Transcriptional Similarities, Dissimilarities, and Conservation of cis-Elements in Duplicated Genes of Arabidopsis

In plants, duplication of individual genes, long chromosomal regions, and complete genomes provides a major source for evolutionary innovation. We investigated two different types of duplications, tandem and segmental duplications, in Arabidopsis for correlation, conservation, and differences of expression characteristics by making use of large genomewide expression data as measured by the massively parallel signature sequencing method. Our analysis indicates that large fractions of duplicated gene pairs still share transcriptional characteristics. However, our results also indicate that expression divergence occurs frequently between duplicated gene pairs, a process which frequently might be employed for the retention of sequence redundant gene pairs. Preserved overall similarity between promoters of duplicated genes as well as preservation of individual cis-elements within the respective promoters indicates that the process of transcriptional neo- and subfunctionalization is restricted to only a fraction of cis-elements. We show that sequence similarities and shared regulatory properties within duplicated promoters provide a powerful means to undertake large-scale cis-regulatory element identification by applying an intragenomic phylogenetic footprinting approach. Our work lays a foundation for future comparative studies to elucidate the molecular manifestation of regulatory similarities and dissimilarities of duplicated genes.