Date of Award

Spring 5-11-2020

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Chemistry and Biochemistry

Committee Chair

Dr. Philip D. Bates

Committee Chair Department

Chemistry and Biochemistry

Committee Member 2

Dr. Sabine Heinhorst

Committee Member 2 Department

Chemistry and Biochemistry

Committee Member 3

Dr. Faqing Huang

Committee Member 3 Department

Chemistry and Biochemistry

Abstract

Acyl-CoA:diacylglycerol acyltransferase (DGAT) catalyzes the transesterification of fatty acid from acyl-CoA to diacylglycerol (DAG) forming triacylglycerol (TAG, a.k.a oils and fats). Most plants have at least two unrelated DGAT genes, DGAT1 and DGAT2. Plants predominantly express only one during oil synthesis; the reason, however is not clear. A few studies have indicated that each enzyme prefers DAG and acyl-CoA substrates with different fatty acid compositions. Industrially desirable seed oil composition can be obtained through genetic engineering by replacing the endogenous enzyme with one that has different substrate selectivity. In Arabidopsis thaliana, DGAT1 and another unrelated enzyme PDAT1 are essential for TAG synthesis in seeds and pollen, and the dgat1-1/pdat1-2 double knock-out is pollen lethal. However, the role of DGAT2 in Arabidopsis tissues remains elusive. It is hypothesized that DGAT2 isozymes from Arabidopsis, castor, and soybean can synthesize TAG but with altered fatty acid composition and they utilize de novo DAG pools whereas AtDGAT1 and AtPDAT1 use PC-derived DAG pools. To test this hypothesis DGAT2s were overexpressed with a strong seed-specific promoter in the dgat1-1 knockout background. Our results suggests that DGAT2s synthesize TAG in seeds with altered fatty acid composition than AtDGAT1 and AtPDAT1. To identify the DAG pool utilized by DGAT1, PDAT1 and different DGAT2s, in vivo labeling was performed utilizing [14C]glycerol substrate. AtDGAT1 and AtPDAT1 were found to be using the PC-derived DAG pool for TAG synthesis. This study provided initial data that DGAT2s also use the PC-derived DAG pool.

ORCID ID

0000-0003-1819-6147

Available for download on Friday, March 27, 2020

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