State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400715, China.
Sci Rep. 2017 Aug 29;7(1):9573. doi: 10.1038/s41598-017-10079-6.
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.
桑树（桑科）是一种具有重要经济价值的植物。已经确定了许多桑树种的多倍体水平。本研究应用荧光原位杂交（FISH）技术，以四个单拷贝序列、端粒重复序列和 5S 和 25S rDNA 作为探针，对蒙椹（Morus notabilis）进行了研究。所有有丝分裂染色体都被清晰地识别并分为 7 对同源染色体。通过 25S rDNA 探针和简单序列重复（SSR2524）的 FISH 模式，区分了三个点状染色体对。根据 FISH 信号、染色体长度和形态，构建了详细的减数分裂前期 I 核型。有趣的是，在减数分裂细胞中仅观察到六个二价染色体。用 25S rDNA 探针来说明染色体的变化。结果表明，有丝分裂染色体 5 和 7 在减数分裂过程中融合成减数分裂染色体 5。在有丝分裂细胞中，融合的染色体 5 断裂成染色体 5 和 7。本文首次报道了同一个体减数分裂和有丝分裂阶段之间的染色体融合-裂变循环。这一发现将有助于理解植物的核型进化。
