Plant endogenous beta-glucuronidase activity: how to avoid interference with the use of the E. coli beta-glucuronidase as a reporter gene in transgenic plants

We have detected a plant beta-glucuronidase activity, present in several tissues and organs of plant species belonging to different families. The fluorimetric beta-glucuronidase assay was used to partially characterize this activity in post-ribosomal supernatants of tobacco leaves. The tobacco activity is very stable at low temperatures, but quickly inactivated above 45 degrees C. It is relatively resistant to proteases and insensitive to -SH group reagents and to ionic conditions. It does not require, nor is it inhibited by, divalent cations. Although these properties are shared by the Escherichia coli beta-glucuronidase, the two activities can be distinguished by: (i) their different sensitivity to the specific inhibitor saccharic acid-1,4-lactone; (ii) their different thermal stability (iii) their different pH optima (5.0 for the plant activity and close to neutral for the bacterial enzyme). Therefore, under appropriate experimental conditions, it should be possible to assay the E. coli beta-glucuronidase in transgenic plants without interference from the endogenous plant activity.

In-situ seed production after pollination with in-vitro-matured, isolated pollen

Immature tobacco (Nicotiana tabacum L.) pollen has been isolated from anthers in three distinct stages of development, including the microspore stage. In in-vitro cultures, fully functional, mature pollen was obtained. In a germination medium, this pollen produced pollen tubes. After application to stigmas in situ, the in-vitro-matured pollen fertilized ovules, and seeds were produced. Genetic tests with seedlings obtained from pollinations with in-vitro-matured pollen from a transgenic plant revealed normal Mendelian segregation of two marker genes, the neomycin-phosphotransferase II gene and the nopaline-synthase gene. These results are of interest with respect to the control of self-incompatibility, cytoplasmic male sterility and pollen-allergen formation, and it offers an alternative route for gene transfer in those plants which cannot be regenerated in vitro.