β-Glucuronidase (gus) is widely used as a reporter gene to study transcriptional regulation in transgenic plants, based on the assumption that the level of GUS activity is indicative of the rate of gus transcription driven by the promoter investigated. Here we examined tobacco BY-2 cultures transformed with Arabidopsis cyclin promoters fused to gus. In cultures leaving the stationary state, levels of the gus mRNA remarkably increased, indicating that the plant cyclins are transcribed only in actively dividing cells. Nevertheless, at the same time GUS protein activity decreased. Our observations highlight the need for special precautions while using the gus reporter gene in conditions that represent a rapid change in a developmental or a metabolic state. These precautions are expected to hold true also for other reporter genes encoding relatively stable proteins.
Bibliographical noteFunding Information:
We thank the Tobacco Science Research Laboratory, Japan Tobacco, for permitting us use of the tobacco BY-2 cell suspension culture, T. Nagata for helpful discussions, B. Scheres for the Arabidopsis histone H4 gene, and Y. Avivi for critical reading of the manuscript. This work was supported by grants from the Belgian Programme on Interuniversity Poles of Attraction (Prime Minister’s Office, Science Policy Programming, No. 38), the Vlaams Actieprogramma Biotechnologie (ETC 002), the Körber Stiftung, and the Fonds voor Geneeskundig Wetenschappelijk Onderzoek (G.0121.96). O.S. is indebted to the Rothschild Foundation and the European Molecular Biology Organization for fellowships. D.I. is a Research Director of the Institut National de la Recherche Agronomique (France).
- Reporter gene
- Transcriptional regulation
- Transgenic plants
- β-glucuronidase (gus)