1. Department of Applied Genetics, Vrije Universiteit, de Boelelaan 1087, 1081 HV Amsterdam, The Netherlands

Abstract

In most plants flower pigments derive from the flavonoid biosynthesis pathway. Consistent with this pathway in Petunia hybrida the key enzyme in flavonoid synthesis, chalcone synthase, is synthesized in the flower corolla, tube and anthers¹. Here we show that constitutive expression of an 'anti-sense' chalcone synthase gene in transgenic petunia and tobacco plants results, with high frequency, in an altered flower pigmentation due to a reduction in levels of both the messenger RNA for the enzyme and the enzyme itself. The pattern of pigmentation varies among flowers of different transgenic plants, indicating that the activity of the anti-sense gene is influenced by DNA sequences that border its site of insertion in both a quantitative and a qualitative way. Backcrossing experiments show that the different pigmentation phenotypes resulting from the expression of anti-sense chalcone synthese gene(s) are stably inherited. These data establish that secondary metabolism in plants can be manipulated using transgenic plants that constitutively synthesize anti-sense RNA.