Apocarotenoid signals and plant enzymes: new tools for biotechnological applications. PID2020-114761RB-I00

Carotenoids are isoprenoid compounds synthesized by all photosynthetic organisms and many heterotrophic microorganisms. They are equipped with a conjugated double-bond system that builds the basis for their role in harvesting light energy and in protecting the cell from photo-oxidation. In addition, the electron-rich polyene system of carotenoids makes them susceptible to oxidative cleavage, yielding carbonyl products called apocarotenoids. This oxidation can be catalyzed by carotenoid cleavage dioxygenases (CCD), which build up a ubiquitous family of non-heme iron enzymes or triggered non-enzymatically. Plant growth and development, response to the environmental changes and stress factors, and plant’s communication with surrounding organisms, are regulated by a set of hormones, and signaling molecules, which includes apocarotenoids. Some apocarotenoids can immediately act as signaling molecules, or growth regulators; while others suffer further modifications leading to the active molecule. Certain apocarotenoids have high economic value in feed, food, cosmetics, pharmaceutical and agricultural industries. Which includes vitamin A, retinoic acid, abscisic acid (ABA), strigolactones (SLs), the aromatic β-ionone, and the pigments bixin and crocins. Crocins, are produced by a restricted number of plant species, and saffron is the main source of these colored apocarotenoids. Recently, the key enzymes of the pathway in saffron and in other two plant species, gardenia and buddleja, have been identified, providing the tools to produce crocins through metabolic engineering in other hosts. However, known apocarotenoids constitute a small fraction over the possible global presence of apocarotenoids, not just in plants, but also in all other living organism. Therefore, the full range of apocarotenoid structures and associated bioactivities is still unknown. Apocarotenoid biosynthesis is a booming field in plant secondary metabolism, and CCDs can be envisaged as a novel source of enzymes able to process carotenoids to render apocarotenoids for health and species fitness. APOBIOTEC has a main goal, which is to establish a battery of CCDs enzymes, with different and improved functions for a broad range of biotechnological applications and characterize new apocarotenoids from plants. To reach this goal, APOBIOTEC has four more specific objectives. We aim to identify the CCDs enzymes responsible for crocetin-dialdehyde formation in several plant species, to understand their functional evolution, determine their biochemical properties, and improve their activities. Search for new CCDs among the plants genomes that are being released, and characterize their activities; and finally, to identify the new apocarotenoids produced by the isolated CCDs and to study their potential benefits.