Abstract
In this study, key genes in carotenoid biosynyhetic pathway encoding phytoene synthase (PSY), phytoene desaturase (PDS), ζ-carotene desaturase (ZDS) and lycopene cyclase (LCY) were amplified by RT-PCR (reverse transcription-polymerase chain reaction) and then cloned into plant expression vector pH2GW7. This vector contains a hygromycin-resistant marker, and the target gene was inserted between CaMV 35S promoter and CaMV 35S terminator. Cotyledons from in vitro grown tomato (Lycopersicon esculentum cv. CL5915) were excised, and then were infected by Agrobacterium tumefaciens strain LBA4404. After antibiotic (hygromycin) selection and then verified by genomic PCR analysis, 10 to 24 transgenic plants from each construct were finally transferred into green house until maturity. All transgenic plants looked similar with the wild-type plant including color pattern in flowers and fruits, except for PSY26. Flowers of wild-type plant were bright yellow, whereas flowers of the transgenic line PSY26 were slight yellow to complete white. Fruits of wild-type plant were red at the end of fruit development, whereas fruits of PSY26 were slight red to yellow. Fruits from 8 transgenic plants (2 plants were randomly selected from each construct) as well as PSY26 were harvested and dried, and HPLC analysis was conducted to examine the contents of lycopene and β-carotene. We found that all the transgenic lines accumulated more lycopene, ranging from 1 to 3 folds, as compared to the wild-type plant, especially 3.84 folds was detected in PDS-4. Also, β-carotene has increased in all transgenic lines we examined. By contrast, both contents of lycopene and β-carotene in PSY26 (yellow fruits) were found similar to wild-type plant (red fruits).