Mandrioli M, Azzoni P, Lombardo G, Manicardi G C
Dipartimento di Biologia, Università di Modena e Reggio Emilia, Modena, Italia.
Cytogenet Genome Res. 2011;133(1):67-77. doi: 10.1159/000323510. Epub 2011 Jan 28.
A detailed karyotype analysis of the oleander aphid Aphis nerii focusing on the distribution, molecular composition and epigenetic modifications of heterochromatin was done in order to better understand the structure and evolution of holocentric/holokinetic chromosomes in aphids. The female karyotype (2n = 8) consisted of 3 pairs of autosomes and a pair of X chromosomes that were the longest elements in the karyotype and carried a single, terminally located nucleolar organizer region. Males showed 2n = 7 chromosomes due to the presence of a single X chromosome. Heterochromatin was located in the X chromosomes only and consisted of 4 satellite DNAs that have been identified. A. nerii constitutive heterochromatin was enriched in mono-, di- and tri-methylated H3 histones and HP1 proteins but, interestingly, it lacked DNA methylation that was widespread in euchromatic chromosomal regions. These results suggest that aphid heterochromatin is assembled and condensed without any involvement of DNA methylation.
为了更好地理解蚜虫全着丝粒/全动粒染色体的结构和进化，对夹竹桃蚜进行了详细的核型分析，重点关注异染色质的分布、分子组成和表观遗传修饰。雌性核型（2n = 8）由3对常染色体和一对X染色体组成，X染色体是核型中最长的元件，携带一个位于末端的核仁组织区。由于存在一条单一的X染色体，雄性显示2n = 7条染色体。异染色质仅位于X染色体上，由已鉴定的4种卫星DNA组成。夹竹桃蚜的组成型异染色质富含单甲基化、二甲基化和三甲基化的H3组蛋白和HP1蛋白，但有趣的是，它缺乏在常染色体区域广泛存在的DNA甲基化。这些结果表明，蚜虫的异染色质在没有DNA甲基化参与的情况下组装和浓缩。
