A new type of plasmodium formation inPhysarum polycephalum

Abstract

SUMMARYHaploid amoebae ofPhysarum polycephalummay form plasmodia sexually by ‘crossing’, which involves cellular and nuclear fusion, or asexually by ‘selfing’, which occurs without nuclear fusion. In most amoebal strains, selfing is seen in clonal cultures only at very low frequency. In the present study, we have shown that selfing occurs at a similarly low frequency in mixtures of crossing-incompatible amoebae, but is stimulated in crossing-compatible mixtures. In certain compatible mixtures involving mutant strains, where crossing is temperature-sensitive, selfing may be stimulated even at a temperature that largely or wholly abolishes crossing. The extent to which selfing is stimulated appears to be influenced bymatB, a locus which is known to affect the frequency of amoebal fusion. We have failed to detect any filter-transmissible factor that might be responsible for the effects we have observed. We suggest a sequence of events that might bring about ‘stimulated selfing’ as a consequence of abortive crossing.

Complementation ofnpfmutations in diploid amoebae ofPhysarum polycephalum: the basis for a general method of complementation analysis at the amoebal stage

“…Progeny were classified for imz alleles by testing their ability to cross with a matAl matB3 imz-1 tester strain at elevated pH (Shinnick et al 1978). Wheals, 1973Anderson & Dee, 1977Adler, 1975Davidow & Holt, 1977Youngman et al 1979CH207 x LU906 Anderson, 1979Anderson, 1979Anderson, 1979Anderson, 1979 fusC2 , 1977Anderson & Dee, 1977Anderson & Dee, 1977Anderson, 1976Anderson, 1976Anderson, 1977Anderson & Truitt, 1983 …”