Characterization of a baculovirus newly isolated from the tea slug moth, Iragoidae fasciata

Granulovirus GP37 Facilitated ODVs Cross Insect Peritrophic Membranes and Fuse with Epithelia

The Cydia pomonella granulovirus (CpGV) GP37 has synergistic effects on the infectivity of nucleopolyhedroviruses (NPVs), however, the mechanism employed is unclear. In this study, in vitro and in vivo binding assays indicated that GP37 efficiently bound to the midgut peritrophic membrane (PM) of Spodoptera exigua larvae. Treatment with GP37 led to the damage of the PM's compacted structure and the generation of the PM perforations, and the enhancement of the PM's permeability. qPCR results further demonstrated that GP37 increased the ability of occlusion-derived virions (ODV) to cross the PM. R18-labeling experiments exhibited that GP37 also promoted the fusion of ODVs and insect midgut epithelia. Altogether, our present results revealed that the synergistic mechanism of GP37 to the infectivity of NPV might involve two parts. GP37 damaged the integrity of the PM after binding, which enhanced the PM's permeability and increased the ability of ODVs to cross the PM, finally facilitating the ODVs reaching the midgut. In addition, GP37 promoted the fusion of ODVs and insect midgut epithelia. Our data expand the understanding of the mechanism used by baculovirus synergistic factors and provide a foundation for the development of high-efficiency baculoviral insecticides.

Microbial management of arthropod pests of tea: current state and prospects

Sustainable tea cultivation will rely increasingly on alternatives to conventional chemical insecticides for pest management that are environment-friendly and reduce the amount of pesticide residues in made tea. Entomopathogens can provide effective control, conserve biodiversity, and serve as alternatives to chemical insecticides under several conditions. Due to their specificity for insects, these pathogens including viruses, bacteria, and fungi are ideal candidates for incorporation in the integrated pest management strategies for tea where their effects on other natural enemies will be minimal. Biological and ecological characteristics of several dominant natural entomopathogenic microorganisms have been well documented throughout the tea-growing countries particularly China, Japan, and India. But research to convert them to microbial insecticide formulations for tea pest control by evolving suitable techniques for production, standardization, formulation, and application has not progressed well except in Japan and China to some extent. Increased use of microbial control will depend on a variety of factors including improvements in the pathogens' virulence, formulation, delivery, etc. and an increased awareness of their attributes by growers and the general public. In this review, we provide an overview of microbial control of the key insect pests of tea and also the scope for future studies for their better utilization.

Molecular Characterization of a Nucleopolyhedrovirus Newly Isolated from Ophiusa disjungens in China

Ophiusa disjungens nucleopolyhedrovirus (OpdiNPV) was newly found in Guangdong Province, China. Using BamHI, EcoRI, HindIII, PstI, XhoI, XbaI digestion, the size of the OpdiNPV genome was estimated to be 92,000 base pair. The pstI-G genomic fragment of OpdiNPV was cloned and sequenced. Searches of databases identified at least four open reading frames (ORFs) within this fragment. These ORFs encode odv-e66 (EU 623602), p87/vp80 (EU 732665), odv-ec43 (EU617337) and ac108 gene (EU 732666) respectively. The phylogenetic tree of NPVs based on the combined sequences of odv-ec43 and ac108 indicated that OpdiNPV was most closely related to Mamestra configurata NPV-A and Mamestra configurata NPV-B. The characterization of OpdiNPV in this paper would provide better understanding molecular properties of this virus and be helpful in the development of the newly isolated virus as a biopesticide or an engineered pesticide to control more species of insect pests.

Synergistic effects of Cydia pomonella granulovirus GP37 on the infectivity of nucleopolyhedroviruses and the lethality of Bacillus thuringiensis

To initiate an efficient primary infection, it is important for baculovirus virions to penetrate through the peritrophic membrane (PM) of the host insect. It is frequently reported that enhancins of baculoviruses significantly enhance viral infection by degrading the various protein components of PMs. However, not all baculoviruses encode enhancins. GP37s of baculoviruses share high amino acid identity with fusolins, synergistic factors found in entomopoxviruses. In this study, a truncated Cydia pomonella granulovirus GP37 was expressed in Escherichia coli. The expressed GP37 effectively bound to chitin, and binding occurred predominantly within 3 h. GP37 altered the protein profiles of Spodoptera exigua PMs, from which a 50-kDa protein was dissociated. Droplet-feeding bioassays indicated that GP37 significantly enhanced the infectivity of nucleopolyhedroviruses (NPVs) and the lethality of Bacillus thuringiensis (Bt) in S. exigua larvae. This is the first demonstration of the enhancement of NPVs and Bt infection by a baculovirus GP37.