title: Genome-wide characterization of non-reference transposons in crops suggests non-random insertion.
abstract: Transposons (transposable elements or TEs) are DNA sequences that can change their position within the genome. A large number of TEs have been identified in reference genome of each crop(named accumulated TEs), which are the important part of genome. However, whether there existed TEs with different insert positions in resequenced crop accession genomes from those of reference genome (named non-reference transposable elements, non-ref TEs), and what the characteristics (such as the number, type and distribution) are. To identify and characterize crop non-ref TEs, we analyzed non-ref TEs in more than 125 accessions from rice (Oryza sativa), maize (Zea mays) and sorghum (Sorghum bicolor) using resequenced data with paired-end mapping methods.
  
  
  
  We identified 13,066, 23,866 and 35,679 non-ref TEs in rice, maize and sorghum, respectively. Genome-wide characterization analysis shows that most of non-ref TEs were unique and non-ref TE classes shows different among rice, maize and sorghum. We found that non-ref TEs have a strong positive correlation with gene number and have a bias toward insertion near genes, but with a preference for avoiding coding regions in maize and sorghum. The genes affected by non-ref TE insertion were functionally enriched for stress response mechanisms in all three crops.
  
  
  
  These observations suggest that transposon insertion is not a random event and it makes genomic diversity, which may affect the intraspecific adaption and evolution of crops.
authors.affiliation: Maize Research Institute, Sichuan Agricultural University, Chengdu, 611130, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Wei
authors.affiliation: College of Life Science, Sichuan Agricultural University, Ya'an, 625014, China.
authors.forename: Hanmei
authors.initials: H
authors.lastname: Liu
authors.affiliation: Beijing Genome Institute and the Key Laboratory of Genomics of the Minister of Agriculture, Shenzhen, 518083, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Liu
authors.affiliation: Maize Research Institute, Sichuan Agricultural University, Chengdu, 611130, China.
authors.forename: Qianlin
authors.initials: Q
authors.lastname: Xiao
authors.affiliation: Maize Research Institute, Sichuan Agricultural University, Chengdu, 611130, China.
authors.forename: Yongbin
authors.initials: Y
authors.lastname: Wang
authors.affiliation: College of Life Science, Sichuan Agricultural University, Ya'an, 625014, China.
authors.forename: Junjie
authors.initials: J
authors.lastname: Zhang
authors.affiliation: College of Agronomy, Sichuan Agricultural University, Chengdu, 611130, China.
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Maize Research Institute, Sichuan Agricultural University, Chengdu, 611130, China.
authors.forename: Yinghong
authors.initials: Y
authors.lastname: Liu
authors.affiliation: College of Agronomy, Sichuan Agricultural University, Chengdu, 611130, China.
authors.forename: Guowu
authors.initials: G
authors.lastname: Yu
authors.affiliation: Maize Research Institute, Sichuan Agricultural University, Chengdu, 611130, China. yubihuang@sohu.com.|College of Agronomy, Sichuan Agricultural University, Chengdu, 611130, China. yubihuang@sohu.com.
authors.forename: Yubi
authors.initials: Y
authors.lastname: Huang
mesh_terms: D032461:Chromosomes, Plant; D018556:Crops, Agricultural / Q000235:genetics*; D004251:DNA Transposable Elements; D063990:Gene Ontology; D018745:Genome, Plant; D023281:Genomics / Q000379:methods; D016254:Mutagenesis, Insertional
chemical_list: D004251:DNA Transposable Elements
keywords: Crop; Genome-wide analysis; Non-random insertion; Non-reference transposons; Stress response