Flavonoid role in plant stress responses

Flavonoids are the most powerful bioactive plants metabolites, able to interact with both plant and animal metabolism. They have occurred in terrestrial plants since their land colonization and are part of mammalian diet since millions of years. Flavonoids exert many different biological activities both in plants (UV-protection, ROS scavenging, enzymatic activity modulation, flower and fruit coloration, signalling and cellular communication) and in mammals (antioxidant activity, cancer cell proliferation inhibition, enzymatic activity modulation). Flavonoid biological activities are strongly connected to plant cellular ability to transport, store, excrete and sequester them into specific cellular compartments. The scientific community has debated upon flavonoid metabolism many times in the last 30 years, trying to obtain a complete overview of the synthesis, the transport systems and the role in plants, but up to date a full understanding of such a complicated mechanism is far from being elucidated. This PhD thesis aims to provide a contribution to the comprehension of flavonoid function in plants, particularly considering the role of quercetin (QC), the most abundant flavonoid in plant kingdom, in different physiological contests. The role of flavonoids has been explored starting from pathogen attack, up to the senescence, and from cellular transport, up to the role in heavy metal detoxification