Repetitive DNA sequences cotranscribed with developmentally regulated Dictyostelium discoideum mRNAs.

We have isolated a clone of Dictyostelium discoideum genomic DNA, pB41-6, that contains sequences that are reiterated and interspersed in the genome. The expression of these reiterated sequences is developmentally regulated, and they appear to be linked only to developmentally regulated mRNAs. We have used clone pB41-6 to isolate a set of complementary cDNA clones. Analysis of two selected clones indicates that they encode developmentally regulated mRNA species and, by means of the repetitive elements they contain, hybridize to many developmentally regulated mRNAs. In addition, we have defined two families of mRNA species carrying these repetitive sequences: one is induced at 5.5 hr of development and the other is induced between 5.5 and 15 hr of development. Since most of the mRNA species that have sequences complementary to clone pB41-6 accumulate in a coordinated fashion during development, these sequences may play an important regulatory role in the developmental program of Dictyostelium.