Molecular cloning of stage specific mRNAs from amoebae and Plasmodia of Physarum polycephalum

Abstract

We constructed cDNA libraries from plasmodia and amoebal poly(A)+ RNA of Physarum polycephalum. The libraries were screened by differential hybridization with labeled poly(A)+ RNA of amoebae and plasmodia. The 136 plasmodial specific clones that gave the strongest hybridization signals were analysed in detail. From this group six different cDNA sequences were found. Four of the cDNAs each accounted for between 1 and 4.8% of all the clones in the library and represented abundant mRNAs. Two other clones constituted 0.2 and 0.4% of the total library. Seventeen clones in the amoebal library were amoebal specific. From these clones, seven different sequences were found. One of the sequences was present in nine clones (1.2%) of the library and considered abundant. The other six sequences were each found in only one or two clones. The specificity of these amoebal and plasmodial mRNAs was confirmed by Northern hybridization. Our results show that amoebae and plasmodia have different mRNA populations, which are most likely the result of differential gene expression in these two developmental stages.