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Plasmodium formation without change in nuclear DNA content in Physarum polycephalum

Published online by Cambridge University Press:  14 April 2009

D. J. Cooke  and
Jennifer Dee
D. J. Cooke
Affiliation:
Department of Genetics, University of Leicester, Leicester LE1 7RH, England
Jennifer Dee
Affiliation:
Department of Genetics, University of Leicester, Leicester LE1 7RH, England
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The Colonia isolate of Physarum polycephalum produces plasmodia within amoebal clones. Wheals demonstrated genetically that amoebae of the C50 strain of this isolate, when crossed with heterothallic amoebae, yielded recombinant progeny. He concluded that nuclear fusion and meiosis occurred in these crosses and suggested that nuclear fusion was also involved in plasmodia formation in clones. He thus designated the strain ‘homothallic’.

In the present work genetic evidence is presented which indicates that the Colonia strain CL, when crossed with heterothallic strains, also yields recombinant progeny and thus undergoes nuclear fusion and meiosis. Microdensitometric measurements of nuclear DNA content are reported which indicate that CL amoebae are haploid like heterothallic amoebae, and crossed plasmodia are diploid. However, clonally formed CL plasmodia were found to have the same G2 nuclear DNA content as CL amoebae. This observation excludes the possibility of nuclear fusion when plasmodia form within clones of CL amoebae and therefore the strain cannot be homothallic. Two alternatives, apogamy and coalescence, are proposed as the most likely mechanisms for clonal plasmodium formation in strain CL.

Type
Research Article
Information
Genetics Research , Volume 23 , Issue 3 , June 1974 , pp. 307 - 317
Copyright
Copyright © Cambridge University Press 1974

References

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