A Gossypium BAC clone contains key repeat components distinguishing sub-genome of allotetraploidy cottonsReport as inadecuate

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Molecular Cytogenetics

, 9:27

Animals and plants


BackgroundDissecting genome organization is indispensable for further functional and applied studies. As genome sequences data shown, cotton genomes contain more than 60 % repetitive sequences, so study on repetitive sequences composition, structure, and distribution is the key step to dissect cotton genome.

ResultsIn this study, a bacterial artificial chromosome BAC clone enriched in repetitive sequences, was discovered initiatively by fluorescence in situ hybridization FISH. FISHing with allotetraploidy cotton as target DNA, dispersed signals on most regions of all A sub-genome chromosomes, and only middle regions of all D sub-genome chromosomes were detected. Further FISHing with other cotton species bearing A or D genome as target DNA, specific signals were viewed. After BAC sequencing and bioinformational analysis, 129 repeat elements, size about 57,172 bp were found, accounting for more than 62 % of the BAC sequence 91,238 bp. Among them, a type of long terminal repeat-retrotransposon LTR-RT, LTR-Gypsy was the key element causing the specific FISH results. Using the fragments of BAC matching with the identified Gypsy-like LTR as probes, the BAC-57I23-like FISH signals were reappeared. Running BLASTN, the fragments had good match with all chromosomes of G. arboreum A2 genome and A sub-genome of G. hirsutum AD1, and had relatively inferior match with all chromosomes of D sub-genome of AD1, but had little match with the chromosomes of G. raimondii D5 genome, which was consistent with the FISH results.

ConclusionA repeats-enriched cytogenetic marker to identify A and D sub-genomes of Gossypium was discovered by FISH. Combined sequences analysis with FISH verification, the assembly quality of repetitive sequences in the allotetraploidy cotton draft genome was assessed, and better chromosome belonging was verified. We also found the genomic distribution of the identified Gypsy-LTR-RT was similar to the distribution of heterochromatin. The expansion of this type of Gypsy-LTR-RT in heterochromatic regions may be one of the major reasons for the size gap between A and D genome. The findings showed here will help to understand the composition, structure, and evolution of cotton genome, and contribute to the further perfection of the draft genomes of cotton.

KeywordsGossypium BAC Repetitive sequences LTR-RT FISH  Download fulltext PDF

Author: Yuling Liu - Renhai Peng - Fang Liu - Xingxing Wang - Xinglei Cui - Zhongli Zhou - Chunying Wang - Xiaoyan Cai - Yuhong W

Source: https://link.springer.com/

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