NEW INSIGHTS ON THE AGAMOUS SUBFAMILY GENES IN ORYZA SATIVA

More than 30 years of plant biology have assessed the tight relationship existing between MADS-box genes and plant development and reproduction. Transcription factors of the MADS-box family have been associated with crucial processes throughout the whole life plant: germination, hormonal signalling, vegetative growth, transition from vegetative to reproductive phase, flower, fruit and seed development, embryogenesis. MADS-box are key regulators of the gene networks behind all of these processes; therefore, they have been (and continue to be) the subject of a number of molecular and functional studies which aim to add more and more details on the overall picture of how plants are made. Among MADS-box, the AGAMOUS subfamily plays a fundamental role in plant reproduction; genes belonging to this subfamily have been associated with reproductive organ development and seed and fruit development in many different species. During evolution, the AGAMOUS subfamily underwent various events of duplication which led to the presence, in the extant plant species, of multiple AGAMOUS-like genes, often acquiring different functions thanks to subfunctionalization and neofunctionalization. The aim of this thesis is to shed some more light upon the AGAMOUS-like genes present in rice (Oryza sativa). In the first part, we demonstrate how the alternative splicing of a single aminoacid in rice AGAMOUS ortholog OsMADS3 can alter its functionality, as proven by the different ability of the two isoforms to interact with other MADS-box proteins and by the different phenotype generated by their ectopic expression in A. thaliana. In the second part, we present preliminary data about the role of rice AGAMOUS subfamily genes in controlling rice seed development. AGAMOUS-like genes have been associated with fruit and seed development in various species, but functional characterization experiments are difficult to perform on fruit plants because of their long life cycle; thus, rice represent the perfect model species to start with. Our experiments show that in multiple mutants in AGAMOUS-like genes fertility and seed development are severely impaired.