Transformation of Medicago truncatula with the arginine decarboxylase gene to modify polyamine metabolism toward water deficit resistance

Abstract

Dissertation submitted to obtain a Ph.D. (Doutoramento) degree in Biology at the Instituto de Tecnologia Química e Biológica da Universidade Nova de LisboaThe main purpose of this thesis was to introduce and express in the model legume Medicago truncatula the arginine decarboxylase encoding gene (Adc) from Avena sativa, that codes for a key enzyme of the polyamine biosynthetic pathway, to modify polyamine metabolism aiming to alter the plant responses to water deficit. Water deficit is the major abiotic stress that severely limits crop yields and controls the distribution of vegetation over the earth's surface. Due to their capacity to grow on nitrogen-poor soils, legumes are important candidates for improving saline soil fertility and helping to reintroduce agriculture to dehydrated lands. Efforts in developing legume crops with better drought/water deficit resistance through conventional breeding have been restricted, mainly because of underprovided understanding of the physiological mechanisms underlying stress resistance and to the lack of sufficient polymorphism for drought resistancerelated traits. The alternative process of generating transgenic cultivars requires success in the transformation method and proper incorporation of stress resistance into plants. Further evaluation of the transgenic plants under stress conditions and understanding the physiological effect of the inserted genes at the whole plant level are also essential for the success of this technology. Towards the usefulness of developing a model system, Medicago truncatula has become increasingly relevant in latest years due to significant progress at the genetic and genomic levels in this specie.(...