TAILIEUCHUNG - Báo cáo khoa học: Cytokinin oxidase/dehydrogenase genes in barley and wheat

The cloning of two novel genes that encode cytokinin oxidase/dehydrogenase (CKX) in barley is described in this work. Transformation of both genes intoArabidopsisand tobacco showed that at least one of the genes codes for a functional enzyme, as its expression caused a cytokinin-deficient phenotype in the heterologous host plants. Addi-tional cloning of two gene fragments, and anin silicosearch in the public expressed sequence tag clone databases, revealed the presence of at least 13 more members of the CKXgene family in barley and wheat. . | Eur. J. Biochem. 271 3990-4002 2004 FEBS 2004 doi Cytokinin oxidase dehydrogenase genes in barley and wheat Cloning and heterologous expression Petr Galuszka1 Jitka Frebortova2 Tomas Werner3 Mamoru Yamada4 Miroslav Strnad2 Thomas Schmulling3 and Ivo Frebort1 Division of Molecular Biology Department of Biochemistry Faculty of Science Palacky Univesity Olomouc Czech Republic laboratory of Growth Regulators Palacky University Institute of Experimental Botany of the Academy of Science Olomouc Czech Republic 3Institute of Biology Applied Genetics Free University of Berlin Germany 4Department of Biological Chemistry Faculty of Agriculture Yamaguchi University Japan The cloning of two novel genes that encode cytokinin oxidase dehydrogenase CKX in barley is described in this work. Transformation of both genes into Arabidopsis and tobacco showed that at least one of the genes codes for a functional enzyme as its expression caused a cytokinindeficient phenotype in the heterologous host plants. Additional cloning of two gene fragments and an in silico search in the public expressed sequence tag clone databases revealed the presence of at least 13 more members of the CKX gene family in barley and wheat. The expression of three selected barley genes was analyzed by RT-PCR and found to be organ-specific with peak expression in mature kernels. One barley CKX HvCKX2 was characterized in detail after heterologous expression in tobacco. Interestingly this enzyme shows a pH optimum at and a preference for cytokinin ribosides as substrates which may indicate its vacuolar targeting. Different substrate specificities and the pH profiles of cytokinin-degrading enzymes extracted from different barley tissues are also presented. Keywords cereals cloning cytokinin oxidase dehydro-genase expression gene family. Cytokinins were initially viewed as factors promoting cell division and differentiation in plants. Since then however cytokinins have been shown .

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