RNR1, a 3′–5′ exoribonuclease belonging to the RNR superfamily, catalyzes 3′ maturation of chloroplast ribosomal RNAs in Arabidopsis thaliana

Arabidopsis thaliana chloroplasts contain at least two 3′ to 5′ exoribonucleases, polynucleotide phosphorylase (PNPase) and an RNase R homolog (RNR1). PNPase has been implicated in both mRNA and 23S rRNA 3′ processing. However, the observed maturation defects do not affect chloroplast translation, suggesting that the overall role of PNPase in maturation of chloroplast rRNA is not essential. Here, we show that this role can be largely ascribed to RNR1, for which homozygous mutants germinate only on sucrose-containing media, and have white cotyledons and pale green rosette leaves. Accumulation of chloroplast-encoded mRNAs and tRNAs is unaffected in such mutants, suggesting that RNR1 activity is either unnecessary or redundant for their processing and turnover. However, accumulation of several chloroplast rRNA species is severely affected. High-resolution RNA gel blot analysis, and mapping of 5′ and 3′ ends, revealed that RNR1 is involved in the maturation of 23S, 16S and 5S rRNAs. The 3′ extensions of the accumulating 5S rRNA precursors can be efficiently removed in vitro by purified RNR1, consistent with this view. Our data suggest that decreased accumulation of mature chloroplast ribosomal RNAs leads to a reduction in the number of translating ribosomes, ultimately compromising chloroplast protein abundance and thus plant growth and development

Formation of large viroplasms and virulence of Cauliflower mosaic virus in turnip plants depend on the N-terminal EKI sequence of viral protein TAV

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Virus preparations from the mixed-infected P70 Pinot Noir accession exhibit GLRaV-1/GVA ‘end-to-end’ particles

P70 is a Pinot Noir grapevine accession that displays strong leafroll disease symptoms. A high-throughput sequencing (HTS)-based analysis established that P70 was mixed-infected by two variants of grapevine leafroll-associated virus 1 (GLRaV-1, genus Ampelovirus) and one of grapevine virus A (GVA, genus Vitivirus) as well as by two viroids (hop stunt viroid [HSVd] and grapevine yellow speckle viroid 1 [GYSVd1]) and four variants of grapevine rupestris stem pitting-associated virus (GRSPaV). Immunogold labelling using gold particles of two different diameters revealed the existence of ‘hybrid’ particles labelled at one end as GLRaV-1, with the rest labelled as GVA. In this work, we suggest that immunogold labelling can provide information about the biology of the viruses, going deeper than just genomic information provided by HTS, from which no recombinant or ‘chimeric’ GLRaV-1/GVA sequences had been identified in the dataset. Our observations suggest an unknown interaction between members of two different viral species that are often encountered together in a single grapevine, highlighting potential consequences in the vector biology and epidemiology of leafroll and rugose-wood diseases

Antagonism between DNA and H3K27 Methylation at the Imprinted Rasgrf1 Locus

At the imprinted Rasgrf1 locus in mouse, a cis-acting sequence controls DNA methylation at a differentially methylated domain (DMD). While characterizing epigenetic marks over the DMD, we observed that DNA and H3K27 trimethylation are mutually exclusive, with DNA and H3K27 methylation limited to the paternal and maternal sequences, respectively. The mutual exclusion arises because one mark prevents placement of the other. We demonstrated this in five ways: using 5-azacytidine treatments and mutations at the endogenous locus that disrupt DNA methylation; using a transgenic model in which the maternal DMD inappropriately acquired DNA methylation; and by analyzing materials from cells and embryos lacking SUZ12 and YY1. SUZ12 is part of the PRC2 complex, which is needed for placing H3K27me3, and YY1 recruits PRC2 to sites of action. Results from each experimental system consistently demonstrated antagonism between H3K27me3 and DNA methylation. When DNA methylation was lost, H3K27me3 encroached into sites where it had not been before; inappropriate acquisition of DNA methylation excluded normal placement of H3K27me3, and loss of factors needed for H3K27 methylation enabled DNA methylation to appear where it had been excluded. These data reveal the previously unknown antagonism between H3K27 and DNA methylation and identify a means by which epigenetic states may change during disease and development

Structure, Function, and Evolution of the Thiomonas spp. Genome

Bacteria of the Thiomonas genus are ubiquitous in extreme environments, such as arsenic-rich acid mine drainage (AMD). The genome of one of these strains, Thiomonas sp. 3As, was sequenced, annotated, and examined, revealing specific adaptations allowing this bacterium to survive and grow in its highly toxic environment. In order to explore genomic diversity as well as genetic evolution in Thiomonas spp., a comparative genomic hybridization (CGH) approach was used on eight different strains of the Thiomonas genus, including five strains of the same species. Our results suggest that the Thiomonas genome has evolved through the gain or loss of genomic islands and that this evolution is influenced by the specific environmental conditions in which the strains live

ETUDE DES PROTEINES DE MOUVEMENT DE DEUX PHYTOVIRUS A RNA, LE PCV ET LE BNYVV (LOCALISATION IN SITU DES PROTEINES DE MOUVEMENT ET MISE EN EVIDENCE D'INTERACTIONS SPECIFIQUES ENTRE CES PROTEINES VIRALES)

STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

In situ localization of micropollutants and associated stress response in Populus nigra leaves

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