AGFD 22 |
| Sorgoleone, produced in root hair cells of sorghum (Sorghum bicolor), is likely responsible for much of the allelopathic properties of sorghum root exudates against broadleaf and grass weeds. Previous studies suggest that the biosynthetic pathway of this compound initiates with the synthesis of an unusual 16:3 fatty acid possessing a terminal double bond. To identify and characterize the corresponding enzymes responsible for the biosynthesis of the 16:3 fatty acyl-CoA precursor, a root hair specific EST (expressed sequence tag) collection was mined. We identified and cloned three putative fatty acid desaturases, designated SbDES1, SbDES2 and SbDES3, from this EST database. Quantitative real-time RT-PCR analyses revealed that these three genes were preferentially expressed in sorghum root hairs where the 16:2 and 16:3 fatty acids were exclusively localized. Heterologous expression of the cDNAs in S. cerevisiae revealed that SbDES2 converted palmitoleic acid to hexadecadienoic acid, and that SbDES3 was capable of converting hexadecadienoic acid into hexadecatrienoic acid possessing a terminal double bond between carbons 15 and 16 of the aliphatic chain. The molecular and biochemical characterization of these desaturases will be presented.
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Plant Genomics
1:00 PM-3:15 PM, Sunday, August 19, 2007 BCEC -- 255, Oral
Division of Agricultural & Food Chemistry |