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Abstract Detail


Evolutionary Developmental Biology (Evo-Devo)

Xiang, Qiuyun (Jenny) [1], Feng, Chunmiao [2], Liu, Xiang [3], Yu, Yi [3], Franks, Robert [1].

Post-gene-duplication alteration in selection, co-evolution, expression, and post-transcription regulation of MADS-box B-classgenes in dogwoods (Cornus, Cornaceae) - Deciphering the genetic links to bract petaloidy evolution.

TheMADS-box B-class genes have duplicated repeatedly during angiosperm evolution. It is hypothesized that the extensive duplication of B-class genes accounts for the floral diversification observed in angiosperm and is responsible for the heterotopic petaloidy via ectopic expression (Homeoheterotopy). However, the molecular and evolutionary mechanisms underlying the hypothesis has not been well understood.The two B-class genes PI and AP3 homologs were derived from an ancient gene duplication event, and are known to form obligate heterodimers in regulating petal development in the model plants. This predicts co-evolution of gene sequences and co-expression of AP3 and PI homologs in petals and petaloid organs, according to Homeoheterotopy. We test this hypothesis by analyses of sequence co-evolution, comparative gene expression and analysis of floral and bract development for six species of Cornus that are divergent in inflorescence architecture and bract morphology. Our preliminary results showed that PI and AP3 homologs in Cornus have co-evolved. They are co-expressed in floral development. However, in bract development, alteration in selection, co-evolution partnership, and expression pattern have occurred following PI duplication, which have likely contributed to the evolution of petaloidy in the flowering dogwood C.florida. Our results further suggest that bract petaloidy probably evolved independently in the bunchberry C.canadensis, via a different molecular mechanism that may not involve PI. The data raise a possibility of AP3 functioning by forming homodimers. Finally, we report the expression of petal specific AP3 splice isoforms not detected in the petaloid bracts that are predicted to encode truncated AP3 proteins, suggesting deviation of the molecular mechanism in bract petaloidy from that of petals.

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1 - North Carolina State University, Genetics, Raleigh, NC, 27695, USA
2 - North Carolina State University, 2214-A Gardner Hall , Campus Box 7612, Raleigh, NC, 27695-7612, USA
3 - North Carolina State University, Plant Biology, Gardner Hall 2115, Campus Box 7612, Raleigh, NC, 27695, USA

Keywords:
B-class genes
co-evolution
expression
alternative splicing
selection
Cornus (Cornaceae)
bract petaloidy.

Presentation Type: Oral Paper:Papers for Topics
Session: 41
Location: Lindell D/Chase Park Plaza
Date: Wednesday, July 13th, 2011
Time: 8:30 AM
Number: 41002
Abstract ID:399


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