Nuclear transcriptiońal activity of the tobacco plastidpsbA promoter

Abstract

The plastid psbA promoter of tobacco was used with the aim to construct plastid specific marker genes. Upon transfer to the tobacco nuclear genome the plastid promoter fragment appeared to specify a messenger RNA. Placed 5' to the bar or nptll coding sequences the level of expression is sufficient to obtain a selectable phenotype. The transcription start site in the nucleus is site specific and is located 4 nucleotides downstream relative to the start site used in plastids. Translational fusions of the psbA coding sequence with the nptll and bar coding sequences revealed that the psbA leader sequence and the psbA translation start codon, being the second ATG codon, are recognized by the plant cytoplasmic translation apparatus.