Flavonoids are the largest group of secondary metabolites that function in plant protecting against various stresses.Theirs occurrence in human diet also plays important roles in health protection by preventing oxidative stress affected from degenerative diseases.In this study, transgenic tobacco overexpressing TRANSPARENT TESTA8 (TT8) cDNA was engineered.TT8 cDNA encoded a regulatory protein from Arabidopsis thaliana displays a basic helix-loop-helix at its C terminus which can attach promoter and elevate the expression of structural gene in flavoniod biosynthesis.Genetic screening using PCR technique was performed and 20 trangenic plants containing TT8 cDNA were obtained.4 week old of transgenic plants grown in tissue culture were induced the expression of flavonoid biosynthetic gene under fluorescent light combined with long wave UV at 500 lux intensity.After incubation for 7 days, each transgenic tobacco was analyzed for the content of flavonoids (naringenin, apigenin, kaemferol, gallotannin and pelagonidin). The result showed that transgenic tobacco lines with the same cDNA have unequal expression of flavonoid biosynthetic pathways.The integrated position of cDNA into plant chromosome should be effected on the gene expression. Our result showed that all of transgenic have naringenin and apigenin levels higher than that of wild type at least 4 fold, while the highest performance of transgenic tobacco expressed both of substance 15 folds higher and also produced kaemferol, gallotannin, pelagonidin 7-9 fold higher than that of wild type. Thus this transgenic line of TT8 produced by metabolic engineering technique should be suitable process increasing production for commercial propose.
