Molecular Ecology and Evolution
Buggs, Richard J. A. , Doust, Andrew N. , Tate, Jennifer A. , Soltis, Pamela S. , Soltis, Douglas E. .
Tissue-specific silencing of homoeologs in the recent allopolyploid Tragopogon miscellus L.
One reason why gene duplication is an important evolutionary process is because redundant copies of genes may shift in function without detriment to the organism in which they are found. Such functional shifts can occur though one or both duplicate copies becoming specialized for only part of the function of the ancestral gene. For example, each duplicate may be expressed in different tissues. Subfunctionalization occurs where both duplicate copies have different, but complementary functions that were once carried out by the single ancestral gene. After an organism undergoes whole genome duplication every gene is present in two copies, known as homoeologs. Where a polyploid is formed from a hybrid between two species (an allopolyploid) the homoeologs may have significant sequence divergence from the outset. Tissue-specific homoeolog expression has been shown in synthetic allopolyploids of cotton, Arabidopsis and Brassica and in natural allopolyploid cotton and wheat. Actual subfunctionalization of one homeolog pair has been documented in natural and synthetic allopolyploids of cotton. Here, we report tissue-specific homeolog silencing in the allopolyploid Tragopogon miscellus (Asteraceae). This species arose naturally multiple times 70-80 years ago from parental species T. dubius and T. pratensis, with reciprocal crosses differing in ligule length. Using cleaved amplified polymorphic sequence (CAPS) analysis, we examined expression of homeologs in ligule, style, ovary, pappus, phyllary, bud, stem leaf and rosette leaf tissues of natural populations. We found several cases of homoeolog silencing, including examples where both homoeologs are expressed in all tissues, except the ligule, where only one is expressed. Such cases of organ-specific homoeolog silencing were not fixed within populations, suggesting that although they are present in a young natural polyploid, they are not automatic consequences of the polyploidization event itself.
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Richard Buggs' webpage
1 - University of Florida, Department of Botany, PO Box 118526, 214 Bartram Hall, Gainesville, FL, 32611, USA
2 - Oklahoma State University, Botany Department, Stillwater, OK, 74078, USA
3 - Massey University, Institute of Molecular BioSciences, Private Bag 11222, Science Tower D, Riddet Road, Palmerston North, New Zealand
4 - Florida Museum of Natural History, Dickinson Hall, P.O. Box 117800, Gainesville, Florida, 32611, USA
5 - University of Florida, Botany, PO Box 117800, Gainesville, FL, 32611, USA
Presentation Type: Oral Paper:Papers for Topics
Date: Tuesday, July 29th, 2008
Time: 2:45 PM