title: Activation of cell proliferation by brassinolide application in tobacco BY-2 cells: effects of brassinolide on cell multiplication, cell-cycle-related gene expression, and organellar DNA contents.
abstract: Brassinosteroids (BRs) are steroidal phytohormones that are essential for many processes in plant growth and development, such as cell expansion, vascular differentiation, and responses to stress. The effects of BRs on cell division are unclear, as attested by contradictory published results. To determine the effect of BRs on cell division, the tobacco (Nicotiana tabacum) BY-2 cell line, which is a widely-used model system in plant cell biology, was used. It was found that brassinolide (BL) promoted cell division only during the early phase of culture and in the absence of auxin (2,4-D). This promotion of cell division was confirmed by RNA gel blot analyses using cell-cycle-related gene probes. At later stages in the culturing periods of BL-supplied and 2,4-D-supplied BY-2 cells, differences in cell multiplication and cell-cycle-related gene expression were observed. Moreover, the BL-treated BY-2 cells had morphological differences from the 2,4-D-treated cells. To determine whether suppressed organellar DNA replication limited this promotion of cell division during the early culture phase, this replication was examined and it was found that BL treatment had no effect on activating organellar (plastid- and mitochondrial-) DNA synthesis. As preferential organellar DNA synthesis, which is activated by 2,4-D, is necessary during successive cell divisions in BY-2 cells, these data suggest that the mechanism of the promotion of cell division by BL treatment is distinct from that regulated by the balance of auxin and cytokinin.
authors: Plant Functions Laboratory RIKEN, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan. yutakam@postman.riken.go.jp
authors: Yutaka
authors: Y
authors: Miyazawa
authors: Naoko
authors: N
authors: Nakajima
authors: Tomoko
authors: T
authors: Abe
authors: Atsushi
authors: A
authors: Sakai
authors: Shozo
authors: S
authors: Fujioka
authors: Shigeyuki
authors: S
authors: Kawano
authors: Tsuneyoshi
authors: T
authors: Kuroiwa
authors: Shigeo
authors: S
authors: Yoshida
mesh_terms: D060406:Brassinosteroids; D002453:Cell Cycle / Q000187:drug effects* / Q000235:genetics; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D002777:Cholestanols / Q000494:pharmacology*; D003470:Culture Media; D018744:DNA, Plant / Q000187:drug effects / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects* / Q000502:physiology; D007210:Indoleacetic Acids / Q000494:pharmacology; D015388:Organelles / Q000187:drug effects / Q000502:physiology; D010937:Plant Growth Regulators / Q000494:pharmacology*; D013260:Steroids, Heterocyclic / Q000494:pharmacology*; D014026:Nicotiana / Q000166:cytology* / Q000187:drug effects
chemical_list: D060406:Brassinosteroids; D002777:Cholestanols; D003470:Culture Media; D018744:DNA, Plant; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D013260:Steroids, Heterocyclic; C023623:brassinolide