Fusions between green fluorescent protein and beta-glucuronidase as sensitive and vital bifunctional reporters in plants

By fusing the genes encoding green fluorescent protein (GFP) and beta-glucu ronidase (GUS) we have created a set of bifunctional reporter constructs wh ich are optimized for use in transient and stable expression studies in pla nts. This approach makes it possible to combine the advantage of GUS, its h igh sensitivity in histochemical staining, with the advantages of GFP as a vital marker. The fusion proteins were functional in transient expression s tudies in tobacco using either DNA bombardment or potato virus X as a vecto r, and in stably transformed Arabidopsis thaliana and Lotus japonicus plant s. The results show that high level of expression does not interfere with e fficient stable transformation in A. thaliana and L. japonicus. Using confo cal laser scanning microscopy we show that the fusion constructs are very s uitable for promoter expression studies in all organs of living plants, inc luding root nodules. The use of these reporter constructs in the model legu me L japonicus offers exciting new possibilities for the study of the root nodulation process.