Methods and constructs for the introduction of multiple genes encoding enzymes in a multi-
enzyme biosynthetic pathway are provided. In one embodiment, the constructs contain two or more
enzyme-encoding genes, each under the control of an inducible
promoter and each with a
polyadenylation signal. The constructs are used to produce transgenic plants, in which the expression of the enzymes are increased when a chemical inducing agent is applied, and a
biosynthetic product of the series of enzymes encoded by the transgenes is produced. Constructs may be used which contain two or more
enzyme-encoding genes under the control of one or more promoters activated by activator molecules or complexes expressed from a
transgene or transgenes, which are themselves under the control of one or more
inducible promoters and switched on following the
external application of a chemical. The
transgene or transgenes expressing the activator molecules or complexes may be included in the same construct containing multiple genes encoding enzymes in a multi-enzyme biosynthetic pathway. Alternatively, the
transgene or transgenes expressing the activator molecules or complexes may be on a different construct from the construct containing multiple genes encoding enzymes in a multi-enzyme biosynthetic pathway. The activator molecule can be expressed using a constitutive
promoter in an inactive form which is converted to the active form following application of the chemical inducing agent.