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by claude@2026-06, 2026-06-24
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This paper studies the problem of sequence collapse in polyploid genome assemblies caused by high similarity between homologous or homeologous chromosomes, focusing on two perennial Brachypodium species with previously conflicting collapsed chromosomal segments. Using a newly developed bioinformatic pipeline called CollapsedChrom, the authors combine depth-of-read profiling with prior karyotypic information to detect and rescue collapsed regions in allotetraploid B. phoenicoides and autohexaploid B. boissieri. The approach recovered 328.9 Mb of collapsed sequences in B. phoenicoides and 195.8 Mb in B. boissieri, and the resulting chromosomal-level assemblies passed comprehensive quality assessments. The paper does not explicitly discuss endometriosis or adenomyosis; it was included in the corpus via a keyword match in the upstream search index.
Abstract
Polyploidization plays a fundamental role in plant evolution and crop domestication. However, due to the high similarity of genomic sequences between some homologous or homeologous chromosomes, the assembly of some polyploid genomes is extremely difficult, frequently resulting in erroneous assemblies, such as sequence chimeras and sequence collapse. The genus Brachypodium is an important model system for the study of polyploidy in grasses. However, high-quality reference genomes are still lacking for its complex polyploid perennial species. In this study, we developed a bioinformatic pipeline for the accurate assembly of high-quality reference genomes at the chromosomal level for two representative perennial Brachypodium species with conflicting collapsed segments, the allotetraploid B. phoenicoides (2n = 4x = 28) and the autohexaploid B. boissieri (2n = 6x = 48). We developed an innovative methodology (CollapsedChrom) that uses depth-of-read profiling and relies on prior karyotypic information to systematically detect and rescue collapsed regions. This depth-sensitive curation strategy successfully recovered 328.9 Mb and 195.8 Mb of previously collapsed sequences in the genomes of B. phoenicoides and B. boissieri, respectively. Comprehensive quality assessments demonstrated the high quality of our final assemblies. Our chromosomal-level assemblies fully capture the genomic architectures of these species. These robust genomic resources overcome long-standing challenges in polyploid assembly and provide an essential foundation for future research on the evolutionary dynamics, subgenomic interactions, and functional biology of complex polyploid plant genomes.
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Abstract
Polyploidization plays a fundamental role in plant evolution and crop domestication. However, due to the high similarity of genomic sequences between some homologous or homeologous chromosomes, the assembly of some polyploid genomes is extremely difficult, frequently resulting in erroneous assemblies, such as sequence chimeras and sequence collapse. The genus Brachypodium is an important model system for the study of polyploidy in grasses. However, high-quality reference genomes are still lacking for its complex polyploid perennial species. In this study, we developed a bioinformatic pipeline for the accurate assembly of high-quality reference genomes at the chromosomal level for two representative perennial Brachypodium species with conflicting collapsed segments, the allotetraploid B. phoenicoides (2n = 4x = 28) and the autohexaploid B. boissieri (2n = 6x = 48). We developed an innovative methodology (CollapsedChrom) that uses depth-of-read profiling and relies on prior karyotypic information to systematically detect and rescue collapsed regions. This depth-sensitive curation strategy successfully recovered 328.9 Mb and 195.8 Mb of previously collapsed sequences in the genomes of B. phoenicoides and B. boissieri, respectively. Comprehensive quality assessments demonstrated the high quality of our final assemblies. Our chromosomal-level assemblies fully capture the genomic architectures of these species. These robust genomic resources overcome long-standing challenges in polyploid assembly and provide an essential foundation for future research on the evolutionary dynamics, subgenomic interactions, and functional biology of complex polyploid plant genomes.
Competing Interest Statement
The authors have declared no competing interest.
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