Metabolic engineering of xanthophyll content in tomato fruits.

Ripe tomato fruits accumulate significant amounts of the linear carotene lycopene, but only trace amounts of xanthophylls (oxygenated carotenoids). We overexpressed the lycopene beta-cyclase (b-Lcy) and beta-carotene hydroxylase (b-Chy) genes under the control of the fruit-specific Pds promoter. Transgene and protein expression was followed through semi-quantitative reverse transcription-PCR, Western blotting, and enzyme assays.