12/28/2023 0 Comments Number sequence meaning 544![]() ![]() ![]() This increased the contiguity as measured by the N50 value (the scaffold size above which 50% of the total length of the sequence was included in the assembly) from 79 kb to 1.9 Mb. In a second step, overlaps between adjacent clones 15 were detected and validated by physical map information 16, a genetic linkage 17 and a highly contiguous optical map 18 to construct super-scaffolds composed of merged assemblies of individual BACs ( Table 1 and Extended Data Table 1). First, a total of 87,075 bacterial artificial chromosomes (BACs) were sequenced, mainly using Illumina paired-end and mate-pair technology and assembled individually from 4.5 terabases of raw sequence data 12, 13, 14 ( Supplementary Note 1). We adopted a hierarchical approach to generate a high-quality reference genome sequence of the barley cultivar Morex, a US spring six-row malting barley. Moreover, chromosomal compartments are differentiated by an exponential gradient of gene density and recombination rate, striking contrasts in the distribution of retrotransposon families, and distinct patterns of genetic diversity. The resource highlights a conspicuous distinction between distal and proximal regions of chromosomes that is reflected by the intranuclear chromatin organization. Here we present a map-based reference sequence of the barley genome including the first comprehensively ordered assembly of the pericentromeric regions of a Triticeae genome. Thus, a detailed investigation of the composition of the repetitive fraction of the genome-including expanded gene families-and of the distribution of targets of selection and crop improvement in (genetically defined) pericentromeric regions has been beyond reach. These factors have limited the contiguity of whole-genome assemblies to kilobase-sized sequences originating from low-copy regions of the genome. The limitations are often direct consequences of two characteristic genomic features: the extreme abundance of repetitive elements, and the severely reduced frequency of meiotic recombination in pericentromeric regions 11. However, these and other efforts have also revealed limitations of the current draft assembly. This community resource has underpinned gene isolation 8, 9 and population genomic studies 10. Since 2012, both genetic research and crop improvement in barley have benefited from a partly ordered draft sequence assembly 7. Moreover, brewing beer may also have played a role in the eastward spread of the crop after its initial domestication in the Fertile Crescent 5, 6. ![]() In addition to indications that barley was an important food crop, recent excavations have fuelled speculation that beverages from fermented grains may have motivated early Neolithic hunter–gatherers to erect some of humankind’s oldest monuments 3, 4. We demonstrate the importance of the barley reference sequence for breeding by inspecting the genomic partitioning of sequence variation in modern elite germplasm, highlighting regions vulnerable to genetic erosion.īarley remains dated to the dawn of agriculture have been found at several archaeological sites 1, 2. Gene family analyses reveal lineage-specific duplications of genes involved in the transport of nutrients to developing seeds and the mobilization of carbohydrates in grains. The composition of genes and repetitive elements differs between distal and proximal regions. We use chromosome conformation capture mapping to derive the linear order of sequences across the pericentromeric space and to investigate the spatial organization of chromatin in the nucleus at megabase resolution. Here we present a high-quality reference genome assembly for barley ( Hordeum vulgare L.). Their large genomes are characterized by a high content of repetitive elements and large pericentromeric regions that are virtually devoid of meiotic recombination. Nature volume 544, pages 427–433 ( 2017) Cite this articleĬereal grasses of the Triticeae tribe have been the major food source in temperate regions since the dawn of agriculture. ![]() A chromosome conformation capture ordered sequence of the barley genome ![]()
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