title: Cytokinin-induced abnormal shoot organogenesis is associated with elevated Knotted1-type homeobox gene expression in tobacco.
abstract: The molecular mechanisms that regulate the transcription of key developmental genes involved in shoot organogenesis have yet to be fully elucidated. However, it is clear that plant growth regulators, such as cytokinin, play a critical role in the differentiation of adventitious shoots. In Nicotiana tabacum zz100 leaf discs, high frequency shoot formation could be induced with 5 microM of the cytokinin N6-benzyladenine (BA). Increasing the exogenous BA concentration to greater than 20 microM resulted in stunted explants with abnormal shoot morphology and altered mineral composition. Explants with abnormal shoots did not appear to be hyperhydric. Abnormalities were, however, associated with an increase in the expression of a knotted1-type homeobox gene (TobH1) isolated from normal shoot-forming cultures. The results suggest that the development of cytokinin-induced abnormal shoot morphology possibly involves changes in TobH1 gene expression.
authors.affiliation: Agricultural Molecular Biotechnology Laboratory, School of Agronomy and Horticulture, University of Queensland-Gatton, 4343, Queensland, Australia. carl.ramage@dpi.vic.gov.au
authors.forename: Carl M
authors.initials: CM
authors.lastname: Ramage
authors.forename: Richard R
authors.initials: RR
authors.lastname: Williams
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D001593:Benzyl Compounds; D018929:Cell Culture Techniques / Q000379:methods; D003583:Cytokinins / Q000494:pharmacology*; D018744:DNA, Plant / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D005801:Genes, Homeobox / Q000235:genetics*; D017343:Genes, Plant / Q000235:genetics; D018398:Homeodomain Proteins / Q000235:genetics*; D007701:Kinetin; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics*; D018520:Plant Shoots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D011687:Purines; D018749:RNA, Plant / Q000235:genetics; D014026:Nicotiana / Q000187:drug effects / Q000196:embryology / Q000235:genetics*
chemical_list: D001593:Benzyl Compounds; D003583:Cytokinins; D018744:DNA, Plant; D018398:Homeodomain Proteins; C095848:Kn1 protein, plant; D010940:Plant Proteins; D011687:Purines; D018749:RNA, Plant; D000225:Adenine; C480551:benzylaminopurine; D007701:Kinetin