Abstract Detail

Genetics Section

Qi, Xinshuai [1], Li, Zheng [1], Baniaga, Anthony Ernest-Fiorentino [1], Barker, Michael [1].

Higher substitution rates and more deleterious loci in polyploid plants.

Polyploidy is a common phenomenon in plants, especially in fern and flowering plants. Genome duplication due to polyploidy has a profound impact on plant phenotypically and genetically. Whether these effects during polyploidization leads to plants diversification has been long debated. Recent studies have shown neopolyploids exhibit higher extinction rates, and indicate polyploidy is often an evolutionary dead end. In theory, this might due to polyploid has great ability to mask deleterious mutation, this can facilitate the establishment of newly formed polyploid in short term, but also leads to the accumulation of more deleterious mutation, therefore give rise to a high extinction rate. However, in what extent empirical data support this hypothesis is still unclear. Here, we utilized the pre-existing transcriptome data to test whether polyploidy in general has (1) under relaxed purifying selection and (2) accumulate more deleterious mutation when compare with its diploid sister species. Ten representative angiosperms genera were chosen, each including at least one polyploid, one close-related diploid and one outgroup species. We use OrthoMCL to generate gene families for each genus. Then, we compared polyploid Ka/Ks ratio with diploid in gene families shown significant branch length differentiation. We also compared the percentage of deleterious mutation between polyploid and diploid gene copies for each gene family. Nine of the ten tested genera shown >60% mean Ka/Ks ratio that polyploid higher than the sister diploid, six of them were significant, which indicates relaxation of purifying selection in polyploid. Paleopolyploid genus also shown higher deleterious rate in poly polyploid than the sister diploid, while neopolyploid hadn't shown clear pattern. Our results indicate polyploid was under relaxed purifying selection and accumulates more deleterious mutation in comparison with diploid in plants. The faster accumulation of deleterious mutation in polyploid is a major constraints for survival of polyploid after its establishment.

1 - University Of Arizona, Department Of Ecology & Evolutionary Biology, P.O. Box 210088, Tucson, AZ, 85721, USA

Keywords:
Polyploidy
deleterious mutations
purifying selection
substitution rates.

Presentation Type: Oral Paper:Papers for Sections
Session: 6
Location: Salon 15/16/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 8:30 AM
Number: 6003
Abstract ID:902
Candidate for Awards:Margaret Menzel Award