Genetic diversity and silencing suppression effects of Rice yellow mottle virus and the P1 protein

<p>Abstract</p> <p>Background</p> <p>PTGS (post-transcriptional gene silencing) is used to counter pathogenic invasions, particularly viruses. In return, many plant viruses produce proteins which suppress silencing directed against their RNA. The diversity of silencing suppression at the species level in natural hosts is unknown.</p> <p>Results</p> <p>We investigated the functional diversity of silencing suppression among isolates of the African RYMV (<it>Rice yellow mottle virus</it>) in rice. The RYMV-P1 protein is responsible for cell-to-cell movement and is a silencing suppressor. Transgenic <it>gus</it>-silencing rice lines were used to investigate intra-specific and serogroup silencing suppression diversity at two different levels: that of the virion and the P1 silencing suppressor protein. Our data provide evidence that silencing suppression is a universal phenomenon for RYMV species. However, we found considerable diversity in their ability to suppress silencing which was not linked to RYMV phylogeny, or pathogenicity. At the level of the silencing suppressor P1 alone, we found similar results to those previously found at the virion level. In addition, we showed that cell-to-cell movement of P1 was crucial for the efficiency of silencing suppression. Mutagenesis of P1 demonstrated a strong link between some amino acids and silencing suppression features with, one on the hand, the conserved amino acids C95 and C64 involved in cell-to-cell movement and the strength of suppression, respectively, and on the other hand, the non conserved F88 was involved in the strength of silencing suppression.</p> <p>Conclusion</p> <p>We demonstrated that intra-species diversity of silencing suppression is highly variable and by mutagenesis of P1 we established the first link between silencing suppression and genetic diversity. These results are potentially important for understanding virus-host interactions.</p

Emergence of a resistance breaking isolate of Rice yellow mottle virus during serial inoculations is due to a single substitution in the genome-linked viral protein VPg

International audienceThe recessive gene rymv-1 responsible for the high resistance of Oryza sativa cultivar Gigante to Rice yellow mottle virus (Sobemovirus) was overcome by the variant CI4* which emerged after serial inoculations of the non-resistance-breaking (nRB) isolate CI4. By comparison of the full-length sequences of CI4 and CI4*, we identified a non-synonymous mutation at position 1729 localised in the putative VPg domain and developed an assay based on this single nucleotide polymorphism. The mutation G1729T was detected as early as the first passage in resistant plants and was found in all subsequent passages. Neither reversion nor additional mutation were observed. The substitution G1729T introduced by mutagenesis in the VPg of an nRB infectious clone is sufficient to induce symptoms in non-inoculated leaves of cultivar Gigante. This is the first evidence that VPg is a virulence factor in plants with recessive resistance against viruses outside the family Potyviridae

Clinical utility of nuclear imaging in the evaluation of pediatric adrenal neoplasms

Adrenal neoplasms rarely occur in children. They can be diagnosed in the presence of endocrine, metabolic or neurological problems, an abdominal mass, more rarely an adrenal incidentaloma, or in the context of an adrenal mass discovered in the evaluation of childhood cancer including hematologic malignancy. According to standard medical practice, pediatric malignancies are almost always evaluated by 18F-fluorodeoxyglucose positron emission tomography with computed tomography ([18F]FDG PET/CT). Nuclear imaging using specific radiotracers is also an important tool for diagnosing and staging neuroblastoma, pheochromocytoma, hormone hypersecretion, or indeterminate adrenal masses. The Hippocratic oath “primum non nocere” encourages limitation of radiation in children per the ALARA concept (as low as reasonably achievable) but should not lead to the under-use of nuclear imaging because of the potential risk of inaccurate diagnosis or underestimation of the extent of disease. As in adults, nuclear imaging in children should be performed in conjunction with hormone evaluation and morphological imaging

Molecular imaging of endocrine neoplasms with emphasis on 18F-DOPA PET: a practical approach for well-tailored imaging protocols

International audience6-[18F]-L-fluoro-L-3, 4-dihydroxyphenylalanine (18F-DOPA) PET/CT can be a useful tool for the detection of different neuroendocrine tumors (NETs). The main determinants of 18F-DOPA uptake and retention by NETs are related to expression of LAT1/LAT2 transporters, expression and activity of AADC and biochemical phenotype, all being intimately inter-connected to their embryological origin. In order to improve sensitivity of 18F-DOPA PET, it is of main importance to perform indivisualized imaging protocols across primaries. This review provides a practical approach for performing well-tailored imaging protocols and describes the clinical value of the recommended radiopharmaceuticals

Genetic diversity and silencing suppression effects of and the P1 protein-2

Tic delivery (ND), buffer delivery (BD), biolistic delivery with a empty 35S vector (35S), or vectors containing different sP1 from RYMV isolates representative of the viral phylogeny (CI63, Mg1, Tz8, Tz3, BF1). Non transgenic Tai and transgenic L4 served as controls. (A) Photographs correspond to GUS staining at 2 dpd of inoculated leaves. (B) Quantitative effect of different P1 at 2 dpd on -specific siRNA with Northern blot experiments. EtBr staining of rRNA served as a loading control.<p><b>Copyright information:</b></p><p>Taken from "Genetic diversity and silencing suppression effects of and the P1 protein"</p><p>http://www.virologyj.com/content/5/1/55</p><p>Virology Journal 2008;5():55-55.</p><p>Published online 30 Apr 2008</p><p>PMCID:PMC2390521.</p><p></p