Plant Genome IV Conference Plant Genome IV Conference
Chalcone synthase is a key enzyme in anthocyanin biosynthesis. It is essential for coloured pigment production in the epidermal layer of petals. Transgenic petunias carrying one or more copies of a transgene constructed from the coding sequence of a petunia chalcone synthase A gene under the control of the CaMV 35S promoter and nos terminator, often display white sectors or completely white flowers. This is due to the loss of expression of the trans and endogenous copies of chalcone synthase A genes. The loss of gene expression involves postranscriptional RNA turnover. The patterns of RNA turnover have been studied by RT-PCR in a range of genotypes with different patterns of pigment loss. A complex pattern of RNA structures and turnover has been revealed. This will be described and hypotheses presented for how this turnover is promoted by the presence of trangenes. Studies of cytosine methylation and of other characteristics of the chalcone synthase genes in these transgenic plants will also be described.