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Chromosome-scale comparative sequence analysis unravels molecular mechanisms of genome dynamics between two wheat cultivars


Thind, Anupriya Kaur; Wicker, Thomas; Müller, Thomas; Ackermann, Patrick M; Steuernagel, Burkhard; Wulff, Brande B H; Spannagl, Manuel; Twardziok, Sven O; Felder, Marius; Lux, Thomas; Mayer, Klaus F X; Keller, Beat; Krattinger, Simon G (2018). Chromosome-scale comparative sequence analysis unravels molecular mechanisms of genome dynamics between two wheat cultivars. Genome Biology, 19:104.

Abstract

Background Recent improvements in DNA sequencing and genome scaffolding have paved the way to generate high-quality de novo assemblies of pseudomolecules representing complete chromosomes of wheat and its wild relatives. These assemblies form the basis to compare the dynamics of wheat genomes on a megabase scale. Results Here, we provide a comparative sequence analysis of the 700-megabase chromosome 2D between two bread wheat genotypes—the old landrace Chinese Spring and the elite Swiss spring wheat line ‘CH Campala Lr22a’. Both chromosomes were assembled into megabase-sized scaffolds. There is a high degree of sequence conservation between the two chromosomes. Analysis of large structural variations reveals four large indels of more than 100 kb. Based on the molecular signatures at the breakpoints, unequal crossing over and double-strand break repair were identified as the molecular mechanisms that caused these indels. Three of the large indels affect copy number of NLRs, a gene family involved in plant immunity. Analysis of SNP density reveals four haploblocks of 4, 8, 9 and 48 Mb with a 35-fold increased SNP density compared to the rest of the chromosome. Gene content across the two chromosomes was highly conserved. Ninety-nine percent of the genic sequences were present in both genotypes and the fraction of unique genes ranged from 0.4 to 0.7%. Conclusions This comparative analysis of two high-quality chromosome assemblies enabled a comprehensive assessment of large structural variations and gene content. The insight obtained from this analysis will form the basis of future wheat pan-genome studies. Keywords Genome diversity Structural variation High-quality assembly Wheat

Abstract

Background Recent improvements in DNA sequencing and genome scaffolding have paved the way to generate high-quality de novo assemblies of pseudomolecules representing complete chromosomes of wheat and its wild relatives. These assemblies form the basis to compare the dynamics of wheat genomes on a megabase scale. Results Here, we provide a comparative sequence analysis of the 700-megabase chromosome 2D between two bread wheat genotypes—the old landrace Chinese Spring and the elite Swiss spring wheat line ‘CH Campala Lr22a’. Both chromosomes were assembled into megabase-sized scaffolds. There is a high degree of sequence conservation between the two chromosomes. Analysis of large structural variations reveals four large indels of more than 100 kb. Based on the molecular signatures at the breakpoints, unequal crossing over and double-strand break repair were identified as the molecular mechanisms that caused these indels. Three of the large indels affect copy number of NLRs, a gene family involved in plant immunity. Analysis of SNP density reveals four haploblocks of 4, 8, 9 and 48 Mb with a 35-fold increased SNP density compared to the rest of the chromosome. Gene content across the two chromosomes was highly conserved. Ninety-nine percent of the genic sequences were present in both genotypes and the fraction of unique genes ranged from 0.4 to 0.7%. Conclusions This comparative analysis of two high-quality chromosome assemblies enabled a comprehensive assessment of large structural variations and gene content. The insight obtained from this analysis will form the basis of future wheat pan-genome studies. Keywords Genome diversity Structural variation High-quality assembly Wheat

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Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Plant and Microbial Biology
Dewey Decimal Classification:580 Plants (Botany)
Language:English
Date:1 December 2018
Deposited On:10 Jan 2019 10:45
Last Modified:13 Oct 2019 05:54
Publisher:BioMed Central
ISSN:1474-7596
OA Status:Gold
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1186/s13059-018-1477-2

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