title: Functional characterisation of a cytokinin oxidase gene DSCKX1 in Dendrobium orchid.
abstract: Cytokinin oxidase plays an important role in the cytokinin regulatory processes. We have cloned a novel putative cytokinin oxidase, DSCKX1 (Dendrobium Sonia cytokinin oxidase), by mRNA differential display from shoot apices of Dendrobium Sonia cultured in the presence of BA. The DSCKX1 gene appears to have three alternative splicing forms and its expression of DSCKX1 was induced in a tissue-specific manner by cytokinins. In transgenic orchid plants overexpressing DSCKX1, the elevated level of cytokinin oxidase activity was accompanied by a reduction of cytokinin content. These plants exhibited slow shoot growth with numerous and long roots in vitro. Their calli also showed decreased capability of shoot formation. Conversly, antisense transgenic plants showed rapid proliferation of shoots and inhibition of root growth combined with a higher endogenous cytokinin content than wild-type plants. Thus DSCKX1 appears to play an important role on cytokinin metabolism and the related developmental programmes in orchid.
authors.affiliation: Plant Growth and Development Laboratory, Department of Biological Sciences, Faculty of Science, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, Republic of Singapore.
authors.forename: Shu Hua
authors.initials: SH
authors.lastname: Yang
authors.forename: Hao
authors.initials: H
authors.lastname: Yu
authors.forename: Chong Jin
authors.initials: CJ
authors.lastname: Goh
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001593:Benzyl Compounds; D015152:Blotting, Northern; D003001:Cloning, Molecular; D003583:Cytokinins / Q000494:pharmacology; D016373:DNA, Antisense / Q000235:genetics; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D031667:Dendrobium / Q000201:enzymology / Q000235:genetics*; D005091:Exons; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D007438:Introns; D007701:Kinetin; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D011687:Purines; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D001593:Benzyl Compounds; D003583:Cytokinins; D016373:DNA, Antisense; D018076:DNA, Complementary; D011687:Purines; D018749:RNA, Plant; D010088:Oxidoreductases; C019984:cytokinin oxidase; D000225:Adenine; C480551:benzylaminopurine; D007701:Kinetin