Presentation Detail

SSB Symposium: Ernst Mayr Symposium

Zhong, Jinshun [1], Kellogg, Elizabeth [2].

The duplication, expression and co-option of CYC and RAD in shaping floral zygomorphy.

Floral zygomorphy is thought to have played an important role in the diversification of angiosperm flowers. Studies in distantly related eudicot lineages have shown that CYCLOIDEA (CYC)-like genes have been recruited repeatedly for floral zygomorphy. Furthermore, the persistent expression of CYC-like in later developmental stages and the co-option of CYC-RADIALIS (RAD) have shown to be crucial for floral zygomorphy. Duplication and expression of CYC-like have been extensively investigated, yet the results are still too scattered to assess how preservation and diversification of CYC-like and co-option of CYC-RAD have contributed to the origin and maintenance of floral zygomorphy. Lamiales, with an early origin of floral zygomorphy are our study system. The early diverging lineages Oleaceae and Tetrachondraceae have actinomorphic flowers and are successively sister to core Lamiales with predominantly zygomorphic flowers.Here we presented a densely sampled phylogeny of CYC-like across the order and examined the expression of CYC-like and RAD-like in early diverging and higher core Lamiales. The results show at least four independent duplications have occurred and produced extra copies of CYC-like in core Lamiales. The parallel duplications of CYC-like genes during the diversification of core Lamiales suggest that extra copies of CYC-like genes are important for the origin of floral zygomorphy. Furthermore, losses of CYC-like paralogs have also occurred commonly within core clade,which mostly have been restored by subsequent gene duplication and thus have no effect on floral symmetry. However, in some lineages only one copy of CYC-like has been preserved with conspicuous zygomorphic flowers indicates that the extra copy of CYC-like is less important in the maintenance of floral zygomorphy in the core clade. Episodic positive selection has facilitated the retention of the duplicates, and their subsequent differential expression and probable functional divergence as in higher core Lamiales (HCL). Molecular dating analyses suggest four parallel duplications of CYC-like in core Lamiales occurred around K/T boundary when the major pollinators of core Lamiales (i.e. bees) have diversified. The absent expression of CYC-like in Oleaceae and its persistent expression in Tetrachondraceae indicate positive autoregulatory expression of CYC-like is not correlated with but has evolved before the origin of floral zygomorphy. RAD-like are expressed in both Oleaceae and Tetrachondraceae. Our further analyses of DNA binding sites in the promoters of CYC-like and RAD-like in Oleaceae and Tetrachondraceae will also help determine when persistent expression of CYC-like and co-option of CYC-RAD have emerged.

1 - University of Missouri-St. Louis, Biology, Research Bldg 223, One University Blvd, St. Louis, MO, 63121, USA
2 - University Of Missouri - St. Louis, Department Of Biology, One University Boulevard, St. Louis, MO, 63121-4499, USA

Keywords:
floral symmetry
CYC-like gene
RAD-like gene
Lamiales
Gene duplication.

Presentation Type: Symposium Presentation
Session: 212
Location: Ballroom 2/Cliff Lodge
Date: Sunday, June 23rd, 2013
Time: 10:30 AM
Number: 212001
Abstract ID:991
Candidate for Awards:Ernst Mayr Award