Monti Valentina, Lombardo Giorgia, Loxdale Hugh D, Manicardi Gian Carlo, Mandrioli Mauro
Dipartimento di Biologia, Università di Modena e Reggio Emilia, Via Campi 213/D, 41125 Modena, Italy.
Genetica. 2012 Mar;140(1-3):93-103. doi: 10.1007/s10709-012-9661-x. Epub 2012 May 27.
Analysis of the holocentric mitotic chromosomes of the peach-potato aphid, Myzus persicae (Sulzer), from clones labelled 50, 51 and 70 revealed different chromosome numbers, ranging from 12 to 14, even within each embryo, in contrast to the standard karyotype of this species (2n = 12). Chromosome length measurements, combined with fluorescent in situ hybridization experiments, showed that the observed chromosomal mosaicisms are due to recurrent fragmentations of chromosomes X, 1 and 3. Contrary to what has generally been reported in the literature, X chromosomes were frequently involved in recurrent fragmentations, in particular at their telomeric ends opposite to the nucleolar organizer region. Supernumerary B chromosomes have been also observed in clones 50 and 51. The three aphid clones showed recurrent fissions of the same chromosomes in the same regions, thereby suggesting that the M. persicae genome has fragile sites that are at the basis of the observed changes in chromosome number. Experiments to induce males also revealed that M. persicae clones 50, 51 and 70 are obligately parthenogenetic, arguing that the reproduction by apomictic parthenogenesis favoured the stabilization and inheritance of the observed chromosomal fragments.
对来自标记为50、51和70的克隆体的桃蚜（烟蚜，Myzus persicae (Sulzer)）的全着丝粒有丝分裂染色体进行分析发现，即使在每个胚胎内部，染色体数目也有所不同，范围从12到14，这与该物种的标准核型（2n = 12）形成对比。染色体长度测量结合荧光原位杂交实验表明，观察到的染色体嵌合体是由于X、1和3号染色体反复发生断裂所致。与文献中普遍报道的情况相反，X染色体频繁参与反复断裂，特别是在其与核仁组织区相对的端粒末端。在克隆体50和51中还观察到了B染色体。这三个蚜虫克隆体在相同区域的相同染色体上出现反复分裂，从而表明桃蚜基因组存在脆弱位点，这是观察到的染色体数目变化的基础。诱导雄性的实验还表明，桃蚜克隆体50、51和70是专性孤雌生殖的，这表明无融合生殖的孤雌生殖方式有利于观察到的染色体片段的稳定和遗传。
