An Investigation of the Conservatism of Sequences Defining trans-Splicing in the mod(mdg4) Locus across Drosophila and Silkworm Species

Splicing, a key step in mRNA maturation, plays a crucial role in the regulation of eukaryotic gene expression. The formation of chimeric mRNAs from two transcripts during splicing is typically a prohibited process; however, in insects, trans-splicing is a primary mechanism for increasing protein diversity for several loci. The aim of this study is to investigate the evolutionary conservativeness of sequences responsible for trans-splicing in the mod(mdg4) locus among species from the Drosophilidae family (order Diptera) and the silkworm (Bombyx mori), which belongs to the order Lepidoptera. Using model transgenic lines, it was shown that sequences from distant Drosophila species retain the ability to support trans-splicing in D. melanogaster. In contrast, analogous sequences in Bombyx mori do not support trans-splicing. Thus, the RNA motifs and their binding hypothetical protein factors, defining trans-splicing, remain conserved among the Drosophilidae group, but have functionally diverged between Diptera and Lepidoptera.