An optimized protocol for the
transient transformation of tobacco protoplasts mediated
by polyethylene\u2013glycol (PEG) is here described. As expected, the quantitative
b\u2013glucuronidase (Gus) activity driven by pCaMVGus
was dependent on the amount of plasmid used.
Nevertheless, we demonstrate by an immunodetection
method that transformation efficiency did not depend on
the amount of plasmid used but on the limitation imposed
by cell competence. In fact, we obtained the same
percentage of transformed cells (about 60%) using a wide
range of plasmid concentrations (0.1\u201310 mg per test).
Finally, we show that, when we used two plasmid types in
a mixture at a concentration ranging from 0.1 to 10 mg for
each, all transformed cells expressed proteins encoded by
both plasmids. Transient expression and co-transformation
experiments are routinely used methods and, probably,
the major results from this work were assumed by
many researchers in this field, but our data experimentally
support this assumption
