Genome-wide analysis of cis-regulatory divergence between species in the Arabidopsis genus.

Cis-regulatory DNA has been suspected to play a preeminent role in adaptive evolution, but understanding the role of cis-regulatory mutations in gene expression divergence first requires an accurate analysis of the functional differences associated with these regions. We analyzed allele-specific expression (ASE) in leaf and floral tissues of F1 interspecific hybrids generated between the two closely related species Arabidopsis thaliana and A. lyrata with a whole-genome SNP (single nucleotide polymorphism) tiling array. We observed 2,205 genes showing ASE pattern in at least one tissue. Nearly 90% of genes displaying ASE preferentially expressed the allele of A. lyrata. Genome-wide comparison of sequence divergence revealed that genes displaying ASE had a higher ratio of nonsynonymous to synonymous substitutions in coding regions. We further observe that the epigenetic landscape of histone methylation in A. thaliana genome associate with ASE. The asymmetry in the direction of allele-specific expression suggests interspecific differences in the efficiency of gene silencing in F1 hybrids.