A single-strand-specific chemical probe, potassium permanganate (KMnO4), was used to study the sequence-dependent conformation periodicity of tandem multicopy repetitive DNA sequences HRS60 and GRS (Nicotiana Species) at the level of single base pair and dinucleotide step. Local DNA structures, sensitive to KMnO4, revealed periodicity of 182 +/- 2 bp, equal to the length of repeat units. Permanganate-sensitive local structures were mapped to both DNA strands of genomic HRS60 sequences and were found to be linked to d(A)n tracts. These adenine tracts are located in the proximity of the intrinsically curved domains. Distamycin A increased reactivity of the DNA but decreased the specificity of DNA cleavage. Similar conformation periodicity has been detected also in the 'canrep' family of repeats (Brassica species). All studied repetitive sequences are predominantly located in the constitutive heterochromatin. We discuss the role of conformation periodicities in relation to a structural code for nucleosome phasing at tandem arrays of DNA repeats.

• MeSH
• Brassica genetics   MeSH
• Distamycins MeSH
• DNA Primers genetics   MeSH
• DNA, Plant chemistry   genetics   MeSH
• Plants, Toxic MeSH
• Nucleic Acid Conformation * MeSH
• Potassium Permanganate MeSH
• Chromosome Mapping MeSH
• Molecular Sequence Data MeSH
• Molecular Probes MeSH
• Polymorphism, Genetic MeSH
• Repetitive Sequences, Nucleic Acid * MeSH
• Base Sequence MeSH
• Nicotiana genetics   MeSH
• Binding Sites MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Distamycins MeSH
• DNA Primers MeSH
• DNA, Plant MeSH
• Potassium Permanganate MeSH
• Molecular Probes MeSH
• stallimycin MeSH Browser

Melandrium album (syn. Silene latifolia) is a model dioecious species in which the Y chromosome, present only in heterogametic males, plays both a male-determining and a strict female-suppressing role. We showed that treatment with 5-azacytidine (5-azaC) induces a sex change to androhermaphroditism (an-dromonoecy) in about 21% of male plants, while no apparent phenotypic effect was observed in females. All of these bisexual androhermaphrodites (with the standard male 24, AA + XY karyotype) were mosaics possessing both male and hermaphrodite flowers and, moreover, the hermaphrodite flowers displayed various degrees of gynoecium development and seed setting. Southern hybridization analysis with a repetitive DNA probe showed that the 5-azacytidine-treated plants were significantly hypomethylated in CG doubles, but only to a minor degree in CNG triplets. The bisexual trait was transmitted to two successive generations, but only when androhermaphrodite plants were used as pollen donors. The sex reversal was inherited with incomplete penetrance and varying expressivity. Based on the uniparental inheritance pattern of androhermaphroditism we conclude that it originated either by 5-azaC induced inhibition of Y-linked female-suppressing genes or by a heritable activation of autosomal female-determining/promoting genes which can be reversed, on passage through female meiosis, by a genomic imprinting mechanism. The data presented indicate that female sex suppression in M. album XY males is dependent on methylation of specific DNA sequences and can be heritably modified by hypomethylating drugs.

• MeSH
• Azacitidine pharmacology   MeSH
• DNA, Plant metabolism   MeSH
• Phenotype MeSH
• Methylation MeSH
• Gene Expression Regulation, Plant physiology   MeSH
• Plants genetics   metabolism   MeSH
• Reproduction MeSH
• Plant Development MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Azacitidine MeSH
• DNA, Plant MeSH

We have recently shown that hypomethylation of cytosine residues in the HRS60 family of repetitive DNA sequences can be induced with 5-azacytidine (5-azaC) in tobacco tissue cultures. We have also proven that such a DNA methylation status is maintained during the recovery of protoplasts, plant regeneration, and vegetative development. In the present paper we follow meiotic transmission of hypomethylated HRS60 DNA. Plants obtained from seeds treated with 5-azaC were either self pollinated or crossed with a non-treated control in a reciprocal way. Analysis of the methylation status of the HRS60 DNA revealed that these sequences were hypomethylated in the progenies up to the extent found in the parental 5-azaC-treated plant. Since no parent-of-origin effect was observed, we presume that both male and female gametes transmit an artificial methylation imprint to a similar extent. This result is supported by methylcytosine evaluation in the total genomic DNA samples. A temporal analysis of 5-azaC effects on germinating seeds and a phenotypic evaluation of 5-azaC-treated tobacco plants are also presented.

• Publication type
• Journal Article MeSH

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.

• MeSH
• Chromatin MeSH
• DNA, Plant analysis   genetics   metabolism   MeSH
• Species Specificity MeSH
• Genome, Plant MeSH
• Plants, Toxic * MeSH
• Cloning, Molecular MeSH
• Methylation MeSH
• Molecular Sequence Data MeSH
• Nucleosomes MeSH
• Polymorphism, Restriction Fragment Length MeSH
• Repetitive Sequences, Nucleic Acid genetics   MeSH
• Base Sequence MeSH
• Sequence Analysis, DNA MeSH
• Sequence Alignment MeSH
• Nicotiana genetics   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Chromatin MeSH
• DNA, Plant MeSH
• Nucleosomes MeSH