PARENT SESSION
Posters P5D Emerging techniques and systems. Abstracts (731-741)

Effect of tetracycline on wild type and IPT-transgenic tobacco plants studied by fluorescence imaging. Lieve Quanten^*,1, Christy Huybrechts¹, Birgit Gielen², Roland Valcke¹, ¹ Laboratory of Molecular and Physical Plant Physiology, Diepenbeek, Belgium² Research Group of Plant and Vegetation Ecology, Wilrijk, Belgium

ABSTRACT- The exact role of cytokinins on the photosynthetic apparatus is still not clear. The biosynthetic pathway of cytokinins in plants is poorly understood, but has been clearly demonstrated in the phytopathogenic bacterium Agrobacterium tumefaciens (Barry G.F. et al., 1984 Proceedings of the National Academy of Sciences USA 81, 4776-4780). Those bacteria contain a cytokinin biosynthetic ipt-gene coding for isopentenyl transferase, which is a key enzyme in the biosynthesis of cytokinin. Plants transformed with the ipt-gene under control of different promoters indeed lead to elevated cytokinin levels (Beinsberger S.E.I. et al., 1991 Plant Cell Physiology 32(4), 489-496). The transgenic plants used in this work (P35So IPT-5/TETR) contain the ipt-gene under control of a tetracycline-inducible promoter. Using the Tn10-encoded Tet repressor (TetR) in combination with a suitable engineered CaMV 35S promoter (Gatz C. et al., 1992 Plant J. 2, 397-404) leads to such a highly specific expression system inducible by tetracycline (Gatz C., 1995 Methods Cell Biol. 50, 411-424). Besides the effects of an elevated level of cytokinin, it is important to investigate the possible effect of tetracycline on the plants as such. Therefore both wild type plants and transgenic plants are used in this study. The physiological state of plants can be determined by red-light chlorophyll fluorescence induced after excitation with UV or blue light. In this experiment, a transportable chlorophyll fluorescence imaging system build in the laboratory of Molecular and Physical Plant Physiology was used to study the effects of a tetracycline treatment and/or an increase in cytokinin content on the physiology of tobacco plants. Each image taken from a leaf consists of 65536 (=256x256) pixels; 51431 pixels are used for calculations. An increase in fluorescence is seen when comparing treated transgenics with respectively treated wild types and untreated transgenics.

KEY WORDS: ipt-transgenic tobacco plants, fluorescence, cytokinins, tetracycline-inducible promoter