The expansion and evolution of the OPR gene family in land plants. (A) Chromosomal location of OPR genes in monocots (Oryza sativa and Sorghum bicolor) and dicots (Arabidopsis thaliana and Medicago truncatula). (B) Gene duplications and syntenic relationships of OPR genes in higher land plants. Paralogous gene pairs generated by gene duplications and gene pairs based on cross-genome syntenic relationships within the OPR family of four species (Arabidopsis thaliana, Populus trichocarpa, Oryza sativa, and Sorghum bicolor) were analyzed using the PGDD. All intra/cross-species blocks for each query gene display regions of only ~100 kb. Blue arrows indicate the other anchor genes in the region, and red arrows indicate the query locus. Green lines connect gene pairs. (C) A schematic pattern for the expansion and evolution of the OPR gene family in land plants. The phylogenetic relationship of seven OPR subfamilies is represented in the upper right, while the expansion and evolution relationship of six OPR subfamilies (shaded, Sub. I–VI) in land plants is showed in the bottom left. The areas circled in different colors represent different plant lineages: red = mosses, pink = lycophytes, green = gymnosperms, blue = monocots, black = dicots. The "Sub. I" legend in the common area shared by gymnosperms, monocots and dicots indicates that this subfamily exists in all three lineages. Similarly, subfamily II is shared by all lineages, and subfamily VI is shared by lycophytes and mosses; subfamilies III, IV and V, however, only exist in monocots. The "black upright diamond" symbol in the upper diagram and the shaded circle in the lower diagram both represent the common ancestor of the OPR gene family in land plants.