The Role of Peroxidases in the Development of Plants and Their Responses to Abiotic Stresses.

Peroxidases and its effects on plants were analysed. Peroxidases are involved in many physiological processes in plants, involving responses to biotic and abiotic stresses and the biosynthesis of lignin. Liglin is a polymer responsible for rendering the plant stronger and more rigid and also making the cell walls hydrophobic. Peroxidases are involved in the polymerization of the precursors of lignin. They are also involved in the scavenging of Reactive Oxygen Species (ROS), which are partially reduced forms of atmospheric oxygen, highly reactive, and capable of causing oxidative damage to the cell. Peroxidases can be a source of hydrogen peroxide (H2O2) but also are capable of scavenging it. The overexpression of a peroxidase gene with the consequent elevated levels of the enzyme were analysed in this study. A pathogen related cell wall peroxidise gene from barley (prx8) isolated by the Thordal-Christensen et al. (1992) was cloned into a binary vector Burbridge (2001). This gene was transformed into Nicotiana tabacum L. cx. Xanthi. Also, the prx8 gene was cloned into a vector driven by the chlorophyll a/b binding promoter (cab) and transformed into Malus domestica var. Greensleeves. This plant was chosen as a woody species, due to the involvement of peroxidises in the lignification process and its importance in wood production. Transgenic plants from both species were characterised and analysed. They were submitted to abiotic stresses, such as heat and cold stress, high salinity and metal ions in high concentrations. Transgenic plants overexpressing the prx8 gene showed an increased tolerance to these abiotic stresses. In fact, germination rates of transgenic tobacco seeds in the presence of high salinity levels and metal ions in the medium were higher than wild type seeds. Electrolyte leakage of leaf discs presented with higher temperatures was reduced in transgenic plants, showing a higher tolerance to the heat stress. This was further proved on soil grown plants presented with high temperatures. The role of peroxidises in the development of plants was also studied. Plants showed acceleration in the growth rate when compared to wild type plants. Experiments on the apple plants also showed an increase in the number of xylem vessels. These transgenic plants proved the very important role of this cell wall peroxidise in the responses to environmental changes as well as the development of the plants

Increased Tolerance to Abiotic Stresses in Tobacco Plants Expressing a Barley Cell Wall Peroxidase

This study aimed to explore the prospects for enhancing abiotic stress tolerance through expression of a cell wall-targeted peroxidase in transgenic plants. Abiotic stresses result in the production of several Reactive Oxygen Species (ROS), including hydrogen peroxide (H2O2), in higher plants. H2O2 is highly diffusible and has a stress signalling role, but is also the source, through Fenton reactions, of highly destructive hydroxyl free radicals. Type III peroxidases, a family of heme-containing proteins which oxidise a range of substrates using H2O2 as oxidant, are capable of depleting H2O2 levels in several cellular compartments and specific peroxidases have been linked to stress defences. In the present study, we demonstrate expression of a pathogen-induced apoplastic barley peroxidase in transgenic tobacco plants and show that it confers improved tolerance to several abiotic stresses, including high and low temperatures, salinity, metal ion and osmotic stress

Increased Tolerance to Abiotic Stresses in Tobacco Plants Expressing a Barley Cell Wall Peroxidase

This study aimed to explore the prospects for enhancing abiotic stress tolerance through expression of a cell wall-targeted peroxidase in transgenic plants. Abiotic stresses result in the production of several Reactive Oxygen Species (ROS), including hydrogen peroxide (H2O2), in higher plants. H2O2 is highly diffusible and has a stress signalling role, but is also the source, through Fenton reactions, of highly destructive hydroxyl free radicals. Type III peroxidases, a family of heme-containing proteins which oxidise a range of substrates using H2O2 as oxidant, are capable of depleting H2O2 levels in several cellular compartments and specific peroxidases have been linked to stress defences. In the present study, we demonstrate expression of a pathogen-induced apoplastic barley peroxidase in transgenic tobacco plants and show that it confers improved tolerance to several abiotic stresses, including high and low temperatures, salinity, metal ion and osmotic stress

Increased Tolerance to Abiotic Stresses in Tobacco Plants Expressing a Barley Cell Wall Peroxidase

This study aimed to explore the prospects for enhancing abiotic stress tolerance through expression of a cell wall-targeted peroxidase in transgenic plants. Abiotic stresses result in the production of several Reactive Oxygen Species (ROS), including hydrogen peroxide (H2O2), in higher plants. H2O2 is highly diffusible and has a stress signalling role, but is also the source, through Fenton reactions, of highly destructive hydroxyl free radicals. Type III peroxidases, a family of heme-containing proteins which oxidise a range of substrates using H2O2 as oxidant, are capable of depleting H2O2 levels in several cellular compartments and specific peroxidases have been linked to stress defences. In the present study, we demonstrate expression of a pathogen-induced apoplastic barley peroxidase in transgenic tobacco plants and show that it confers improved tolerance to several abiotic stresses, including high and low temperatures, salinity, metal ion and osmotic stress

Increased Tolerance to Abiotic Stresses in Tobacco Plants Expressing a Barley Cell Wall Peroxidase

This study aimed to explore the prospects for enhancing abiotic stress tolerance through expression of a cell wall-targeted peroxidase in transgenic plants. Abiotic stresses result in the production of several Reactive Oxygen Species (ROS), including hydrogen peroxide (H2O2), in higher plants. H2O2 is highly diffusible and has a stress signalling role, but is also the source, through Fenton reactions, of highly destructive hydroxyl free radicals. Type III peroxidases, a family of heme-containing proteins which oxidise a range of substrates using H2O2 as oxidant, are capable of depleting H2O2 levels in several cellular compartments and specific peroxidases have been linked to stress defences. In the present study, we demonstrate expression of a pathogen-induced apoplastic barley peroxidase in transgenic tobacco plants and show that it confers improved tolerance to several abiotic stresses, including high and low temperatures, salinity, metal ion and osmotic stress

Expression of a Barley Peroxidase in Transgenic Apple (Malus domestica L.) Results in Altered Growth, Xylem Formation and Tolerance to Heat Stress

Heterologous expression of peroxidase genes has been shown to influence morphology and stress responses of several crop plants but little is known about the effect in woody species. In this study, a barley cell-wall peroxidase gene (prx8), peviously shown to influence growth and stress tolerance in tobacco, was introduced into the genome of apple (Malus domestica cv. Greensleeves) via Agrobacterium-mediated transformation and the presence of the transgene confirmed by PCR and Southern blot analysis. The transgenic plants had up to 4-fold higher levels of peroxidase activity compared to wild type plants and exhibited faster growth and increased xylem production. Leaf discs were incubated at high temperatures (44°C) and electrolyte leakage measurements indicated enhanced tolerance against temperature stress. This effect was confirmed when whole plants were subjected to heat stress after 6 and 12 months growth in soil. These results indicate a link between peroxidase activity levels and resistance to thermal stress, as well as biochemical and physiological changes, in this woody plant

Development of a green binder system for paper products

Background: It is important for industries to find green chemistries for manufacturing their products that have utility, are cost-effective and that protect the environment. The paper industry is no exception. Renewable resources derived from plant components could be an excellent substitute for the chemicals that are currently used as paper binders. Air laid pressed paper products that are typically used in wet wipes must be bound together so they can resist mechanical tearing during storage and use. The binders must be strong but cost-effective. Although chemical binders are approved by the Environmental Protection Agency, the public is demanding products with lower carbon footprints and that are derived from renewable sources. Results In this project, carbohydrates, proteins and phenolic compounds were applied to air laid, pressed paper products in order to identify potential renewable green binders that are as strong as the current commercial binders, while being organic and renewable. Each potential green binder was applied to several filter paper strips and tested for strength in the direction perpendicular to the cellulose fibril orientation. Out of the twenty binders surveyed, soy protein, gelatin, zein protein, pectin and Salix lignin provided comparable strength results to a currently employed chemical binder. Conclusions These organic and renewable binders can be purchased in large quantities at low cost, require minimal reaction time and do not form viscous solutions that would clog sprayers, characteristics that make them attractive to the non-woven paper industry. As with any new process, a large-scale trial must be conducted along with an economic analysis of the procedure. However, because multiple examples of “green” binders were found that showed strong cross-linking activity, a candidate for commercial application will likely be found.Forestry, Faculty ofWood Science, Department ofNon UBCReviewedFacult

Assessment of Field-Grown Cellulase-Expressing Corn

Transgenic plants in the US and abroad generated using genetic engineering technology are regulated with respect to release into the environment and inclusion into diets of humans and animals. For crops incorporating pharmaceuticals or industrial enzymes regulations are even more stringent. Notifications are not allowed for movement and release, therefore a permit is required. However, growing under permit is cumbersome and more expensive than open, non- regulated growth. Thus, when the genetically engineered pharmaceutical or industrial crop is ready for scale-up, achieving non-regulated status is critical. Regulatory compliance in the US comprises petitioning the appropriate agencies for permission for environmental release and feeding trials. For release without yearly permits, a petition for allowing non-regulated status can be filed with the United States Department of Agriculture with consultations that include the Food and Drug Administration and possibly the Environmental Protection Agency, the latter if the plant includes an incorporated pesticide. The data package should ensure that the plants are substantially equivalent in every parameter except for the engineered trait. We undertook a preliminary study on transgenic maize field-grown hybrids that express one of two cellulase genes, an exo-cellulase or an endo-cellulase. We performed field observations of whole plants and numerous in vitro analyses of grain. Although some minor differences were observed when comparing genetically engineered hybrid plants to control wild type hybrids, no significant differences were seen