Duplication and expression of CYC2-like genes in the origin and maintenance of corolla zygomorphy in Lamiales

New Phytol. 2015 Jan;205(2):852-68. doi: 10.1111/nph.13104. Epub 2014 Oct 20.

Abstract

Duplication, retention, and expression of CYCLOIDEA2 (CYC2)-like genes are thought to affect evolution of corolla symmetry. However, exactly what and how changes in CYC2-like genes correlate with the origin of corolla zygomorphy are poorly understood. We inferred and calibrated a densely sampled phylogeny of CYC2-like genes across the Lamiales and examined their expression in early diverging (EDL) and higher core clades (HCL). CYC2-like genes duplicated extensively in Lamiales, at least six times in core Lamiales (CL) around the Cretaceous-Paleogene (K-Pg) boundary, and seven more in EDL relatively more recently. Nested duplications and losses of CYC2-like paralogs are pervasive but may not correlate with transitions in corolla symmetry. We found evidence for dN/dS (ω) variation following gene duplications. CYC2-like paralogs in HCL show differential expression with higher expression in adaxial petals. Asymmetric expression but not recurrent duplication of CYC2-like genes correlates with the origin of corolla zygomorphy. Changes in both cis-regulatory and coding domains of CYC2-like genes are probably crucial for the evolution of corolla zygomorphy. Multiple selection regimes appear likely to play important roles in gene retention. The parallel duplications of CYC2-like genes are after the initial diversification of bumble bees and Euglossine bees.

Keywords: CYCLOIDEA2 (CYC2)-like gene; Lamiales; corolla symmetry; gene duplication and retention; positive selection.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Biological Evolution
  • Evolution, Molecular
  • Flowers / physiology*
  • Gene Duplication*
  • Gene Expression Regulation, Plant*
  • Magnoliopsida / genetics*
  • Phylogeny
  • Plant Proteins / genetics

Substances

  • Plant Proteins