The effect of Ca-formaldehyde fixation on the activity of the reporter enzyme beta-glucuronidase (GUS) in transgenic tobacco.

The inhibition of beta-glucuronidase (GUS) activity by Ca-formaldehyde fixation was investigated in leaves of transgenic tobacco (Nicotiana tabacum L.) expressing the beta-glucuronidase uidA reporter gene from Escherichia coli. One-hour fixation of a free-floating leaf disc in a cold fixative decreased the activity of GUS by 60% as compared with the untreated control disc kept in a moist chamber. The inhibition was identical in the periphery and centre of the disc. Fixation including initial vacuum infiltration of the fixative led to almost complete inactivation of the enzyme. The incubation of discs in H2O, either with or without vacuum infiltration, did not lower GUS activity.