Summary Extracellular DNA, released by damaged plant cells, acts as a damage‐associated molecular pattern (DAMP). We demonstrated previously that the small brown planthopper (Laodelphax striatellus, SBPH) secreted DNase II when feeding on artificial diets. However, the function of DNase II in insect feeding remained elusive. The influences of DNase II on SBPHs and rice plants were investigated by suppressing expression of DNase II or by application of heterogeneously expressed DNase II. We demonstrated that DNase II is mainly expressed in the salivary gland and is responsible for DNA‐degrading activity of saliva. Knocking down the expression of DNase II resulted in decreased performance of SBPH reared on rice plants. The dsDNase II‐treated SBPH did not influenced jasmonic acid (JA), salicylic acid (SA), ethylene (ET) pathways, but elicited a higher level of H2O2 and callose accumulation. Application of heterogeneously expressed DNase II in DNase II‐deficient saliva slightly reduced the wound‐induced defence response. We propose a DNase II‐based invading model for SBPH feeding on host plants, and provide a potential target for pest management.

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Wolbachia‐induced reproductive regulation in hosts has been used to control pest populations, but little is known about the molecular mechanism underlying Wolbachia regulation of host genes. Here, reproductive regulation by Wolbachia in the spider mite Tetranychus truncatus was studied at the molecular level. Infection with Wolbachia resulted in decreasing oviposition and cytoplasmic incompatibility in T. truncatus. Further RNA‐seq revealed genes regulated by Wolbachia in T. truncatus. Real‐time quantitative polymerase chain reaction (qPCR) showed that genes, including chorion protein S38‐like and Rop were down‐regulated by Wolbachia. RNA interference (RNAi) of chorion protein S38‐like and Rop in Wolbachia‐uninfected T. truncatus decreased oviposition, which was consistent with Wolbachia‐induced oviposition decrease. Interestingly, suppressing Rop in Wolbachia‐infected T. truncatus led to increased Wolbachia titres in eggs; however, this did not occur after RNAi of chorion protein S38‐like. This is the first study to show that chorion protein S38‐like and Rop facilitate Wolbachia‐mediated changes in T. truncatus fertility. In addition, RNAi of Rop turned the body colour of Wolbachia‐uninfected T. truncatus black, which indicates that the role of Rop is not limited to the reproductive regulation of T. truncatus.

The spider mite Tetranychus evansi has a remarkable ability to suppress and manipulate plant defenses, which makes it an ideal model to investigate plant–herbivores interactions. In this study, a de novo assembly of the transcriptome of T. evansi is performed and the proteins in its secreted saliva by LC–MS/MS are characterized. A total of 29 365 unigenes are assembled and 136 saliva proteins are identified. Comparative analysis of the saliva proteins in T. evansi, T. truncatus, and T. urticae shows that 64 protein groups are shared by at least two Tetranychus species, and 52 protein groups are specifically identified in T. evansi. In addition, some saliva proteins are common in arthropod species, while others are species‐specific. These results will help to elucidate the molecular mechanisms by which T. evansi modulates plant defenses.

Herbivore-associated molecular patterns (HAMPs) enable plants to recognize herbivores and may help plants adjust their defense responses. Here, we report on herbivore-induced changes in a protein disulfide isomerase (PDI) widely distributed across arthropods. PDI from the spider mite Tetranychus evansi (TePDI), a mesophyll-feeding agricultural pest worldwide, triggered immunity in multiple Solanaceae plants. TePDI-mediated cell death in Nicotiana benthamiana required the plant signaling proteins SGT1 (suppressor of the G2 allele of skp1) and HSP90 (heat shock protein 90), but was suppressed by spider mite effectors Te28 and Te84. Moreover, PDIs from phylogenetically distinct herbivorous and non-herbivorous arthropods all triggered plant immunity. Finally, although PDI-induced plant defenses impaired the performance of spider mites on plants, RNAi experiments revealed that PDI genes are essential for the survival of mites and whiteflies. Our findings indicate that plants recognize evolutionarily conserved HAMPs to activate plant defense and resist pest damage, pointing to opportunities for broad-spectrum pest management.

Background: Host adaptation is the major determinant of insect diversification. However, knowledge of different host ranges in very close-related species remains scarce. The brown planthopper (Nilaparvata lugens, BPH) and small brown planthopper (Laodelphax striatellus, SBPH) are the most destructive insect pests belonging to Delphacidae. These two species differ in the host range (SBPH can well colonize on rice and wheat plants, while BPH survive on rice plants only), but the underlying mechanism still remains unknown. High-throughput sequencing technology provides a powerful approach for analyzing the association between gene expression changes and physiological responses of insects. Therefore, the gut transcriptomes were performed to elucidate the genes associated with host adaptation in planthoppers. Comparative analysis of planthoppers’ responses to different diets would improve our knowledge of host adaptation regarding herbivores insects.Results: In the present study, we analyzed the gene expression change of SBPH that transferred from rice plants to wheat plants in a short term (rSBPH vs tSBPH) and colonized on wheat plants for a long term (rSBPH vs wSBPH). The results showed that the majority of differentially expressed genes in SBPH showed similar expression change between short-term transfer and long-term colonization. Based on the comparative analysis of BPH and SBPH after transferring, genes associated with sugar transporters and heat shock proteins varied similarly. However, most of genes were differentially regulated between two species. The detoxification-related genes were upregulated in SBPH after transferring while downregulated in BPH under the same condition. Ribosomal-related genes were downregulated in SBPH after transferring while upregulated in BPH under the same condition.Conclusion: The results of this study provided evidence that host plants played dominant roles in shaping the gene expression, and unfitness of BPH on wheat plants might be determined within 24 hours after transferring. This study deepens our understanding of different host ranges regarding two planthopper species, which may provide a potential strategy for pest management.

Background: Host adaptation is the primary determinant of insect diversification. However, knowledge of different host ranges in closely related species remains scarce. The brown planthopper (Nilaparvata lugens, BPH) and the small brown planthopper (Laodelphax striatellus, SBPH) are the most destructive insect pests within the family Delphacidae. These two species differ in their host range (SBPH can well colonize rice and wheat plants, whereas BPH survives on only rice plants), but the underlying mechanism of this difference remains unknown. Highthroughput sequencing provides a powerful approach for analyzing the association between changes in gene expression and the physiological responses of insects. Therefore, gut transcriptomes were performed to elucidate the genes associated with host adaptation in planthoppers. The comparative analysis of planthopper responses to different diets will improve our knowledge of host adaptation regarding herbivorous insects. Results: In the present study, we analyzed the change in gene expression of SBPHs that were transferred from rice plants to wheat plants over the short term (rSBPH vs tSBPH) or were colonized on wheat plants over the long term (rSBPH vs wSBPH). The results showed that the majority of differentially expressed genes in SBPH showed similar changes in expression for short-term transfer and long-term colonization. Based on a comparative analysis of BPH and SBPH after transfer, the genes associated with sugar transporters and heat-shock proteins showed similar variation. However, most of the genes were differentially regulated between the two species. The detoxificationrelated genes were upregulated in SBPH after transfer from the rice plants to the wheat plants, but these genes were downregulated in BPH under the same conditions. In contrast, ribosomal-related genes were downregulated in SBPH after transfer, but these genes were upregulated in BPH under the same conditions. Conclusions: The results of this study provide evidence that host plants played a dominant role in shaping gene expression and that the low fitness of BPH on wheat plants might be determined within 24 h after transfer. This study deepens our understanding of different host ranges for the two planthopper species, which may provide a potential strategy for pest management.