Rice stripe virus (RSV) causes severe diseases in Oryza sativa (rice) in many Eastern Asian countries. Disease-specific protein (SP) of RSV is a non-structural protein and its accumulation level in rice plant was shown to determine the severity of RSV symptoms. Here, we present evidence that expression of RSV SP alone in rice or Nicotiana benthamiana did not produce visible symptoms. Expression of SP in these two plants, however, enhanced RSV- or Potato virus X (PVX)-induced symptoms. Through yeast two-hybrid screening, GST pull-down, and bimolecular fluorescence complementation assays, we demonstrated that RSV SP interacted with PsbP, a 23-kDa oxygen-evolving complex protein, in both rice and N. benthamiana. Furthermore, our investigation showed that silencing of PsbP expression in both plants increased disease symptom severity and virus accumulation. Confocal microscopy using N. benthamiana protoplast showed that PsbP accumulated predominantly in chloroplast in wild-type N. benthamiana cells. In the presence of RSV SP, most PsbP was recruited into cytoplasm of the assayed cells. In addition, accumulation of SP during RSV infection resulted in alterations of chloroplast structure and function. Our findings shed light on the molecular mechanism underlying RSV disease symptom development.

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.

Rice stripe disease caused by Rice stripe virus (RSV) is one of the most devastating plant viruses of rice and causes enormous losses in production. RSV is transmitted from plant to plant by the small brown planthopper ( Laodelphax striatellus) in a circulative–propagative manner. The recent reemergence of this pathogen in East Asia since 2000 has made RSV one of the most studied plant viruses over the past two decades. Extensive studies of RSV have resulted in substantial advances regarding fundamental aspects of the virus infection. Here, we compile and analyze recent information on RSV with a special emphasis on the strategies that RSV has adopted to establish infections. These advances include RSV replication and movement in host plants and the small brown planthopper vector, innate immunity defenses against RSV infection, epidemiology, and recent advances in the management of rice stripe disease. Understanding these issues will facilitate the design of novel antiviral therapies for management and contribute to a more detailed understanding of negative-sense virus–host interactions at the molecular level.

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.