Poster: Hormones

Abs # 644: Isolation, identification and biological activity of new endogenous cytokinin class.

Presenter:	Dolezal, Karel , dolezal@aix.upol.cz
Authors	Dolezal, Karel  (A) (C)  Tarkowska, Danuse  (A) (C)  Tarkowski, Petr  (A) (C)  Popa, Igor  (A)   Astot, Crister  (C) (D)  Holub, Jan  (A)   Fuksova, Kvetoslava  (B)   Schmulling, Thomas  (E)   Sandberg, Goran  (C)   Strnad, Miroslav  (A)
Affiliations:	(A): Laboratory of Growth Regulators, Palacky University & Institute of Experimental Botany AS CR (B): Institute of Nuclear Medicine, First Faculty of Medicine, Charles University (C): Umea Plant Science Center, Dept. of Forest Genetics & Plant Physiology, Swedish Univ. of Agric. Sciences (D): Swedish Defense Research Agency (E): Free University of Berlin, Institute of Biology/Applied Genetics

Our search for naturally occurring aromatic cytokinins in plants led to the discovery of four new plant hormone substances: 6-(2-methoxybenzylamino)purine, 6-(3-methoxybenzylamino)purine and their 9-ß-D-ribofuranosyl derivatives. These substances were identified in Arabidopsis thaliana plants and Populus c canadensis leaves by liquid chromatography - electrospray ionisation mass spectrometry and capillary-liquid chromatography/frit-fast atom bombardment – mass spectrometry after pre-column derivatization. Endogenous levels of the methoxytopolins were studied using enzyme-linked immunosorbent assays of HPLC-fractionated extracts. Their high cytokinin activity was demonstrated in three bioassays testing their ability to stimulate tobacco callus growth, to delay chlorophyll degradation in excised wheat leaves, and to induce betacyanin synthesis in Amaranthus caudatus var. atropurpurea cotyledons. The results showed particularly their great potential as anti-senescence factors. Moreover, the ability of new derivatives (in mmolar concentrations) to inhibit growth of selected human tumour cell lines was confirmed. Results of synthesis and structure-activity studies of this cytokinin subgroup will be also presented. The project was supported by MSMT (153100008) and GACR (522/01/0275).