Stability of the cytokinin requirement in Paul's scarlet rose cells in culture |
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Authors: | Donald E Fosket |
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Institution: | (1) Department of Developmental and Cell Biology, University of California, Irvine, 92717 Irvine, California |
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Abstract: | Summary Cells ofRosa sp. cv Paul's scarlet have been reported to require cytokinin for growth in suspension culture. This report was verified
in the present study. However, a rose cell line that was maintained for 2 yr in suspension culture by routine subculturing
developed the capacity to grow without exogenous cytokinin. The stability of the cytokinin requirement and the basis for this
altered response to cytokinin was investigated. The parental cell line, which has been maintained independently on agar-solidified
medium, was subcloned and the cytokinin dependence of the subclones was determined. The subclones were found to exhibit a
continuous spectrum of responses, ranging from a high degree of cytokinin dependence for growth to rapid growth upon the initial
transfer to cytokinin-deficient medium. The average growth constant (K=1n W/Wo; Wo=initial fresh weight,W=fresh weight after growth for the stated time interval) of 30 subclones grown on medium containing 0.5 μM zeatin was 3.1, with a range of 1.1 to 4.0. The average growth constant of the same subclones when grown on medium lacking
a cytokinin was 1.5, with a range of 0 to 3.9. By comparison, the parental cell line exhibited growth constants of 3.5 in
the presence of 0.5 μM zeatin and 1.6 in the absence of exogenous cytokinin. Although the growth of some of the subclones after transfer to cytokinin-deficient
medium suggested that they were cytokinin autotrophs, this was not the case because none of them grew after a second transfer
to medium lacking cytokinin. Culture in medium containing cytokinin conferred upon the cells the capacity for a limited amount
of growth after subsequent transfer to medium lacking cytokinin. The extent of this cytokinin-induced growth potential varied
from subclone to subclone. Efforts to determine the frequency with which cytokinin autotrophs appeared in a subclone that
required cytokinin suggested that it is a rare event and that the cytokinin requirement is a fairly stable phenotypic characteristic
of these cells.
This research was supported by Grant PCM 7722398 from the National Science Foundation. |
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Keywords: | cytokinin habituation rose cell suspension growth cell cloning |
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