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Oligo-painting and GISH reveal meiotic chromosome biases and increased meiotic stability in synthetic allotetraploid Cucumis ×hytivus with dysploid parental karyotypes.

ABSTRACT: BACKGROUND:Meiosis of newly formed allopolyploids frequently encounter perturbations induced by the merging of divergent and hybridizable genomes. However, to date, the meiotic properties of allopolyploids with dysploid parental karyotypes have not been studied in detail. The allotetraploid Cucumis ×hytivus (HHCC, 2n?=?38) was obtained from interspecific hybridization between C. sativus (CC, 2n?=?14) and C. hystrix (HH, 2n?=?24) followed by chromosome doubling. The results of this study thus offer an excellent opportunity to explore the meiotic properties of allopolyploids with dysploid parental karyotypes. RESULTS:In this report, we describe the meiotic properties of five chromosomes (C5, C7, H1, H9 and H10) and two genomes in interspecific hybrids and C. ×hytivus (the 4th and 14th inbred family) through oligo-painting and genomic in situ hybridization (GISH). We show that 1) only two translocations carrying C5-oligo signals were detected on the chromosomes C2 and C4 of one 14th individual by the karyotyping of eight 4th and 36 14th plants based on C5- and C7-oligo painting, and possible cytological evidence was observed in meiosis of the 4th generation; 2) individual chromosome have biases for homoeologous pairing and univalent formation in F1 hybrids and allotetraploids; 3) extensive H-chromosome autosyndetic pairings (e.g., H-H, 25.5% PMCs) were observed in interspecific F1 hybrid, whereas no C-chromosome autosyndetic pairings were observed (e.g. C-C); 4) the meiotic properties of two subgenomes have significant biases in allotetraploids: H-subgenome exhibits higher univalent and chromosome lagging frequencies than C-subgenome; and 5) increased meiotic stability in the S14 generation compared with the S4 generation, including synchronous meiosis behavior, reduced incidents of univalent and chromosome lagging. CONCLUSIONS:These results suggest that the meiotic behavior of two subgenomes has dramatic biases in response to interspecific hybridization and allopolyploidization, and the meiotic behavior harmony of subgenomes is a key subject of meiosis evolution in C. ×hytivus. This study helps to elucidate the meiotic properties and evolution of nascent allopolyploids with the dysploid parental karyotypes.

SUBMITTER: Zhao Q

PROVIDER: S-EPMC6833230 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Oligo-painting and GISH reveal meiotic chromosome biases and increased meiotic stability in synthetic allotetraploid Cucumis ×hytivus with dysploid parental karyotypes.

Zhao Qinzheng Q Wang Yunzhu Y Bi Yunfei Y Zhai Yufei Y Yu Xiaqing X Cheng Chunyan C Wang Panqiao P Li Ji J Lou Qunfeng Q Chen Jinfeng J Chen Jinfeng J

BMC plant biology 20191106 1

<h4>Background</h4>Meiosis of newly formed allopolyploids frequently encounter perturbations induced by the merging of divergent and hybridizable genomes. However, to date, the meiotic properties of allopolyploids with dysploid parental karyotypes have not been studied in detail. The allotetraploid Cucumis ×hytivus (HHCC, 2n = 38) was obtained from interspecific hybridization between C. sativus (CC, 2n = 14) and C. hystrix (HH, 2n = 24) followed by chromosome doubling. The results of this study ...[more]

PMID: 31694540

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Project description:The Iris series Chinenses in Korea comprises four species (I. minutoaurea, I. odaesanensis, I. koreana, and I. rossii), and the group includes some endangered species, owing to their high ornamental, economic, and conservation values. Among them, the putative allotetraploid, Iris koreana (2n = 4x = 50), is hypothesized to have originated from the hybridization of the diploids I. minutoaurea (2n = 2x = 22) and I. odaesanensis (2n = 2x = 28) based on morphological characters, chromosome numbers, and genome size additivity. Despite extensive morphological and molecular phylogenetical studies on the genus Iris, little is known about Korean irises in terms of their complete chloroplast (cp) genomes and molecular cytogenetics that involve rDNA loci evolution based on fluorescence in situ hybridization (FISH). This study reports comparative analyses of the karyotypes of the three Iris species (I. koreana, I. odaesanensis, and I. minutoaurea), with an emphasis on the 5S and 35S rDNA loci number and localization using FISH together with the genome size and chromosome number. Moreover, the cp genomes of the same individuals were sequenced and assembled for comparative analysis. The rDNA loci numbers, which were localized consistently at the same position in all species, and the chromosome numbers and genome size values of tetraploid Iris koreana (four 5S and 35S loci; 2n = 50; 1C = 7.35 pg) were additively compared to its putative diploid progenitors, I. minutoaurea (two 5S and 35S loci; 2n = 22; 1C = 3.71 pg) and I. odaesanensis (two 5S and 35S loci; 2n = 28; 1C = 3.68 pg). The chloroplast genomes were 152,259-155,145 bp in length, and exhibited a conserved quadripartite structure. The Iris cp genomes were highly conserved and similar to other Iridaceae cp genomes. Nucleotide diversity analysis indicated that all three species had similar levels of genetic variation, but the cp genomes of I. koreana and I. minutoaurea were more similar to each other than to I. odaesanensis. Positive selection was inferred for psbK and ycf2 genes of the three Iris species. Phylogenetic analyses consistently recovered I. odaesanensis as a sister to a clade containing I. koreana and I. minutoaurea. Although the phylogenetic relationship, rDNA loci number, and localization, together with the genome size and chromosome number of the three species, allowed for the inference of I. minutoaurea as a putative maternal taxon and I. odaesanensis as a paternal taxon, further analyses involving species-specific molecular cytogenetic markers and genomic in situ hybridization are required to interpret the mechanisms involved in the origin of the chromosomal variation in Iris series Chinenses. This study contributes towards the genomic and chromosomal evolution of the genus Iris.

Dataset Information

Oligo-painting and GISH reveal meiotic chromosome biases and increased meiotic stability in synthetic allotetraploid Cucumis ×hytivus with dysploid parental karyotypes.

Publications

Oligo-painting and GISH reveal meiotic chromosome biases and increased meiotic stability in synthetic allotetraploid Cucumis ×hytivus with dysploid parental karyotypes.

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