Metabolic engineering of astaxanthin production in tobacco flowers

Using metabolic engineering, we have modified the carotenoid biosynthesis p athway in tobacco (Nicotiana tabacum) to produce astaxanthin, a red pigment of considerable economic value. To alter the carotenoid pathway in chromop lasts of higher plants, the cDNA of the gene CrtO from the alga Haematococc us pluvialis, encoding beta-carotene ketolase, was transferred to tobacco u nder the regulation of the tomato Pds (phytoene desaturase) promoter. The t ransit peptide of PDS from tomato was used to target the CRTO polypeptide t o the plastids. Chromoplasts in the nectary tissue of transgenic plants acc umulated (3S,3'S) astaxanthin and other ketocarotenoids, changing the color of the nectary from yellow to red. This accomplishment demonstrates that p lants can be used as a source of novel carotenoid pigments such as astaxant hin, The procedures described in this work can serve as a platform technolo gy for future genetic manipulations of pigmentation of fruits and flowers o f horticultural and floricultural importance.