Rice stripe virus (RSV) is a single-stranded (ss) RNA virus belonging to the genus Tenuivirus. RSV is present in many East Asian countries and causes severe diseases in rice fields, especially in China. In this study, we analyzed six proteins encoded by the virus for their abilities to suppress RNA silencing in plant using a green fluorescent protein (GFP)-based transient expression assay. Our results indicate that NS3 encoded by RSV RNA3, but not other five RSV encoded proteins, can strongly suppress local GFP silencing in agroinfiltrated Nicotiana benthamiana leaves. NS3 can reverse the GFP silencing, it can also prevent long distance spread of silencing signals which have been reported to be necessary for inducing systemic silencing in host plants. The NS3 protein can significantly reduce the levels of small interfering RNAs (siRNAs) in silencing cells, and was found to bind 21-nucleotide ss-siRNA, siRNA duplex and long ssRNA but not long double-stranded (ds)-RNA. Both N and C terminal of the NS3 protein are critical for silencing suppression, and mutation of the putative nuclear localization signal decreases its local silencing suppression efficiency and blocks its systemic silencing suppression. The NS3-GFP fusion protein and NS3 were shown to accumulate predominantly in nuclei of onion, tobacco and rice cells through transient expression assay or immunocytochemistry and electron microscopy. In addition, transgenic rice and tobacco plants expressing the NS3 did not show any apparent alteration in plant growth and morphology, although NS3 was proven to be a pathogenicity determinant in the PVX heterogenous system. Taken together, our results demonstrate that RSV NS3 is a suppressor of RNA silencing in planta, possibly through sequestering siRNA molecules generated in cells that are undergoing gene silencing.

BackgroundSmall RNA-mediated gene silencing plays evolutionarily conserved roles in gene regulation and defense against invasive nucleic acids. Virus-derived small interfering RNAs (vsiRNAs) are one of the key elements involved in RNA silencing-based antiviral activities in plant and insect. vsiRNAs produced after viruses infecting hosts from a single kingdom (i.e., plant or animal) are well described. In contrast, vsiRNAs derived from viruses capable of infecting both plants and their insect vectors have not been characterized.Methodology/Principal FindingsWe examined Rice stripe virus (RSV)-derived small interfering RNAs in three different hosts, Oryza sativa, Nicotiana benthamiana and a natural RSV transmitting vector Laodelphgax striatellus, through deep sequencing. Our results show that large amounts of vsiRNAs generated in these hosts after RSV infection. The vsiRNAs from N. benthamiana and L. striatellus mapped equally to the genomic- and antigenomic-strand of RSV RNAs. They showed, however, a significant bias in those from O. sativa. Furthermore, our results demonstrate that the number and size distributions of vsiRNAs in the three hosts were very different. In O. sativa and N. benthamiana, most vsiRNAs were mapped to the discrete regions in the RSV genome sequence, and most of the vsiRNAs from these two hosts were generated from RSV genomic RNAs 3 and 4. In contrast, the vsiRNAs identified in L. striatellus distributed uniformly along the whole genome of RSV. We have also shown that silencing Agronaute 2 in L. striatellus enhanced RSV accumulation in this host.Conclusions/SignificanceOur study demonstrates that the core RNA-induced gene silencing (RNAi) machinery is present in L. striatellus. We also provide evidence that the RNAi-mediated immunity against RSV is present in L. striatellus. We propose that a common small RNA-mediated virus defense mechanism exists in both helipterum insects and plants, but the vsiRNAs are generated differentially in different hosts.

Cubic silicon carbide (3C-SiC) nanowires were synthesized through a reduction-carburization route by using silicon powders and tetrachloride (CCl 4 ) as Si and C sources, and metallic Na as the reductant at 700 °C. The as-prepared SiC nanowires were characterized and studied by X-ray powder diffraction, transmission electron microscopy, X-ray photoelectron spectra, Raman backscattering, and photoluminescence spectra at room temperature. The SiC nanowires produced from the present route typically have diameters of 15-20 nm and lengths of 5-10 µm. The influencing factors of the formation of the SiC nanowires were discussed and a possible growth mechanism for the SiC nanowires was proposed.

Background and purpose: Advanced glycation end products (AGEs) and endothelial progenitor cells (EPCs) play key roles in pathogenesis of diabetes-related vascular complications. AGEs can induce dysfunction in EPCs. The peroxisome proliferatoractivated receptor-gamma (PPARg) agonists are widely used in the treatment of type 2 diabetes, and it remains unknown if they could attenuate EPC dysfunction induced by AGEs. Experimental approach: EPCs isolated from healthy adults were cultured with various concentrations of AGEs (0, 50, 100 and 200 mg·L -1 ) with or without rosiglitazone (10 nM), antibody for the receptors for AGE-human serum albumin (anti-receptor for advanced glycation end products (RAGE); 50 mg·mL -1 ), phosphatidylinositol-3-kinase (PI3K) inhibitor (LY294002, 5 mM), nitric oxide (NO) synthase inhibitor (L-N G -nitro-arginine methyl ester (L-NAME), 100 mM) or sodium nitroprusside (SNP, 25 mM). Proliferation, apoptosis, cell adhesion, migration and NO production in EPCs were assessed, and expressions of endothelial NO synthase (eNOS) and Akt were determined. Key results: Number, proliferation/migration capacities, eNOS and Akt phosphorylation as well as NO synthesized by EPCs were increased by rosiglitazone and reduced by AGEs. AGEs promoted while rosiglitazone reduced EPC apoptosis. The AGE-induced effects were significantly ameliorated by pre-incubation with rosiglitazone, RAGE antibody and SNP. The beneficial effects of rosiglitazone could be blocked by pretreatment with L-NAME and LY294002. Conclusions and implications:The PPARg agonist rosiglitazone increased EPC function and attenuated EPC dysfunction induced by AGEs via upregulating the Akt-eNOS signal pathways of EPCs.

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Many persistent transmitted plant viruses, including rice stripe virus (RSV), cause serious damage to crop production worldwide. Although many reports have indicated that a successful insect-mediated virus transmission depends on a proper interaction between the virus and its insect vector, the mechanism(s) controlling this interaction remained poorly understood. In this study, we used RSV and its small brown planthopper (SBPH) vector as a working model to elucidate the molecular mechanisms underlying the entrance of RSV virions into SBPH midgut cells for virus circulative and propagative transmission. We have determined that this non-enveloped tenuivirus uses its non-structural glycoprotein NSvc2 as a helper component to overcome the midgut barrier(s) for RSV replication and transmission. In the absence of this glycoprotein, purified RSV virions were unable to enter SBPH midgut cells. In the RSV-infected cells, this glycoprotein was processed into two mature proteins: an amino-terminal protein (NSvc2-N) and a carboxyl-terminal protein (NSvc2-C). Both NSvc2-N and NSvc2-C interact with RSV virions. Our results showed that the NSvc2-N could bind directly to the surface of midgut lumen via its N-glycosylation sites. Upon recognition, the midgut cells underwent endocytosis followed by compartmentalization of RSV virions and NSvc2 into early and then late endosomes. The NSvc2-C triggered cell membrane fusion via its highly conserved fusion loop motifs under the acidic condition inside the late endosomes, leading to the release of RSV virions from endosomes into cytosol. In summary, our results showed for the first time that a rice tenuivirus utilized its glycoprotein NSvc2 as a helper component to ensure a proper interaction between its virions and SBPH midgut cells for its circulative and propagative transmission.