Submitted to: Journal of Biological Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 27, 2003
Publication Date: August 1, 2003
Citation: Dayan, F.E., Kagan, I., Rimando, A.M. 2003. Elucidation of the Biosynthetic Pathway of the Allelochemical Sorgoleone Using Retrobiosynthetic NMR Analysis. Journal of Biological Chemistry. 278(31):28607-28611. Interpretive Summary: Sorgoleone is an important natural product produced by the roots of sorghum. The growth of other plants around sorghum is repressed by this natural herbicide. In order to better understand how sorghum produces its own natural herbicide, it is necessary to determine the biosynthetic pathway of sorgoleone. This was achieve in this study by using labeled substrates and analysis by nuclear magnetic resonance. This work will serve as the foundation from which the genes and enzymes involved will be identified.
Technical Abstract: The labeling pattern obtained using various 13C-labeled precursors indicated that both the lipid tail and the quinone head of sorgoleone, the main allelopathic component of the oily root exudate of Sorghum bicolor, were derived from acetate units, but that the two moieties were synthesized in different subcellular compartments. The 16:3 fatty acid precursor of the tail is synthesized by the combined action of fatty acid synthase and desaturases most likely in the plastids. It is then exported out of the plastids and converted to 5-pentadecatriene resorcinol by a polyketide synthase. This resorcinol intermediate was identified in root hair extracts. The lipid resorcinol intermediate is then methylated by a SAM-dependent O-methyltransferase and subsequently dihydroxylated by a P450 monooxygenase to yield the reduced form of sorgoleone.