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Systematics Section / ASPT

Zhang, Wenheng [1], Xiang, Jenny Qiu-Yun [2].

Evolution of PISTILLATA homologues in Cornus (Cornaceae).

Genomic DNA sequences of PISTILLATA (PI) homologues were compared among species of Cornus to examine the molecular evolution and its relationship to petaloidy of inflorescence bracts. Analysis of the 5' end of the gene revealed different numbers of copies in lineages with different inflorescence morphology. In light of a species phylogeny of the genus inferred from other genes, duplications of PI genes in different time scales were detected. Two major copies (CorPI-A and CorPI-B) of the gene were identified, with the duplication event occurring before the origin of the genus; CorPI-A duplicated once in the lineage with large petaloid bracts and at least once in the lineage without modified bracts, independently, before each diversified. Recent duplication events within species were detected for both CorPI-A and CorPI-B in most species analyzed. Comparisons of synonymous (Ks) and nonsynonymous (Ka) substitution rates between the two copies indicated that both CorPI-A and CorPI-B are under purifying selection. However, an elevated Ka/Ks ratio was detected in the large-bracted group, suggesting relaxed selection pressure in the group. The gene genealogy of CorPI-A also appears to track the phylogeny of the genus.


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1 - North Carolina State University, Department of Botany, 3211 Gardner Hall, Campus Box 7612, Raleigh, North Carolina, 27695-7612, USA
2 - North Carolina State University, Department of Botany, Campus Box 7612, Raleigh, North Carolina, 27695-7612, USA

Keywords:
PISTILLATA
MADS-box
nuclear gene phylogeny
gene duplication
molecular evolution
Cornus.

Presentation Type: Oral Paper
Session: 38-11
Location: 400/Hilton
Date: Tuesday, August 16th, 2005
Time: 4:45 PM
Abstract ID:309


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