Submitted to: Federation of European Biochemical Societies Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2001
Publication Date: 3/21/2001
Interpretive Summary: Vegetable oils are used throughout the world for both nutritional and industrial purposes. The quality of a vegetable oil is largely determined by its fatty acid composition, which can vary quite dramatically. Although the genes responsible for making various fatty acids in plants have been identified, very little is known about how these enzymes are organized in plant cells. We have performed the first study that describes in detail how these enzymes are arranged in plant cells. The cell is a very complex environment, and enzymes must be located at very specific regions of the cell in order to do their job correctly. Determining exactly how and where these enzymes perform their job in plant cells is critical for understanding how plants are able to make the great variety of vegetable oils present in nature. The information presented in this study will be of interest to all scientists interested in the production of vegetable oils, whether they are used for nutritional or industrial purposes.
Technical Abstract: The subcellular location of two integral membrane-bound fatty acid desaturases (Fads), Fad2 and Fad3, was elucidated by immunofluorescence microscopic analyses of tobacco suspension cells transiently transformed with different epitope-tagged versions of the enzymes. Both myc- or hemagglutinin-tagged Fad2 and Fad3 localized to the same region of the endoplasmic reticulum (ER), as evidenced by their co-localization with the endoplasmic reticulum lumenal protein calreticulin. Results from differential permeabilization experiments revealed that the N-termini of both epitope-tagged Fad2 and Fad3 were exposed on the cytosolic side of endoplasmic reticulum membranes. These data define the subcellular location and topological orientation of plant desaturases in endoplasmic reticulum membranes.