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Diversification of CYCLOIDEA expression in the evolution of bilateral flower symmetry in Caprifoliaceae and Lonicera (Dipsacales).

ABSTRACT: BACKGROUND AND AIMS: The expression of floral symmetry genes is examined in the CYCLOIDEA lineage following duplication, and these are linked to changes in flower morphology. The study focuses on Dipsacales, comparing DipsCYC2 gene expression in Viburnum (radially symmetrical Adoxaceae) to members of early-diverging lineages of the bilaterally symmetrical Caprifoliaceae (Diervilla and Lonicera). METHODS: Floral tissue from six species, which included dorsal, lateral and ventral regions of the corolla, was dissected. RNA was extracted from these tissues and each copy of DipsCYC2 was amplified with reverse transcriptase PCR. KEY RESULTS: Members of DipsCYC2 were expressed across the corolla in the radially symmetrical Viburnum plicatum. A shift to bilaterally symmetrical flowers at the base of the Caprifoliaceae was accompanied by a duplication of the DipsCYC2 gene, resulting in DipsCYC2A and DipsCYC2B, and by loss of expression of both of these copies in the ventral petal. In Lonicera (Caprifolieae), there is a shift from flowers with two dorsally and three ventrally oriented corolla lobes to a clear differentiation of dorsal, lateral and ventral lobes. This shift entailed a decoupling of expression of DipsCYC2A and DipsCYC2B; DipsCYC2B continues to be expressed in the dorsal and lateral lobes, while DipsCYC2A expression is restricted to just the two dorsal lobes. A reversion to more radially symmetrical flowers within Lonicera was accompanied by a re-expansion of expression of both DipsCYC2A and DipsCYC2B. CONCLUSIONS: The transition to bilateral symmetry in Caprifoliaceae involved: (a) duplication of an ancestral DipsCYC2 gene; (b) the loss of expression of both of these copies in the ventral petal; and (c) changes in the zone of expression, with one copy continuing to be expressed across the dorsal and lateral petals, and the other copy becoming restricted in expression to the dorsal corolla lobes.

SUBMITTER: Howarth DG

PROVIDER: S-EPMC3108805 | biostudies-literature | 2011 Jun

REPOSITORIES: biostudies-literature

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Diversification of CYCLOIDEA expression in the evolution of bilateral flower symmetry in Caprifoliaceae and Lonicera (Dipsacales).

Howarth Dianella G DG Martins Tiago T Chimney Edward E Donoghue Michael J MJ

Annals of botany 20110407 9

<h4>Background and aims</h4>The expression of floral symmetry genes is examined in the CYCLOIDEA lineage following duplication, and these are linked to changes in flower morphology. The study focuses on Dipsacales, comparing DipsCYC2 gene expression in Viburnum (radially symmetrical Adoxaceae) to members of early-diverging lineages of the bilaterally symmetrical Caprifoliaceae (Diervilla and Lonicera).<h4>Methods</h4>Floral tissue from six species, which included dorsal, lateral and ventral regi ...[more]

PMID: 21478175

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Project description:BackgroundCYCLOIDEA (CYC)-like genes have been implicated in the development of capitulum inflorescences (i.e. flowering heads) in Asteraceae, where many small flowers (florets) are packed tightly into an inflorescence that resembles a single flower. Several rounds of duplication of CYC-like genes have occurred in Asteraceae, and this is hypothesized to be correlated with the evolution of the capitulum, which in turn has been implicated in the evolutionary success of the group. We investigated the evolution of CYC-like genes in Dipsacaceae (Dipsacales), a plant clade in which capitulum inflorescences originated independently of Asteraceae. Two main inflorescence types are present in Dipsacaceae: (1) radiate species contain two kinds of floret within the flowering head (disk and ray), and (2) discoid species contain only disk florets. To test whether a dynamic pattern of gene duplication, similar to that documented in Asteraceae, is present in Dipsacaceae, and whether these patterns are correlated with different inflorescence types, we inferred a CYC-like gene phylogeny for Dipsacaceae based on representative species from the major lineages.ResultsWe recovered within Dipsacaceae the three major forms of CYC-like genes that have been found in most core eudicots, and identified several additional duplications within each of these clades. We found that the number of CYC-like genes in Dipsacaceae is similar to that reported for members of Asteraceae and that the same gene lineages (CYC1-like and CYC2B-like genes) have duplicated in a similar fashion independently in both groups. The number of CYC-like genes recovered for radiate versus discoid species differed, with discoid species having fewer copies of CYC1-like and CYC2B-like genes.ConclusionsCYC-like genes have undergone extensive duplication in Dipsacaceae, with radiate species having more copies than discoid species, suggesting a potential role for these genes in the evolution of disk and ray florets. The similarity in CYC-like gene diversification seen in Dipsacaceae and some members of the Asteraceae sets the stage to investigate whether the convergent evolution of capitulum inflorescences in both groups may have been underlain by convergent evolution in the same gene family.

Dataset Information

Diversification of CYCLOIDEA expression in the evolution of bilateral flower symmetry in Caprifoliaceae and Lonicera (Dipsacales).

Publications

Diversification of CYCLOIDEA expression in the evolution of bilateral flower symmetry in Caprifoliaceae and Lonicera (Dipsacales).

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