Carotenoid Steady-State Regulation

• Applicant: Privatdozent Dr. Ralf Welsch
• Subject Area: Plant Biochemistry and Biophysics
• Term: from 2011 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 191484648

Carotenoids fulfil important functions in photosynthetically active and in non-green plant tissues. Their content represents a steady state determined by carotenoid formation and breakdown. Carotenoid decay occurs from both non-enzymatic destruction and enzyme-mediated degradation, the latter includes the synthesis of carotenoid-derived plant hormones. The biosynthetic capacity is mostly determined by the enzyme phytoene synthase (PSY). Enhanced PSY levels, as achieved through transgenic overexpression in planta or naturally in chromoplast-bearing tissues, can overrun carotenoid degradation in favour of their accumulation, leading to their sequestration into specific structures in many cases. It is hypothesized here that the mode of carotenoid deposition reduces their accessibility towards catabolism. While the enzymes involved in carotenoid biosynthesis and degradation (carotenoid cleaving dioxygenases, CCDs) were intensively investigated in the past, attempts to integrate both processes are largely missing. The proposed project aims to investigate the interplay of both processes focussing mainly on PSY and CCDs. These analyses will be enabled by the use of introduced carotenoid steady-state perturbations by PSY overexpression, combined with impaired carotenoid degradation. Furthermore, the cauliflower OR mutant accumulating high levels of β-carotene as carotenoid crystals will be functionally characterized. The study also aims to lay the molecular grounds for increased carotenoid (provitamin A) stability in biofortified crop plants, such as Golden Rice.

• DFG Programme: Research Grants