IMPORTANCE Many viral pathogens that cause significant global health and agricultural problems are transmitted via insect vectors. The first bottleneck in viral infection, the midgut epithelium, is a principal determinant of the ability of an insect species to transmit a virus. Southern rice black streaked dwarf virus (SRBSDV) is restricted exclusively to the midgut epithelium of an incompetent vector, the small brown planthopper (SBPH).Here, we show that silencing of the core component Dicer-2 of the small interfering RNA (siRNA) pathway increases viral titers in the midgut epithelium past the threshold (1.99 ؋ 10 9 copies of the SRBSDV P10 gene/g of midgut RNA) for viral dissemination into the midgut muscles and then into the salivary glands, allowing the SBPH to become a competent vector of SRBSDV. This result is the first evidence that the siRNA antiviral pathway has a direct role in the control of viral dissemination from the midgut epithelium and that it affects the competence of the virus's vector. Many viral pathogens that cause significant global health and agricultural problems are arthropod borne and transmitted via an insect vector. Many plant viruses are transmitted in a persistent manner by sap-sucking insects, including planthoppers, leafhoppers, thrips, and aphids (1-3). Plant viruses, when ingested by their insect vectors, establish their initial infection in the midgut epithelium, from where they disseminate to the midgut visceral muscles (1-3). The viruses then move from the midgut muscles into the hemolymph and finally into the salivary glands, from where they can be introduced into plant hosts (1-3). Efficient viral infection of the midgut epithelium, where initial infection is established, is thus a determinative factor in the ability of an insect species to transmit a certain plant virus.This ability of an insect species to transmit a virus, which has been described as vector competence, is common in nature (4, 5). For many years, the midgut barrier has been believed to be the principal determinant of vector competence (1-9). For example, infection of the incompetent insect vectors of Rice dwarf virus and SRBSDV, two plant reoviruses, and Tomato spotted wilt virus (TSWV), a tospovirus, is restricted to the midgut epithelium (7-10). The inability of incompetent insect vectors to transmit these viruses may be caused by a failure of the virus to efficiently replicate in or disseminate from the midgut epithelium (1-5). It is possible that viral titers in the midgut epithelium of incompetent vectors are unable to reach the threshold needed for viral dissemination. The innate immune response in the midgut epithelium may effectively control viral accumulation, thus blocking viral transmission by incompetent vectors. However, whether the initial antiviral immune pathway(s) in the insect midgut can modulate the competence of plant virus vectors is not unknown.Several mosquito and Drosophila innate immune responses have been reported to have an antiviral effect. These responses include RNA interfere...

The glucosinolates (GLs) and myrosinase defensive systems in cruciferous plants were circumvented by Plutella xylostella using glucosinolate sulfatases (PxGSSs) during pest-plant interaction. Despite identifying three duplicated GSS-encoding genes in P. xylostella, limited information regarding their spatiotemporal and induced expression is available. Here, we investigated the tissue- and stage-specific expression and induction in response to GLs of PxGSS1 and PxGSS2 (PxGSS1/2) at the protein level, which shares a high degree of similarity in protein sequences. Western blotting (WB) analysis showed that PxGSS1/2 exhibited a higher protein level in mature larvae, their guts, and gut content. A significantly high protein and transcript levels of PxGSS1/2 were also detected in the salivary glands using WB and qRT-PCR. The immunofluorescence (IF) and immunohistochemistry (IHC) results confirmed that PxGSS1/2 is widely expressed in the larval body. The IHC was more appropriate than IF when autofluorescence interference was present in collected samples. Furthermore, the content of PxGSS1/2 did not change significantly under treatments of GL mixture from Arabidopsis thaliana ecotype Col-0, or commercial ally (sinigrin), 4-(methylsulfinyl)butyl, 3-(methylsulfinyl)propyl, and indol-3-ylmethyl GLs indicating that the major GLs from leaves of A. thaliana Col-0 failed to induce the expression of proteins for both PxGSS1 and PxGSS2. Our study systemically characterized the expression properties of PxGSS1/2 at the protein level, which improves our understanding of PxGSS1/2-center adaptation in P. xylostella during long-term insect-plant interaction.

Jasmine virus H (JaVH) is a novel virus associated with symptoms of yellow mosaic on jasmine. The JaVH genome is 3,867 nt in length with five open reading frames (ORFs) encoding a 27-kDa protein (ORF 1), an 87-kDa replicase protein (ORF 2), two centrally located movement proteins (ORF 3 and 4), and a 37-kDa capsid protein (ORF 5). Based on genomic and phylogenetic analysis, JaVH is predicted to be a member of the genus Pelarspovirus in the family Tombusviridae.

Jasmine virus H (JaVH) is a newly reported viral pathogen of jasmine in China and USA. To study the viral gene function and pathogenic mechanism, a full-length infectious clone of JaVH (pXT-JaVHFJ) was constructed under the control of the cauliflower mosaic virus 35S promoter. pXT-JaVHFJ induced a systemic infection in Nicotiana benthamiana plants by Agro-infiltration, which demonstrated that pXT-JaVHFJ was biologically active. Jasmine showed yellow spots after rubbing with total RNA extracted from Agro-infiltrated N. benthamiana, indicating that JaVH was highly associated with yellow mosaic symptoms observed on jasmine. To investigate the occurrence and mutations of the virus, jasmine samples were collected from eight provinces of China and were tested for JaVH. The samples that were tested positive for JaVH were used to determine the complete genome sequences. They were comprised of 3867 or 3868 nucleotides and their genome organizations resembled that we previous reported for JaVH-FJ. Phylogenetic analyses and sequence comparisons suggest that the eight virus isolates were close isolates of JaVH-FJ and the isolate from Jilin Province was most closely related to JaVH-FJ with 99.2% nucleotide identity over the entire genome and 99.7% identity of coat protein. Further comparative analyses of JaVH-FJ and JaVH-JL revealed additional nucleotide differences in the 3′-untranslated region (3′ UTR). An infectious clone of JaVH-JL and chimeric mutants containing JaVH-FJ or JaVH-JL 3′ UTRs were then constructed for further study. The differential accumulation of JaVH with distinct 3′ UTR suggested that the 3′ UTR of JaVH plays a crucial role in viral RNA accumulation.

Complete chloroplast genome (cpDNA) sequence of Fagus hayatae Palib. is yet to be reported, and the phylogenetic position of this species is still under debate. In this study, the complete cpDNA sequence of F. hayatae was determined from Illumina NovaSeq pair-end sequencing data. Results revealed that it has a sequence length of 158,360 bp and contains 131 annotated genes, which consist of 83 protein-coding genes, 40 tRNA genes, and eight rRNA genes. The phylogenetic analysis of the complete cpDNA sequence indicates that Fagus represents a monophyletic clade within Fagaceae. The species relatedness between F. hayatae and F. engleriana is relatively close.