Polyploidy: Genetics, Evolution and Ecology
Wendel, Jonathan F. .
Polyploidy and gene expression evolution in Gossypium.
Increasingly powerful technologies are being applied to polyploids in many plant groups, resulting in dramatic discoveries of novel genomic interactions). Gossypium includes classic allopolyploids arising from a chance biological reunion 1-2 MYA of divergent diploids from different hemispheres. This serendipitous merger generated a spectrum of responses, including gene silencing, gene conversion, and genome-wide disruption of ancestral gene expression patterns. Using several microarray platforms and other technologies, we are studying global transcriptional changes in synthetic and natural Gossypium allopolyploids and reconstructed hybrids, using differing tissues and genetic backgrounds. Allopolyploid formation induces massive alteration in gene expression and complex transcriptomic responses, including genomic dominance and novel expression patterns contingent upon expression states of the parents. Using a novel microarray that simultaneously distinguishes transcript levels for each homoeolog, we are studying homoeolog contributions to the transcriptome of a natural allopolyploid and a synthetic interspecific F1, both derived from merger of Gossypium A-genome and D-genome species. About ΒΌ of homoeolog expression biases occur instantaneously with hybridization, with the remaining arising from long-term evolutionary forces such as duplicate gene neofunctionalization and subfunctionalization. Expression is biased toward the paternal D-genome, demonstrating an overall unequal contribution of two genomes to the transcriptome. Allopolyploidization entails significant homoeolog expression modulation, both immediately as a consequence of genomic merger, and secondarily as a result of long-term evolutionary transformations in duplicate gene expression. Microarrays are being used to explore gene expression patterns in cotton fiber and the possibility of novel gene recruitment following genome doubling. The fiber transcriptome is extraordinarily complex, and homoeolog expression varies widely even at the level of development and maturation of a single cell. Most homoeolog expression bias reflects polyploidy rather than domestication, but domestication has increased expression bias in fibers towards the D-genome, potentially implicating novel recruitment of D-genome homoeologs under human selection.
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1 - Iowa State University, Department of Ecology, Evolution & Organismal Biology, 253 Bessey Hall, Ames, Iowa, 50011-1020, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Room 2/Woodward
Date: Tuesday, July 29th, 2008
Time: 1:00 PM