Conversion of 5-(1,2-epoxy-2,6,6-trimethylcyclohexyl)-3-methylpenta-cis-2-trans-4-dienoic acid into abscisic acid in plants.
(+/-)-5-(1,2-Epoxy-2,6,6-trimethylcyclohexyl) -3-methyl[2-(14)C]penta-cis-2-trans-4-dienoic acid is converted into abscisic acid by tomato fruit in 1.8% yield (or 3.6% of one enantiomer if only one is utilized) and 15% of the abscisic acid is derived from the precursor. The 2-trans-isomer is not converted. The amounts of [2-(3)H]mevalonate incorporated into abscisic acid have shown that the 40-times higher concentration of (+)-abscisic acid in wilted wheat leaves in comparison with unwilted ones reported by Wright & Hiron (1969) arises by synthesis. The conversion of (+/-)-5-(1,2-epoxy-2,6,6-trimethylcyclohexyl) -3-methyl-[2-(14)C]penta-cis-2-trans-4-dienoic acid into abscisic acid by wheat leaves is also affected in the same way by wilting and it is concluded from this that the epoxide or a closely related compound derived from it is on the biosynthetic pathway leading to abscisic acid. The oxygen of the epoxy group was shown, by (18)O-labelling, to become the oxygen of the tertiary hydroxyl group of abscisic acid.
D002247:Carbon Isotopes; D002845:Chromatography; D004988:Ethers, Cyclic / Q000378:metabolism*; D008798:Mevalonic Acid / Q000378:metabolism; D010103:Oxygen Isotopes; D010937:Plant Growth Regulators / Q000096:biosynthesis*; D010944:Plants / Q000378:metabolism*; D014316:Tritium; D014675:Vegetables
D002247:Carbon Isotopes; D004988:Ethers, Cyclic; D010103:Oxygen Isotopes; D010937:Plant Growth Regulators; D014316:Tritium; D008798:Mevalonic Acid