title: Characterization of an O-methyltransferase specific to guaiacol-type benzenoids from the flowers of loquat (Eriobotrya japonica).
abstract: Volatile benzenoids, including methyl p-methoxybenzoate, p-anisaldehyde, and p-anisalcohol, are responsible for the sweet and characteristic fragrance of loquat (Eriobotrya japonica, Rosaceae) flowers. Although the full pathway of volatile benzenoid synthesis has yet to be elucidated, their chemical structures suggest that O-methyltransferases are present in loquat and function in the methylation of the para-OH groups. In the present study, we used RNA-sequencing to identify four loquat genes (EjOMT1, EjOMT2, EjOMT3, and EjOMT4) that encode O-methyltransferases. We found that EjOMT1 was highly expressed in floral tissues, with an expression pattern that coincided with changes in intracellular volatile benzenoids during flower development. Recombinant EjOMT1 protein expressed in Escherichia coli showed the highest activity towards guaiacol with a Kmvalue of 35 μM. Furthermore, the protein also showed lesser activities towards guaiacol-type benzenoids including eugenol, isoeugenol, vanillin, and ferulic acid, in addition to much weaker activities towards catechol and p-hydroxybenzenoid derivatives. However, no activity was shown towards phenylpropenes without m-methoxy substitution, t-anol and chavicol. Taken together, our findings indicate that EjOMT1 has a broad substrate specificity towards compounds with both para-OH and meta-OCH3groups, unlike previously characterized O-methyltransferases for volatile benzenoid/phenylpropanoid biosynthesis.
authors.affiliation: Department of Biological Chemistry, Faculty of Agriculture and Division of Agricultural Sciences, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi 753-8515, Japan. Electronic address: takaori@yamaguchi-u.ac.jp.
authors.forename: Takao
authors.initials: T
authors.lastname: Koeduka
authors.affiliation: Department of Biological Chemistry, Faculty of Agriculture and Division of Agricultural Sciences, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi 753-8515, Japan.
authors.forename: Mami
authors.initials: M
authors.lastname: Kajiyama
authors.affiliation: Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
authors.forename: Takumi
authors.initials: T
authors.lastname: Furuta
authors.affiliation: Department of Research and Development, Kazusa DNA Research Institute, Chiba 292-0818, Japan.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Suzuki
authors.affiliation: Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan.
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Tsuge
authors.affiliation: Department of Biological Chemistry, Faculty of Agriculture and Division of Agricultural Sciences, Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi 753-8515, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Matsui
mesh_terms: D000595:Amino Acid Sequence; D001547:Benzaldehydes / Q000378:metabolism; D003001:Cloning, Molecular; D031983:Eriobotrya / Q000201:enzymology / Q000235:genetics*; D005054:Eugenol / Q000031:analogs & derivatives / Q000378:metabolism; D035264:Flowers / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006139:Guaiacol / Q000378:metabolism*; D008780:Methyltransferases / Q000235:genetics* / Q000378:metabolism*; D010802:Phylogeny; D016415:Sequence Alignment; D013379:Substrate Specificity
chemical_list: D001547:Benzaldehydes; D005054:Eugenol; C036643:isoeugenol; D006139:Guaiacol; C024896:4-anisaldehyde; D008780:Methyltransferases
keywords: Eriobotrya japonica; Guaiacol; Loquat; O-Methyltransferase; Volatile benzenoid