Tobacco BY2 cells containing a tomato mosaic virus vector for protein production

A process for producing a tobacco BY2 cell for protein production, comprising:

• a first transforming step of transfecting tobacco BY2 cells with a plasmid, the plasmid comprising
• a transcription factor-expressing DNA comprising a coding gene of a transcription factor, wherein the transcription factor is LexA-VP16-hER which is activated by estrogen;
• and
• a promoter for expressing the transcription factor;
• a screening step of screening tobacco BY2 cells, obtained in the first transforming step, for an individual tobacco BY2 cell expressing the transcription factor;
• and
• a second transforming step of transfecting the individual tobacco BY2 cell, obtained in the screening step, with a plasmid, the plasmid comprising a protein-expressing DNA comprising
• cDNA of a RNA virus vector having incorporated therein a gene encoding a target protein, wherein the RNA virus vector is a tomato mosaic virus vector;
• an inducible promoter which is OLexA-46 located upstream of the cDNA of the RNA virus vector, wherein the virus vector cDNA is transcribed under the control of the inducible promoter;
• and
• a ribozyme sequence of satellite tobacco ringspot virus directly ligated to the 3′ end of the RNA virus vector cDNA with no sequence ligated therebetween.