How Plants Make Oil

Applied Genetics News,  April, 2001  

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For 30 years, plant scientists have searched for the critical enzyme necessary for plants to create oil. The mystery may have been solved by three groups of researchers at Iowa State University. Their discovery may make it possible for plant breeders and genetic engineers to adjust the oil-producing capacity of soybeans, corn and other plants. The three groups were led by Basil Nikolau, biochemistry professor and interim director of the Center for Designer Crops; David Oliver, botany professor and department chair; and Eve Syrkin Wurtele, botany professor.

Commercial oils produced by plants are made from the biosynthesis of fatty acids. The precursor for this biosynthesis is acetyl- coenzyme A (acetyl-CoA). Acetyl-CoA is also the substrate for the biosynthesis of several other compounds.

By the late '80s, most interested scientists had agreed that acetyl CoA was made by an enzyme called acetyl-CoA synthetase (ACS).

Unconvinced, Nikolau, Wurtele and Oliver were able to take advantage of new sequencing data available from the Arabidopsis plant genome project. Their research groups worked independently, studying different parts of the same puzzle in search of genes for enzymes that could make acetyl-CoA.

"We found that another enzyme-pyruvate dehydrogenase (PDH)-which was known to be involved, was actually responsible," Nikolau says.

"We looked at how the ACS- and PDH-coding genes are expressed during the development of the seeds when oil was being produced in the seeds. It turned out that the PDH gene is coordinately expressed as other fatty acid biosynthetic genes consistent with its role in making oil, but the expression of the ACS gene was not coordinated with the other fatty acid biosynthetic genes or oil accumulation,"adds Wurtele.

The Iowa State researchers are working on the absolute proof that PDH is the source. "By eliminating the ACS and PDH genes one at a time, we can see which one affects oil formation," Nikolau explains. "When we eliminated ACS, there was no effect on oil."

Iowa State has a patent pending for the genes and for methods of altering acetyl-CoA generation.

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