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JPSS Jülich Plant Science Seminar Series:
Dr. Ralf Welsch, Department of Cell Biology, University of Freiburg, Germany

18.11.2014 13:00 Uhr
18.11.2014 14:00 Uhr
Forschungszentrum Jülich, Gebäude 06.2 IBG-2, Seminarraum 406, 2.Stock

Rate-limiting Function of Phytoene Synthase in Carotenoid Biosynthesis

- A key to color, photosynthetic integrity, phytohormone supply and nutritional enhancement -

Dr. Ralf Welsch


Carotenoids are isoprenoids which are exclusively synthesized in plants and some non-photosynthetic bacteria and fungi while animals need to absorb them from their diets. In chloroplasts of higher plants, these pigments or their derivatives have crucial functions as essential light-harvesting and photoprotective pigments while in chromoplasts they represent colorants of flowers and fruits attracting pollinating insects or zoochoric animals. The synthesis of the first carotene phytoene branches off from common prenyl phosphate metabolism and is catalyzed by the enzyme phytoene synthase (PSY). Its rate-limiting function for the pathway flux was already concluded in early studies from the correlation between PSY induction and carotenoid increases accompanying tomato fruit ripening. Recent investigations confirmed its crucial role also for the light-induced carotenoid accumulation during deetiolation but also for increased abscisic acid formation in response to abiotic stress. While PSY overexpression in photosynthetically active leaves is compensated by higher xanthophyll turnover and does not change pigment amounts, enhanced pathway flux results in strong carotenoid increases in a variety of non-green tissues. Moreover, carotenoid accumulation in various agronomically important crops, such as orange carrots and cassava roots, but also the yellow cauliflower OR mutant, are caused by enhanced pathway flux at the level of PSY. However, in contrast to tomatoes, a direct correlation with PSY expression is not observed. Our investigations aiming to identify the molecular mechanisms causing higher PSY activity in these examples elucidated different posttranscriptional mechanisms and further support its key function for carotenoid biosynthesis.


For contact to Ralf please ask Shizue Matsubara

Contact:  Shizue Matsubara