Transgenic expression of two marker genes under the control of an Arabidopsis rbcS promoter: Sequences encoding the Rubisco transit peptide increase expression levels

Summary Chimeric gene constructs were made in which two reporter genes, the neo and bar genes, encoding neomycin phosphotransferase II and phosphinothricin acetyl transferase, respectively, were placed under the control of the promoter of ats1A, one of four genes encoding the ribulose-1,5-bisphosphate carboxylase (Rubisco) small subunit (SSU) in Arabidopsis thaliana. In one set of constructs the fusions were made at the initiation codons, while in the second set the sequences encoding the ats1 A transit peptide were included. Significantly higher steady-state levels of RNA and protein were observed in leaves of transgenic plants varrying the latter constructions. Individual transgenic plants varied in their degree of tissue specific expression of the chimeric genes as well as in absolute levels of expression. Preliminary results suggest that the ats1 A promoter may be only weakly responsive to phytochrome.