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Open AccessArticle

Genome-Wide Identification and Analysis of High-Copy-Number LTR Retrotransposons in Asian Pears

Forestry and Pomology Research Institute, Shanghai Key Lab of Protected Horticultural Technology, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China
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Genes 2019, 10(2), 156; https://doi.org/10.3390/genes10020156
Received: 7 January 2019 / Revised: 12 February 2019 / Accepted: 14 February 2019 / Published: 18 February 2019
(This article belongs to the Section Plant Genetics and Genomics)
A large proportion of the genome of ‘Suli’ pear (Pyrus pyrifolia) contains long terminal repeat retrotransposons (LTR-RTs), which suggests that LTR-RTs have played important roles in the evolution of Pyrus. Further analysis of retrotransposons, particularly of high-copy-number LTR-RTs in different species, will provide new insights into the evolutionary history of Pyrus. A total of 4912 putative LTR-RTs classified into 198 subfamilies were identified in the ‘Suli’ pear genome. Six Asian pear accessions, including cultivars and wild species, were resequenced. The comparison of copy number for each LTR-RT subfamily was evaluated in Pyrus accessions, and data showed up to four-fold differences for some subfamilies. This contrast suggests different fates for retrotransposon families in the evolution of Pyrus. Fourteen high-copy-number subfamilies were identified in Asian pears, and more than 50% of the LTR-RTs in the genomes of all Pyrus accessions were from these 14 identified LTR-RT subfamilies. Their average insertion time was 3.42 million years ago, which suggests that these subfamilies were recently inserted into the genome. Many homologous and specific retrotransposon insertion sites were identified in oriental and occidental pears, suggesting that the duplication of retrotransposons has occurred throughout almost the entire origin and evolution of Pyrus species. The LTR-RTs show high heterogeneity, and their copy numbers vary in different Pyrus species. Thus, our findings suggest that LTR-RTs are an important source of genetic variation among Pyrus species. View Full-Text
Keywords: copy number; dynamics; insertion time; resequencing; retroelements copy number; dynamics; insertion time; resequencing; retroelements
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Jiang, S.; Wang, X.; Shi, C.; Luo, J. Genome-Wide Identification and Analysis of High-Copy-Number LTR Retrotransposons in Asian Pears. Genes 2019, 10, 156.

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