title: The O-methyltransferase gene MdoOMT1 is required for biosynthesis of methylated phenylpropenes in ripe apple fruit.
abstract: Phenylpropenes, such as eugenol and trans-anethole, are important aromatic compounds that determine flavour and aroma in many herbs and spices. Some apple varieties produce fruit with a highly desirable spicy/aromatic flavour that has been attributed to the production of estragole, a methylated phenylpropene. To elucidate the molecular basis for estragole production and its contribution to ripe apple flavour and aroma we characterised a segregating population from a Royal Gala (RG, estragole producer) × Granny Smith (GS, non-producer) apple cross. Two quantitative trait loci (QTLs; accounting for 9.2 and 24.8% of the variation) on linkage group (LG) 1 and LG2 were identified that co-located with seven candidate genes for phenylpropene O-methyltransferases (MdoOMT1-7). Of these genes, only expression of MdoOMT1 on LG1 increased strongly with ethylene and could be correlated with increasing estragole production in ripening RG fruit. Transient over-expression in tobacco showed that MdoOMT1 utilised a range of phenylpropene substrates and catalysed the conversion of chavicol to estragole. Royal Gala carried two alleles (MdoOMT1a, MdoOMT1b) whilst GS appeared to be homozygous for MdoOMT1b. MdoOMT1a showed a higher affinity and catalytic efficiency towards chavicol than MdoOMT1b, which could account for the phenotypic variation at the LG1 QTL. Multiple transgenic RG lines with reduced MdoOMT1 expression produced lower levels of methylated phenylpropenes, including estragole and methyleugenol. Differences in fruit aroma could be perceived in these fruit, compared with controls, by sensory analysis. Together these results indicate that MdoOMT1 is required for the production of methylated phenylpropenes in apple and that phenylpropenes including estragole may contribute to ripe apple fruit aroma.
authors.affiliation: The New Zealand Institute for Plant and Food Research Limited (PFR), Private Bag 92169, Auckland, 1142, New Zealand.
authors.forename: Yar-Khing
authors.initials: YK
authors.lastname: Yauk
authors.affiliation: Plant and Food Research Limited (PFR), Private Bag 11600, Palmerston North, 4442, New Zealand.
authors.forename: David
authors.initials: D
authors.lastname: Chagné
authors.affiliation: The New Zealand Institute for Plant and Food Research Limited (PFR), Private Bag 92169, Auckland, 1142, New Zealand.
authors.forename: Sumathi
authors.initials: S
authors.lastname: Tomes
authors.affiliation: Plant and Food Research Limited (PFR), Private Bag 11600, Palmerston North, 4442, New Zealand.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Matich
authors.affiliation: The New Zealand Institute for Plant and Food Research Limited (PFR), Private Bag 92169, Auckland, 1142, New Zealand.
authors.forename: Mindy Y
authors.initials: MY
authors.lastname: Wang
authors.affiliation: The New Zealand Institute for Plant and Food Research Limited (PFR), Private Bag 92169, Auckland, 1142, New Zealand.
authors.forename: Xiuyin
authors.initials: X
authors.lastname: Chen
authors.affiliation: The New Zealand Institute for Plant and Food Research Limited (PFR), Private Bag 92169, Auckland, 1142, New Zealand.
authors.forename: Ratnasiri
authors.initials: R
authors.lastname: Maddumage
authors.affiliation: Plant and Food Research Limited (PFR), Private Bag 11600, Palmerston North, 4442, New Zealand.
authors.forename: Martin B
authors.initials: MB
authors.lastname: Hunt
authors.affiliation: Plant and Food Research Limited (PFR), Private Bag 11600, Palmerston North, 4442, New Zealand.
authors.forename: Daryl D
authors.initials: DD
authors.lastname: Rowan
authors.affiliation: The New Zealand Institute for Plant and Food Research Limited (PFR), Private Bag 92169, Auckland, 1142, New Zealand.
authors.forename: Ross G
authors.initials: RG
authors.lastname: Atkinson
mesh_terms: D000081248:Allylbenzene Derivatives; D000840:Anisoles / Q000378:metabolism*; D005030:Ethylenes / Q000378:metabolism; D005054:Eugenol / Q000031:analogs & derivatives / Q000378:metabolism; D005638:Fruit / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D027845:Malus / Q000235:genetics / Q000378:metabolism*; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009812:Odorants; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D040641:Quantitative Trait Loci
chemical_list: D000081248:Allylbenzene Derivatives; D000840:Anisoles; D005030:Ethylenes; D007527:Isoenzymes; D010940:Plant Proteins; C005223:methyleugenol; D005054:Eugenol; C036216:ethylene; C007633:estragole; D008780:Methyltransferases
keywords: Malus domestica; O-methyltransferase; apple; aroma; estragole; flavour; fruit; phenylpropene