The brown planthopper (Nilaparvata lugens Stål; BPH) is a specialist herbivore on rice (Oryza sativa) that ingests phloem sap from the plant through its stylet mouthparts. Electronic penetration graphs revealed that BPH insects spent more time wandering over plants carrying the resistance genes Bph14 and Bph15, but less time ingesting phloem than they did on susceptible plants. They also showed that their feeding was frequently interrupted. Tests with [¹⁴C]sucrose showed that insects ingested much less phloem sap from the resistant than the susceptible plants. BPH feeding up-regulated callose synthase genes and induced callose deposition in the sieve tubes at the point where the stylet was inserted. The compact callose remained intact in the resistant plants, but genes encoding β-1,3-glucanases were activated, causing unplugging of the sieve tube occlusions in susceptible plants. Continuing ingestion led to a remarkable reduction in the susceptible plants9 sucrose content and activation of the RAmy3D gene, leading to starch hydrolysis and ultimately carbohydrate deprivation in the plants. Our results demonstrate that BPH feeding induces the deposition of callose on sieve plates in rice and that this is an important defense mechanism that prevents insects from ingesting phloem sap. In response, however, the BPH can unplug sieve tube occlusions by activating β-1,3-glucanase genes in rice plants.

Brown planthopper (BPH) Nilaparvata lugens Stål is a serious insect pest of rice in Asian countries. Active compounds have close relationship with rice resistance against BPH. In this study, HPLC, MS/MS, and NMR techniques were used to identify active compounds in total flavonoids of rice. As a result, a BPH resistance-associated compound, Peak 1 in HPLC chromatogram of rice flavonoids, was isolated and identified as schaftoside. Feeding experiment with artificial diet indicated that schaftoside played its role in a dose dependent manner, under the concentration of 0.10 and 0.15 mg mL-1, schaftoside showed a significant inhibitory effect on BPH survival (p < 0.05), in comparison with the control. The fluorescent spectra showed that schaftoside has a strong ability to bind with NlCDK1, a CDK1 kinase of BPH. The apparent association constant KA for NlCDK1 binding with schaftoside is 6.436×103 L/mol. Docking model suggested that binding of schaftoside might affect the activation of NlCDK1 as a protein kinase, mainly through interacting with amino acid residues Glu12, Thr14 and Val17 in the ATP binding element GXGXXGXV (Gly11 to Val18). Western blot using anti-phospho-CDK1 (pThr14) antibody confirmed that schaftoside treatment suppressed the phosphorylation on Thr-14 site of NlCDK1, thus inhibited its activation as a kinase. Therefore, this study revealed the schaftoside-NlCDK1 interaction mode, and unraveled a novel mechanism of rice resistance against BPH.

The ribosomal proteins play important roles in the growth and development of organisms. This study aimed to explore the function of NlRPL5 (GenBank KX379234), a ribosomal protein L5 gene, in the brown planthopper Nilaparvata lugens. The open reading frame of NlRPL5 was cloned from N. lugens based on a previous transcriptome analysis. The results revealed that the open reading frame of NlRPL5 is of 900 bp, encoding 299 amino acid residues. The reverse transcription quantitative PCR results suggested that the expression of NlRPL5 gene was stronger in gravid females, but was relatively low in nymphs, males, and newly emerged females. The expression level of NlRPL5 in the ovary was about twofolds of that in the head, thorax, or fat body. RNAi of dsNlRPL5 resulted in a significant reduction of mRNA levels, ∼50% decrease in comparison with the dsGFP control at day 6. Treatment of dsNlRPL5 significantly restricted the ovarian development, and decreased the number of eggs laid on the rice (Oryza sativa) plants. This study provided a new clue for further study on the function and regulation mechanism of NlRPL5 in N. lugens.

The advancement in CRISPR-Cas biosensors has transmuted the detection of plant viruses owing to their rapid and higher sensitivity. However, false positives and restricted multiplexing capabilities are still the challenges faced by this technology, demanding the exploration of novel methodologies. In this study, a novel detection system was developed by integrating reverse transcriptome (RT) techniques with recombinase polymerase isothermal amplification (RPA) and Pyrococcus furiosus Argonaute (PfAgo). The RT-RPA-PfAgo system enabled the simultaneous detection of rice ragged stunt virus (RRSV), rice grassy stunt virus (RGSV), and rice black streaked dwarf virus (RBSDV). Identifying targets via guide DNA without being hindered by protospacer adjacent motif sequences is the inherent merit of PfAgo, with the additional advantage of it being simple, cost-effective, and exceptionally sensitive, with detection limits between 3.13 and 5.13 copies/µL, in addition to it effectively differentiating between the three distinct viruses. The field evaluations were also in accordance with RT-PCR methods. The RT-RPA-PfAgo system proved to be a robust, versatile, highly specific, and sensitive method with great potential for practicality in future plant virus diagnostics.

Cuticular proteins (CPs) are a large family and perform a variety of functions. However, the physiological roles of cuticle protein 21-like (Cpr21L) in the brown planthopper (Nilaparvata lugens, BPH), one of the most destructive insect pests of rice, are largely unclear. In this study, Cpr21L was revealed to be expressed in both BPH nymphs and adults, and the mRNA expression level was much higher in male adults than female adults. Spatially, the expression of Cpr21L in the testis was higher than in the ovary. The RNA interference (RNAi) of Cpr21L seriously decreased nymph survival, and no individual survived 8 days post-dsCpr21L injection. The RNAi of Cpr21L in adults also decreased the fertility of males, especially in the dsCpr21L♂ × dsGFP♀ group. The average number of eggs laid by one female in this group significantly decreased by 50.1%, and the eggs’ hatchability decreased from 76.5% to 23.8% compared with the control (dsGFP♂ × dsGFP♀). Furthermore, observations under a stereomicroscope showed that the RNAi of Cpr21L severely impaired the development of the testes. Therefore, Cpr21L is essential for the nymphal survival and male fecundity of BPH, thus providing a possible target for pest control.