Characterization of the Nicotiana tabacum L. genome by molecular cytogenetics

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. sylvestris. 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.

Isolation and characterization of a microspore-specific gene from tobacco

“…Nicotiana sylvestris is accepted as an ancestor, but for the second ancestor N. tomentosiformis and N. otophora are candidates [14,37].…”

“…Two periods of temporal gene expression are defined in pollen development by Mascarenhas [20]. The early developmental stage starts after meiosis and ends with the microspore mitosis, the late stage covers the period after mitosis up to mature pollen [ 14]. During pollen development the mRNA content present in different stages changes qualitatively [27].…”

Telomerase activity in plant cells

“…Fax: (42) (5) 41211293. E-mail: fajkus@zoncna.ibp.cz 5'(TTTAGGG) 3' was first characterized in Arabidopsis thaliana [8] and was subsequently found at chromosome ends in several other plant species including Nicotiana tabacum and related species [9,10]. Each of the Nicotiana species studied shows a specific pattern of terminal restriction fragments, reflecting distinct telomere lengths in individual chromosomes [11].…”

Research advances in animal distant hybridization

“…Genome structural changes may include deletion, insertion, duplication, translocation, and transposition events [86]. Through the use of chromosome-specific fluorescent in situ hybridi-zation (FISH) markers, at least nine reciprocal translocations have been detected in tetraploid Nicotiana tabacum, confirming that most tobacco chromosomes are associated with one of the two parental genomes [88]. Based on whole-genome in situ hybridization analysis, five reciprocal translocations have been found within the tetraploid Avena sativa genome, with as many as 18 detected in hexaploid Avena sativa [89].…”