Characterisation of the Dunaliella tertiolecta RbcS genes and their promoter activity in Chlamydomonas reinhardtii

The availability of highly active homologous promoters and terminators is critical in the development of a transformation system for the unicellular microalga Dunaliella tertiolecta. To facilitate transformation of this species, we isolated and characterised two native ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit genes (RbcS) including flanking sequences. The two non-allelic cDNA sequences share approximately 80% identity and have approximately 60% identity to the RbcS genes of Chlamydomonas reinhardtii. The D. tertiolecta RbcS promoter and 3′ untranslated regions were shown to drive expression of the bleomycin resistance gene (ble) in C. reinhardtii. This is the first demonstration of a heterologous algal promoter being used to drive transgene expression in C. reinhardtii. In addition, promoter deletions were shown to further increase transformation efficiency.