Plasmodium formation without change in nuclear DNA content in Physarum polycephalum
1974; Cambridge University Press; Volume: 23; Issue: 3 Linguagem: Inglês
10.1017/s0016672300014944
ISSN1469-5073
Autores Tópico(s)Enzyme-mediated dye degradation
ResumoSUMMARY 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 G 2 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 .
Referência(s)