Jc. Thomas et al., LIGHT-INDUCED EXPRESSION OF IPT FROM AGROBACTERIUM-TUMEFACIENS RESULTS IN CYTOKININ ACCUMULATION AND OSMOTIC-STRESS SYMPTOMS IN TRANSGENIC TOBACCO, Plant molecular biology, 27(2), 1995, pp. 225-235
Cytokinins are plant growth regulators that induce shoot formation, in
hibit senescence and root growth. Experiments with hydroponically grow
n tobacco plants, however, indicated that exogenously applied cytokini
n led to the accumulation of proline and osmotin. These responses were
also associated with environmental stress reactions, such as salt str
ess, in many plant species. To test whether increased endogenous cytok
inin accumulation led to NaCl stress symptoms, the gene ipt from Agrob
acterium tumefaciens, encoding isopentenyl transferase, was transforme
d into Nicotiana tabacum cv. SR-1 under the control of the light-induc
ible rbcS-3A promoter from pea. In high light (300 mu mol PPFD m(-2) s
(-1)), ipt mRNA was detected and zeatin/zeatin glucoside levels were 1
0-fold higher than in control plants or when transformants were grown
in low light (30 mu mol PPFD m(-2) s(-1)). High light treatment was ac
companied 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 flowe
ring or environmental stress.