Isolation and characterization of strong gene regulatory sequences from apple, Malus x domestica

For the strong expression of genes in plant tissue, the availability of specific gene regulatory sequences is desired. We cloned promoter and terminator sequences of an apple (Malus x domestica) ribulose biphosphate carboxylase small subunit gene (MdRbcS), which is known for its high expression and used gus reporter gene expression to test the regulatory activity of the isolated promoter and terminator sequences in transgenic tobacco. The MdRbcS promoter itself seemed to be less strong than the CaMV35S promoter when both used in combination with the nos terminator. However, the combination of the promoter and terminator of MdRbcS was able to drive gus to similar expression levels as the reference construct with CaMV35S promoter and nos terminator. This observation indicates the importance of the terminator sequence for gene expression. It is concluded that the combination of the MdRbcS promoter and terminator is a suitable regulatory sequence set for the expression of transgenes to a high level in plants and for intragenesis in apple specificall