Abstract
Mulberry (Morus spp.), in family Moraceae, is a plant with important economic value. Many polyploid levels of mulberry have been determined. In the present study, the fluorescence in situ hybridization (FISH) technique was applied in Morus notabilis, using four single-copy sequences, telomere repeats, and 5S and 25S rDNAs as probes. All the mitotic chromosomes were clearly identified and grouped into seven pairs of homologous chromosomes. Three dot chromosome pairs were distinguished by the FISH patterns of the 25S rDNA probe and a simple sequence repeat (SSR2524). According to the FISH signals, chromosome length and morphology, detailed meiotic diakinesis karyotype was constructed. Interestingly, only six bivalent chromosomes were observed in diakinesis cells. The 25S rDNA probe was used to illustrate chromosome alterations. The results indicated that mitotic chromosomes 5 and 7 fused into diakinesis chromosome 5 during the meiotic phase. In mitotic cells, the fused chromosome 5 broke into chromosomes 5 and 7. A chromosomal fusion-fission cycle between the meiotic and mitotic phases in the same individual is reported here for the first time. This finding will contribute to the understanding of karyotype evolution in plants.
Highlights
Mulberry (Morus spp.), in family Moraceae, is a deciduous woody plant of great economic importance that is distributed worldwide
We used the Fluorescence in situ hybridization (FISH) technique to further examine the karyotype of M. notabilis, especially to identify the two pairs of middle length chromosomes and three pairs of dot chromosomes
Chromosome 4 was recognized by the 5S rDNA probe (Fig. 1d)
Summary
Mulberry (Morus spp.), in family Moraceae, is a deciduous woody plant of great economic importance that is distributed worldwide. The basic chromosome number (x = 14) of mulberry was proposed a long time ago[6, 7]. This idea has been widely cited in later studies[8,9,10]. Fluorescence in situ hybridization (FISH) is more powerful than the classical methods and has been used widely in cytogenetic studies of plants, especially in species with small and similar chromosomes[14]. FISH-based karyotypes on mitotic and meiotic diakinesis chromosomes of M. notabilis were determined. All the individual chromosomes were identified by four single-copy sequence probes, and 5S and 25S rDNA probes. We describe a chromosomal fusion–fission cycle between the mitotic and meiotic phases in the same individual M. notabilis for the first time
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