We live in a time when genetically engineered organisms are becoming more and more common and accepted by the general public. One of the most exciting examples of genetic engineering is the production of biodegradable plastics in plants. The technical name for this plastic is polyhydroxybuterate (PHB for short). Some bacteria synthesize this polymer as a way to store energy during good times so it will help them make it through bad times, much as we store glycogen and plants store starch. PHB is made using Acetyl-CoA and requires only three gene products one of which is already in plants. In 1992 Scientists at Michigan State University inserted the remaining 2 genes originally isolated by Dr. Doug Dennis formerly of James Madison University into Arabidopsis plants and detected PHA granules in the transgenic plants. The trick now is to get plants to make enough PHA to be profitable without making the plants sick.

Besides introducing the coding sequences for the two genes into the plant, promoters were also required to get them expressed. In the first experiments the promoters used were constitutive promoters so that they would be on all of the time and in all plant cells. Because PHB synthesis draws metabolites away from normal plant metabolism, the transgenic plants did not thrive.

Questions: What sort of promoters might be better to use for this project? Hint: If you were to want to engineer a plant that made PHB instead of starch, which plant and which plant part would you try to change?

8/22/04 Copyright (C) 2004, Jonathan Monroe, monroejd@jmu.edu. All rights reserved.
URL: http://csm.jmu.edu/biology/courses/bio220/qotw8.html