Abstract Detail

Developmental and Structural Section

Galimba, Kelsey [1], Martínez-Gomez, Jesús [2], Di Stilio, Veronica [3].

Duplication and Divergence of the Floral Organ Identity Genes.

Gene duplications result in paralogs that may remain redundant or be maintained due to the gain of novel functions (neo-functionalization) or the partitioning of ancestral function (sub-functionalization). Plant genomes are especially prone to duplication, and paralogs are particularly widespread in the floral MADS box transcription factors that control organ identity through the ABC model of flower development. In the ranunculid Thalictrum thalictroides, order-level duplication events have led to two orthologs of the C-class gene AGAMOUS (AG) and three orthologs of the B-class gene APETALA3 (AP3). AG has a dual role specifying stamen and carpel identity and floral meristem determinacy; in its absence reproductive organs are homeotically converted to perianth organs resulting in a “double flower”. Using a combination of forward and reverse genetic approaches, we have previously determined that in T. thalictroides, ThtAG1 has a comparable role to AG. Here we show evidence that its paralog ThtAG2 has sub-functionalized to ovule identity. The B-class gene APETALA3 (AP3) is necessary for the development of stamens and petals; loss of function results in homeotic conversions of petals to sepals and stamens to carpels, leading to a phenotype consisting of two whorls of sepals surrounding two whorls of carpels. The genus Thalictrum is apetalous and we show that, in T. thalictroides, the ThtAP3s are involved in in ectopic petaloidy of sepals as well as stamen identity. We are currently determining the extent of partial redundancy vs. compartmentalization of function among the AP3s. Taken together, the duplicated floral organ identity genes in T. thalictroides have diverse fates, either sub-functionalizing or remaining partially redundant. In addition, while some of the genes match the canonical roles described by the original core eudicot ‘ABC Model’, their paralogs often deviate from this archetype, confirming that the developmental model has been subject to selective pressures over evolutionary time.

1 - University Of Washington, Biology, 407 N 87th St., Apt #6, Seattle, WA, 98103, USA
2 - University Of Washington, Biology, Hitchcock Hall, Seattle , WA, 98105, USA
3 - University Of Washington, Department Of Biology, PO Box 351800, Seattle, WA, 98115-1800, USA

Keywords:
floral development
sub-functionalization
MADS box genes
gene duplication
Agamous
APETALA3.

Presentation Type: Oral Paper:Papers for Sections
Session: 45
Location: Salon 11/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 2:30 PM
Number: 45005
Abstract ID:1109
Candidate for Awards:Katherine Esau Award,Maynard F. Moseley Award