Isolation and characterization of the fragrant cyclamen -methyltransferase involved in flower coloration

Akita, Yusuke; Kitamura, Satoshi; Hase, Yoshihiro; Narumi, Issei; Ishizaka, Hiroshi*; Kondo, Emiko*; Kameari, Naoko*; Nakayama, Masayoshi*; Tanikawa, Natsu*; Morita, Yasumasa*; Tanaka, Atsushi

Anthocyanin -methyltransferase (OMT) is one of the key enzymes for anthocyanin modification and flower pigmentation. We previously bred a novel red-purple-flowered fragrant cyclamen (KMrp) from the purple-flowered fragrant cyclamen "Kaori-no-mai" (KM) by ion-beam irradiation. Since the major anthocyanins in KMrp and KM petals were delphinidin 3,5-diglucoside and malvidin 3,5-diglucoside, respectively, inactivation of a methylation step in the anthocyanin biosynthetic pathway was indicated in KMrp. We isolated and compared genes expressed in KM and KMrp petals. RT-PCR analysis revealed that was expressed in the petals of KM but not in KMrp. Three additional s with identical sequences were expressed in petals of both KM and KMrp. Genomic PCR analysis revealed that was not amplified from the KMrp genome, indicating that ion-beam irradiation caused a loss of the entire region in KMrp. In vitro enzyme assay demonstrated that CkmOMT2 catalyzes the 3' or 3',5' -methylation of the B-ring of anthocyanin substrates. These results suggest that CkmOMT2 is functional for anthocyanin methylation, and defective expression of is responsible for changes in anthocyanin composition and flower coloration in KMrp.