Dutrillaux A-M, Dutrillaux B
UMR 5202 CNRS/MNHN, Structure et Evolution de la Biodiversité, Département Systématique et Evolution, Muséum National d'Histoire Naturelle, Paris, France.
Cytogenet Genome Res. 2012;136(3):208-19. doi: 10.1159/000336694. Epub 2012 Mar 1.
The aim of this study was the identification of the ancestral location of the nucleolus organizer region (NOR) in the Scarabaeoidea superfamily, and its evolutive trends in the karyotypes. For this purpose, the mitotic and meiotic chromosomes at pachynema of 82 species belonging to 4 families and 8 subfamilies, including 49 species without any published data, were examined after Giemsa staining, C-banding and NOR staining. It could be perceived that most karyotypes are composed of 18 nonacrocentric autosomes, an acrocentric X and a punctiform Y. NORs are frequently located on the X independent of its morphology. In contrast, autosomal NORs are frequently on the rare acrocentric short arms. Thus, it could be shown that the ancestral karyotype was very probably composed of 18 metacentric/submetacentric autosomes, an NOR carrier acrocentric X and a punctiform Y. The NOR translocation on autosomes parallels the passage to their acrocentric morphology. It is proposed that the frequent location of the NOR on the X of beetles, and possibly other insects, is made possible by their mode of dosage compensation of the X chromosome, consisting in the overexpression of the unique X of the males.
本研究的目的是确定金龟总科核仁组织区（NOR）的原始位置及其在核型中的进化趋势。为此，对属于4个科和8个亚科的82个物种在粗线期的有丝分裂和减数分裂染色体进行了检查，其中包括49个无任何已发表数据的物种，检查方法为吉姆萨染色、C带染色和NOR染色。可以看出，大多数核型由18条非近端着丝粒常染色体、一条近端着丝粒X染色体和一条点状Y染色体组成。NOR通常位于X染色体上，与其形态无关。相比之下，常染色体NOR通常位于罕见的近端着丝粒短臂上。因此，可以证明原始核型很可能由18条中着丝粒/亚中着丝粒常染色体、一条携带NOR的近端着丝粒X染色体和一条点状Y染色体组成。常染色体上的NOR易位与其向近端着丝粒形态的转变平行。有人提出，甲虫以及可能其他昆虫的NOR在X染色体上频繁定位是由于它们的X染色体剂量补偿模式，即雄性个体中唯一的X染色体过度表达。
