The preservation of bidirectional promoter architecture in Eukaryotes - Functional or co-regulation constraint?

The bidirectional promoter architecture has been reported in many organisms, and the conservation of bidirectional arrangement has also been studied in several former researches. However, the explanation for the evolutionary conservation about this genomic structure is still insufficient. In this study the large scale identification and pathway enrichment analysis for bidirectional genes were performed in several eukaryotes, and the comparative analysis of this arrangement between human and mouse were dissected for the purpose of discovering the drive force of the preservation of this genomic structure. The comparative analysis about the gene expression and biological functions between human and mouse bidirectional genes were performed. It was observed that the selective constraint of this architecture mainly derives from the function bias of bidirectional genes rather than the co-regulation between paired genes. The results of our analyses indicated that the bidirectional genes are conserved in pathway level and the potential selective constraints of bidirectional architecture conservation comes from the gene function preference rather than the co-regulation of paired genes' expression.