Secondary Products from Plant Cell Cultures: Early Experiences with Agrobacterium rhizogenes-Transformed Hairy Roots

Abstract

The enormous range of secondary metabolites produced within the plant kingdom includes many of scientific and commercial interest. There are frequently problems associated both with the study of secondary product biosynthesis in planta, and the reliability of agricultural systems for the production of commercially valuable products. In recent decades there has thus been an interest in developing in vitro cell culture systems that produce high levels of selected secondary metabolites. While callus and cell suspension cultures have been widely developed, their secondary metabolite productive capacities can be rather low and unpredictable. A major step forward came with the development of organ cultures, particularly the so-called hairy roots produced by transformation of plants with the bacterium Agrobacterium rhizogenes. The group at the Institute of Food Research, Norwich, was one of the first to exploit the technology, and this article describes their experiences with hairy roots and illustrates the range of approaches that can be taken to maximize their potential. In particular, because hairy root formation already involves a genetic transfer, they are especially good systems in which to study the effects of transgenesis. While some of the techniques described have now been extensively exploited, others have still not reached their full potential, and hopefully this article might serve to throw some light on possible future developments.