viruses ( Tobacco mosaic virus and Tobacco necrosis virus ) in comparison to control plants ( N. edwardsonii and N. tabacum cv. Samsun, respectively). We found that all of these plant hosts display a transient suppression of catalase and alternative oxidase transcript levels starting within six hours after virus inoculation. Our results suggest that the transient decline in antioxidant activity during early stages of an HR does not significantly influence the extent of localized cell death around infection sites.

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Abstract  

Four different samples of NdX, NdY, NdNH4X and NdNH4Y-zeolites were prepared by ionexchange methods. DTA and XRD analyses have been carried out for the samples. The thermally activated zeolites were irradiated by 1.5 and 10.0 Mrad -rays. The catalytic activities of these samples were tested in dehydration of isopropanol. The results of DTA indicated that all samples showed endothermic peaks at about 215 °C related to the release of physically adsorbed water and exothermic peaks at 850–950 °C indicating the collapses of the zeolite. The X-ray analysis revealed that the exchange of sodium by neodymium or ammonium followed by neodymium ions did not change the crystal structure but some decrease in the crystallinity was observed. The catalytic activities of these zeolites were measured in dehydration of isopropanol as a function of temperature. It was found that the activity of the prepared Nd-zeolites depends on the crystallinity of zeolites and on the condensation products formed on catalyst surface. However, the irradiated samples exhibited higher catalytic activities in isopropanol conversion than the unirradiated ones. The observed higher activity for irradiated samples was attributed to the increase of the number of acidic centers responsible for dehydration of alcohols. These centers were formed as a result of the formation of tricoordinate aluminium atoms in -irradiated zeolites.

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The effect of the porcine myogenin (Myog) 3' polymorphism on birth weight, growth rate, carcass weight, lean weight, lean meat percentage and backfat thickness has been investigated in Hungarian Large White pigs. MYOG genotypes were determined by PCR-RFLP assay. The obtained MYOGA frequency value was 0.6275. Due to the small number of BB piglets the effect of the MYOG genotypes on birth weight was not significant; however, an increasing tendency was observed from genotype AA to BB. The growth rate difference between MYOG genotypes was significant: BB animals showed the highest growth rate values during the fattening period. Since few results are available on the possible use of MYOG gene polymorphism in selection to improve carcass and growth traits, by this study the authors hope to provide additional data on this particular subject.

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High concentrations of the reactive oxygen species (ROS) superoxide (O2 •−) and hydrogen peroxide (H2O2) contribute to the induction of plant cell and tissue death (necrosis). In an effort to create transgenic plants with high antioxidant capacity that could resist necrotic symptoms we produced two transgenic tobacco (Nicotiana tabacum cv. SR1) lines (S1 and S2) overexpressing a tomato chloroplast superoxide dismutase (SlChSOD). SOD genes encode for antioxidant enzymes that dismutate superoxide to hydrogen peroxide. Therefore, SOD-overproducing plants may contain high levels of hydrogen peroxide and are sensitive to stress-related necrosis unless sufficient degradation of hydrogen peroxide is conferred by elevated expression of antioxidants like e.g. catalases and peroxidases. Indeed, line S1 displayed elevated expression of a glutathione peroxidase (NtGPX) and a glutathione S-transferase (NtGSTU1b), as compared to wild type plants. Interestingly, however, expression of a catalase (NtCAT1) was repressed in both SOD-overexpressing lines. This predicts that such plants could be sensitive to localized necrosis (HR) caused by virus infection, since repression of NtCAT1 has been shown to occur during virus-induced HR (e.g. Dorey et al., 1998; Künstler et al., 2007). To elucidate whether other catalases might play a role in resistance to virus induced HR-type necrotic symptoms, a maize catalase (ZmCat2) was transiently overexpressed in Nicotiana edwardsonii and N. edwardsonii var. Columbia plants by agroinfiltration. Inoculation of agroinfiltrated plants with Tobacco mosaic virus (TMV) revealed that ZmCat2 confers enhanced resistance to HR-type necrosis during TMV infection. It seems that catalases may play different roles in influencing resistance to virus-induced hypersensitive necrosis.

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Erwinia amylovora (Burrill, Winslow et al.) is one of the most important pathogens of pear and apple and subject to strict quarantine regulations worldwide. Fire blight disease causes serious damages in pear orchards in Hungary. The aim of our experiment was to test the susceptibility of pear cultivars to Hungarian E. amylovora isolates under laboratory conditions. For inoculation test isolates were chosen from different host plants, areas and years. Seven traditional pear cultivars were chosen for testing. Fruit infection was rated according to the diameter of spots produced by the pathogen around the inoculation puncture. Cultivars and isolates were assigned to five susceptibility groups (symptomless, low susceptibility, moderate susceptibility, susceptible and very susceptible). The Hungarian Erwinia amylovora isolates showed different results. We found different susceptibility of traditional pear cultivars. The cultivars Alexander Lucas and Stössel tábornok represented the less susceptible category. Eldorado, Serres Olivér, Diel vajkörte were moderately susceptible. Thus, the most susceptible cultivars were Téli esperes and Drouard elnök. In conclusion, these results can be used for the classification of Erwinia amylovora isolates and in future breeding programmes for resistance.

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Fatty acid hydroperoxide-producing lipoxygenase (LOX) and hydroperoxide-degrading glutathione peroxidase (GPOX) enzyme activities were studied in leaves of virus resistant Xanthi-nc and susceptible Samsun-nn tobacco cultivars after inoculation with Tobacco mosaic virus (TMV). Total LOX activity showed a maximum at pH 5.5 in cell-free extracts of uninfected leaves. LOX activity markedly increased at this pH after TMV inoculation, but a substantial induction was detected also in the basic pH range with an emerging peak around pH = 8.5. TMV-elicited LOX induction was weaker and appeared later in Samsun-nn than in Xanthi-nc leaves. GPOX activity was also substantially induced by TMV infection. However, this induction appeared only 4 days post-inoculation in resistant Xanthi-nc plants in tissues surrounding the localized necrotic lesions. In contrast, GPOX activity did not change in TMV-inoculated, susceptible Samsun-nn leaves. Several glutathione S-transferase (GST) isoenzymes also display GPOX activity. The expression of a tau class GST gene was markedly induced by TMV inoculation in Xanthi-nc leaves. This tobacco GST gene was partially cloned and sequenced.

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Abstract  

Different Nd-zeolites were prepared from the original NaX and NaY zeolites by ion exchange. The hydrated and thermally activated (at 550 °C) samples obtained were irradiated with -rays of 1.5 and 10.0 Mrad. The unirradiated and irradiated samples were characterized mainly by X-ray diffraction and tested for catalytic activity in cumene cracking. The X-ray diffraction patterns indicated a slight decrease of crystallinity after irradiation. However, the irradiated samples exhibited higher catalytic activities than unirradiated ones. -Irradiated hydrated zeolites were found to possess comparable activities, whereas the irradiated dehydrated samples were more active. Higher irradiation doses resulted in more active dehydrated zeolites than those irradiated with a lower dose. The observed higher activity was attributed to the formation of tricoordinate aluminium atoms in the zeolite structure, leading to increase of the number of acidic sites and consequently to a catalytic activity.

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The plasmid profiles of virulent Rhodococcus equistrains isolated on three horse-breeding farms located in different parts of Hungary were investigated. From 49 soil samples collected on the three farms, 490 R. equiisolates (10 from each sample) were obtained and tested for the presence of 15- to 17-kDa antigens (VapA) by immunoblotting and PCR. Ninety-eight VapA-positive isolates were detected from 30 of the 49 culture-positive samples with a prevalence ranging from 13.1% to 23.2%. Of the 98 virulent isolates, 70 contained an 85-kb type I plasmid, 13 contained an 87-kb type I plasmid, and 15 contained an 85-kb type III plasmid which had been uniquely isolated from soil isolates in the United States. This study demonstrates that the virulent form of R. equiis very widespread in the soil environment of these stud farms in Hungary and the plasmid pattern is different from farm to farm.

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Acta Botanica Hungarica
Authors: Cs. Molnár, Zs. Molnár, Z. Barina, N. Bauer, M. Biró, L. Bodonczi, A. Csathó, J. Csiky, J. Deák, G. Fekete, K. Harmos, A. Horváth, I. Isépy, M. Juhász, J. Kállayné Szerényi, G. Király, G. Magos, A. Máté, A. Mesterházy, A. Molnár, J. Nagy, M. Óvári, D. Purger, D. Schmidt, G. Sramkó, V. Szénási, F. Szmorad, Gy. Szollát, T. Tóth, T. Vidra and V. Virók

The first version of the map of the Hungarian vegetation-based landscape regions were prepared at the scale of 1: 200,000 (1 km or higher resolution). The primary goal of the map was to provide an exact background for the presentation and evaluation of the data of the MÉTA database. Secondly, we intended to give an up-to-date and detailed vegetation-based division of Hungary with a comprehensive nomenclature of the regions. Regions were primarily defined on the basis of their present zonal vegetation, or their dominant extrazonal or edaphic vegetation. Where this was not possible, abiotic factors that influence the potential vegetation, the flora were taken into consideration, thus, political and economical factors were ignored. All region borders were defined by local expert botanists, mainly based on their field knowledge. The map differs in many features from the currently used, country-wide, flora-or geography-based divisions in many features. We consider our map to be temporary (i.e. a work map), and we plan to refine and improve it after 5 years of testing.

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