Plasmids were constructed that contained promoters of ;plant' genes fused to the bacterial gene for chloramphenicol acetyl transferase. The promoters were isolated from a developmentally regulated Zea mays seed storage protein gene and from the mannopine synthase gene of the octopine type Ti plasmid of Agrobacterium tumefaciens which is constitutively expressed in crown gall tumors. These plasmids were introduced into carrot protoplasts made permeable by electroporation. Expression of chloramphenicol acetyl transferase activity directed by both promoters was positively correlated with DNA concentration. The efficiency of gene transfer was increased by inclusion of polyethylene glycol and by optimization of the voltage used in electroporation.