Die Tomate ist weltweit eines der am meist konsumierten Gemüse, doch der hohe Verzehr erhöht auch das Risiko einer allergischen Reaktion. Zu den Allergenen zählen viele Proteine der Pflanzenabwehr, welche durch verschiedenste biotische und abiotische Stressoren induziert werden. Allerdings ist bis heute der Einfluss biotischer Faktoren auf die Allergenität von Obst und Gemüse weitestgehend unbekannt. Diese Dissertation befasst sich mit den Auswirkungen der symbiontischen Mykorrhiza und des pathogenen Pepino Mosaikvirus auf die Allergenität von Tomaten. Früchte von mykorrhizierten Tomatenpflanzen wiesen eine höhere Expression allergenkodierender Gene auf als die nicht mykorrhizierten Kontrollen, allerdings übertrug sich dies nicht auf die Allergenität der Tomaten. Pepino Mosaikvirus-infizierte Tomatenpflanzen zeigten keine generelle Aktivierung der Allergenexpression und auch keine erhöhte Allergenität. Aufgrund großer individueller Reaktionsunterschiede der Probanden in den klinischen Allergietests konnten einzeln auftretende Unterschiede nicht über die Gesamtheit der getesteten Allergiker abgesichert werden. Die individuellen Reaktionen der Probanden konnten wiederum nicht auf die Anzahl und Identität der Allergene von Tomatenpflanzen mit unterschiedlichen genetischen Hintergründen oder aus verschiedenen Anbauweisen zurückgeführt werden. Während der Experimente wurden 13 neue putative Tomatenallergene identifiziert unter denen das Cyclophilin rekombinant in Escherichia coli hergestellt und seine allergene Aktivität bestätigt wurde. Schlussfolgernd nahmen biotische Faktoren keinen nennenswerten Einfluss auf die Allergenität von kommerziell angebauten Tomaten. Über dies hinaus wurden neue Erkenntnisse über persistente Virus-Pflanzen Interaktionen gewonnen. Schließlich konnte die Liste der putativen Tomatenallergene um einige Kandidaten erweitert werden, von denen das Cyclophilin als Allergen bestätigt wurde. / Tomatoes are now among most consumed vegetables worldwide; unfortunately accompanied by an increasing risk of allergic reactions. Pathogenesis-related proteins can act as allergens and are induced by various biotic and abiotic stresses. Up to now nearly nothing is known about the impact of biotic factors on allergenic potentials. This thesis investigates the allergenicity of symbiotically mycorrhized and Pepino mosaic virus-infected tomato fruits. Although induced allergen-encoding gene expression was detected in the fruits of mycorrhizal tomato plants, there was no impact on allergenicity. In contrast, general induction of defence-related allergens in Pepino mosaic virus-infected tomato fruits was not observed. Consequently, clinical allergy tests did not reveal any generally increased allergenic potential of Pepino mosaic virus-infected tomato fruits. High inter-individual differences in clinical allergy tests made it difficult to make statistically confirmed statements about the allergenicity of colonised tomato fruits. However, the hypothesis that such individual variability is based on differential reactions of individual subjects to particular allergens in tomato fruits, from plants with certain genetic backgrounds or cultivated under distinct conditions, had to be rejected. During these investigations, 13 new putative tomato allergens were identified. One of the candidates, cyclophilin, was recombinantly produced in Escherichia coli and its allergenic activity was confirmed in different clinical allergy tests with tomato-allergic subjects. In conclusion, this study demonstrates that biotic factors are only of minor importance for the allergenic potential of commercially produced tomatoes. Moreover, the experiments revealed new insights into persistent plant-virus interactions. In particular, these extended the list of putative tomato allergens to include new candidates, and confirmed the allergenic activity of one of these, namely cyclophilin.

No description available.

Stretches of forest along the Limpopo and Shashe Rivers have been classified as a unique forest type in the vegetation of South Africa and are considered as being "critically endangered" by the South African Biodiversity Institute. Roughly 400 hectares of this riverine forest area inside the western section of the Mapungubwe National Park (MNP), a UNESCO World Heritage site, were deforested and therefore degraded due to previous agricultural cultivation practices. Given the extent of forest degradation that has occurred, the restoration of this area by means of the re–vegetation of indigenous trees to its former composition is one of the objectives of the MNP's management plan. The successful establishment of tree seedlings, especially in semi–arid systems, is however presented with a wide range of constraints and limiting conditions, which often result in very high mortality rates during restoration projects. An experimental exclosure, as identified by South African National Parks (SANParks), was therefore fenced off inside the degraded old lands to act as a demonstration site for the restoration of indigenous trees. A pilot study conducted in 2006, involved the transplantation of selected indigenous tree species with the aim of evaluating suitable re–vegetation technologies. The research contained in this dissertation was also conducted inside the experimental exclosure, where recommendations derived from the pilot study were evaluated, including the assessment of new re–vegetation technologies to enhance the establishment of the indigenous trees. This study was therefore a follow–up project which involved both field– and greenhouse trials. Seedlings of the following species were either transplanted into the experimental exclosure (field trial) or cultivated inside a controlled environment in the greenhouse at the North–West University: Acacia xanthophloea Benth. (fever tree), Berchemia discolor (Klotzsch) Hemsl. (brown–ivory), Combretum imberbe Wawra (leadwood), Faidherbia albida (Delile) A. Chev. (ana tree), Philenoptera violacea (Klotzsch) Schrire (apple–leaf), Salvadora australis Schweick. (narrow–leaved mustard tree) and Xanthocercis zambesiaca (Baker) Dumaz–le–Grand (nyala tree). During the follow–up study the effects of various enhancement treatments were tested regarding the survival, growth and physiological performance of seedlings in both the field– and greenhouse trials. The enhancement treatments consisted of the addition of compost and indigenous arbuscular mycorrhizal fungi (AMF). In addition, seedlings transplanted during the pilot study, which did not include enhancement treatments, were also monitored for establishment and growth. The potential use of established Acacia tortilis Hayne trees to facilitate growth and establishment and to act as "nursing plants", was also assessed. In addition, various pre–sowing treatments were also applied to seeds of selected tree species in the greenhouse to assess the germination rate. The survivorship and growth of seedlings in both the field– and greenhouse trial were determined by using three growth parameters, namely "stem diameter at the base", "stem diameter 30 cm from the base", and "height of the tree in its natural growth form". Chlorophyll fluorescence induction (JIP test) was measured on seedlings in both trials, using the multi–parametric expression, namely performance index (PIABS), as a measure of the overall vitality of the plants of each species–treatment combination. Physical and chemical analyses were carried out on the soil inside the experimental exclosure. Basic descriptive statistics were used to analyse seedling survival and germination rates, and a two–way analysis of variance (ANOVA) was used to determine the statistical significant effects of the various enhancement treatments on diameter growth in each species (p < 0.05). Fluorescence data were processed using the Biolyzer software and significant effects in each species were determined using the Student's t–test (p < 0.05). Multivariate data ordinations using the CANOCO package were used to determine the differences in soil types inside the experimental exclosure. Moisture stress due to transplantation shock, competition with dense grass cover and herbivory, resulted in an overall 55.8% seedling survival rate and negative stem diameter growth for transplanted seedlings in the field. In comparison, seedlings cultivated in the greenhouse had much higher survival rates and showed positive stem diameter growth. Most species in the greenhouse showed higher growth rates and significantly higher vitality values when planted with enhancement treatments. The responses of transplanted seedlings to the enhancement treatments were very species–specific in the field trials. Based on these results, it was concluded that the enhancement treatments were beneficial with regard to the establishment and growth of most of the species. The beneficial effect was however cancelled out by the various abiotic and biotic factors encountered in the natural environment. Seedlings transplanted in the understory of established pioneer A. tortilis trees had much lower survival rates as the extensive root system of A. tortilis most likely out–competed the transplanted seedlings for moisture and nutrients. Many seedlings were also predated by insects or small mammals which reduced the growing potential. The germination trials recorded the highest germination rates for most species when germinated in the compost–containing treatments. These trials also indicated that all of the investigated species showed higher survival rates when pre–sowing treatments, such as soaking, mechanical scarification and removing the seed from fruit, were applied. Various recommendations emphasising long–term monitoring, proper maintenance and after–care of future restoration efforts are made. These include experimental layout of exclosure plots and pretransplantation treatments of seedlings while cultivated in the nursery. During this study, the experimental exclosure was also used as a demonstration site for training and capacity building for SANParks personnel and students from academic institutions. / Thesis (M.Sc. (Environmental Science))--North-West University, Potchefstroom Campus, 2011.

Stretches of forest along the Limpopo and Shashe Rivers have been classified as a unique forest type in the vegetation of South Africa and are considered as being "critically endangered" by the South African Biodiversity Institute. Roughly 400 hectares of this riverine forest area inside the western section of the Mapungubwe National Park (MNP), a UNESCO World Heritage site, were deforested and therefore degraded due to previous agricultural cultivation practices. Given the extent of forest degradation that has occurred, the restoration of this area by means of the re–vegetation of indigenous trees to its former composition is one of the objectives of the MNP's management plan. The successful establishment of tree seedlings, especially in semi–arid systems, is however presented with a wide range of constraints and limiting conditions, which often result in very high mortality rates during restoration projects. An experimental exclosure, as identified by South African National Parks (SANParks), was therefore fenced off inside the degraded old lands to act as a demonstration site for the restoration of indigenous trees. A pilot study conducted in 2006, involved the transplantation of selected indigenous tree species with the aim of evaluating suitable re–vegetation technologies. The research contained in this dissertation was also conducted inside the experimental exclosure, where recommendations derived from the pilot study were evaluated, including the assessment of new re–vegetation technologies to enhance the establishment of the indigenous trees. This study was therefore a follow–up project which involved both field– and greenhouse trials. Seedlings of the following species were either transplanted into the experimental exclosure (field trial) or cultivated inside a controlled environment in the greenhouse at the North–West University: Acacia xanthophloea Benth. (fever tree), Berchemia discolor (Klotzsch) Hemsl. (brown–ivory), Combretum imberbe Wawra (leadwood), Faidherbia albida (Delile) A. Chev. (ana tree), Philenoptera violacea (Klotzsch) Schrire (apple–leaf), Salvadora australis Schweick. (narrow–leaved mustard tree) and Xanthocercis zambesiaca (Baker) Dumaz–le–Grand (nyala tree). During the follow–up study the effects of various enhancement treatments were tested regarding the survival, growth and physiological performance of seedlings in both the field– and greenhouse trials. The enhancement treatments consisted of the addition of compost and indigenous arbuscular mycorrhizal fungi (AMF). In addition, seedlings transplanted during the pilot study, which did not include enhancement treatments, were also monitored for establishment and growth. The potential use of established Acacia tortilis Hayne trees to facilitate growth and establishment and to act as "nursing plants", was also assessed. In addition, various pre–sowing treatments were also applied to seeds of selected tree species in the greenhouse to assess the germination rate. The survivorship and growth of seedlings in both the field– and greenhouse trial were determined by using three growth parameters, namely "stem diameter at the base", "stem diameter 30 cm from the base", and "height of the tree in its natural growth form". Chlorophyll fluorescence induction (JIP test) was measured on seedlings in both trials, using the multi–parametric expression, namely performance index (PIABS), as a measure of the overall vitality of the plants of each species–treatment combination. Physical and chemical analyses were carried out on the soil inside the experimental exclosure. Basic descriptive statistics were used to analyse seedling survival and germination rates, and a two–way analysis of variance (ANOVA) was used to determine the statistical significant effects of the various enhancement treatments on diameter growth in each species (p < 0.05). Fluorescence data were processed using the Biolyzer software and significant effects in each species were determined using the Student's t–test (p < 0.05). Multivariate data ordinations using the CANOCO package were used to determine the differences in soil types inside the experimental exclosure. Moisture stress due to transplantation shock, competition with dense grass cover and herbivory, resulted in an overall 55.8% seedling survival rate and negative stem diameter growth for transplanted seedlings in the field. In comparison, seedlings cultivated in the greenhouse had much higher survival rates and showed positive stem diameter growth. Most species in the greenhouse showed higher growth rates and significantly higher vitality values when planted with enhancement treatments. The responses of transplanted seedlings to the enhancement treatments were very species–specific in the field trials. Based on these results, it was concluded that the enhancement treatments were beneficial with regard to the establishment and growth of most of the species. The beneficial effect was however cancelled out by the various abiotic and biotic factors encountered in the natural environment. Seedlings transplanted in the understory of established pioneer A. tortilis trees had much lower survival rates as the extensive root system of A. tortilis most likely out–competed the transplanted seedlings for moisture and nutrients. Many seedlings were also predated by insects or small mammals which reduced the growing potential. The germination trials recorded the highest germination rates for most species when germinated in the compost–containing treatments. These trials also indicated that all of the investigated species showed higher survival rates when pre–sowing treatments, such as soaking, mechanical scarification and removing the seed from fruit, were applied. Various recommendations emphasising long–term monitoring, proper maintenance and after–care of future restoration efforts are made. These include experimental layout of exclosure plots and pretransplantation treatments of seedlings while cultivated in the nursery. During this study, the experimental exclosure was also used as a demonstration site for training and capacity building for SANParks personnel and students from academic institutions. / Thesis (M.Sc. (Environmental Science))--North-West University, Potchefstroom Campus, 2011.

Symbiosis with endomycorrhiza is found in a majority of plant-fungal symbioses. The symbiosis helps with various stressors such as drought and malnutrition. This study looked at how four different field, meadow and brook plants - Centaurea cyanus, Galium verum, Viscaria vulgaris and Veronica beccabunga - are affected by mycorrhiza and fertilizer treatment. The hypotheses tested whether mycorrhiza occurrence and fertilizer treatment affected the total number and number of mature and open flowers in C. cyanus as well as whether mycorrhiza occurrence and fertilizer treatment affected the aboveground biomass and the underground biomass of the four plant species. The study looked at 160 plants and a total of 40 plants of each species were planted. Per species, there were 10 control plants, 10 pots with mycorrhiza and 10 pots with fertilizer as well as 10 pots with both mycorrhiza and fertilizer. The pot arrangement was randomized. Mycorrhizal fungi were collected together with plant roots from different grass and forest habitats. The fertilizer treatment was applied once a week and lasted for six weeks. Two-way ANOVA was used in the analyses of the number of flowers in C. cyanus and three-way ANOVA was used in the analyses of aboveground and underground biomass. Fertilizer treatment had statistically significant effects on both the total number of flowers and the number of mature and open flowers. Fertilizer treatment also increased the aboveground of the selected species as well as the underground biomass of C. cyanus. The underground biomass of the other species decreased. However, the study could not find any significant effect of mycorrhiza treatment nor any significant interaction between mycorrhiza treatment and fertilizer treatment. The study did not test whether or how much of the mycorrhiza colonization was successful and the nonsignificant result may be due to several reasons. More research is needed to confirm the results in this study. / Symbios med endomykorrhiza återfinns hos en majoritet av växt-svampsymbioser. Symbiosen hjälper vid olika typer av stress såsom torka och näringsbrist. Denna studie tittade på hur fyra olika åker-, ängs- och bäckväxter - Centaurea cyanus, Galium verum, Viscaria vulgaris och Veronica beccabunga - påverkas av mykorrhiza och gödsling. Hypoteserna testade om mykorrhizaförekomst och gödsling påverkar det totala antalet och antalet utslagna blommor hos C. cyanus samt ovanjordsbiomassan och underjordsbiomassan hos de fyra växterna. Undersökningen tittade på 160 plantor och totalt planterades 40 plantor av varje art. Per art fanns 10 kontrollplantor, 10 krukor med mykorrhiza och 10 krukor med gödsling samt 10 krukor med både mykorrhiza och gödsling. Krukorna planterades ut slumpmässigt. Mykorrhizasvampar samlades in tillsammans med växtrötter från olika gräs- och skogshabitat. Kvävebehandlingen skedde en gång i veckan och varade i sex veckor. Två-vägs-ANOVA användes vid analys av antal blommor hos C. cyanus och tre-vägs-ANOVA användes vid analys av ovanjords- och underjordsbiomassa. Kvävebehandling kunde signifikant visas öka både det totala antalet blommor och antalet utslagna blommor. Kvävebehandling ökade även ovanjordsbiomassan hos de utvalda arterna samt underjordsbiomassan hos C. cyanus. Underjordsbiomassan minskade hos de andra arterna. Studien kunde emellertid inte hitta någon signifikant effekt av mykorrhizabehandling och inte heller någon signifikant interaktion mellan mykorrhizabehandling och kvävebehandling. I studien testades inte om eller hur mycket av mykorrhizakoloniseringen var framgångsrik och det icke-signifikanta resultatet kan ha haft flera orsaker. Mer forskning behövs för att bekräfta resultaten i denna studie.

Mycorrhizal fungi are soil-borne organisms that form symbiotic associations with the majority of land plants. These fungi gather and exchange mineral nutrients with plants for photosynthetically derived carbohydrates. Mycorrhizal fungi can also confer other benefits onto plants, e.g. defense against pathogens, improved water relations, tolerance to heavy metal toxicity and herbivory. The influence of mycorrhizal fungi on plant mineral nutrition and response to stress suggests that these organisms may have a role to play sustainable agriculture as well as in bioremediation and ecosystem restoration. In contributing to this important research, I investigated host-specific interactions between mycorrhizal fungi and the sex morphs of the gynodioecious perennial herb Polemonium foliosissimum (Polemoniaceae) and their mycorrhizal associates in the field. I hypothesized that the genders of this species differed in their associations with mycorrhizal fungi in benefits received. I performed a full factorial simulated herbivory experiment and evaluated the extent of mycorrhizal colonization in the roots as well as the concentrations of nutrients in leaf tissue. Mycorrhizal colonization and leaf nutrient concentrations did not differ between the genders nor were influenced by the experimental treatments. This suggests that the genders of Polemonium foliosissimum do not interact differently with mycorrhizal fungi, and thus do not represent different "hosts". Also, I investigated local adaptation of mycorrhizal associations by exploring the effect of large herbivore grazing on plant-mycorrhizal associations. I hypothesized that grazing by large herbivores results in locally adapted symbioses that enhance plant response to herbivory. I grew the perennial bunchgrass Themeda triandra (Poaceae) in inoculum prepared from soils collected from three field exclosures with differing histories of large herbivore exclusion in the Kenya Long Term Exclosure Experiment. I conducted a full factorial simulated herbivory experiment in which plants were subject to two clipping events over the course of 5-months, and evaluated plant regrowth as well as mycorrhizal colonization for plants in the experiment. Plants grown in inoculum from exclosures in which large herbivores have had access produced more root mass when mycorrhizal fungi were present. Further, I found equivalent biomass production of clipped and non-clipped plants in inoculum prepared from the exclosure with only native large herbivore access while equivalent biomass production was not found in the substrate prepared from areas with a history of large herbivore exclusion. This suggests that mycorrhizal fungi mediate plant growth and response to herbivory in this system.

The thesis deals with the effect of arbuscular mycorrhiza (AM) on the growth of selected plant species at a locality in České středohoří. This locality is characterized by close neighborhood of a semi-natural dry grassland and a former field abandonned in the 1990s, typical for the mosaic of biotopes in the region. The study is based on previous findings that some plant species, which are common at the semi-natural dry grasslands, do not colonize the abandoned fields. As AM is an important factor affecting diversity and productivity of plant communities we hypothesized that this phenomenon could be related to changes in AM fungal communities at the abandoned field. The hyphothesis was tested in a greenhouse pot experiment with three taxonomically related pairs of plant species, always one species growing at the abandoned field and the second one not. Growth and phosphorus uptake of the plants was followed in soils of both biotopes after factorial inoculation with AM fungal communities from both biotopes. The experiment was complemented by description of AM fungal communities in the roots of six plant species pairs from the locality using terminal restriction fragment length polymorphism (T-RFLP). The greenhouse experiment revealed positive mycorrhizal response in all plant species, but the origin...

The decomposition of plant biomass is associated with changes of the associated fungal community which is crucial in the process of degradation due to their production of extracellular enzymes. Moreover, fungal communities as well as enzymatic activity are specific for soil microhabitats. This thesis focused on the importance of fungi associated with the roots of Norway spruce (Picea abies) trees. Forest with dominating Norway spruce, located in the School Forest Enterprise Křtiny area in Moravia, was selected for the experiment. The aim of this thesis was to compare the community composition of fungi in the roots, rhizosphere and bulk soil and to describe the gradual development of this community after the death of the roots. The next aim was to isolate, describe and characterize those fungi that decomposed roots 5 and 9 months after tree harvest. Identification of fungal isolates was based on DNA sequencing. Degradation capabilities were determined as the activity of enzymes involved in the degradation of lignocellulose. Composition of fungal communities was described by sequencing of environmental DNA on the Illumina platform. Before the flow of assimilates from the live trees stopped, communities of ectomycorrhizal fungi dominated with 60 % of all sequences. Increased abundance of saprotrophic...

Micorrizas arbusculares (MAs) são associações simbióticas entre os fungos do filo Glomeromycota e a maioria das plantas. Os mecanismos moleculares que controlam o processo de colonização e desenvolvimento das MAs são ainda pouco conhecidos, mas proteínas com acúmulo diferencial em MAs podem ter papel regulatório importante. O presente trabalho teve como objetivo detectar, por meio de eletroforese bi-dimensional (2D-PAGE) e espectrometria de massas, proteínas com acúmulo diferencial no fluido intercelular (FI), membrana plasmática ou tecido radicular de cana-de-açúcar colonizada por Glomus clarum. Plântulas de cana-de-açúcar micropropagadas foram inoculadas com G. clarum e cultivadas com 20 ou 200 mg de P kg-1 de substrato. Raízes micorrizadas e não-micorrizadas, 8 semanas após a inoculação, foram utilizadas para a extração de proteínas do FI, membrana plasmática e tecido radicular (solúveis totais). As proteínas foram separadas por 2D-PAGE e analisadas por espectrometria de massas. Os perfis de proteínas solúveis totais e de membrana plasmática não revelaram proteínas relacionadas à simbiose. No entanto, três proteínas do FI, uma hidrolase aspártica putativa, uma histidina quinase putativa e uma peroxidase putativa apresentaram acúmulo induzido em raízes micorrizadas. As atividades de peroxidases nas raízes e apoplasto das raízes foram determinadas. A atividade de peroxidase apoplástica foi maior em raízes colonizadas e cultivadas em baixo teor de P, quando comparado com controles não-inoculados. Com base na seqüência parcial de aminoácidos dessa peroxidase, um fragmento de seu gene (POX1) foi amplificado e clonado a partir de cDNA de raízes de cana-de-açúcar. A sequência obtida mostrou 90% e 91% de identidade com peroxidase de milho (NCBI) e cana-de-açúcar (TIGR), respectivamente. A análise de expressão de POX1 foi feita por PCR quantitativo a partir de transcritos extraídos de raízes micorrizadas e não-micorrizadas, em condições de baixo e alto P. O acúmulo de transcritos de POX1 em raízes micorrizadas em condições de baixo P foi 6,8 vezes maior do que em raízes micorrizadas cultivadas em condições de alto P. Raízes micorrizadas e cultivadas em condições de alto P apresentaram acúmulo de transcritos 3,9 vezes menor do que em raízes nãomicorrizadas cultivadas nas mesmas condições de P. Os dados obtidos sugerem que o controle do metabolismo de espécies ativas de oxigênio é um dos fatores que contribuem para a regulação do desenvolvimento de MAs. Estudos com plantas alteradas para a expressão de POX1 são, no entanto, necessários para elucidar a essencialidade dessa peroxidase nas MAs. / Arbuscular mycorrhizae (AM) are symbiotic associations between fungi of the phylum Glomeromycota and most of the plant species. Even though the molecular mechanisms controlling the colonization process and AM development are largely unknown, proteins with differential accumulation in AM may have important regulatory roles. The aim of this work was to detect, by bi-dimensional electrophoresis (2D-PAGE) and mass spectrometry, proteins with differential accumulation in the intercellular fluid (IF), plasma membrane or radicular tissue of sugarcane colonized by Glomus clarum Micropropagated sugarcane plantlets were inoculated with G. clarum and growth under low or high P conditions, 20 or 200 mg P kg-1 substrate, respectively. Mycorrhizal and non-mycorrhizal roots, eight weeks after inoculation, were used to extract proteins from the IF, plasma membrane and root tissue (total soluble proteins). Protein separation and analyses were performed using 2D-PAGE and mass spectrometry. The total soluble and plasma membrane protein profiles did not reveled symbiosis-related proteins. However, three proteins from the IF, a putative aspartic hydrolase, a putative histidine kinase and a putative peroxidase showed induced accumulation in mycorrhizal roots. Peroxidase activities in roots and apoplastic fluid were determined, and shown to be higher in mycorrhizal roots at low P than in non-mycorrhizal control roots. Based on the partial amino acid sequence of this peroxidase, a partial cDNA sequence of its gene (POX1) was cloned from PCR-amplified cDNA from sugarcane roots. The POX1 sequence showed 90% and 91% identity to maize (NCBI) and sugarcane (TIGR) peroxidase, respectively. Expression analyses of POX1 were perfomed using quantitative PCR of reverse transcripts from mycorrhizal and non-mycorrhizal roots at low and high P conditions. The steady state level of POX1 transcripts in mycorrhizal roots at low P condition was 6.8-fold higher than in mycorrhizal roots at high P conditions. In mycorrhizal roots at high P conditions the steady state level of POX1 transcripts was 3.9-fold lower than in nonmycorrhizal control roots. These data suggest that the metabolism of reactive oxygen species may be an important factor controlling the development of AM. Studies with plants altered in POX1 expression are, however, required to elucidate the essentiality of this peroxidase in AM.

Os solos brasileiros são predominantemente ácidos, ocorrência comum nas regiões tropicais. Esta condição, aliada a outros fatores abióticos e bióticos, pode resultar em toxicidade de manganês (Mn) às plantas, o que limita o seu desenvolvimento. A utilização de práticas agrícolas convencionais propicia o aumento da toxidez de Mn, à medida que reduz o teor de matéria orgânica. Para atenuar este problema, algumas práticas como a calagem e o melhoramento genético são amplamente utilizados. Entretanto, a utilização de alternativas de manejo da cultura através do uso da simbiose micorrízica, para induzir maior resistência das plantas a altos níveis de Mn, parece bastante promissora. Para investigar possíveis mecanismos de indução da resistência e interações de nutrientes no controle da toxicidade de Mn em soja, foram avaliados o crescimento, a absorção e a acumulação de Mn, Fe, P e Ca e a atividade de catalase, peroxidase, superóxido dismutase e oxidase de AIA, nas folhas e raízes das plantas micorrizadas e não micorrizadas, além do nível de colonização de raízes pelo fungo micorrízico arbuscular (FMA). A planta teste foi a soja (Glycine max L. Merr. CV. IAC 8-2). O experimento foi executado em casa de vegetação, em vasos preenchidos com 4 Kg de solo classificado como Neossolo Quartzarênico típico, previamente autoclavado para eliminar fungos micorrízicos arbusculares. O delineamento foi inteiramente casualizado, em esquema fatorial, 4x5: dois isolados de FMA, Glomus etunicatum e Glomus macrocarpum, cada qual com 30 mg kg -1 de P adicionado ao substrato e dois controles não inoculados, sendo um com 30 mg kg -1 e outro com 50 mg kg -1 de P, 5 níveis de Mn (0, 5, 10, 20, 40 mg kg -1 ). Foram realizadas duas épocas distintas de colheita, aos 45 e 90 dias. As atividades enzimáticas foram avaliadas pelo método PAGE não-denaturante através de análise visual. Os resultados demonstram que níveis de Mn entre 10 e 40 mg kg -1 no substrato podem induzir respostas de toxidez de Mn em plantas de soja, acompanhadas de redução de crescimento e alterações no padrão de absorção de vários nutrientes vegetais. O aumento da dose de P e a presença da micorriza são fatores de atenuação da toxidez de Mn em soja, visto que plantas micorrizadas contêm menor concentração de Mn em seus tecidos e, de uma maneira geral, menor atividade enzimática de peroxidase (PO) e oxidase do ácido-indolacético (AIA) do que as plantas controles. Aumentos no nível de Mn do substrato podem causar um aumento da atividade de PO e de oxidase de AIA nas plantas, sendo que as plantas mais estressadas quase sempre apresentam maior atividade dessas enzimas. Apesar da superóxido dismutase (SOD) ser também enzima antioxidativa, apresenta um padrão eletroforético diferenciado da PO, sendo que na raiz sua maior atividade está correlacionada com a presença do FMA. / Brazilian soils are predominantly acid, which is considered a common incident in tropical regions. Soil acidity in combination with biotic and non-biotic factors can result manganese toxicity in plants, limiting their development. The use of conventional agricultural practices promotes an increase in Mn toxicity, as it reduces the soil content of organic matter. This problem can be minimized by the use of some tilling practicies like liming and breeding, which are widely used. However, crop management alternatives through the use of mycorrhizae to induce greater Mn tolerance in plants under high levels of Mn seem to be promising. In this work, plant growth, the absorption, distibution of Mn, Fe, P, Ca and activity of catalase, peroxidase, superoxide dismutase and indolacetic acid oxidase were evaluated in leaves and roots of plants inoculated with mycorrhizal fungi and non-inoculated ones, to invetigate a possible resistance induction mechanism and nutrient interactions in control of toxic levels of Mn. A greenhouse experiment was conducted with soybean plant (Glycine max L. Merr. CV. IAC 8-2) in a completely randomized factorial design 4x5: inoculation of two different arbuscular mycorrhizal fungi (AMF): Glomus etunicatum and Glomus macrocarpum, which received 30 mg kg -1 of P, and two non-inoculated controls, one that received 30 mg kg -1 and the other with 50 mg kg -1 of P; 5 levels of Mn (0, 5, 10, 20, 40 mg kg -1 ). There were two harvest periods, 45 and 90 days. The enzymatic activities were evaluated in non-denaturing polyacrilamyde gel eletrophoresis (PAGE). Manganese levels between 10 and 40 mg kg -1 in the substrate can induce Mn toxicity in soybean plants, that results in a growth reduction and in alterations in the nuttrient absorption alterations of the plants. The increase of P and the presence of mycorrhizae result in the alleviation of Mn toxicity in soybean plants. Micorrhizal plants present lower Mn concentration and generally less enzymatic activity of indolacetic acid oxidase and peroxidase than control plants. Although both, peroxidase and superoxide dismutase are antioxidant enzymes, they present differentiated electrophoretic standards. Most of the time peroxidase and indolacetic acid oxidase activities increase due to increasing Mn levels. Superoxide dismutase activity, however, is higher in the shoots of micorrhizal plants when compared to control plants.