Polyamines Induce Rapid Biosynthesis of Nitric Oxide in Arabidopsis thaliana Seedlings
Santa-Catarina, C.1*; Tun, N.N.2; Silveira, V.1; Begum, T.2; Handro, W.1; Scherer, G.F.E.2 and Floh, E.I.S.1
1) Plant Cell Biology Laboratory, Department of Botany, IB -University of São Paulo, São Paulo, Brazil, C.P.: 11461, 05422-970. 2) Universität Hannover, Institut für Zierpflanzenbau, AG Spezielle Ertragsphysiologie, Herrenhäuser Str. 2, D-30419 Hannover, Germany. *E-mail: claudete_sc@yahoo.com.br
In this study we examined the regulation by putrescine, spermidine and spermine of nitric oxide (NO) biosynthesis in Arabidopsis thaliana seedlings. NO release to the medium was determined using the cell-impermeable NO-binding dye diaminorhodamine-4M (DAR-4M) in a fluorometric assay. Intracellular NO was visualized under fluorescence microscope using the cell-permeable NO-binding dye diaminorhodamine-4M acetoxymethyl ester (DAR-4M AM). Using a fluorimetric method, we observed that the polyamines spermidine and spermine increased NO release in the seedlings strongly whereas arginine and putrescine had little or no effect. Spermine, the most active polyamine, stimulated NO release with no apparent lag phase. The response was quenched by addition of 2-aminoethyl-2-thiopseudourea (AET), an inhibitor of the animal nitric oxide synthase (NOS) and plant NO biosynthesis, and by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-1-oxy-3-oxide (PTIO), an NO scavenger. By fluorescence microscopy, we observed that polyamines induced NO biosynthesis in specific tissues in Arabidopsis seedlings. Spermine and spermidine increased NO biosynthesis in the elongation zone of the Arabidopsis root tip and in primary leaves, especially in the veins and trichomes, while in cotyledons little or no effect of polyamines beyond the endogenous levels of NO-induced fluorescence was observed. We conclude that polyamines induce NO biosynthesis in plants. Supported by: FAPESP, CNPq and DAAD (Germany)
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