Submitted to: International Symposium on Plant Lipids
Publication Type: Abstract Only
Publication Acceptance Date: July 16, 2006
Publication Date: July 16, 2006
Citation: Dietrich, C.R., Cahoon, E.B. 2006. Chemically induced expression of fatty acid conjugases in arabidopsis seeds allows for novel approaches to study channeling of unusual fatty acids [abstract]. International Symposium on Plant Lipids. Paper No. P62. Technical Abstract: Conjugated fatty acids contain non-methylene interrupted double bonds, which is in contrast to the methylene-interrupted configuration of double bonds that is typically found in polyunsaturated fatty acids in plants. These unusual fatty acids occur in the seed oils of certain species such as Calendula officinalis and Momordica charantia where they accumulate to levels ranging from 50% to 80% of the total fatty acids. Conjugated fatty acids are of commercial and biotechnological interest because they enhance the drying properties of vegetable oils and reduce fat accumulation in livestock. We are currently using seeds engineered to produce conjugated fatty acids as tools to identify metabolic constraints that limit the accumulation of unusual fatty acids in seeds of transgenic plants. To this end, expression of FAD2-related fatty acid conjugases from C. officinalis or M. charantia in soybean or Arabidopsis seeds was accompanied by the accumulation of conjugated fatty acids to as high as 20% of the total fatty acids. In addition, soybean and wild-type Arabidopsis seeds engineered to produce the conjugated fatty acid eleostearic acid had a wrinkled morphology and severely reduced germination rates. These phenotypes appear to be due to an inability of the engineered seeds to exclude the accumulation of conjugated fatty acids from phosphatidylcholine (PC) and other membrane phospholipids. We have generated Arabidopsis lines carrying fatty acid conjugase genes under control of a chemically-inducible seed-specific promoter. With this system, seeds engineered with various conjugase genes are viable under non-inductive conditions, but do not germinate upon application of the chemical inducer. These inducible lines are currently being used in screens to identify genes for enzymes that are specialized for the channeling of conjugated fatty acids from PC to triacylglycerol in seeds of M. charantia.