The white backed planthopper (WBPH), Sogatella furcifera (Horváth), causes great damage to many crops by direct feeding or transmitting plant viruses. Southern rice black-streaked dwarf virus (SRBSDV), transmitted by WBPH, has become a great threat to rice production in East Asia. By de novo transcriptome assembling and massive parallel pyrosequencing, we constructed two transcriptomes of WBPH and profiled the alternation of gene expression in response to SRBSDV infection in transcriptional level. Over 25 million reads of high-quality DNA sequences and 81388 different unigenes were generated using Illumina technology from both viruliferous and non-viruliferous WBPH. WBPH has a very similar gene ontological distribution to other two closely related rice planthoppers, Nilaparvata lugens and Laodelphax striatellus. 7291 microsatellite loci were also predicted which could be useful for further evolutionary analysis. Furthermore, comparative analysis of the two transcriptomes generated from viruliferous and non-viruliferous WBPH provided a list of candidate transcripts that potentially were elicited as a response to viral infection. Pathway analyses of a subset of these transcripts indicated that SRBSDV infection may perturb primary metabolism and the ubiquitin-proteasome pathways. In addition, 5.5% (181 out of 3315) of the genes in cell cytoskeleton organization pathway showed obvious changes. Our data also demonstrated that SRBSDV infection activated the immunity regulatory systems of WBPH, such as RNA interference, autophagy and antimicrobial peptide production. We employed massively parallel pyrosequencing to collect ESTs from viruliferous and non-viruliferous samples of WBPH. 81388 different unigenes have been obtained. We for the first time described the direct effects of a Reoviridae family plant virus on global gene expression profiles of its insect vector using high-throughput sequencing. Our study will provide a road map for future investigations of the fascinating interactions between Reoviridae viruses and their insect vectors, and provide new strategies for crop protection.

Small 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. We 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. Our 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.

A novel virus, tentatively named Maize Yellow Mosaic Virus (MaYMV), was identified from the field-grown maize plants showing yellow mosaic symptoms on the leaves collected from the Yunnan Province of China by the deep sequencing of small RNAs. The complete 5642 nucleotide (nt)-long genome of the MaYMV shared the highest nucleotide sequence identity (73%) to Maize Yellow Dwarf Virus-RMV. Sequence comparisons and phylogenetic analyses suggested that MaYMV represents a new member of the genus Polerovirus in the family Luteoviridae. Furthermore, the P0 protein encoded by MaYMV was demonstrated to inhibit both local and systemic RNA silencing by co-infiltration assays using transgenic Nicotiana benthamiana line 16c carrying the GFP reporter gene, which further supported the identification of a new polerovirus. The biologically-active cDNA clone of MaYMV was generated by inserting the full-length cDNA of MaYMV into the binary vector pCB301. RT-PCR and Northern blot analyses showed that this clone was systemically infectious upon agro-inoculation into N. benthamiana. Subsequently, 13 different isolates of MaYMV from field-grown maize plants in different geographical locations of Yunnan and Guizhou provinces of China were sequenced. Analyses of their molecular variation indicate that the 3′ half of P3–P5 read-through protein coding region was the most variable, whereas the coat protein- (CP-) and movement protein- (MP-)coding regions were the most conserved.

Background: Cucumber green mottle mosaic virus (CGMMV), a member of the genusTobamovirus, can be transmitted by seeds and infects many cucurbit species, causing serious yield losses in cucumber and watermelon plants. In this paper, five serological methods including antigen-coated plate enzyme-linked immunosorbent assay (ACP-ELISA), triple antibody sandwich enzyme-linked immunosorbent assay (TAS-ELISA), Dot-immunobinding assay (DBIA), direct tissue blot immunoassay (DTBIA) and immunocapture reverse transcriptase polymerase chain reaction (IC-RT-PCR) were described for detection and diagnosis of CGMMV.Results: Using the purified CGMMV particles as immunogens, six murine monoclonal antibodies (MAbs) were produced. Five serological methods were established using the MAb 4H1 and detection sensitivity was compared using purified preparations and infected-plant tissue extracts. The detection sensitivity of ACP-ELISA was 0.16 ng of purified CGMMV, whereas TAS-ELISA was more sensitive than ACP-ELISA with a minimum detection of 0.04 ng of purified CGMMV. The sensitivities of TAS-ELISA and DBIA were similar for detecting CGMMV in infected-plant tissue extracts, and were four times higher than ACP-ELISA. The IC-RT-PCR was the most sensitive method, which could detect as little as 0.1 pg of purified virus. The detection sensitivity of IC-RT-PCR for CGMMV-infected plant tissues was about 400 times higher than that of TAS-ELISA and DBIA.Conclusions: The established ACP-ELISA, TAS-ELISA, DBIA and DTBIA are suitable for routine CGMMV detection of large-scale samples in the field survey, while IC-RT-PCR is more sensitive and suitable for acquiring information about the viral genome.

Plant survival requires an ability to adapt to differing concentrations of nutrient and toxic soil ions, yet ion sensors and associated signaling pathways are mostly unknown. Aluminum (Al) ions are highly phytotoxic, and cause severe crop yield loss and forest decline on acidic soils which represent ∼30% of land areas worldwide. Here we found an Arabidopsis mutant hypersensitive to Al. The gene encoding a leucine-rich-repeat receptor-like kinase, was named Al Resistance1 (ALR1). Al ions binding to ALR1 cytoplasmic domain recruits BAK1 co-receptor kinase and promotes ALR1-dependent phosphorylation of the NADPH oxidase RbohD, thereby enhancing reactive oxygen species (ROS) generation. ROS in turn oxidatively modify the RAE1 F-box protein to inhibit RAE1-dependent proteolysis of the central regulator STOP1, thus activating organic acid anion secretion to detoxify Al. These findings establish ALR1 as an Al ion receptor that confers resistance through an integrated Al-triggered signaling pathway, providing novel insights into ion-sensing mechanisms in living organisms, and enabling future molecular breeding of acid-soil-tolerant crops and trees, with huge potential for enhancing both global food security and forest restoration.