title: Molecular cloning of mRNAs expressed specifically during spherulation of Physarum polycephalum.
abstract: A cDNA library was constructed using the poly(A)+ RNA extracted from spherulating Physarum polycephalum microplasmodia. This library (740 clones) was screened by differential hybridization with 32P-labeled poly(A)+ RNA from growing plasmodia and developing spherules. The results showed that at least 30% of the clones corresponded to mRNAs expressed specifically in spherulating plasmodia. The 35 spherulation-specific cDNA clones giving the strongest hybridization signals were analysed. From this group, four different sequences complementary to very abundant mRNAs were identified. They each accounted for 1.5% of 4.5% of all the clones in the library and probably represented the most abundant spherulation-specific mRNAs. In addition, four less abundant mRNAs were identified from stage-specific clones giving weaker hybridization signals. These sequences represented individually between 0.3% and 0.7% of the clones in the library. Northern blots showed that these eight different sequences were absent from plasmodia and were most abundant 24-36 h after the induction of spherulation. Similar results were also obtained when spherulation was induced by the addition of a sublethal concentration of ferrous iron ions to the growth medium. Hybridization of the spherule-specific clones to Southern blots of genomic DNA suggested the presence of one copy for each gene.
mesh_terms: D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D004271:DNA, Fungal / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics; D005786:Gene Expression Regulation; D005800:Genes, Fungal; D009693:Nucleic Acid Hybridization; D010804:Physarum / Q000235:genetics* / Q000254:growth & development; D012333:RNA, Messenger / Q000235:genetics
chemical_list: D004271:DNA, Fungal; D005656:Fungal Proteins; D012333:RNA, Messenger; D004247:DNA