A BamHI family of highly repeated DNA sequences of Nicotiana tabacum

Abstract

HRS60.1, a monomer unit (184 bp) of a highly repeated nuclear DNA sequence of Nicotiana tabacum, has been cloned and sequenced. Following BamHI digestion of tobacco DNA, Southern hybridization with HRS60.1 revealed a ladder of hybridization bands corresponding to multiples of the basic monomer unit. If the tobacco DNA was digested with restriction endonucleases which have no target site in HRS60.1, the larger part of DNA homologous to HRS60.1 remained as uncleaved "relic" DNA. These results suggest a tandem arrangement of this DNA repeat unit. Four other clones of tobacco nuclear DNA cross-hybridized with HRS60.1, thus forming a "HRS60-family". Sequencing their inserts has shown their strong mutual homology. HRS60-family comprised about 2% of the nuclear genome of N. tabacum. Computer comparisons with other tandem plant-repeated DNA sequences could not detect any other homologous sequence.

Hypomethylation of CNG targets induced with dihydroxypropyladenine is rapidly reversed in the course of mitotic cell division in tobacco

“…The overall density of CG and CCG methylation along the repeats can be approximately estimated from the sequence. Within the 182-bp to 184-bp HRS60 monomeric unit 10-11 CG dinucleotides and two to three CCG trinucleotides occur (Koukalova et al 1989). DHPA treatment reduces CCG methylation to almost zero ( Fig.…”

“…The cloned tobacco DNA repeats, HRS60 (Koukalova et al 1989), NTRS (Matyasek et al 1997), 5S rDNA (Fulnecek et al 1998) and GRD5 (Bejarano et al 1996) were used as probes. The subtelomeric HRS60 and intercalary NTRS satellites comprise about 2% and 0.2% of the tobacco genome, respectively; there are about 2,000 copies of 5S rDNA and about 100 copies of endogenous geminiviral GRD5 sequences in the genome.…”

Molecular cytogenetics and tandem repeat sequence evolution in the allopolyploid <i>Nicotiana rustica</i> compared with diploid progenitors <i>N. paniculata</i> and <i>N. undulata</i>

“…Each is a predominantly subtelomeric repeat and are members of a divergent family of Nicotiana repeats called here the HRS60 family of repeats after the first member that was described (Koukalova et al, 1989). Individual sections have derivatives of the HRS60 family which are characteristic, i.e.…”

“…Individual sections have derivatives of the HRS60 family which are characteristic, i.e. sections Tomentosae and Nicotiana -GRS ; section Alatae -NP4R3 (Chen et al, 1997); sections Alatae and Nicotiana -HRS60 (Koukalova et al, 1989); sections Paniculatae and Rusticae -NPAMBO and NPAMBE (isolated here). Clearly the speed of divergence of these repeats is equal to, or greater than, the speed of divergence of Nicotiana sections since individual family members seem to be species or Nicotiana section specific.…”

“…the HRS6O family after the first member HRS60 to be isolated form N. tabacum (Koukalova et al, 1989), the other family members being GRS and NTREECO (Suter-Crazzolara et al, 1995) sequences isolated from N. tomentosiformis, and NP4R/3R sequences (Chen et al, 1997) isolated from N. plumbaginifolia (Table 1). The members of HRS60 family are clearly diverged from the subtelomeric satellite (LESAT) of tomato.…”