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Homoeologous nonreciprocal recombination in polyploid cotton
Armel Salmon1, Lex Flagel, Bao Ying
1Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011, USA.
The New Phytologist
|November 21, 2009
Summary
Gene conversion via homoeologous exchange reshuffles duplicate genes in polyploid cotton. This process has occurred continuously throughout cotton evolution, not just during polyploid formation.
Area of Science:
- Evolutionary biology
- Genomics
- Plant genetics
Background:
- Polyploid formation creates redundant genomic information, offering raw material for evolution.
- Mechanisms like gene conversion can retard divergence between duplicate genes.
- Nonreciprocal homoeologous exchange is a key process influencing the fate of duplicated genes.
Purpose of the Study:
- To investigate the occurrence and timing of nonreciprocal homoeologous exchanges in allopolyploid cotton (Gossypium).
- To quantify the proportion of genes affected by homoeologous exchange since polyploidization.
- To determine if homoeologous exchanges occurred during polyploid formation or throughout subsequent evolution.
Main Methods:
- Utilized genomic resources from diploid and allopolyploid cotton species.
- Detected homoeologous single nucleotide polymorphisms (HSNPs) from expressed sequence tags (ESTs) of different Gossypium genomes (A, D, AD).
- Employed phylogenetic analysis to date the timing of homoeologous recombination events.
Main Results:
- Estimated 1.8–1.9% of contigs in G. hirsutum experienced nonreciprocal homoeologous exchanges since polyploidization (1-2 Mya).
- Phylogenetic analysis revealed that homoeologous exchanges occurred continuously throughout polyploid divergence and speciation.
- Identified specific genomic regions exhibiting multiple patterns of homoeologous recombination across different cotton species.
Conclusions:
- Nonreciprocal homoeologous exchange is an ongoing evolutionary process in polyploid cotton, shaping genome evolution.
- These exchanges are not restricted to the initial polyploidization event but persist over evolutionary time.
- The findings provide insights into the dynamic nature of duplicated gene evolution in allopolyploids.
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