The lawc gene emerged de novo from conserved genomic elements and acquired a broad expression pattern in Drosophila.

It has recently become evident that the de novo emergence of genes is widespread and documented for a variety of organisms. De novo genes frequently emerge in proximity to existing genes, forming gene overlaps. Here, we present an analysis of the evolutionary history of a putative de novo gene, lawc, which overlaps with the conserved Trf2 gene, which encodes a general transcription factor in Drosophila melanogaster. We demonstrate that lawc emerged approximately 68 million years ago in the 5'-untranslated region of Trf2 and displays an extensive spatiotemporal expression pattern. One of the most remarkable features of the lawc evolutionary history is that its emergence was facilitated by the engagement of Drosophilidae-specific short highly conserved regions located in Trf2 introns. This represents a unique example of putative de novo gene birth involving conserved DNA regions localized in introns of conserved gene. The observed lawc expression pattern may be due to overlap of lawc with the 5'-untranslated region of Trf2. This study not only enriches our understanding of gene evolution but also highlights the complex interplay between genetic conservation and innovation.