Differential gene expression during the amoebal-plasmodial transition in Physarum

We have prepared cDNA libraries for amoebae and plasmodia of the acellular slime mould, Physarum polycephalum. Differential screening was used to isolate cell-type-specific cDNA clones (in bacteriophage M13) and both libraries yielded approximately 5% of such sequences. The amoebal- and plasmodial-specific clones were used to assay changes in transcription during the amoebal-plasmodial transition. The results obtained substantiate the view that the switch from amoebal to plasmodial characteristics occurs over several nuclear division cycles. With one exception, the specific cDNAs came from single-gene families. Southern blotting experiments also showed that they hybridised to identical restriction fragments from amoebal and plasmodial DNAs indicating that genomic rearrangements are unlikely to be involved in the regulation of these genes.