Characterization of a new family of tobacco highly repetitive DNA, GRS, specific for theNicotiana tomentosiformis genomic component

Abstract

Members of a new family of highly repetitive DNA sequences called GRS were isolated from Nicotiana tabacum L. genomic DNA and characterized. Cloned, sequenced monomeric units (180-182 bp) of GRS exhibit properties characteristic of molecules that possess a stable curvature. The GRS family represents about 0.15% of total genomic DNA (10(4) copies per haploid genome) and could be derived from either Nicotiana tomentosiformis or Nicotiana otophora, two possible ancestors of the T genome of the amphidiploid N. tabacum. Sequence homology between the HRS60 (Koukalová et al. 1989) and the GRS family has been estimated to be 57%. In situ hybridization was used to localize GRS on mitotic chromosomes. Hybridization signals were obtained on five pairs of chromosomes at intercalary sites of the longer chromosome arms. The majority of GRS sequences appeared to be organized in tandem arrays and a minority were found to be dispersed through the genome in short clusters, interspersed with other types of DNA repeats, including 25S rDNA sequences. Several loci containing both GRS and HRS60 were also found. Such hybrid loci may indicate intergenomic transfer of the DNA in the amphidiploid N. tabacum. GRS sequences, like HRS60 (Fajkus et al. 1992), were found to specify the location of nucleosomes. The position of the nucleosome core has been mapped with respect to a conserved Mbol site in the GRS sequence and an oligo A/T tract is a major centre of the DNA curvature.

Isolation of centromeric-tandem repetitive DNA sequences by chromatin affinity purification using a HaloTag7-fused centromere-specific histone H3 in tobacco

“…Furthermore, six different tandem repetitive DNA sequences were identified (Table 1), and the sizes of the repeat units ranged from 48 to 180 bp ( Table 1). Two of the sequences, HT1B11 and HT3E06, were similar to sequences reported previously as ''GRS'' (Gazdova et al 1995) and ''NTS9'' (Jakowitsch et al 1998), respectively. However, chromosomal locations of the GRS and NTS9 Fig.…”

“…The immunosignals are indicated by red in the merged image. Scale bar 10 lm have been reported as on chromosome arms and pericentric, respectively (Gazdova et al 1995, Jakowitsch et al 1998. The other sequences showed no homology to the sequences in GenBank.…”

Sequence homogenization and chromosomal localization of VicTR-B satellites differ between closely related Vicia species

“…It has been pointed out by several authors that this size corresponds to the length of DNA wrapped around a nucleosome particle (Kubis et al 1998;Schmidt and Heslop-Harrison 1998). Nucleosome phasing has been reported for some plant satellites (Gazdová et al 1995;Matyášek et al 1997;Vershinin and Heslop-Harrison 1998), suggesting that nucleosome positioning at certain sequences could provide a constraint for their recombination, which is one of the key processes in satellite repeat evolution (Stephan 1989;Stephan and Cho 1994). However, the occurrence of nucleosome phasing and its exact role in satDNA evolution requires further investigation in a wider range of repeat families, including VicTR-B repeats of Vicia.…”

Molecular cytogenetic analyses and phylogenetic studies in the Nicotiana section Tomentosae

“…The individual monomeric members of the GRS family display the highest sequence heterogeneity (~ 80%, Gazdova et al 1995) compared with the other tobacco repeats, e.g. HRS60 (92%, Koukalová et al 1989) or NTRS (89%, Matyášek et al 1997).…”