The blue colour of Vanda coerulea petals is slowly produced during flower development but quickly disappears when the flowers are pollinated. To investigate the molecular basis of the phenomenon, we isolated a novel cytochrome P450 gene, CYP76AB1, from this plant by polymerase chain reaction (PCR) based on the conserved regions of flavonoid 3´,5´-hydroxylase amino acid sequences. CYP76AB1 transcripts were detectable at low level in the late phase of flower development when the petals were light blue, but became abundant in the subsequent opening flower stage, as the petals turned blue. When the flowers were pollinated they turned white, and the CYP76AB1 transcripts returned to low level. This indicates that the expression of CYP76AB1 may regulate petal colour of V. coerulea, and be a target for developing permanently blue flowers.

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