植物病毒Plant Virus
Several viroids in the genus Pospiviroid can infect tomato (Solanum lycopersicum) and cause severe diseases, posing a serious threat to tomato production. For simultaneous detection of six tomato-infecting pospiviroids - columnea latent viroid (CLVd), pepper chat fruit viroid (PCFVd), potato spindle tuber viroid (PSTVd), tomato apical stunt viroid (TASVd), tomato chlorotic dwarf viroid (TCDVd), and tomato planta macho viroid (TPMVd), we developed a universal probe based on a highly conserved 61 nt long sequence shared among them. Compared with their specific probes, the universal probe has a similar, though slightly reduced, detection sensitivity and has the advantages of simple and cost-effective preparation and simultaneous detection of the six pospiviroids. In addition, the universal probe was used in dot-blot hybridization assays for a large-scale survey of viroid(s) in tomato plantings in China. Only PSTVd was detected in a few greenhouse-planted tomato plants. Sequence analysis revealed that these tomato PSTVd isolates may have been introduced from tomato seeds imported from abroad.
Rice stripe disease, caused by rice stripe virus (RSV) which is transmitted by small brown planthopper (SBPH, Laodelphax striatellus Fallen), resulted in serious losses to rice production during the last 2 decades. Research on the molecular differences between resistant and susceptible rice varieties and the interaction between rice and RSV remains inadequate. In this study, RNA-Seq was used to analyze the transcriptomic differences between the resistant and susceptible rice varieties at different times post RSV infection. Through Gene Ontology (GO) annotation, the differentially expressed genes (DEGs) related to transcription factors, peroxidases, and kinases of 2 varieties at 3 time points were identified. Comparing these 2 varieties, the DEGs associated with these 3 GOs were numerically less in the resistant variety than in the susceptible variety, but the expression showed a significant up- or down-regulation trend under the conditions of |log2(Fold change)|>0 & Padj<0.05 by significance analysis. Then through Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation, DEGs involved in some pathways that have a contribution to disease resistance including plant hormone signal transduction and plant–pathogen interaction were found. The results showed that resistance responses regulated by abscisic acid (ABA) and brassinosteroids (BR) were the same for 2 varieties, but that mediated by salicylic acid (SA) and jasmonic acid (JA)/ethylene (ET) were different. The DEGs in resistant and susceptible varieties at the 3 time points were identified in both PAMP-triggered immunity (PTI) and Effector protein-triggered immunity (ETI), with that most of the unigenes of the susceptible variety were involved in PTI, whereas most of the unigenes of the resistant variety were involved in ETI. These results revealed the different responses of resistant and susceptible varieties in the transcription level to RSV infection.
A headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME/GC-MS) method was used to study the volatile organic compounds (VOCs) associated with the differential immune response of tomato plants infected with the recombinant strain of potato virus Y (PVYC-to), necrogenic to tomato. Analysis was carried out in UC82 (UC), a virus susceptible tomato variety, comparing the same UC plants grafted or not onto a virus tolerant tomato ecotype, Manduria (Ma); the three types of samples used for the GC-MS analysis were mock-inoculated UC/Ma plants, UC/Ma+PVYC-to and UC+PVYC-to plants; the VOCs obtained were 111. Results from symptomatic PVYC-to-infected UC plants showed a VOCs composition enriched in alcohols, fatty acid derivates, benzenoids, and salicylic acid derivatives, while in mock-inoculated UC/Ma plants VOCs were mainly characterized by methyl ester compounds. The VOC profile was in line with RNAseq data analyses, denoting that PVYC-to viral RNA accumulation and disease symptoms induce the specific transcriptional activation of genes involved in VOCs biosynthesis. Furthermore, principal component analysis highlighted that VOCs of PVYC-to-infected and mock-inoculated grafted plants were much closer each other than that of symptomatic PVYC-to-infected non-grafted UC plants. These results suggest that VOCs profiles of tomato plants are related to the viral RNA accumulation, disease intensity and graft-derived tolerance to PVYC-to infection.
Tobacco (Nicotiana tabacum) and tomato (Solanum lycopersicum) are two major economic crops in China. Tobacco mosaic virus (TMV; genus Tobamovirus) is the most prevalent virus infecting both crops. Currently, some widely cultivated tobacco and tomato cultivars are susceptible to TMV and there is no effective strategy to control this virus. Cross-protection can be a safe and environmentally friendly strategy to prevent viral diseases. However, stable attenuated TMV mutants are scarce. In this study, we found that the substitutions in the replicase p126, arginine at position 196 (R196) with aspartic acid (D), glutamic acid at position 614 (E614) with glycine (G), serine at position 643 (S643) with phenylalanine (F), or D at position 730 (D730) with S, significantly reduced the virulence and replication of TMV. However, only the mutation of S643 to F reduced the RNA silencing suppression activity of TMV p126. A double-mutant TMV-E614G-S643F induced no visible symptom and was genetically stable through six successive passages in tobacco plants. Furthermore, our results showed that TMV-E614G-S643F double-mutant could provide effective protection against the wild-type TMV infection in tobacco and tomato plants. This study reports a promising mild mutant for cross-protection to control TMV in tobacco and tomato plants.
A bacterial protein Rhp-PSP inhibits plant viral proliferation through endoribonuclease activity
Plant virus causes massive crop losses globally. However, there is currently no effective measure to control plant viral disease. Previously, we identify an antiviral protein Rhp-PSP, produced by the bacterial Rhodopseudomonas palustris strain JSC-3b. In this study, we discover that the antiviral activity of Rhp-PSP relies on its endoribonuclease activity. Converting the arginine (R) residue at position 129 onto alanine (A) abolishs its endoribonuclease activity on coat protein (CP) RNA of tobacco mosaic virus (TMV), consequentially, compromises the antiviral activity of Rhp-PSP. Further investigation demonstrates that, the mutant Rhp-PSPR129A is unable to form the homotrimer as the wild type, indicating the importance of quaternary junction for the endoribonuclease activity. Overexpression of Rhp-PSP in Nicotiana benthamiana significantly enhances the resistance against TMV of seedlings, while expression of Rhp-PSPR129A did not, confirming that endoribonuclease activity is responsible for the antiviral activity of Rhp-PSP. In addition, foliar spray of Rhp-PSP solution on tomato and pepper plants significantly reduces the disease index of viral diseases, indicating that Rhp-PSP shows potential to develop antiviral agent in practice.
Eureka lemon zinc finger protein ClDOF3.4 interacts with citrus yellow vein clearing virus coat protein to inhibit viral infection