Production of plant secondary metabolites: a historical perspective

Studies on plant secondary metabolites have been increasing over the last 5 0 years. These molecules are known to play a major role in the adaptation o f plants to their environment, but also represent an important source of ac tive pharmaceuticals. Plant cell culture technologies were introduced at th e end of the 1960s as a possible tool for both studying and producing plant secondary metabolites. Different strategies, using in vitro systems, have been extensively studied with the objective of improving the production of secondary plant compounds. Undifferentiated cell cultures have been mainly studied, but a large interest has also been shown in hairy roots and other organ cultures. Specific processes have been designed to meet the requireme nts of plant cell and organ cultures in bioreactors. Despite all of these e fforts of the last 30 years, plant biotechnologies have led to very few com mercial successes for the production of valuable secondary compounds. Compa red to other biotechnological fields such as microorganisms or mammalian ce ll cultures, this can be explained by a lack of basic knowledge about biosy nthetic pathways, or insufficiently adapted reactor facilities. More recent ly, the emergence of recombinant DNA technology has opened a new field with the possibility of directly modifying the expression of genes related to b iosyntheses. It is now possible to manipulate the pathways that lead to sec ondary plant compounds. Many research projects are now currently being carr ied out and should give a promising future for plant metabolic engineering. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.