Evolution and divergence of SBP-box genes in land plants

BMC Genomics. 2015 Oct 14;16:787. doi: 10.1186/s12864-015-1998-y.

Abstract

Background: Squamosa 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.

Methods: 104 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.

Results: We 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.

Conclusions: Our 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence / genetics
  • Arabidopsis / genetics
  • Bryophyta / genetics
  • Embryophyta / genetics
  • Evolution, Molecular*
  • Gene Duplication
  • Gene Expression Regulation, Plant
  • Genome, Plant
  • Multigene Family / genetics*
  • Oryza / genetics
  • Phylogeny*
  • Plant Proteins / biosynthesis
  • Plant Proteins / genetics*
  • Populus / genetics
  • Zea mays / genetics

Substances

  • Plant Proteins
  • SBP protein, Papaver rhoeas