TABLE OF CONTENTS Transgenic crops from agriculture, forestry or aquaculture face significant challenges before they can become part of the mainstream global food and non-food supply chains. In addition to the well-known and complex problem of public acceptability, there are also unresolved scientific and management issues that should be addressed.
Manipulating metabolic pathways The rapid pace of development in molecular biology over the past twenty years has not always been matched by our understanding of many of the basic physiological processes or biochemical pathways that we are attempting to manipulate. This is equally true for animal, plant and microbial systems. While many transgenic manipulations do indeed have the predicted effect, this is not always the case and in the past few years there have been several sobering reminders of our ignorance of some of the key metabolic pathways that are targets for transgenic modification. Bailey (1999) has pointed out the difficulties involved in trying to manipulate even relatively simple organisms like E. coli. To give just one example, a mutant strain of E. coli was made in which the pyruvate kinase gene was deleted. Quite unexpectedly, in view of the metabolic importance of pyruvate kinase, the bacteria grew completely normally. This was because the mutants were able to synthesise pyruvate from phosphoenolpyruvate via the tricarboxylic acid cycle and malic enzyme, which according to conventional biochemical wisdom should not have been possible.
Two further examples of surprising discoveries about what were believed to...
