Light-induced expression of ipt from Agrobacterium tumefaciens results in cytokinin accumulation and osmotic stress symptoms in transgenic tobacco

• Published in: Plant molecular biology 1995-01, Vol.27 (2), p.225-235
• Main Authors: Thomas, J.C. (Arizona Univ., Tucson, AZ (USA). Dept. of Biochemistry), Smigocki, A.C, Bohnert, H.J
• Format: Article
• Language: English
• Subjects: Adenine - analogs & derivatives; Adenine - pharmacology; AGROBACTERIUM TUMEFACIENS; Agrobacterium tumefaciens - enzymology; Agrobacterium tumefaciens - genetics; Alkyl and Aryl Transferases; Base Sequence; Benzyl Compounds; Cells, Cultured; CHLORURE DE SODIUM; CITOQUININAS; CLORURO SODICO; CYTOKININE; CYTOKININS; Cytokinins - biosynthesis; ESTRES; Gene Expression Regulation, Enzymologic - drug effects; Gene Expression Regulation, Enzymologic - genetics; Gene Expression Regulation, Enzymologic - radiation effects; GENETIC TRANSFORMATION; Kinetin; Light; Molecular Sequence Data; Nicotiana - genetics; Nicotiana - physiology; NICOTIANA TABACUM; Osmotic Pressure - drug effects; Plant Proteins - biosynthesis; PLANTAS TRANSGENICAS; PLANTE TRANSGENIQUE; Plants, Genetically Modified; Plants, Toxic; PROLINA; PROLINE; Proline - biosynthesis; Promoter Regions, Genetic - genetics; Purines; Ribulose-Bisphosphate Carboxylase - genetics; RNA, Messenger - biosynthesis; RNA, Plant - biosynthesis; SODIUM CHLORIDE; Sodium Chloride - pharmacology; STRESS; Transferases - genetics; TRANSFORMACION GENETICA; TRANSFORMATION GENETIQUE; TRANSGENIC PLANTS
• ISSN: 0167-4412; 1573-5028
• DOI: 10.1007/BF00020179

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 mumol 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 mumol 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.