Changes in the sequence diversity of polyadenylated cytoplasmic RNA during testis differentiation in rainbow trout (Salmo gairdnerii).

We have compared the sequence diversity of polyadenylated cytoplasmic RNA derived from naturally maturing trout testis at three different stages of spermatogenesis, by performing hybridization experiments between cDNA synthesized on a template of polyadenylated RNA and a vast excess of polyadenylated RNA. Polyadenylated RNA from early testis has a base sequence complexity of 7.2x10(9) daltons. As testis maturation proceeds, there is a decrease in the complexity of polyadenylated mRNA sequences in testis cells and the relative abundance of individual mRNAs varies over a more narrow range. Heterologous hybridization reactions demonstrate that a substantial fraction of polyadenylated RNA sequences present in early testis cytoplasm is absent from late testis cytoplasm. Nevertheless, all the sequences of late testis mRNA are represented in the population of early testis mRNA molecules.