Modification of flower color and fragrance by antisense suppression of the flavanone 3-hydroxylase gene

Anthocyanins are the major pigments contributing to carnation flower coloration. Most carnation varieties are sterile and hence molecular breeding is an attractive approach to creating novel colors in this commercially important crop. Characterization of anthocyanins in the flowers of the modern carnation cv. Eilat revealed that only the orange pelargonidin accumulates, due to a lack of both flavonoid 3′,5′-hydroxylase and flavonoid 3′-hydroxylase activities. To modify flower color in cv. Eilat, we used antisense suppression to block the expression of a gene encoding flavanone 3-hydroxylase, a key step in the anthocyanin pathway. The transgenic plants exhibited flower color modifications ranging from attenuation to complete loss of their original orange/reddish color. In the latter, only traces of pelargonidin were detected. Dramatic suppression of flavanone 3-hydroxylase level/activity in these transgenes was confirmed by northern blot, RT-PCR and enzymatic assays. The new phenotype has been stable for over 4 years of vegetative propagation. Moreover, transgenic plants with severe color modification were more fragrant than control plants. GC-MS headspace analyses revealed that transgenic anti-f3h flowers emit higher levels of methyl benzoate. The possible interrelation between pathways leading to anthocyanin and fragrance production is discussed.