Methylation Pattern of Radish (<i>Raphanus sativus</i>) Nuclear Ribosomal RNA Genes

Delseny, Michel; Laroche, Monique; Penon, Paul

doi:10.1104/pp.76.3.627

Cited by 35 publications

(21 citation statements)

References 14 publications

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“…This phenomenon cannot be attributed to the differences in methylation of coding regions of rDNA, because Southern hybridization does not reveal any differences in this respect among the organs studied. Similar results have been obtained in Raphanus sativus (Delseny, Laroche & Penon, 1984).…”

Section: Discussionsupporting

confidence: 93%

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DNA content, interphase AgNOR-area, number of3HrDNA hybridization signals and the methylation level in coding rDNA sequence in different organs ofLupinus luteus L.

Sakowicz¹,

Olszewska²

1997

Genetica

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Nuclear DNA and AgNOR-area quantity have been measured cytophotometrically, the number of silver grains after in situ 3H rDNA/DNA hybridization has been counted, and the level of rDNA methylation has been estimated in root meristems, differentiated root zones, hypocotyls, cotyledons, and leaves of 7-day-old seedlings of Lupinus luteus. DNA content increases by endoreplication, reaching the average DNA C-value of 4.2 in the meristem, 6.6C in hypocotyl, 15.9C in cotyledon, and 3.3C in leaf. The quantity of AgNOR-area, the highest in root meristem, does not follow DNA C-value. Number of grains after in situ 3H rDNA/DNA hybridization corresponds to DNA amount, but their distribution differs, showing in many cases perinucleolar localization in organs displaying low AgNOR-area quantity. Southern hybridization has not demonstrated detectable changes in level rDNA methylation. We suggest that the low level of rDNA expression in non-meristematic tissues could be related to rDNA inactivation caused by its translocation into nucleolus-associated heterochromatin.

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Section: Discussionsupporting

confidence: 93%

“…Thompson et al, 1988). On the other hand, in Raphanus sativus, discrete changes in the methylation pattern of rDNA depending on the development stage cannot be correlated with transcriptional activity (Delseny, Laroche & Penon, 1984).…”

Section: Introductionmentioning

confidence: 99%

DNA content, interphase AgNOR-area, number of3HrDNA hybridization signals and the methylation level in coding rDNA sequence in different organs ofLupinus luteus L.

Sakowicz¹,

Olszewska²

1997

Genetica

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“…A DNA methyltransferase was characterized in the green algae, Chlumydomonus reinhardii [7, algae have low msCyt content, like other lower eukaryotes and animal cells, the algal enzyme may not be truly representative for the plant kingdom. In higher plants the distribution of methylcytosines in the genome has been analyzed in cotton [9], tobacco [lo, 111, melon and cucumber [12, 131, radish [14], flax [15], rice [16], wheat [ll] and the bluebell (Scilla sp.) [17].…”

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confidence: 99%

DNA methylation in wheat

Theiss

Schleicher

Schimpff-Weiland

et al. 1987

European Journal of Biochemistry

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The origin and function of the large amount of 5-methylcytosine in plant DNA is not well understood. As a tool for in vitro studies of methylcytosine formation in plants we have isolated and characterized the DNA methyltransferase present in germinating wheat embryo. An enzyme fraction enriched 300-fold over the tissue homogenate was obtained by salt extraction of nuclei, chromatography on DEAE-cellulose, Sephadex (3-75, blue Sepharose and on DNA immobilized on cellulose. It catalyzes the methylation of cytosine residues in doublestranded DNAs isolated from wheat, maize, calf thymus or bacteria using S-adenosylmethionine as methyl donor. The efficient methylation of both an unmethylated plasmid DNA and its hemimethylated derivative indicate that the wheat DNA methylase can function de now and in maintenance methylation. A relative molecular mass of 50000 -55 000 was estimated by gel permeation chromatography and sucrose density gradient centrifugation. Polyacrylamide gel electrophoresis showed the presence of a protein of M , = 50000 and one other componentThe preference for endogenous, double-stranded DNA as substrate and the lower molecular mass distinguish wheat DNA methyltransferase from the DNA methylases obtained from mammalian sources. The properties of the wheat enzyme resemble, however, those of the DNA methylase isolated from the alga Chlamydomonas reinhardii, suggesting that plant cells possess their own type of DNA methyltransferase for the biosynthesis of their high methylcytosine content in DNA. ( M , = 35000).Plant DNA is distinguished from the DNA of all other organisms by its substantial content of the modified base, 5-methylcytosine, which can constitute up to 8 mo1/100 mol of the total base composition, or one-third of all cytosine residues [l, 21. The origin and functions of this high level of DNA methylation in plants are unknown. Vertebrates have much lower proportions of their cytosine residues in DNA methylated (approximately 0.9 mo1/100 mol). Here, changes in methylation are involved in the control of gene expression during development and cell differentiation, with a general correlation between undermethylation in active gene sequences and full methylation in non-transcribed regions [3, 41. Whether a similar signal function occurs in plant tissues is not well established; the above correlation seems to hold for zein genes, but not for the alcohol dehydrogenase gene of maize [5, 61. In any event it is difficult to conceive that the entire amount of msCyt in plants takes part in control mechanisms.In spite of the abundance of 5-methylcytosine in plants, its biosynthesis has not received much attention. A DNA methyltransferase was characterized in the green algae, Chlumydomonus reinhardii [7, 81 but because the unicellular Correspondence to H . Follmann,

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“…Lilium rDNA, like that of many other plants (4,5,6,7,18,19,22) is heavily methylated. Only two sites were detected using 10 restriction enzymes whose six-base recognition sites contain methylatable CG or CNG, whereas 17 sites were mapped with 10 other enzymes lacking such CG or CNG sequences (Fig.…”

Section: Discussionmentioning

confidence: 99%

An under-methylated region in the spacer of ribosomal RNA genes of Lilium henryi

1986

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Ribosomal RNA genes of Lilium henryi are almost completely methylated at CG and CNG sequences. A short under-methylated region was detected between 2.05 and 2.4 kbp upstream of the 18S sequences. It included the only sites of digestion by four methylation-sensitive restriction endonucleases - PstI, Hae II, Eco RII and Hpa II. Only about 15%-20% of rDNA repeats from shoot meristem are susceptible to each of the enzymes. The same repeats are apparently cut by all enzymes and occur in contiguous blocks. Because the region involved is likely to include regulatory sequences it may be that under-methylation occurs specifically in active rDNA repeats. To test this, rDNA was examined from pollen mother cells at pachytene where transcription has fallen to near zero. Under-methylation levels here were similar to those in shoot meristem tissue. Thus methylation of this region is not the agent responsible for rDNA gene inactivation in pachytene cells and it does not occur immediately genes become inactive. Even so, sequences in this region might be prevented from becoming methylated in transcribing repeats.

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Methylation Pattern of Radish (Raphanus sativus) Nuclear Ribosomal RNA Genes

Cited by 35 publications

References 14 publications

DNA content, interphase AgNOR-area, number of3HrDNA hybridization signals and the methylation level in coding rDNA sequence in different organs ofLupinus luteus L.

DNA content, interphase AgNOR-area, number of3HrDNA hybridization signals and the methylation level in coding rDNA sequence in different organs ofLupinus luteus L.

DNA methylation in wheat

An under-methylated region in the spacer of ribosomal RNA genes of Lilium henryi

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