Enhancement of Chloroplast Transformation Frequency by Using Mesophyll Cells Containing a Few Enlarged Chloroplasts from Nuclear Transformed Plants in Tobacco

In the chloroplast transformation process, a chloroplast containing transformed chloroplast genome copies should be selected over wild-type chloroplasts on selection medium. It is more effective for a cell to become homoplasmic if the cell contains smaller number of chloroplasts. Therefore, to reduce the number of chloroplasts in mesophyll cells in tobacco, we overexpressed FtsZ to generate transgenic plants, of which mesophyll cell contained a few enlarged chloroplasts contrast to a wild-type mesophyll cell containing approximately 100 chloroplasts. It was demonstrated that transgenic leaf tissues comprising cells with a few enlarged chloroplasts gave rise to approximately 40% higher frequency of chloroplast-transformed adventitious shoots.