CG and CNG methyltransferases in plants

Pradhan, Sriharsa; Houlston, Claire E.; Cummings, Michele; Adams, Roger

doi:10.1016/0378-1119(95)00076-i

Cited by 5 publications

(3 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The different types of methylation in plant genomes and the requirement for both de novo and maintenance activities are consistent with the discovery of multiple forms of plant methyltransferase. Biochemical analysis revealed that CpG and CpNpG methylation are controlled by distinct methyltransferase activities in pea (Pradhan et al 1995). All DNA methyltransferases are related to the bacterial enzymes that play a key role in the host defense system.…”

Section: Dna Methylationmentioning

confidence: 99%

Remembrance of Things Past: Chromatin Remodeling in Plant Development

Goodrich

Tweedie

2002

Annu. Rev. Cell Dev. Biol.

View full text Add to dashboard Cite

Chromatin remodeling in plants has usually been discussed in relation to aspects of genome defense such as transgene silencing and the resetting of transposon activity. The role of remodeling in controlling development has been less emphasized, although well established in animal systems. This is because cell fate in plants is often held to be entirely specified on the basis of position, apparently excluding any significant role for cell ancestry and chromatin remodeling. We argue that chromatin remodeling is used to confer mitotically heritable cell fates at late stages in pattern formation. Several examples in which chromatin remodeling factors are used to confer a memory of transient events in plant development are discussed. Because the precise biochemical functions of most remodeling factors are obscure, and little is known of plant chromatin structure, the underlying mechanisms remain poorly understood.

show abstract

Section: Dna Methylationmentioning

confidence: 99%

Remembrance of Things Past: Chromatin Remodeling in Plant Development

Goodrich

Tweedie

2002

Annu. Rev. Cell Dev. Biol.

View full text Add to dashboard Cite

show abstract

“…Transformation of Arabidopsis with a construct that produces an antisense RNA to the known MET-1 MTase resulted in decreased methylation of CpG and CpCpG sequences, but had little effect on methylation of CpWpG (where W is A or T) sequences [32], Biochemical evidence from Pisum sativum also suggests the existence of two different enzymes, one that methylates CpG and one that methylates CpWpG [84]. A single MTase gene has been cloned from pea and charaterization of this protein indicates a Dnmtl family MTase with 65% identity to Arabidopsis MET-1 and a target specificity for both CpG and CpWpG sequences, which could account for the biochemical activity previously identified [83].…”

Section: 2mentioning

confidence: 99%

Eukaryotic Dna Methyltransferases

Vertino¹

1999

S-Adenosylmethionine-Dependent Methyltransferases

View full text Add to dashboard Cite

Establishment of genome methylation patternsDNA methylation in eukaryotes is found only at the 5-position of cytosines (5mC). In vertebrates, 3-8% of cytosines are modified and methylation is found almost exclusively in the short canonical sequence 5'-CpG-3' [45]. Plants generally show a greater fraction of methylated cytosines (4-40%) in part due to the additional methylation of 5'-CpNpG-3' (where N is any base) [44. 125]. Methylcytosine is also S-Adenosylmethionine-Dependent Methyltransferases Downloaded from www.worldscientific.com by NANYANG TECHNOLOGICAL UNIVERSITY on 06/10/16. For personal use only. 342 P. M. Vertino found in some, but not all, fungal species and in these organisms levels range from 0.5-2% of cytosines [3]. A few notable eukaryotic species lack detectable methylation including the yeasts Saccharomyces cerevisiae [3] and Schizosaccharomyces pombe [88], the insect Drosophila melongaster [120], and the nematode Caenorhabditis elegans [99]. However, all long-lived multicellular organisms with genomes of greater than 5xl0 8 bp have methylated genomes and for these, methylation appears necessary for normal development.The distribution of methylation and methylatable sites is non-random in the vertebrate genome. CpG sites have been lost from the vertebrate genome over evolutionary time through the deamination of 5mC to thymidine. A small fraction of the genome in which CpG sites are not under represented are known as CpG 'islands'. CpG islands are frequently found near the 5' ends of genes, and whereas the vast majority of CpG sites in the genome are methylated, most CpG islands are completely devoid of methylation even in the germ line [14]. About half of mammalian genes are thought to have associated CpG islands, particularly housekeeping genes, and the unmethylated state is thought to be permissive for transcription [2,14,36]. Exceptions, where CpG islands are in fact methylated, include genes on the inactive X chromosome, and imprinted genes where dense methylation of CpG islands is part of the mechanism that ensures the heritability of a stably silenced state in somatic cells [90,91]. Clusters of unmethylated CpG residues reminiscent of vertebrate CpG islands are also found in the plant genome, although they are not as frequent as in mammalian genomes and not found at all housekeeping genes.In contrast to prokaryotes in which methylation patterns are a simple function of DNA sequence, methylation patterns in eukaryotes must be cued by more complex signals since methylation of a single locus can differ from cell type to cell type and even between alleles within the same nucleus. In mammals, tissuespecific methylation patterns are re-established at each generation by an ill-defined mechanism that involves the demethylation of gamete-specific methylation in the early zygote followed by a de novo process that methylates most of the genome just prior to implantation of the embryo [52]. How this de novo process selects some sequences for methylation while sparing others (for example, CpG islands) i...

show abstract

“…Cytosine-5 DNA methyltransferases (DNA MTases), enzymes capable of transferring a methyl group from S-adenosyl methionine to cytosine residues of the double helix, are found in both prokaryotes and eukaryotes. DNA methylation in animals is generally confined to cytosines in CpG dinucleotides but, in plants, methylation has been observed in both CpG dinucleotides and CpNpG triplets (Pradhan et al 1995).…”

Section: Introductionmentioning

confidence: 99%

Characterization of two rice DNA methyltransferase genes and RNAi-mediated reactivation of a silenced transgene in rice callus

Teerawanichpan

Chandrasekharan

Jiang

et al. 2004

Planta

View full text Add to dashboard Cite

Two genomic clones ( OsMET1-1, AF 462029 and OsMET1-2, TPA BK001405), each encoding a cytosine-5 DNA methyltransferase (MTase), were isolated from rice ( Oryza sativa L.) BAC libraries. OsMET1-1 has an open reading frame of 4,566 nucleotides with 12 exons and 11 introns while OsMET1-2 has an open reading frame of 4,491 nucleotides with 11 exons and 10 introns. Although OsMET1-1 and OsMET1-2 have high sequence similarity overall, they share only 24% identity in exon 1, and intron 3 of OsMET1-1 is absent from OsMET1-2. As for other eukaryotic DNA MTases of the Dnmt1/MET l class, the derived amino acid sequences of OsMET1-1 and OsMET1-2 suggest that they are comprised of two-thirds regulatory domain and one-third catalytic domain. Most functional domains identified for other MTases were present in the rice MET1 sequences. Amino acid sequence comparison indicated high similarity (56-75% identity) of rice MET1 proteins to other plant MET1 sequences but limited similarity (approx. 24% identity) to animal Dnmt1 proteins. Genomic blot and database analysis indicated the presence of a single copy of OsMET1-1 (on chromosome 3) and single copy of OsMET1-2 (on chromosome 7). Ribonuclease protection assays revealed expression of both OsMET1-1 and OsMET1-2 in highly dividing cells, but the steady-state level of OsMET1-2 was 7- to 12-fold higher than that for OsMET1-1 in callus, root and inflorescence. The functional involvement of the rice DNA MTases in gene silencing was investigated using an RNAi strategy. Inverted repeat constructs of either the N- or C-terminal regions of OsMET1-1 were supertransformed into calli derived from a rice line bearing a silenced 35S-uidA-nos transgene. Restoration of uidA expression in the bombarded calli was consistent with the inactivation of maintenance methylation and with previous evidence for the involvement of methylation in silencing of this line.

show abstract

CG and CNG methyltransferases in plants

Cited by 5 publications

References 10 publications

Remembrance of Things Past: Chromatin Remodeling in Plant Development

Remembrance of Things Past: Chromatin Remodeling in Plant Development

Eukaryotic Dna Methyltransferases

Characterization of two rice DNA methyltransferase genes and RNAi-mediated reactivation of a silenced transgene in rice callus

Contact Info

Product

Resources

About