Department of Medical Research, China Medical University Hospital, Taichung, Taiwan, Republic of China.
Chromosome Res. 2011 Feb;19(2):183-91. doi: 10.1007/s10577-010-9183-2. Epub 2011 Jan 19.
The B-chromosome of maize contains an A-chromosome centromere-specific satellite CentC repeat in its centromere region (CENB) and at multiple locations in its distal heterochromatic regions (BDHs). Because CentC is highly repetitive, it is a challenge to study CentC sequences within individual centromeres or chromosome regions. The combined structure of CentC and a BDH-specific CL-repeat has allowed us to isolate CentC sequences from BDHs. In the study described herein, we have used a PCR method to amplify 13 CL-CentC variant products that were specifically mapped to A-centromeres (CENAs), the CENB, and BDHs via the tertiary trisomes and hypoploids of five B-10L translocations. Cloning and sequence analyses of these CL-CentC products have revealed a local CentC homogenization within the three CentC-containing regions. Phylogenetic analysis has indicated that the CentC sequences of BDHs are more closely related to those of CENAs in comparison to that of the CENB. Furthermore, the CentC monomers that are within the CENB are more diverse than those within BDHs and CENAs. These results shed light on the evolution of CentC repeats on the B-chromosome and provide a better understanding of B-chromosome evolution.
玉米的 B 染色体在其着丝粒区域（CENB）和其远端异染色质区域（BDHs）的多个位置含有一个 A 染色体着丝粒特异性卫星 CentC 重复序列。由于 CentC 高度重复，因此研究单个着丝粒或染色体区域内的 CentC 序列具有挑战性。CentC 和 BDH 特异性 CL 重复的组合结构使我们能够从 BDH 中分离出 CentC 序列。在本文所述的研究中，我们使用 PCR 方法扩增了 13 种 CL-CentC 变体产物，这些产物通过五个 B-10L 易位的三倍体和亚倍体特异性映射到 A 着丝粒（CENAs）、CENB 和 BDHs。对这些 CL-CentC 产物的克隆和序列分析揭示了三个含有 CentC 的区域内局部 CentC 同质化。系统发育分析表明，与 CENB 相比，BDHs 的 CentC 序列与 CENAs 的 CentC 序列更为密切相关。此外，CENB 内的 CentC 单体比 BDHs 和 CENAs 内的 CentC 单体更为多样化。这些结果阐明了 B 染色体上 CentC 重复的进化，并提供了对 B 染色体进化的更好理解。
