BackgroundThe AP2/ERF transcription factor, one of the largest gene families in plants, plays a crucial role in the regulation of growth and development, metabolism, and responses to biotic and abiotic stresses. Castor bean (Ricinus communis L., Euphobiaceae) is one of most important non-edible oilseed crops and its seed oil is broadly used for industrial applications. The available genome provides a great chance to identify and characterize the global information on AP2/ERF transcription factors in castor bean, which might provide insights in understanding the molecular basis of the AP2/ERF family in castor bean.ResultsA total of 114 AP2/ERF transcription factors were identified based on the genome in castor bean. According to the number of the AP2/ERF domain, the conserved amino acid residues within AP2/ERF domain, the conserved motifs and gene organization in structure, and phylogenetical analysis, the identified 114 AP2/ERF transcription factors were characterized. Global expression profiles among different tissues using high-throughput sequencing of digital gene expression profiles (DGEs) displayed diverse expression patterns that may provide basic information in understanding the function of the AP2/ERF gene family in castor bean.ConclusionsThe current study is the first report on identification and characterization of the AP2/ERF transcription factors based on the genome of castor bean in the family Euphobiaceae. Results obtained from this study provide valuable information in understanding the molecular basis of the AP2/ERF family in castor bean.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-14-785) contains supplementary material, which is available to authorized users.

BackgroundSquamosa promoter binding protein (SBP)-box family genes encode plant-specific transcription factors that control many important biological functions, including phase transition, inflorescence branching, fruit ripening, and copper homeostasis. Nevertheless, the evolutionary patterns of SBP-box genes and evolutionary forces driving them are still not well understood.Methods104 SBP-box gene candidates of five representative land plants were obtained from Phytozome database (v10.3). Phylogenetic combined with gene structure analyses were used to identify SBP-box gene lineages in land plants. Gene copy number and the sequence and structure features were then compared among these different SBP-box lineages. Selection analysis, relative rate tests and expression divergence were finally used to interpret the evolutionary relationships and divergence of SBP-box genes in land plants.ResultsWe investigated 104 SBP-box genes from moss, Arabidopsis, poplar, rice, and maize. These genes are divided into group I and II, and the latter is further divided into two subgroups (subgroup II-1 and II-2) based on phylogenetic analysis. Interestingly, subgroup II-1 genes have similar sequence and structural features to group I genes, whereas subgroup II-2 genes exhibit intrinsic differences on these features, including high copy numbers and the presence of miR156/miR529 regulation. Further analyses indicate that subgroup II-1 genes are constrained by stronger purifying selection and evolve at a lower substitution rate than II-2 genes, just as group I genes do when compared to II genes. Among subgroup II-2 genes, miR156 targets evolve more rapidly than miR529 targets and experience comparatively relaxed purifying selection. These results suggest that group I and subgroup II-1 genes under strong selective constraint are conserved. By contrast, subgroup II-2 genes evolve under relaxed purifying selection and have diversified through gene copy duplications and changes in miR156/529 regulation, which might contribute to morphological diversifications of land plants.ConclusionsOur results indicate that different evolutionary rates and selection strengths lead to differing evolutionary patterns in SBP-box genes in land plants, providing a guide for future functional diversity analyses of these genes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1998-y) contains supplementary material, which is available to authorized users.

The combinatorial control of one target by multiple miRNAs brings big challenges to elucidate its precise evolutionary mechanism. Squamosa promoter binding protein-like (SBP) gene family exhibits the different regulatory patterns, in which some members are only regulated by miR156 and others by miR156 and miR529. Here, we explored the different evolutionary patterns and rates between miR156 targets and miR529 ones in three species (moss, rice, and maize). Our work found that the miR529 targets were members of miR156 target dataset, indicative of cooperative control. Further phylogenetic analyses as well as gene structure features demonstrated that miR529 targets derived from a monophyletic branch of miR156 targets which evolved into two independent branches duo to the ancient gene duplication. Moreover, inspection of evolutionary rate parameters (d(N)/d(S), d(N) and d(S)) for miR156 targets and miR529 ones revealed they were under different selection strength. MiR529 targets were more constraint by strong purifying selection and evolved conservatively with a slow rate. By contrast, miR156 targets evolved more rapidly and experienced more relaxed purifying selection, which may contribute to their functional diversification. Our results will enhance the understanding of different evolutionary fates of SBP-box genes regulated by the different numbers of miRNA families before functional studies.