RESUMO
The overuse of fossil-based resources to produce thermoplastic materials and rubbers is dramatically affecting the environment, reflected in its clearest way as global warming. As a way of reducing this, multiple efforts are being undertaken including the use of more sustainable alternatives, for instance, those of natural origin as the main feedstock alternative, therefore having a lower carbon footprint. Contributing to this goal, the synthesis of bio-based rubbers based on ß-myrcene and trans-ß-farnesene was addressed in this work. Polymyrcene (PM) and polyfarnesene (PF) were synthesized via coordination polymerization using a neodymium-based catalytic system, and their properties were compared to the conventional polybutadiene (PB) and polyisoprene (PI) also obtained via coordination polymerization. Moreover, different average molecular weights were also tested to elucidate the influence over the materials' properties. The crosslinking of the rubbers was carried out via conventional and efficient vulcanization routes, comparing the final properties of the crosslinking network of bio-based PM and PF with the conventional fossil-based PB and PI. Though the mechanical properties of the crosslinked rubbers improved as a function of molecular weight, the chemical structure of PM and PF (with 2 and 3 unsaturated double bonds, respectively) produced a crosslinking network with lower mechanical properties than those obtained by PB and PI (with 1 unsaturated double bond). The current work contributes to the understanding of improvements (in terms of crosslinking parameters) that are required to produce competitive rubber with good sustainability/performance balance.
RESUMO
La papa (Solanum tuberosum L.) es el cuarto cultivo más importante a nivel mundial y es el producto agrícola con mayor demanda de fungicidas, insecticidas y fertilizantes químicos. Las pérdidas mundiales ocasionadas por Phytophthora infestans (Mont.) de Bary en este cultivo, ascienden a 6,7 billones de dólares al año y su control químico genera un aumento en los costos, perjudica la salud humana y el ambiente. Todo esto justifica la búsqueda constante de mecanismos alternativos para el control de la enfermedad, entre ellos la obtención de variedades resistentes mediante cisgenesis usando genotipos silvestres. Como un aporte en este sentido, y dada la falta de conocimiento de lo que controla y constituye la diferencia entre una respuesta compatible e incompatible, en el presente estudio se compararon los perfiles de expresión génica obtenidos mediante Despliegue Diferencial de variedades resistentes y susceptibles durante su interacción con P. infestans. Los resultados evidenciaron diferencias en la expresión génica, tanto a distintos tiempos post-inoculación como en el tipo de cambio de expresión, incluyendo la presencia y ausencia de bandas diferenciales y el aumento o disminución en su intensidad. Al analizar las secuencias de fragmentos diferencialmente expresados, se encontró que algunos fragmentos sobre-expresados en las variedades susceptibles, tenían homología con secuencias que codifican para una serina-acetiltranferasa y para la subunidad Î de la RNA polimerasa. Por su parte, fragmentos sobre-expresados en la variedad resistente, tenían homología con una secuencia codificante para un dominio transmembranal.
Potato (Solanum tuberosum L.) is the fourth most important crop worldwide; also, is the agriculture product with most fungicides, insecticides and chemical fertilizers requirement. Worldwide losses caused by Phytophthora infestans (Mont.) de Bary in this crop, amount to 6,7 billion dollars per year and its chemical control increase production costs, harming human health and environment. For these reasons, is necessary constant research for alternative mechanisms to control disease, including development of resistant varieties using cis-genesis from wild genotypes. As a contribution in this way, and the lack of knowledge of what controls and is the difference between compatible and incompatible interaction, in this study we compared gene expression profiles obtained by Differential Display from resistant and susceptible varieties, during their interaction with P. infestans. The results showed differences in gene expression between resistant and susceptible varieties, at different times post-inoculation as well as exchange expression rate, including the presence and absence of differential bands and increase or decrease in their intensity. After analyzing the sequences of differential expressed fragments, we found that some overexpressed fragments from susceptible varieties had homology with an encoded sequence for a serine-acetyltransferase and for a RNA Polymerase Î subunit. On the other hand, overexpressed fragments from resistant variety, had homology with an encoded sequence for a transmembrane domain.