Yutaka Ogura

A highly abundant repetitive DNA sequence family of Arabidopsis, AtCon, is composed of 178-bp tandemly repeated units and is located at the centromeres of all five chromosome pairs. Analysis of multiple copies of AtCon showed 95% conservation of nucleotides, with some alternative bases, and revealed two boxes, 30 and 24 bp long, that are 99% conserved. Sequences at the 3' end of these boxes showed similarity to yeast CDEI and human CENP-B DNA-protein binding motifs. When oligonucleotides from less conserved regions of AtCon were hybridized in situ and visualized by using primer extension, they were detected on specific chromosomes. When used for polymerase chain reaction with genomic DNA, single primers or primer pairs oriented in the same direction showed negligible amplification, indicating a head-to-tail repeat unit organization. Most primer pairs facing in opposite directions gave several strong bands corresponding to their positions within AtCon. However, consistent with the primer extension results, some primer pairs showed no amplification, indicating that there are chromosome-specific variants of AtCon. The results are significant because they elucidate the organization, mode of amplification, dispersion, and evolution of one of the major repeated sequence families of Arabidopsis. The evidence presented here suggests that AtCon, like human alpha satellites, plays a role in Arabidopsis centromere organization and function.

Two highly repetitive DNA sequences have been cloned from Arabidopsis thaliana, ecotype Columbia, and were characterized by molecular and cytological analyses. These two sequences belong to the same repeat family with 180-bp basic unit, being tandemly organized in clusters. Pulsed field gel electrophoresis showed that this repeat sequence family forms at least seven clusters from ca. 100 to 1200 kb in length and ca. 3500 kb in total. Fluorescent in situ hybridization to somatic metaphase cells with the monomeric repeat unit as a probe clearly revealed that this repeat family is located at the centromeric regions of all chromosomes. It was also shown that this repetitive sequence is closely associated with limited parts of heterochromatic blocks on the centromeric regions which are visible distinctly at meiotic prophase from leptotene to diakinesis. Furthermore, this sequence hybridized preferentially to both polar sides of five bivalent chromosomes at the first metaphase. These results suggest that the repetitive sequences of this family were derived from the regions very close to the centromeres or on the centromeres themselves.

Journal Article Cloning, Nucleotide Sequences and Differential Expression of the nifH and nifH-Like (frxC) Genes from the Filamentous Nitrogen-Fixing Cyanobacterium Plectonema boryanum Get access Yuichi Fujita, Yuichi Fujita 1Department of Biology, Faculty of Science, Osaka UniversityToyonaka, Osaka, 560 Japan Search for other works by this author on: Oxford Academic Google Scholar Yasuhiro Takahashi, Yasuhiro Takahashi 1Department of Biology, Faculty of Science, Osaka UniversityToyonaka, Osaka, 560 Japan Search for other works by this author on: Oxford Academic Google Scholar Fumio Shonai, Fumio Shonai 3 1Department of Biology, Faculty of Science, Osaka UniversityToyonaka, Osaka, 560 Japan 3 Present address: Institute for Fundamental Research, Suntory Ltd. 1-1-1, Wakayama-dai Shimamoto-cho, Mishima-gun, Osaka, 618 Japan. Search for other works by this author on: Oxford Academic Google Scholar Yutaka Ogura, Yutaka Ogura 2Department of Agricultural Chemistry, Faculty of Agriculture, Kyoto UniversityKyoto, 606 Japan Search for other works by this author on: Oxford Academic Google Scholar Hiroshi Matsubara Hiroshi Matsubara 1Department of Biology, Faculty of Science, Osaka UniversityToyonaka, Osaka, 560 Japan Search for other works by this author on: Oxford Academic Google Scholar Plant and Cell Physiology, Volume 32, Issue 7, October 1991, Pages 1093–1106, https://doi.org/10.1093/oxfordjournals.pcp.a078173 Published: 01 October 1991 Article history Received: 27 April 1991 Accepted: 12 August 1991 Published: 01 October 1991

Centromere protein C (CENP-C) is a component of the kinetochore essential for correct segregation of sister chromatids in mammals. In Arabidopsis thaliana, a single-copy gene encoding a protein homologous to CENP-C has been found by homology in the whole-genome sequence. To investigate the CENP-C homolog (AtCENP-C), we cloned cDNAs by RT-PCR and determined its full-length coding sequence. Antibodies against the synthetic peptide for the C-terminal residues of AtCENP-C detected a polypeptide in Arabidopsis cell extracts on western blots. Immunofluorescence labeling with the antibodies and fluorescence in situ hybridization demonstrated clearly that AtCENP-C is present at the centromeric regions throughout the cell cycle.