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Title: Sorgoleone

Author
item Dayan, Franck
item Rimando, Agnes
item Pan, Zhiqiang - Peter
item Baerson, Scott
item GIMSING, ANNE LOUISE - University Of Copenhagen
item Duke, Stephen

Submitted to: Phytochemistry
Publication Type: Review Article
Publication Acceptance Date: 3/9/2010
Publication Date: 4/10/2010
Citation: Dayan, F.E., Rimando, A.M., Pan, Z., Baerson, S.R., Gimsing, A., Duke, S.O. 2010. Sorgoleone. Phytochemistry. 71:1032-1039.

Interpretive Summary: Sorgoleone, a major component of the root exudate of sorghum (Sorghum bicolor), is one of the most studied allelochemicals. The exudate also contains an equivalent amount of a lipid resorcinol analog as well as a number of minor sorgoleone congeners. Synthesis of sorgoleone is compartmentalized within root hairs and the biosynthesis pathway involves unique fatty acid desaturases, an alkylresorcinol synthase, a SAM-dependent O-methyltransferase, and a putative cytochrome P450 monooxygenases. The mode of action of sorgoleone may be the result of inhibition of photosynthesis in young seedlings in concert with inhibition of its other molecular target sites in older plants. Sorgoleone is strongly sorbed in soil and it is mineralized by microorganisms over time.

Technical Abstract: Sorgoleone, a major component of the hydrophobic root exudate of sorghum [Sorghum bicolor (L.) Moench], is one of the most studied allelochemicals. The exudate also contains an equivalent amount of a lipid resorcinol analog as well as a number of minor sorgoleone congeners. Synthesis of sorgoleone is constitutive and compartmentalized within root hairs, which can accumulate up to 20 µg of exudate/mg root dry weight. The biosynthesis pathway involves unique fatty acid desaturases which produce an atypical 16:3 fatty acyl-CoA starter unit for an alkylresorcinol synthase that catalyzes the formation of a pentadecatrienyl resorcinol intermediate. This intermediate is then methylated by SAM-dependent O-methyltransferases and dihydroxylated by cytochrome P450 monooxygenases. An EST data set derived from a S. bicolor root hair-specific cDNA library contained all the candidate sequences potentially encoding enzymes involved in the sorgoleone biosynthetic pathway. Sorgoleone interferes with several molecular target sites, including inhibition of photosynthesis in germinating seedlings. Sorgoleone is not translocated acropetally in older plants, but can be absorbed through the hypocotyl and cotyledonary tissues. Therefore, the mode of action of sorgoleone may be the result of inhibition of photosynthesis in young seedlings in concert with inhibition of its other molecular target sites in older plants. Due to its hydrophobic nature, sorgoleone is strongly sorbed in soil which increases its persistence, but experiments show that it is mineralized by microorganisms over time.