title: Increasing ploidy level in cell suspension cultures of Doritaenopsis by exogenous application of 2,4-dichlorophenoxyacetic acid.
abstract: To clarify the causal factors for ploidy variation in plant cell culture, we attempted to alter ploidy distribution in cell cultures of a tetraploid cultivar of Doritaenopsis by changing the plant growth regulators (PGRs) in the culture medium. The original suspension cultured cells, which had been maintained in medium containing 0.1 mg l-1 1-naphthaleneacetic acid and 1 mg l-1 benzyladenine, were transferred onto various gellan gum solidified media with a single application of PGRs, and the ploidy distributions of the cells were examined using flow cytometry analysis during 3 weeks of culture. Among the PGRs tested, 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-amino-3,5,6-trichloropicolinic acid caused a drastic reduction in the 4C-cell proportion in cell cultures with an increased cell proportion of 8C or higher C-values. In the case of 2,4-D application, a reduction of cell viability was observed. A decreasing proportion was also observed in the 8C-cell population accumulated by 2,4-D treatment, following transfer back to the medium containing the standard PGR composition. These results suggest that the exogenous application of 2,4-D arrested the cell cycle at G2 phase in the Doritaenopsis cells, and the removal of 2,4-D might induce further endoreduplication or recover the mitotic cycle of the G2-arrested cells.
authors.affiliation: Laboratory of Plant Cell Technology, Faculty of Horticulture, Chiba University, 648 Matsudo, Matsudo-City, Chiba 271-8510, Japan.
authors.forename: Kei-Ichiro
authors.initials: KI
authors.lastname: Mishiba
authors.forename: Tomonori
authors.initials: T
authors.lastname: Okamoto
authors.forename: Masahiro
authors.initials: M
authors.lastname: Mii