Article

Molecular and General Genetics MGG

, Volume 240, Issue 2, pp 159-169

First online:

Characterization of the Nicotiana tabacum L. genome by molecular cytogenetics

  • Ann KentonAffiliated withJodrell Laboratory, Royal Botanic Gardens
  • , Alex S. ParokonnyAffiliated withJodrell Laboratory, Royal Botanic GardensInstitute of Cell Biology and Genetic Engineering, Ukrainian Academy of Sciences
  • , Yuri Y. GlebaAffiliated withJodrell Laboratory, Royal Botanic Gardens
  • , Michael D. BennettAffiliated withJodrell Laboratory, Royal Botanic Gardens

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Abstract

Nicotiana tabacum (2n=48) is a natural amphidiploid with component genomes S and T. We used non-radioactive in situ hybridization to provide physical chromosome markers for N. tabacum, and to determine the extant species most similar to the S and T genomes. Chromosomes of the S genome hybridized strongly to biotinylated total DNA from N. sylvestris, and showed the same physical localization of a tandemly repeated DNA sequence, HRS 60.1, confirming the close relationship between the S genome and N. sylvesfris. Results of dot blot and in situ hybridizations of N. tabacum DNA to biotinylated total genomic DNA from N. tomentosiformis and N. otophora suggested that the T genome may derive from an introgressive hybrid between these two species. Moreover, a comparison of nucleolus-organizing chromosomes revealed that the nucleolus organizer region (NOR) most strongly expressed in N. tabacum had a very similar counterpart in N. otophora. Three different N. tabacum genotypes each had up to 9 homozygous translocations between chromosomes of the S and T genomes. Such translocations, which were either unilateral or reciprocal, demonstrate that intergenomic transfer of DNA has occurred in the amphidiploid, possibly accounting for some results of previous genetic and molecular analyses. Molecular cytogenetics of N. tabacum has identified new chromosome markers, providing a basis for physical gene mapping and showing that the amphidiploid genome has diverged structurally from its ancestral components.

Key words

Nicotiana tabacum Amphidiploid-Molecular cytogenetics Intergenomic translocations Phylogeny