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Corolla monosymmetry: evolution of a morphological novelty in the Brassicaceae family.
Mol Biol Evol 2012; 29(4):1241-54MB

Abstract

Evolution of floral monosymmetry is thought to be a major driving force of angiosperm radiation, making angiosperms the most successful land plant group in terms of species richness. Monosymmetry evolved from a polysymmetric ancestor repeatedly in different angiosperm lineages, where it likely facilitated diversification through the interaction with insects. Most monosymmetric taxa are thus dominated by monosymmetric members. However, in the Brassicaceae, only few members develop a monosymmetric corolla with two petal pairs of unequal size, making them an ideal system to study the evolution of molecular mechanisms enhancing flower complexity. Monosymmetry is controlled by the TCP transcription factors that belong to the CYC2 clade in distantly related taxa. In Iberis amara, the first crucifer analyzed in terms of monosymmetry development, unequal corolla formation is due to a stronger CYC2 clade gene expression in the smaller adaxial petals compared with the larger abaxial ones. Phylogenetic reconstruction of the crucifer family reveals that the monosymmetric genera Iberis, Calepina, and Teesdalia belong to one major crucifer lineage. Monosymmetry is most pronounced in Iberis and less so in Calepina and Teesdalia, with a positive dosage-dependent correlation between the strength of a CYC2 expression difference and the extent of monosymmetry formation. An early adaxial CYC2 expression in floral meristems, observed in many distantly related taxa, might have facilitated the repeated evolution of CYC2-controlled monosymmetry. Comparison of early and late CYC2 expression in monosymmetric and polysymmetric crucifers representative for the four major crucifer lineages reveals that an adaxial CYC2 expression in floral meristems is likely ancestral for the Brassicaceae. However, it got lost in all analyzed monosymmetric members and is, as such, not a prerequisite for the establishment of corolla monosymmetry in crucifers. Here, monosymmetry evolved via a heterochronic CYC2 expression shift from an ancestral early adaxial expression in floral meristems to an adaxial CYC2 transcript accumulation later in petal development. This study emphasizes the potential of regulatory changes in the evolution of morphological novelties, like corolla monosymmetry in the Brassicaceae. In combination with a corymboid inflorescence, monosymmetry might have served as a key invention driving diversification in the genus Iberis comprising more than 20 monosymmetric species.

Authors+Show Affiliations

Department of Biology, Botany, University of Osnabrueck, Osnabrueck, Germany.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

22135189

Citation

Busch, Andrea, et al. "Corolla Monosymmetry: Evolution of a Morphological Novelty in the Brassicaceae Family." Molecular Biology and Evolution, vol. 29, no. 4, 2012, pp. 1241-54.
Busch A, Horn S, Mühlhausen A, et al. Corolla monosymmetry: evolution of a morphological novelty in the Brassicaceae family. Mol Biol Evol. 2012;29(4):1241-54.
Busch, A., Horn, S., Mühlhausen, A., Mummenhoff, K., & Zachgo, S. (2012). Corolla monosymmetry: evolution of a morphological novelty in the Brassicaceae family. Molecular Biology and Evolution, 29(4), pp. 1241-54. doi:10.1093/molbev/msr297.
Busch A, et al. Corolla Monosymmetry: Evolution of a Morphological Novelty in the Brassicaceae Family. Mol Biol Evol. 2012;29(4):1241-54. PubMed PMID: 22135189.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Corolla monosymmetry: evolution of a morphological novelty in the Brassicaceae family. AU - Busch,Andrea, AU - Horn,Stefanie, AU - Mühlhausen,Andreas, AU - Mummenhoff,Klaus, AU - Zachgo,Sabine, Y1 - 2011/11/30/ PY - 2011/12/3/entrez PY - 2011/12/3/pubmed PY - 2012/9/20/medline SP - 1241 EP - 54 JF - Molecular biology and evolution JO - Mol. Biol. Evol. VL - 29 IS - 4 N2 - Evolution of floral monosymmetry is thought to be a major driving force of angiosperm radiation, making angiosperms the most successful land plant group in terms of species richness. Monosymmetry evolved from a polysymmetric ancestor repeatedly in different angiosperm lineages, where it likely facilitated diversification through the interaction with insects. Most monosymmetric taxa are thus dominated by monosymmetric members. However, in the Brassicaceae, only few members develop a monosymmetric corolla with two petal pairs of unequal size, making them an ideal system to study the evolution of molecular mechanisms enhancing flower complexity. Monosymmetry is controlled by the TCP transcription factors that belong to the CYC2 clade in distantly related taxa. In Iberis amara, the first crucifer analyzed in terms of monosymmetry development, unequal corolla formation is due to a stronger CYC2 clade gene expression in the smaller adaxial petals compared with the larger abaxial ones. Phylogenetic reconstruction of the crucifer family reveals that the monosymmetric genera Iberis, Calepina, and Teesdalia belong to one major crucifer lineage. Monosymmetry is most pronounced in Iberis and less so in Calepina and Teesdalia, with a positive dosage-dependent correlation between the strength of a CYC2 expression difference and the extent of monosymmetry formation. An early adaxial CYC2 expression in floral meristems, observed in many distantly related taxa, might have facilitated the repeated evolution of CYC2-controlled monosymmetry. Comparison of early and late CYC2 expression in monosymmetric and polysymmetric crucifers representative for the four major crucifer lineages reveals that an adaxial CYC2 expression in floral meristems is likely ancestral for the Brassicaceae. However, it got lost in all analyzed monosymmetric members and is, as such, not a prerequisite for the establishment of corolla monosymmetry in crucifers. Here, monosymmetry evolved via a heterochronic CYC2 expression shift from an ancestral early adaxial expression in floral meristems to an adaxial CYC2 transcript accumulation later in petal development. This study emphasizes the potential of regulatory changes in the evolution of morphological novelties, like corolla monosymmetry in the Brassicaceae. In combination with a corymboid inflorescence, monosymmetry might have served as a key invention driving diversification in the genus Iberis comprising more than 20 monosymmetric species. SN - 1537-1719 UR - https://www.unboundmedicine.com/medline/citation/22135189/Corolla_monosymmetry:_evolution_of_a_morphological_novelty_in_the_Brassicaceae_family_ L2 - https://academic.oup.com/mbe/article-lookup/doi/10.1093/molbev/msr297 DB - PRIME DP - Unbound Medicine ER -