Evolutionary conservation of neighbouring gene pairs in plants.

Evolutionary conservation of neighbouring gene pairs has been widely explored in many species, but remains poorly understood in plants. The availability of several plant genome sequences allows for an in-depth investigation of this problem in plants. Here, we analyzed the phylogenetic conservation of physically linked gene pairs in nine plant genomes and compared the conservation in different orientations. We also examined several potential determinants to detect whether they affect the conservation of neighbouring gene pairs. Our results suggested that among the three types of neighbouring gene pairs, closely linked parallel pairs might be the least conserved. Intergenic distance was shown to be a major determinant of linkage conservation, suggesting that the conservation of gene order in plants was determined primarily by chance. The enrichment of housekeeping genes was identified to contribute to the conservation of all three types and the enrichment of genes involved in protein metabolism might contribute to the conservation of parallel pairs. Moreover, a co-expressed signal was detected in conserved divergent pairs, which might be determined by intergenic distance.