Percorrer por autor "Oliveira, Maria Margarida"
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- Alergenicidade de soja e milho geneticamente modificados é equivalente à das variedades controloPublication . Fonseca, Cátia; Oliveira, Maria Margarida; Batista, Rita
- Characterization of maize allergens - MON810 vs. its non-transgenic counterpart.Publication . Fonseca, Cátia; Planchon, Sébastien; Renaut, Jenny; Oliveira, Maria Margarida; Batista, RitaOne of the main concerns about genetically modified foods and their potential impacts on human health is that the introduction of a new/ altered gene may putatively alter the expression of others, namely endogenous allergens. We intended to evaluate, and to compare, using quantitative real time RT-PCR technique, the expression of 5 already known maize allergens (Zea m14, Zea m25, Zea m27kD, 50kD Zein and trypsin inhibitor) in MON 810 vs. its non-transgenic counterpart, throughout seed development (10, 16 and 23 days after pollination). We have shown that none of the tested allergen genes presented differential expression, with statistic significance, along all tested seed development stages, in MON810 vs. its conventional counterpart. We have also used bidimensional gel electrophoresis followed by Western blotting with plasma from two maize allergic subjects to characterize their immunologic responses against MON 810 vs. its non-transgenic control. Immunoreactive spots were characterized by MS. We have identified fourteen new IgE-binding proteins present in both transgenic and non-transgenic maize.
- Facts and fiction of genetically engineered foodPublication . Batista, Rita; Oliveira, Maria MargaridaThe generation of genetically engineered (GE) foods has been raising several concerns and controversies that divide not only the general public but also the scientific community. The fear and importance of the new technology, as well as commercial interests, have supported many of the ongoing discussions. The recent increase in the number of GE foods approved for import into the European Union and the increasingly global commercial food trades justify revisiting the facts and fiction surrounding this technology with the aim of increasing public awareness for well-informed decisions. Techniques that have recently become available for assessing food quality and its impact on human health, as well as the wealth of scientific data previously generated, clearly support the safety of commercialized GE products.
- Inducible and constitutive expression of HvCBF4 in rice leads to differential gene expression and drought tolerancePublication . Lourenço, Tiago; Saibo, Nelson; Batista, Rita; Pinto Ricardo, Cândido; Oliveira, Maria MargaridaThe effects of the ectopic expression of a barley transcription factor (HvCBF4) under the control of a constitutive (maize Ubi1) or a stress-inducible (Arabidopsis RD29A) promoter in the abiotic stress response in rice (Oryza sativa L.) was investigated. The transformed plants were analyzed both at molecular and physiological level and the AtRD29A::HvCBF4 plants were further analyzed using the GeneChip® rice genome array under control conditions. Only the plants constitutively expressing HvCBF4 have shown increased survival to drought stress, but not to cold or high-salinity. These plants have also shown better photosynthetic capacity, as determined by chlorophyll fluorescence. Plants expressing AtRD29A::HvCBF4 did not show increased survival to any of the stresses applied. However in the GeneChip® microarray, these plants have shown up-regulation of many stress-responsive genes (> 400) as compared to non-transformed plants. Interestingly, RT-PCR analysis revealed not only differential gene expression between roots and shoots, but also between transgenic lines with the different promoters. Our results indicate that different HvCBF4 expression levels resulted in different transcriptomes and drought tolerance. Given that AtRD29A::HvCBF4 plants did not show increased tolerance to any of the imposed stresses, we may conclude that this promoter may be inappropriate for rice transformation aiming for enhanced abiotic stress tolerance.
- Lack of detectable allergenicity of transgenic maize and soya samplesPublication . Batista, Rita; Nunes, Baltazar; Carmo, Manuela; Cardoso, Carlos; Helena, São José; Almeida, António Bugalho de; Manique, Alda; Bento, Leonor; Ricardo, Cândido Pinto; Oliveira, Maria MargaridaBackground: The safety issues regarding foods derived from genetically modified (GM) plants are central to their acceptance into the food supply. The potential allergenicity of proteins newly introduced in GM foods is a major safety concern. Objective: We sought to monitor, in potentially sensitive human populations, the allergenicity effects of 5 GM materials obtained from sources with no allergenic potential and already under commercialization in the European Union. Methods: We have performed skin prick tests with protein extracts prepared from transgenic maize (MON810, Bt11, T25, Bt176) and soya (Roundup Ready) samples and from nontransgenic control samples in 2 sensitive groups: children with food and inhalant allergy and individuals with asthmarhinitis. We have also tested IgE immunoblot reactivity of sera from patients with food allergy to soya (Roundup Ready) and maize (MON810, Bt11, Bt176) samples, as well as to the pure transgenic proteins (CryIA[b] and CP4 5-enolpyruvylshikimate- 3-phosphate synthase). Results: None of the individuals undergoing tests reacted differentially to the transgenic and nontransgenic samples under study. None of the volunteers tested presented detectable IgE antibodies against pure transgenic proteins. Conclusion: The transgenic products under testing seem to be safe in terms of allergenic potential. We propose postmarket testing as an important screening strategy for putative allergic sensitization to proteins introduced in transgenic plants.
- Maize Allergens during seed development: transgenic versus non-transgenicPublication . Fonseca, Cátia; Oliveira, Maria Margarida; Renaut, Jenny; Planchon, Sébastien; Batista, RitaRecombinant DNA technology, also known as genetic engineering, allows the transfer of genes between unrelated species. As a result, a genetically modified organism (GMO) may contain one or more proteins coming from other organism/s. The application of genetic engineering to plants improvement and food production is becoming a common practice. New and diverse plant varieties have been obtained which are pest and disease resistant, more productive and with improved nutritional quality, flavour and shelf life. In spite of all these potential benefits, some apprehension persist regarding genetically modified organisms putative effects over human health and environment. One of the main concerns regards GMO’s potential allergenicity. One of the possibilities is that the introduction of a new/ altered gene may putatively alter the expression of others, namely endogenous allergens. In maize, there are already some proteins characterized as allergens, namely a lipid transport protein (Pastorello et al. 2000), a tioredoxin Zea m25 (Weichel et al. 2006), two glutelins Zea m27kD (Frisner et al. 2000) and 50kD Zein (Pasini et al. 2002) and one trypsin inhibitor (Pastorello et al. 2000). In this study, we have evaluated the expression of these 5 allergens, throughout MON 810 vs its non-transgenic counterpart seed development (10, 16 and 23 days after pollination). The expression profile of each one of these allergens varies during seed development, although the observed differences between Transgenic and Non-Transgenic maize were not statistical significant (t-test). Since there is a lack of experimental data regarding the correlation of allergen expression with food allergy clinical relevance, we are now comparing the immunologic response of maize allergic individuals against MON 810 maize vs its non transgenic control. We also intend to characterize the encountered potential maize allergens by mass spectrometry.
- Microarray analyses reveal that plant mutagenesis may induce more transcriptomic changes than transgene insertionPublication . Batista, Rita; Saibo, Nelson; Lourenço, Tiago; Oliveira, Maria MargaridaControversy regarding genetically modified (GM) plants and their potential impact on human health contrasts with the tacit acceptance of other plants that were also modified, but not considered as GM products (e.g., varieties raised through conventional breeding such as mutagenesis). What is beyond the phenotype of these improved plants? Should mutagenized plants be treated differently from transgenics? We have evaluated the extent of transcriptome modification occurring during rice improvement through transgenesis versus mutation breeding. We used oligonucleotide microarrays to analyze gene expression in four different pools of four types of rice plants and respective controls: (i) a gamma-irradiated stable mutant, (ii) the M1 generation of a 100-Gy gamma-irradiated plant, (iii) a stable transgenic plant obtained for production of an anticancer antibody, and (iv) the T1 generation of a transgenic plant produced aiming for abiotic stress improvement, and all of the unmodified original genotypes as controls. We found that the improvement of a plant variety through the acquisition of a new desired trait, using either mutagenesis or transgenesis, may cause stress and thus lead to an altered expression of untargeted genes. In all of the cases studied, the observed alteration was more extensive in mutagenized than in transgenic plants. We propose that the safety assessment of improved plant varieties should be carried out on a case-by-case basis and not simply restricted to foods obtained through genetic engineering.
- A Proteomic Study to Identify Soya Allergens- The Human Response to Transgenic versus Non-Transgenic Soya SamplesPublication . Batista, Rita; Martins, Isabel; Jenö, Paul; Pinto Ricardo, Cândido; Oliveira, Maria MargaridaBackground: In spite of being among the main foods responsible for allergic reactions worldwide, soybean (Glycine max) derived products continue to be increasingly widespread in a variety of food products due to their well-documented health benefits. Soybean also continues to be one of the elected target crops for genetic modification. The aim of this study was to characterize the soya proteome and, specifically, IgE-reactive proteins as well as to compare the IgE response in soya-allergic individuals to genetically modified Roundup Ready soya versus its non-transgenic control. Methods: We performed two-dimensional gel electrophoresis of protein extracts from a 5% genetically modified Roundup Ready flour sample and its non-transgenic control followed by Western blotting with plasma from 5 soya sensitive individuals. We used peptide tandem mass spectrometry to identify soya proteins (55 protein matches), specifically IgE-binding ones, and to evaluate differences between transgenic and non-transgenic samples. Results: We identified 2 new potential soybean allergens – one is maturation associated and seems to be part of the late embryogenesis abundant proteins group and the other is a cysteine proteinase inhibitor. None of the individuals tested reacted differentially to the transgenic versus non-transgenic samples under study. Conclusion: Soybean endogenous allergen expression does not seem to be altered after genetic modification. Proteomics should be considered a powerful tool for functional characterization of plants and for food safety assessment.