Multigenes and multipurpose genes

Plant biotechnologists are moving towards an improved understanding and engineering of multigenic traits, including the manipulation of metabolic pathways and the coordinated expression of multisubunit proteins. In the past, most molecular genetic modification has involved the introduction of only single genes, for the manipulation of relatively simple and well-understood traits. Genetic engineers are now exploring the potential rewards of multigene engineering. Daniell and Dhingra (pp 136–141) discuss this subject in detail, while several other authors note the recent advances made in multigene engineering. Verpoorte and Memelink (pp 181–000), for example, discuss the engineering of multiple steps in metabolic pathways, including the manipulation of regulatory genes. In one case, an entire biosynthetic pathway was transferred between species, achieving a new desired phenotype without any deleterious effects. Other ambitious projects are underway to improve the nutritional content of staple foods, to engineer plants for the production of antibodies and other pharmaceuticals, to produce commercially important secondary metabolites and to improve tolerance to environmental stresses, including pathogens and salinity.