Molecular mechanisms behind the anthocyanin production in tomato plants

Plants are increasingly studied for their ability to produce metabolites having a preventive effect for human health. Among these molecules there are anthocyanins, polyphenolic pigments produced by the plants to colour flowers and fruits and to protect themselves against oxidative damages. Considerable work was done to enrich the spectrum of health-beneficial phytochemicals in cultivated crops, such as tomato (Solanum lycopersicum), whose fruits are typically red at ripening, with high levels of carotenoids but low content in polyphenols. In this thesis we used tomato mutants like atroviolacea (atv), accumulating anthocyanins in vegetative tissues, and Anthocyanin fruit (Aft), producing anthocyanins in fruit peel, to clarify the regulation of the anthocyanin biosynthesis in tomatoes. We identified the gene responsible for the atv phenotype as a locus in chromosome 7 encoding a non-functional R3-MYB protein, named Slmyb-atv, which instead in wild type plants represses the anthocyanin production. The mutation conferring the Aft phenotype is instead associated to a wide region on chromosome 10. By studying four different genes encoding for R2R3-MYB proteins having a close localization (SlAN2, SlANT1, SlAN2like and SlANT1like), significant differences between WT and Aft emerged for one of them, SlAN2like, both in fruit expression levels and protein functionality, with splicing mutations determining a complete loss of function of the WT protein. The collected data were useful for providing a putative model of the whole regulation mechanism of anthocyanins production.