Theoretical and Applied Genetics

, Volume 91, Issue 6–7, pp 928–935

The molecular cytogenetics of Vigna unguiculata (L.) Walp: the physical organization and characterization of 18s-5.8s-25s rRNA genes, 5s rRNA genes, telomere-like sequences, and a family of centromeric repetitive DNA sequences

  • I. Galasso
  • T. Schmidt
  • D. Pignone
  • J. S. Heslop-Harrison
Article

DOI: 10.1007/BF00223902

Cite this article as:
Galasso, I., Schmidt, T., Pignone, D. et al. Theoret. Appl. Genetics (1995) 91: 928. doi:10.1007/BF00223902

Abstract

A knowledge of genome organization is important for understanding how genomes function and evolve, and provide information likely to be useful in plant breeding programmes involving hybridization and genetic manipulation. Molecular techniques, including in situ hybridization, molecular cloning and DNA sequencing, are proving valuable tools to investigate the structure, organization, and diversity of chromosomes in agricultural crops. Heterologous labelled 18 s-5.8 s-25 s (pTa71) and 5 s rDNAs (pTa794) were used for in situ hybridization on Vigna unguiculata (L.) Walp. chromosomes. Hybridization with 18 s-5.8 s-25 s rRNA gene probes occurred at the same chromosomal sites which were positive to the CMA fluorochrome. Silver staining of nucleolar-organizing regions indicated that all the rDNA sites detected using the 18 s-5.8 s-25 s rRNA gene probe possessed active genes. Degenerate telomeric repeats gave hybridization signals at the telomeres of most chromosomes and no intercalary sites were detected at metaphase; the sequences appear to have no preferential distribution in interphase nuclei. A repetitive DraI family from V. unguiculata was cloned (pVuKB1) and characterized. The DraI repeat is 488 nucleotides long, AT rich (74%), and hybridized on all chromosomes in the centromeric areas. The presence of this sequence family was investigated by Southern hybridization in different Vigna species and other Leguminoseae. It was only detected in V. unguiculata, and hence represents a species-specific DNA sequence.

Key words

rDNA sites Centromeric repetitive DNA Telomere In situ hybridization Southern hybridization Ag-NOR Cowpea Physical maps 

Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • I. Galasso
    • 1
  • T. Schmidt
    • 2
  • D. Pignone
    • 1
  • J. S. Heslop-Harrison
    • 2
  1. 1.Istituto del Germoplasma, CNRBariItaly
  2. 2.Karyobiology Group, Department of Cell BiologyJohn Innes CentreNorwichUK

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