SUMARY

	Fruit set is one of the most important processes in plant development, as is needed, for reproduction of the plant, in wild species, and for production in crops. The study of the genes regulated during this process is key to understand the mechanisms involved and to improve fruit set, especially in harsh environments. Tomato, Solanum Lycopersicum, is one of the main vegetable's crop and has been used in basic and applied research. However, most of the studies about fruit development in this crop have been focused on the process of ripening and have not raised the global study of fruit set. About this topic, the research with parthenocarpic accessions is really interesting. The parthenocarpy provides a tool to study the fruit set without the background of the processes related with embryo development, and make possible the study of the first stages of fruit development without taking into account the exit of the pollination. Besides those materials are really useful in crop breeding as allowed the development of fruits even without pollination and fecundation. In tomato there are several accessions with facultative parthenocarpy, such as RP75/59, that can set seedless fruits equal to the seeded ones.

	The general topic of this thesis is to study carpel development and parthenocarpic fruit set in tomato, those studies will be the basis to improve fruit set in harsh conditions. To improve the knowledge of the biological processes involved in fruit set, the genes implicated in this process in tomato have been isolated in tomato from a library subtraction of cDNA libraries and from expression data of the model species Arabidopsis. When the genes isolated were analyzed, were discovered genes related to response to hormones, that have been previously related with fruit set. But also unrelated genes, that could be a valuable source of information for future studies about fruit set. Besides, an analysis of conservation between tomato and Arabidopsis showed a high degree of correlation, greater than 75%, which showed that there are general mechanisms involved in dicotyledonae fruit set.

	To deepen into the study of the genes involved in fruit set and the mechanisms of carpel development, a transcriptomic analysis was made in tomato using UC82 as a control variety. With that variety, carpel development, fruit set and fecundation were analyzed together. We were able to identify 2842 genes regulated along those processes. The functional analysis of those genes has allowed to identify the biological functions related with fruit set, some of which have been previously identified in the analysis made with Arabidopsis.

	The parthenocarpic line RP75/59 has been analyzed at transcriptomic level to study the parthenocarpic fruit set in tomato. The differences between this line and the control variety UC82 non parthenocarpic have been found mainly at anthesis. In contrast to the normal development where the carpel stops its development at anthesis until pollination and fecundation take place, in RP75/59 anthesis was just one step between carpel and fruit. With that line 758 genes regulated differently with respect to the control line were identified. The analysis of the genes related with hormones reveled that in RP75/59 the high concentration in GAs is due to the higher expression of the GA20-oxidase 3. The high concentration of GAs allowed the development of fruits in absence of pollination and fecundation. Besides the high expression of the ACO5 gene during all the stages analyzed would alter ethylene biosynthesis and might induce auxin synthesis.

	The isolation of the genes that cause the RP75/59 phenotype would be really interesting, from a scientific and applied point, as would allow the inclusion of this character in breeding programs. Until now there has not been any significant advances in that direction, probably due to the problems when characterizing this phenotype. During the development of this thesis, the analysis of a segregating offspring from the cross between RP75/59 and UC82 was used to clarify the parthenocarpic phenotype in this accession and to develop a segregating population, that will be the basis for the mapping and isolation of the genes involved in the control of the character and fruit set and development.