title: Duplication and expression of CYC2-like genes in the origin and maintenance of corolla zygomorphy in Lamiales.
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.
authors.affiliation: Department of Biology, The University of Missouri-St Louis, One University Blvd, St Louis, MO, 63121, USA; Department of Plant Biology, The University of Vermont, Carrigan Drive, Burlington, VT 05405, USA.
authors.forename: Jinshun
authors.initials: J
authors.lastname: Zhong
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Kellogg
mesh_terms: D005075:Biological Evolution; D019143:Evolution, Molecular; D035264:Flowers / Q000502:physiology*; D020440:Gene Duplication; D018506:Gene Expression Regulation, Plant; D019684:Magnoliopsida / Q000235:genetics*; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics
chemical_list: D010940:Plant Proteins
keywords: CYCLOIDEA2 (CYC2)-like gene; Lamiales; corolla symmetry; gene duplication and retention; positive selection