THE TOMATO RBCS3A PROMOTER REQUIRES INTEGRATION INTO THE CHROMATIN FOR CORRECT ORGAN-SPECIFIC REGULATION

In tomato, the RBCS1, RBCS2 and RBCS3A genes, encoding the small subun it of ribulose-1,5-bisphosphate carboxylase/oxygenase, are expressed i n leaves and light-grown seedlings, but only RBCS1 and RBCS2 are expre ssed in developing tomato fruits, The activities of the three promoter s have been compared in transgenic plants and after transient transfor mation, Fruit-specific repression of the RBCS3A promoter was observed in transgenic plants, but not after ballistic transient transformation , indicating that chromatin integration is necessary for its correct o rgan-specific regulation, In addition, matrix attachment regions have been identified in the RBCS1, RBCS2 and RBCS3A promoters, This is the second case in plants of absence of correct regulation of a plasmid-bo rne plant promoter and correlating potential nuclear matrix attachment of the gene, (C) 1997 Federation of European Biochemical Societies.