Hybrid origins and the earliest stages of diploidization in the highly successful recent polyploid Capsella bursa-pastoris
2015 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 112, no 9, 2806-2811 p.Article in journal (Refereed) Published
Whole-genome duplication (WGD) events have occurred repeatedly during flowering plant evolution, and there is growing evidence for predictable patterns of gene retention and loss following polyploidization. Despite these important insights, the rate and processes governing the earliest stages of diploidization remain poorly understood, and the relative importance of genetic drift, positive selection, and relaxed purifying selection in the process of gene degeneration and loss is unclear. Here, we conduct whole-genome resequencing in Capsella bursa-pastoris, a recently formed tetraploid with one of the most widespread species distributions of any angiosperm. Whole-genome data provide strong support for recent hybrid origins of the tetraploid species within the past 100,000-300,000 y from two diploid progenitors in the Capsella genus. Major-effect inactivating mutations are frequent, but many were inherited from the parental species and show no evidence of being fixed by positive selection. Despite a lack of large-scale gene loss, we observe a decrease in the efficacy of natural selection genome-wide due to the combined effects of demography, selfing, and genome redundancy from WGD. Our results suggest that the earliest stages of diploidization are associated with quantitative genome-wide decreases in the strength and efficacy of selection rather than rapid gene loss, and that non-functionalization can receive a head start through a legacy of deleterious variants and differential expression originating in parental diploid populations.
Place, publisher, year, edition, pages
2015. Vol. 112, no 9, 2806-2811 p.
polyploidy, population genomics, speciation, gene loss
Earth and Related Environmental Sciences Biological Sciences
IdentifiersURN: urn:nbn:se:su:diva-115981DOI: 10.1073/pnas.1412277112ISI: 000350224900057PubMedID: 25691747OAI: oai:DiVA.org:su-115981DiVA: diva2:802103