TAILIEUCHUNG - Báo cáo khoa học: The purine derivative PI-55 blocks cytokinin action via receptor inhibition

One of several potential approaches to study mechanisms of action of bio-logically active compounds is to develop their agonists and antagonists. In the present study, we report the identification of the first known molecule antagonizing the activity of the plant hormone cytokinin at the receptor level. | The purine derivative PI-55 blocks cytokinin action via receptor inhibition Lukas Spichal1 Tomas Werner2 Igor Popa1 Michael Riefler2 Thomas Schmulling2 and Miroslav Strnad1 1 Laboratory of Growth Regulators Institute of ExperimentalBotany AS CR Palacky University Olomouc Czech Republic 2 Institute of Biology Applied Genetics Free University of Berlin Germany Keywords anticytokinin cytokinin cytokinin receptor cytokinin receptor antagonist hormone signaling Correspondence L. Spichal Slechtitelu 11 CZ-78371 Olomouc Czech Republic Fax 420 58 5634870 Tel 420 58 5634855 E-mail Website http Received 26 August 2008 revised 24 October 2008 accepted 3 November 2008 doi One of several potential approaches to study mechanisms of action of biologically active compounds is to develop their agonists and antagonists. In the present study we report the identification of the first known molecule antagonizing the activity of the plant hormone cytokinin at the receptor level. This compound 6- 2-hydroxy-3-methylbenzylamino purine designated PI-55 in the present study is structurally closely related to cytokinin 6-benzylaminopurine but substitutions at specific positions of the aromatic side chain strongly diminished its cytokinin activity and conferred antagonistic properties. PI-55 competitively inhibited the binding of the natural ligand trans-zeatin to the Arabidopsis cytokinin receptors cytokinin response 1 CREiyArabidopsis histidine kinase AHK 4 and AHK3 and repressed induction of the cytokinin response gene ARR5 GUS. Genetic analysis revealed that CRE1 AHK4 is the primary target of PI-55. Cytokinin bioassays also demonstrated the anticytokinin effect of PI-55 in several other species. Furthermore we show that PI-55 accelerated the germination of Arabidopsis seeds and promoted the root growth and formation of lateral roots thus phenocopying the known consequences of a lowered cytokinin status and demonstrating

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