Presentation Detail

EvoDevo

Savriama, Yoland [1], Ricigliano, Vincent [1], Berger, Brent [1], Howarth, Dianella [1].

Combining quantitative expression of CYCLOIDEA-like genes in Dipsacaceae (Dipsacales) and geometric morphometrics of corolla shape: Further insights into the evolution of bilateral symmetry and radial symmetry in flowers.

Floral symmetry plays a key role in the mechanisms of natural selection and has been examined as a major component in the development and evolution of flowers. Developmental genetic studies have unraveled the molecular basis of flower symmetry and its evolution has been examined both at the microevolutionary and macroevolutionary levels. In particular, gene duplication events have been shown to influence the evolution of transcription factors that in turn affect the developmental pathways responsible for the evolution of floral traits. Among these genes, CYCLOIDEA (CYC) is known to play a major role in the acquisition of bilateral symmetry and is expressed in the dorsal part of the corolla. Recently, CYC-like genes has been implicated in the ontogeny of the capitulum inflorescence, a structure suggested to have contributed to the evolutionary success of groups such as Asteraceae and Dipsacaceae. In radiate species, the outermost flowers (rays) have bilateral symmetry, whereas the innermost flowers have radial symmetry (disks) and in discoid species, the capitulum mostly contains disks. In Dipsacaceae, frequent CYC-like gene duplications took place several times within radiate species possessing more copies than the discoid ones. This has been argued to be an important factor contrasting the evolution of rays and disks.Here, we investigate the patterns of CYC-like floral gene expressions in two radiate species of Dipsacaceae (Knautia arvensis and Scabiosa columbaria) and for the first time we combine this approach with a new geometric morphometric analysis of shape variation to precisely quantify the relationship between morphology and gene expression in floral symmetry. This method explicitly takes symmetry into account and separates out a component of symmetric variation (i.e. variation among flowers) from components of asymmetry(i.e. variation within flowers). Corolla tissue was dissected for dorsal, left, right, and ventral petals. RNA was extracted from these tissues with each copy of CYC amplified and quantified via qrtPCR. We compare patterns of gene expression for each CYC-like gene in each region of the corolla with corolla shape variation. We test the hypothesis that there is more variation between dorsal and ventral compartments than between left and right petals of rays relative to the disks. Preliminary results suggest that rays are larger in size and exhibit twice as much dorsal-ventral asymmetry than for disks, thereby exacerbating bilateral symmetry in these flowers.

Related Links:
Howarth Lab

1 - St. John's University, Biological Sciences, St. Alberts Hall, Rm 272, 8000 Utopia Parkway, Queens, NY, 11439, USA

Keywords:
symmetry
fluctuating asymmetry
phenotypic plasticity
CYC-like gene expression
Geometric morphometrics
flower shape
capitulum inflorescence
RNA extraction
qrtPCR
developmental modularity
phenotypic integration.

Presentation Type: Regular Oral Presentation
Session: 31
Location: Rendezvous A/Snowbird Center
Date: Saturday, June 22nd, 2013
Time: 1:30 PM
Number: 31001
Abstract ID:888
Candidate for Awards:W.D. Hamilton Award for Outstanding Student Presentation