Abstract
It is assumed that betacyanin was synthesized via betanidin since betanidin glucosylating enzymes were reported in early studies. However, we detected the glucosyltransferase activity for cyclo-DOPA that is the precursor of betanidin in petals of four o'clock (Mirabilis jalapa L.) which suggested the existence of betacyanin biosynthetic pathway via cyclo-DOPA glucosylation. Here, we succeeded that isolation and characterization of the cDNA encoding for cyclo-DOPA glucosyltransferase.
Thirteen cDNAs encoding UDP-glucose: flavonoid 3-O-glucosyltransferase homolog were isolated by PCR using the cDNAs synthesized from petals of four o'clock as a template. All of them were introduced into in E. coli to produce proteins encoded in the cDNAs and cyclo-DOPA glucosyltransferase activity was measured to the crude extracts prepared from the E. colis, indicating that one clone cDNA encodes cyclo-DOPA glucosyltranseferase assay. Northern hybridization analysis revealed the corelation between expression of transcripts corresponding to the cDNA and contents of betacyanin in four o'clock.
