Supplementary Material for: Karyotypes and chromosomal mapping of some repetitive DNAs in two stingless bee species (Apidae: Meliponini), with the description of a B chromosome in Plebeia genus

Introduction: Cytogenetic studies on stingless bees have significantly contributed to our understanding of karyotypic evolution and the composition of euchromatin and heterochromatin regions, including repetitive sequences. Methods: In this study, we performed classical cytogenetics, chromosomal banding, and mapping of some repetitive sequences in two stingless bee species, Frieseomelitta trichocerata and Plebeia poecilochroa. Results: The species exhibit the typical diploid chromosome number of each genera, 2n=30 for Frieseomelitta and 2n=34 for Plebeia. Additionally, some individuals of P. poecilochroa presented a small heterochromatic B chromosome, showing a numeric variation of n=17 to 18 in males and 2n=34 to 35 in females. In both species heterochromatin is primarily distributed in the short arm and centromeric regions. Centromeric regions were found to be AT-rich in both species, while subterminal/terminal regions of the short arms of one and six chromosomes presented GC-rich sites in P. poecilochroa and F. trichocerata, respectively. The rDNA clusters mapped on two chromosome pairs in F. trichocerata, and in only one in P. poecilochroa. Microsatellites (GA)n, (GAG)n, and (CAA)n were predominantly mapped in euchromatic regions, while the telomeric motif (TTAGG)n mapped to the ends of most chromosomes, including the B chromosome of P. poecilochroa. The other repetitive probes used, including the rDNA clusters, do not label the B chromosome of P. poecilochroa. Conclusion: Our cytogenetic data highlight both similarities and differences when compared to other congeneric species, expanding the chromosomal data for both genera.

引言：对无刺蜂的细胞遗传学研究，对于我们理解核型进化以及 euchromatin 和 heterochromatin 区域的组成，包括重复序列，做出了显著的贡献。方法：在本研究中，我们采用了经典细胞遗传学、染色体带型分析和某些重复序列在两种无刺蜂物种 Frieseomelitta trichocerata 和 Plebeia poecilochroa 中的定位。结果：这两种物种表现出各自属的典型二倍体染色体数目，Frieseomelitta 为 2n=30，Plebeia 为 2n=34。此外，P. poecilochroa 的一些个体呈现出小型的异染色质 B 染色体，男性中 n=17 至 18 的数量变化，女性中 2n=34 至 35 的数量变化。在两种物种中，异染色质主要分布在短臂和着丝粒区域。着丝粒区域在两种物种中均富含 AT，而在 P. poecilochroa 的短臂一个和六个染色体的亚端/末端区域呈现 GC 富集位点。在 F. trichocerata 中，rDNA 簇定位在两个染色体对上，而在 P. poecilochroa 中仅定位在一个染色体对上。Microsatellites (GA)n、(GAG)n 和 (CAA)n 主要定位在 euchromatic 区域，而 telomeric motif (TTAGG)n 定位于大多数染色体的末端，包括 P. poecilochroa 的 B 染色体。其他重复探针，包括 rDNA 簇，均未标记 P. poecilochroa 的 B 染色体。结论：我们的细胞遗传学数据与其他同属物种相比，既揭示了相似性，也展现了差异性，从而扩展了这两个属的染色体数据。