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Abstract Detail

Evolutionary Developmental Biology (Evo-Devo)

Galimba, Kelsey [1], Di Stilio, Veronica [2].

Evolution of ovule identity following gene duplication in the AGAMOUS lineage of a Ranunculid.

Gene duplications result in paralogs that can be maintained due to the gain of novel functions (neofunctionalization), the partitioning of ancestral function (subfunctionalization), or the preservation of functional redundancy. Duplications are numerous in plant genomes and are particularly widespread throughout the MADS-box organ identity genes of the ABC model of flower development. C-class gene function is necessary for stamen and carpel identity as well as floral meristem determinacy, and is conserved across the angiosperm phylogeny. An additional D-class function was originally identified as controlling ovule identity, yet its designation as a separate class from carpel identity has fallen out of favor, due to subsequent studies that indicate ovule development is more commonly controlled redundantly, by both C and D-lineage genes. The Ranunculid Thalictrum thalictroides has two orthologs of the Arabidopsis C-class gene AGAMOUS (AG), ThtAG1 and ThtAG2. Prior studies have found no evidence of D-class genes in this or any other species within the Ranunculaceae. We previously showed that ThtAG1 exhibits typical C-class function; here we examine the role of ThtAG2. Our results show that ThtAG2 falls within the C-lineage, together with ThtAG1, and is consistent with previous findings of a Ranunculaceae-specific duplication that occurred after the divergence of the C and D lineages. However, ThtAG2 displays an ovule-specific expression pattern identical to that of D-class genes from other angiosperms. Given this divergent expression of ThtAG2, we tested whether it may have acquired ovule function. Down-regulation of ThtAG2 by virus-induced gene silencing (VIGS) resulted in homeotic conversions of ovules into carpels. Taken together, these results suggest that although ThtAG2 does not occur within the D-lineage, it has adopted the classical D-function as an ovule identity gene. This is the first functional example to date of co-option of ovule identity by a single gene in the C-lineage, rather than the D-lineage. Our results support the hypothesis that subfunctionalization has led to the evolution of ovule identity in a T. thalictroides C-class gene following duplication in the AG lineage in the Ranunculaceae.

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1 - University of Washington, Biology, Kincaid, A042B, Seattle, WA, 98115-1800, USA
2 - University of Washington, Kincaid Hall 24, PO BOX 351800, SEATTLE, WA, 98115-1800, USA

Floral development.

Presentation Type: Oral Paper:Papers for Topics
Session: 47
Location: Jasperwood/Riverside Hilton
Date: Wednesday, July 31st, 2013
Time: 4:45 PM
Number: 47013
Abstract ID:344
Candidate for Awards:Katherine Esau Award

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