BIOCHEMICAL COMPLEMENTATION OF THE BETALAIN BIOSYNTHETIC-PATHWAY IN PORTULACA-GRANDIFLORA BY A FUNGAL 3,4-DIHYDROXYPHENYLALANINE DIOXYGENASE

3,4-Dihydroxyphenylalanine (DOPA) dioxygenase from Amanita muscaria ca talyses the key reaction of betalain biosynthesis, namely the conversi on of DOPA to betalamic acid by a 4,5-ring-opening reaction. In additi on, it catalyses a 2,3 opening which yields the fungal pigment muscafl avin, a compound that has never been found in plants. In this work, a cDNA clone (DodA) encoding A. muscaria DOPA-dioxygenase was expressed in white Portulaca grandiflora a petals, using the particle bombardmen t technique. Transformation resulted in the formation of yellow and vi olet spots that contained betalain pigments and muscaflavin. indicatin g that the fungal enzyme was expressed and active in plants, and could complement the plant betalain biosynthetic pathway. The presence of m uscaflavin in transformed plants indicates a difference in tile specif icity of the plant and A. muscaria in enzymes.