Light-induced expression of ipt from Agrobacterium tumefaciens results in cytokinin accumulation and osmotic stress symptoms in transgenic tobacco |
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Authors: | John C Thomas Ann C Smigocki Hans J Bohnert |
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Institution: | (1) Department of Biochemistry, The University of Arizona, 85721 Tucson, AZ, USA;(2) Department of Plant Sciences, The University of Arizona, 85721 Tucson, AZ, USA;(3) Plant Molecular Biology Laboratory, PSI, USDA/ARS, 20705 Beltsville, MD, USA;(4) Present address: Department of Natural Sciences, University of Michigan-Dearborn, 48128-491 Dearborn, MI |
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Abstract: | Cytokinins are plant growth regulators that induce shoot formation, inhibit senescence and root growth. Experiments with hydroponically grown tobacco plants, however, indicated that exogenously applied cytokinin led to the accumulation of proline and osmotin. These responses were also associated with environmental stress reactions, such as salt stress, in many plant species. To test whether increased endogenous cytokinin accumulation led to NaCl stress symptoms, the gene ipt from Agrobacterium tumefaciens, encoding isopentenyl transferase, was transformed into Nicotiana tabacum cv. SR-1 under the control of the light-inducible rbcS-3A promoter from pea. In high light (300 mol PPFD m-2 s-1), ipt mRNA was detected and zeatin/zeatin glucoside levels were 10-fold higher than in control plants or when transformants were grown in low light (30 mol PPFD m-2 s-1). High light treatment was accompanied by increased levels of proline and osmotin when compared to low light grown transformed and untransformed control plants. Elevated in planta cytokinin levels induced responses also stimulated by salt stress, suggesting either common or overlapping signaling pathways are initiated independently by cytokinin and NaCl, setting in motion gene expression normally elicited by developmental processes such as flowering or environmental stress.Abbreviations IPT
isopentenyl, transferase
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rbcS-3A
gene encoding a small subunit protein (SSU) of Rubisco from Pisum sativum
- Rubisco
ribulose 1,5-bisphosphate carboxylase/oxygenase |
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Keywords: | cytokinin isopentenyl transferase osmotin proline salt stress |
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