Cristiano Maykon Passos, Simões Talitta Guimarães, Lopes Denilce Meneses, Pompolo Silvia das Graças
Departamento de Biodiversidade, Evolução e Meio Ambiente, Universidade Federal de Ouro Preto, Morro do Cruzeiro, Ouro Preto, Minas Gerais, Brazil, 35400-000 ; Departamento de Biologia Geral, Universidade Federal de Viçosa, Avenida Peter Henry Rolfs s/n, Viçosa, Minas Gerais, Brazil, 36570-000.
Departamento de Biologia Geral, Universidade Federal de Viçosa, Avenida Peter Henry Rolfs s/n, Viçosa, Minas Gerais, Brazil, 36570-000.
Comp Cytogenet. 2014 Aug 14;8(3):223-31. doi: 10.3897/CompCytogen.v8i3.7510. eCollection 2014.
To date, more than 65 species of Brazilian bees (of the superfamily Apoidea) have been cytogenetically studied, but only a few solitary species have been analyzed. One example is the genus Melitoma Lepeletier & Serville, 1828, for which there is no report in the literature with regard to cytogenetic studies. The objective of the present study is to analyze the chromosome number and morphology of the species Melitoma segmentaria (Fabricius, 1804), as well as to determine the pattern of heterochromatin distribution and identify the adenine-thymine (AT)- and guanine-cytosine (GC)-rich regions. Melitoma segmentaria presents chromosome numbers of 2n=30 (females) and n=15 (males). With C-banding, it is possible to classify the chromosomes into seven pseudo-acrocentric pairs (A(M)), seven pseudo-acrocentric pairs with interstitial heterochromatin (A(Mi)), and one totally heterochromatic metacentric pair (M(h)). Fluorochrome staining has revealed that heterochromatin present in the chromosomal arms is rich in GC base pairs (CMA3 (+)) and the centromeric region is rich in AT base pairs (DAPI(+)). The composition found for Melitoma diverges from the pattern observed in other bees, in which the heterochromatin is usually rich in AT. In bees, few heterochromatic regions are rich in GC and these are usually associated with or localized close to the nucleolus organizer regions (NORs). Silver nitrate impregnation marks the heterochromatin present in the chromosome arms, which makes identification of the NOR in the chromosomes impossible. As this technique reveals proteins in the NOR, the observation that is made in the present study suggests that the proteins found in the heterochromatin are qualitatively similar to those in the NOR.
迄今为止，已经对65种以上的巴西蜜蜂（膜翅目蜜蜂总科）进行了细胞遗传学研究，但仅分析了少数独居蜂种。其中一个例子是1828年的Melitoma Lepeletier & Serville属，文献中尚无关于其细胞遗传学研究的报道。本研究的目的是分析Melitoma segmentaria（Fabricius，1804）的染色体数目和形态，以及确定异染色质分布模式并识别富含腺嘌呤 - 胸腺嘧啶（AT）和鸟嘌呤 - 胞嘧啶（GC）的区域。Melitoma segmentaria的染色体数目为2n = 30（雌性）和n = 15（雄性）。通过C带技术，可以将染色体分为七对假近端着丝粒染色体（A(M)）、七对带有中间异染色质的假近端着丝粒染色体（A(Mi)）和一对完全异染色质的中着丝粒染色体（M(h)）。荧光染色显示，染色体臂上的异染色质富含GC碱基对（CMA3(+)），着丝粒区域富含AT碱基对（DAPI(+)）。Melitoma的组成与其他蜜蜂中观察到的模式不同，在其他蜜蜂中异染色质通常富含AT。在蜜蜂中，很少有异染色质区域富含GC，并且这些区域通常与核仁组织区（NORs）相关或位于其附近。硝酸银染色标记了染色体臂上的异染色质，这使得无法在染色体中识别NOR。由于该技术揭示了NOR中的蛋白质，本研究中的观察结果表明，在异染色质中发现的蛋白质在性质上与NOR中的蛋白质相似。
