Sheng Lin

The Brown Planthopper, Nilaparvata lugens (Stål.) (Hemiptera: Delphinidae), is one of the most destructive pests of rice. Its reproductive and developmental traits are influenced by various environmental and biological factors including endosymbiotic microorganisms. Arsenophonus, a widespread endosymbiotic bacterium of insects, can affect host fitness and metabolic processes. This study investigates the role of Arsenophonus in modulating the developmental and reproductive traits of N. lugens fed on transgenic cry30Fa1 rice (KF30-14) and its parent variety Minghui 86 (MH86). Life table analysis revealed that Arsenophonus infection (Ars⁺) increased the development time and reduced the reproductive capacity of N. lugens, especially those feeding on KF30-14. The first-instar nymphs in MH86 Ars⁺ (infected) exhibited slower development compared to MH86 Ars⁻ (uninfected). Similarly, the third and fourth-instar nymphs in KF30-14 Ars⁺ exhibited prolonged development time compared to KF30-14 Ars⁻. In addition, KF30-14 Ars⁺ females had significantly reduced reproductive capacity, smaller ovarian tubules and lower relative expression levels of reproduction-related genes including Trehalose transporter (Tret), Vitellogenin (Vg) and Cytochrome P450 hydroxylase (cyp314a1), while Juvenile hormone acid methyltransferase (JHAMT) expression was upregulated. RNA sequencing and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed significant enrichment of genes involved in lipid, amino acid, and vitamin metabolisms, with Long-chain acyl-CoA synthetase implicated as a key regulator of lipid metabolism and reproductive fitness. These results highlight the complex interactions between endosymbionts, host plants and pest biology, offering a solid foundation for sustainable approaches to control N. lugens in rice production systems.

The Brown Planthopper, Nilaparvata lugens (Stål.) (Hemiptera: Delphinidae), is one of the most destructive pests of rice. Its reproductive and developmental traits are influenced by various environmental and biological factors including endosymbiotic microorganisms. Arsenophonus , a widespread endosymbiotic bacterium of insects, can affect host fitness and metabolic processes. This study investigates the role of Arsenophonus in modulating the developmental and reproductive traits of N. lugens fed on transgenic cry30Fa1 rice (KF30-14) and its parent variety Minghui 86 (MH86). Life table analysis revealed that Arsenophonus infection (Ars⁺) increased the development time and reduced the reproductive capacity of N. lugens, especially those feeding on KF30-14. The first-instar nymphs in MH86 Ars⁺ (infected) exhibited slower development compared to MH86 Ars^- (uninfected). Similarly, the third and fourth-instar nymphs in KF30-14 Ars⁺ exhibited prolonged development time compared to KF30-14 Ars^-. In addition, KF30-14 Ars⁺ females had significantly reduced reproductive capacity, smaller ovarian tubules and lower relative expression levels of reproduction-related genes including Trehalose transporter (Tret), Vitellogenin (Vg) and Cytochrome P450 hydroxylase (cyp314a1), while Juvenile hormone acid methyltransferase (JHAMT) expression was upregulated. RNA sequencing and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed significant enrichment of genes involved in lipid, amino acid, and vitamin metabolisms, with Long-chain acyl-CoA synthetase implicated as a key regulator of lipid metabolism and reproductive fitness. These results highlight the complex interactions between endosymbionts, host plants and pest biology, offering a solid foundation for sustainable approaches to control N. lugens in rice production systems.

In this study, two vital genes in the serine protease cascade, NlK-serpin and NlVenomase, were identified. Two genes show differential responses in brown planthopper (Nilaparvata lugens, BPH) carrying the insect fungal pathogen Metarhizium anisopliae YTTR and/or the plant viral pathogen rice ragged stunt virus (RRSV). RNA interference (RNAi) combined with/without M. anisopliae YTTR were used to explore the genes’ functions. And BPH mortality, the transcriptional response of four antimicrobial peptides (AMPs) genes, and the phenoloxidase (PO) activity were measured to unveil the underlying mechanism. Results showed that the coding sequences (CDSs) of NlK-serpin and NlVenomase contained 291-bp and 1,194-bp nucleotides, respectively. Phylogenetic analysis showed both genes have the closest kinship to Laodelphax striatellus. NlK-serpin is highly expressed in the adult and 3rd -instar stages and NlVenomase is highly expressed in 2nd and 3rd -instar nymphs. Both genes possess high expression in the fat body. Synthesized dsRNAs have strong interference efficiency against the expression of target genes. DsNlK-serpin injection significantly reduced BPHs survival rates in RRSV-free BPHs. However, when RRSV existed, the differences in survival rates among the three dsRNA treatments were insignificant. DsRNA combined with M. anisopliae YTTR produced a synergistic effect leading to higher BPHs mortality. Results of AMPs expression and PO activity indicated that NlK-serpin and NlVenomase play a vital role in BPH humoral immunity against M. anisopliae YTTR infection. And both genes participate in the process of RRSV-mediated immune responses of BPH to M. anisopliae YTTR infection by regulating AMPs expression and PO activity. Our study provided new targets for BPH control and laid a solid foundation for further research the interaction of “plant virus- insect vector- entomopathogenic fungus”.

Plant viruses and entomopathogenic fungi (EPF) can both elicit immune responses in insects. This study was designed to clarify whether plant viruses could affect the efficacy of EPF and explore the immune responses of brown planthopper (BPH), Nilaparvata lugens, in response to different pathogen infections. In this study, a strain of Metarhizium anisopliae YTTR with high pathogenicity against BPH was selected and explored whether rice ragged stunt virus (RRSV) could affect its lethality against BPH. RNA-seq was used to detect the inner responses of BPH in response to RRSV and M. anisopliae YTTR infection. Results showed that M. anisopliae YTTR has strong lethality against BPH (RRSV-carrying and RRSV-free). RRSV invasion did not affect the susceptibility of BPH against M. anisopliae YTTR at all concentrations. At 1 × 10⁸ spores/mL, M. anisopliae YTTR caused a cumulative mortality of 80% to BPH at 7 days post-treatment. The largest numbers of differentially expressed genes (DEGs) was obtained in BPH treated with the two pathogens than in other single pathogen treatment. In addition, KEGG enrichment analysis showed that the DEGs were mostly enriched in immune and physiological mechanisms-related pathways. Both RRSV and M. anisopliae YTTR could induce the expression changes of immune-related genes. However, most of the immune genes had varying expression patterns in different treatment. Our findings demonstrated that RRSV invasion did not have any significant effect on the pathogenicity of M. anisopliae YTTR, while the co-infection of M. anisopliae YTTR and RRSV induced more immune and physiological mechanisms -related genes’ responses. In addition, the presence of RRSV could render the interplay between BPH and M. anisopliae YTTR more intricate. These findings laid a basis for further elucidating the immune response mechanisms of RRSV-mediated BPH to M. anisopliae infection.