Regarding the GUS-like activity observed in many plants. As reported by
Kosugi et al (1990, Plant Science 70:133-140), addition of methanol to 20%
during GUS staining, or during fluorimetric assays, eliminates the
endogenous activities found in many plants. The methanol appears to have
no effect on the authentic GUS encoded by the UidA coding sequence from E.
coli. We, and others at Davis, have found that the background normally
seen in various tissues of Brassica napus and in the styles and pollen of
tomato flowers is absent when the assays or stainings are carried out in
the presence of methanol. THIS IN NO WAY OBVIATES THE NEED FOR CONTROLS!!!
Each experimenter must determine the activity in plants grown and assayed
in their lab in the same fashion as the experimental plants. The use of
methanol does, however, increase the likelihood that the controls will be
negative, simplifying interpretation of transgenic reuslts.
csgasser at ucdavis.edu