Discovery of novel inhibitors of RNA silencing suppressor P19 based on virtual screening.

To control plant viruses, viral RNA silencing suppressors are important drug targets due to their key roles in interfering antiviral RNA silencing. Here we have presented a strategy, combining virtual and experimental screening, to discover the inhibitors of viral suppressor. By docking 157 026 compounds from a natural product library into P19 model, eighteen candidate compounds were selected. Candidates VS2, VS12, VS14 and VS15 displayed strong binding ability to P19 in the surface plasmon resonance imaging assay with K D values of 136.2, 111.6, 81.2 and 124.5 nM, respectively. Then the inhibition activities of these inhibitors on the association between P19 and siRNA were also affirmed by electrophoretic mobility shift assay. Moreover, the antiviral effects on plants showed that compounds VS14 and VS15 both exhibited antiviral activities against Tomato bushy stunt virus (TBSV) in vivo with inhibition rates of 32.35% and 16.61% in 11 dpi, respectively. This strategy would be a powerful tool for the discovery of novel antiviral agents and provide new insights into the control of plant viruses.

Chiral Surface of Nanoparticles Determines the Orientation of Adsorbed Transferrin and Its Interaction with Receptors.

When nanoparticles are exposed to a physiological environment, a "protein corona" is formed that greatly determines their biological fate. Adsorption of proteins could be influenced by chiral surfaces of nanoparticles; however, very few quantitative studies are available on the interaction of protein with the chiral surface of nanoparticles, and the underlying mechanism remains largely unresolved. We have developed a strategy to quantitatively analyze the adsorption and conformational features of transferrin on gold nanoparticles that are functionalized with d, l, and racemic penicillamine. We used a quartz microbalance platform to monitor the interaction of the adsorbed transferrin with transferrin receptors in HEK cell-derived liposomes. Results show that the chiral surface of nanoparticle determines the orientation and conformation of transferrin, which subsequently affects the interaction and recognition of transferrin with its receptor on the cellular membrane. Transferrin is widely used as a tumor-targeting ligand in cancer treatment and diagnosis since the transferrin receptor is overexpressed on the cell membrane of various types of cancer cells. Thus, the present results will help to expand the knowledge on biological identity of nanoparticles with chiral surfaces in a physiological environment and provide an insight into the rational design of therapeutic nanoparticles.

Transcriptomic analysis of Paulownia infected by Paulownia witches'-broom Phytoplasma.

Phytoplasmas are plant pathogenic bacteria that have no cell wall and are responsible for major crop losses throughout the world. Phytoplasma-infected plants show a variety of symptoms and the mechanisms they use to physiologically alter the host plants are of considerable interest, but poorly understood. In this study we undertook a detailed analysis of Paulownia infected by Paulownia witches'-broom (PaWB) Phytoplasma using high-throughput mRNA sequencing (RNA-Seq) and digital gene expression (DGE). RNA-Seq analysis identified 74,831 unigenes, which were subsequently used as reference sequences for DGE analysis of diseased and healthy Paulownia in field grown and tissue cultured plants. Our study revealed that dramatic changes occurred in the gene expression profile of Paulownia after PaWB Phytoplasma infection. Genes encoding key enzymes in cytokinin biosynthesis, such as isopentenyl diphosphate isomerase and isopentenyltransferase, were significantly induced in the infected Paulownia. Genes involved in cell wall biosynthesis and degradation were largely up-regulated and genes related to photosynthesis were down-regulated after PaWB Phytoplasma infection. Our systematic analysis provides comprehensive transcriptomic data about plants infected by Phytoplasma. This information will help further our understanding of the detailed interaction mechanisms between plants and Phytoplasma.

Transcriptome analysis of Nicotiana tabacum infected by Cucumber mosaic virus during systemic symptom development.

Virus infection of plants may induce a variety of disease symptoms. However, little is known about the molecular mechanism of systemic symptom development in infected plants. Here we performed the first next-generation sequencing study to identify gene expression changes associated with disease development in tobacco plants (Nicotiana tabacum cv. Xanthi nc) induced by infection with the M strain of Cucumber mosaic virus (M-CMV). Analysis of the tobacco transcriptome by RNA-Seq identified 95,916 unigenes, 34,408 of which were new transcripts by database searches. Deep sequencing was subsequently used to compare the digital gene expression (DGE) profiles of the healthy plants with the infected plants at six sequential disease development stages, including vein clearing, mosaic, severe chlorosis, partial and complete recovery, and secondary mosaic. Thousands of differentially expressed genes were identified, and KEGG pathway analysis of these genes suggested that many biological processes, such as photosynthesis, pigment metabolism and plant-pathogen interaction, were involved in systemic symptom development. Our systematic analysis provides comprehensive transcriptomic information regarding systemic symptom development in virus-infected plants. This information will help further our understanding of the detailed mechanisms of plant responses to viral infection.

Rapid on-site detection of Acidovorax citrulli by cross-priming amplification.

Cross-priming amplification (CPA) for Acidovorax citrulli detection was evaluated in this study. The sensitivity of CPA assay for pure bacterial culture was 3.7 × 10(3) CFU/ml. Bacteria on naturally infected watermelon seeds were detected using CPA assay, suggesting this method is suitable for A. citrulli on-site detection from watermelon seeds.

[Complete genomic sequence of a watermelon isolate of cucumber green mottle mosaic virus in northern China].

The complete genomic sequence of a watermelon isolate of Cucumber green mottle mosaic virus (CGMMV-LN) in Liaoning province was determined and compared with other cucurbit-infecting tobamoviruses. The genomic RNA of CGMMV-LN comprised 6422 nt, and 5'- and 3'- noncoding regions consisted of 59 nt and 175 nt, respectively. The encoded four proteins were two replicase proteins of 186 kD and 129 kD, move protein of 29 kD and coat protein of 17.4 kD. The alignment results of complete nucleotide sequence showed that CGMMV-LN shared identities of 97.6%-99.3% with four other CGMMV isolates, but only shared identities of 61.7%-62.8% with three other tobamoviruses. Homology trees generated from replicase proteins of 186 kD and coat proteins suggested that cucurbit-infecting tobamoviruses could be separated into two subgroups: subgroup I comprising all the isolates of CGMMV and subgroup II comprising Cucumber fruit mottle mosaic virus, Kyuri green mottle mosaic virus and Zucchini green mottle mosaic virus.

Detection of Xanthomonas oryzae pv. oryzae in seeds using a specific TaqMan probe.

Xanthomonas oryzae pv. oryzae is the pathogen that causes bacterial leaf blight in rice. Bacterial leaf blight is the main cause for severe rice underproduction in many countries. However, with conventional methods it is difficult to quickly and reliably distinguish this pathogen from other closely related pathogenic bacteria, especially X. oryzae pv. oryzicola, the causal organism of bacterial leaf streak in rice. We have developed a novel and highly sensitive real-time method for the identification of this specific bacteria based on a TaqMan probe. This probe is designed to recognize the sequence of a putative siderophore receptor gene cds specific to X. oryzae pv. oryzae, and can be identified from either a bacterial culture or naturally infected rice seeds and leaves in only 2 h. The sensitivity of the method is 100 times higher than that of the current polymerase chain reaction (PCR) gel electrophoresis method for diagnosis.

[Identification for genetically modified maize T14/T25 with real time fluorescent PCR method].

To identify genetically modified (GM) maize T14/T25 lines, a real-time fluorescent PCR (RTF PCR) assay was performed in this study. Primers and Taqman probes specific for inserted genes in the T14/T25 were used to conduct the real-time fluorescent (RTF) PCR and PCR assays. The RTF PCR method was established to detect and identify GM maize lines. The results show that the TaqMan probe could identify T14/T25 maize used, while other GM and NO-GM maize didn't be detected. The RTF PCR could be a new method for detecting other genetically modified organism.