Enzyme: cytokinin oxidase/dehydrogenase (EC 220.127.116.11).
Cytokinin oxidase/dehydrogenase genes in barley and wheat
Cloning and heterologous expression
Article first published online: 16 SEP 2004
European Journal of Biochemistry
Volume 271, Issue 20, pages 3990–4002, October 2004
How to Cite
Galuszka, P., Frébortová, J., Werner, T., Yamada, M., Strnad, M., Schmülling, T. and Frébort, I. (2004), Cytokinin oxidase/dehydrogenase genes in barley and wheat. European Journal of Biochemistry, 271: 3990–4002. doi: 10.1111/j.1432-1033.2004.04334.x
Note: a web site is available at http://prfholnt.upol.cz/biochhp
- Issue published online: 16 SEP 2004
- Article first published online: 16 SEP 2004
- (Received 29 April 2004, revised 14 July 2004, accepted 16 August 2004)
- cytokinin oxidase/dehydrogenase;
- gene family
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 cytokinin-deficient 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 4.5 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.