Delayed activation of post-transcriptional gene silencing and de novo transgene methylation in plants with the coat protein gene of sweet potato feathery mottle potyvirus

DNA cytosine methylation is one of the main epigenetic mechanisms in higher eukaryotes and is considered to play a key role in transcriptional gene silencing. In plants, cytosine methylation can occur in all sequence contexts (CG, CHG, and CHH), and its levels are controlled by multiple pathways, including de novo methylation, maintenance methylation, and demethylation. Modulation of DNA methylation represents a potentially robust mechanism to adjust gene expression following exposure to different stresses. However, the potential involvement of epigenetics in plant-virus interactions has been scarcely explored, especially with regard to RNA viruses. Here, we studied the impact of a symptomless viral infection on the epigenetic status of the host genome. We focused our attention on the interaction between Nicotiana benthamiana and Pelargonium line pattern virus (PLPV, family Tombusviridae), and analyzed cytosine methylation in the repetitive genomic element corresponding to ribosomal DNA (rDNA). Through a combination of bisulfite sequencing and RT-qPCR, we obtained data showing that PLPV infection gives rise to a reduction in methylation at CG sites of the rDNA promoter. Such a reduction correlated with an increase and decrease, respectively, in the expression levels of some key demethylases and of MET1, the DNA methyltransferase responsible for the maintenance of CG methylation. Hypomethylation of rDNA promoter was associated with a five-fold augmentation of rRNA precursor levels. The PLPV protein p37, reported as a suppressor of post-transcriptional gene silencing, did not lead to the same effects when expressed alone and, thus, it is unlikely to act as suppressor of transcriptional gene silencing. Collectively, the results suggest that PLPV infection as a whole is able to modulate host transcriptional activity through changes in the cytosine methylation pattern arising from misregulation of methyltransferases/demethylases balance.

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Post-transcriptional gene silencing triggers dispensable DNA methylation in gene body in Arabidopsis

Nucleic Acids Research ◽

10.1093/nar/gkz636 ◽

2019 ◽

Vol 47 (17) ◽

pp. 9104-9114 ◽

Cited By ~ 3

Author(s):

Christelle Taochy ◽

Agnès Yu ◽

Nicolas Bouché ◽

Nathalie Bouteiller ◽

Taline Elmayan ◽

...

Keyword(s):

Dna Methylation ◽

Gene Silencing ◽

De Novo ◽

Transcriptional Silencing ◽

Transcriptional Gene Silencing ◽

Gene Body ◽

Coding Sequence ◽

Post Transcriptional Gene Silencing ◽

Methylation Signal ◽

Rule Out

Abstract Spontaneous post-transcriptional silencing of sense transgenes (S-PTGS) is established in each generation and is accompanied by DNA methylation, but the pathway of PTGS-dependent DNA methylation is unknown and so is its role. Here we show that CHH and CHG methylation coincides spatially and temporally with RDR6-dependent products derived from the central and 3′ regions of the coding sequence, and requires the components of the RNA-directed DNA methylation (RdDM) pathway NRPE1, DRD1 and DRM2, but not CLSY1, NRPD1, RDR2 or DCL3, suggesting that RDR6-dependent products, namely long dsRNAs and/or siRNAs, trigger PTGS-dependent DNA methylation. Nevertheless, none of these RdDM components are required to establish S-PTGS or produce a systemic silencing signal. Moreover, preventing de novo DNA methylation in non-silenced transgenic tissues grafted onto homologous silenced tissues does not inhibit the triggering of PTGS. Overall, these data indicate that gene body DNA methylation is a consequence, not a cause, of PTGS, and rule out the hypothesis that a PTGS-associated DNA methylation signal is transmitted independent of a PTGS signal.

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Identification of the Coat Protein Gene of a Sweet Potato Sunken Vein Closterovirus Isolate from Kenya and Evidence for a Serological Relationship Among Geographically Diverse Closterovirus Isolates from Sweet Potato

Phytopathology ◽

10.1094/phyto-86-744 ◽

1996 ◽

Vol 86 (7) ◽

pp. 744 ◽

Cited By ~ 45

Author(s):

Ute Hoyer

Keyword(s):

Coat Protein ◽

Sweet Potato ◽

Coat Protein Gene ◽

Protein Gene ◽

Serological Relationship

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Homology-Dependent Virus Resistance in Transgenic Plants with the Coat Protein Gene of Sweet Potato Feathery Mottle Potyvirus: Target Specificity and Transgene Methylation

Phytopathology ◽

10.1094/phyto.1999.89.5.385 ◽

1999 ◽

Vol 89 (5) ◽

pp. 385-391 ◽

Cited By ~ 26

Author(s):

S. Sonoda ◽

M. Mori ◽

M. Nishiguchi

Keyword(s):

Coat Protein ◽

Sweet Potato ◽

Virus Resistance ◽

Potato Virus X ◽

Transcriptional Gene Silencing ◽

Target Specificity ◽

Post Transcriptional Gene Silencing ◽

Resistant Lines ◽

Nontranslated Region ◽

Transgenic Lines

Nicotiana benthamiana plants were transformed with the coat protein (CP) coding sequence and the 3′ nontranslated region (NTR) of the severe strain of sweet potato feathery mottle potyvirus (SPFMV-S). Regenerated lines were screened for virus resistance using recombinant potato virus X (PVX) engineered to contain the sequence homologous to the transgene. Out of 19 transgenic lines, 7 showed virus resistance after inoculation by the recombinant PVX. In most of the resistant lines, relatively low steady-state accumulation of the CP gene mRNA and little or no protein products were observed, suggesting that the resistance was manifested by a post-transcriptional gene-silencing mechanism. The resistant lines could be divided into two groups according to the target specificity of the silencing mechanism; one group recognizing the 3′ part of the transgene mRNA and the other not only the 3′ part, but also the 5′ and the central part of the transgene mRNA. Particular regions of the transgene corresponding to the RNA target in the resistant lines were differentially methylated compared with the transgene sequence in a susceptible line.

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Virus-Induced Gene Silencing in Transgenic Plants Expressing the Minor Capsid Protein of Beet western yellows virus

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2002.15.8.799 ◽

2002 ◽

Vol 15 (8) ◽

pp. 799-807 ◽

Cited By ~ 6

Author(s):

V. Brault ◽

S. Pfeffer ◽

M. Erdinger ◽

J. Mutterer ◽

V. Ziegler-Graff

Keyword(s):

Coat Protein ◽

Gene Silencing ◽

Nicotiana Benthamiana ◽

Transcriptional Gene Silencing ◽

Virus Induced Gene Silencing ◽

Minor Capsid Protein ◽

Beet Western Yellows Virus ◽

Post Transcriptional Gene Silencing ◽

Low Levels ◽

Minor Coat Protein

Transgenic Nicotiana benthamiana expressing the minor coat protein P74 of the phloem-limited Beet western yellows virus (BWYV) exhibited an unusual spatial pattern of post-transcriptional gene silencing (PTGS) when infected with BWYV or related viruses. Following infection, transgenic P74 and its mRNA accumulated to only low levels, 21 to 23 nucleotide RNAs homologous to the transgene appeared, and the transgene DNA underwent methylation. The infecting viral RNA, however, was not subject to significant silencing but multiplied readily and produced P74 in the phloem tissues, although the P74 encoded by the transgene disappeared from the phloem as well as the nonvascular tissues.

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