Brown Planthopper Nilaparvata Lugens Research Articles

Candidate genes and molecular markers associated with brown planthopper (Nilaparvata lugens Stål) resistance in rice cultivar Rathu Heenati

Brown planthopper (BPH) is a destructive insect pest of rice and causes severe yield loss. In attempts to develop a BPH-resistant rice variety, Rathu Heenati (RH), a rice cultivar with a strong BPH resistance, has been used as the donor in breeding programs. Quantitative trait loci analysis was conducted for the area under the curve of BPH damage scores of a backcross (BC3F5) population infested by six different BPH populations. Single nucleotide polymorphism (SNP) markers on chromosome 4, i.e., LecRK2-SNP and LecRK3-SNP, and markers on chromosome 6, i.e., Bph32-SNP and SSR23, were identified to be associated with resistance against five BPH populations. To identify genes on chromosome 6 that are involved in BPH resistance, expression analysis was conducted for genes located in the genomic region of Bph32-SNP and SSR23. Genes that showed differential expression ofRH at 24 h after BPH infestation, when compared to an RH control, were identified. Those that encode proteins putatively involved in the BPH resistance mechanism are LOC_Os06g03240, LOC_Os06g03380, LOC_Os06g03486, LOC_Os06g03514, LOC_Os06g03520, LOC_Os06g03610, LOC_Os06g03676, and LOC_Os06g03890. SNP markers were developed from several differentially expressed genes and were validated by genotyping in the backcross population. The SNP marker developed from LOC_Os06g03514 showed the highest association with BPH resistance and the gene may be involved in the BPH resistance mechanism. This SNP marker will be useful in breeding programs for BPH resistance.

Regulation of NlE74A on vitellogenin may be mediated by angiotensin converting enzyme through a fecundity-related SNP in the brown planthopper, Nilaparvata lugens

The major yolk protein precursors (YPP) gene, vitellogenin (Vg), usually considered as a reproductive indicator and molecular marker for evaluating insect fecundity, is controlled by insect hormone (mainly ecdysteroids and juvenile hormone), transcription factors and many other fecundity-related genes. To better understand the underlying molecular regulation mechanisms of the NlVg in the brown planthopper Nilaparvata lugens (N. lugens), the correlation between one early ecdysone response gene E74 and one important fecundity-related gene angiotensin converting enzyme (ACE) on the regulation of Vg gene expression, was investigated. We first showed that the mRNA expression level of NlACE were significantly higher in a high-fecundity population (HFP) than a low-fecundity population (LFP) at different development stages, and knockdown of NlACE expression by RNA interference (RNAi) results in a reduced level of NlVg expression and N. lugens fecundity. Subsequently, we analyzed the promoter of NlACE and found an E74A binding site, which was also differentially expressed in HFP and LFP. Then a gene putatively encoding E74A, namely NlE74A, predominant in the ovary and fat body was cloned and characterized. Furthermore, the developmental profile during female adult and the tissue-specific expression pattern of NlACE and NlE74A were similar to the expression pattern of NlVg gene, implying that both NlACE and NlE74A may be involved in regulating the expression of NlVg. Finally, after injecting the dsRNA of NlE74A, the NlACE expression levels were significantly reduced simultaneously at 24 h and 48 h post-injection, and the NlVg expression level was significant reduced at 24 h post-injection and the downswing was more significant at 48 h post-injection. These results imply that regulation of NlE74A on NlVg transcription might be mediated by NlACE through the E74 binding site at the NlACE promoter region in N. lugens.

Furan carbonylhydrazones-derived elicitors that induce the resistance of rice to the brown planthopper Nilaparvata lugens

To obtain new elicitors that could induce plant defense against pests, a series of furan carbonylhydrazones were synthesized. Phenotypic high-throughput screening of β-glucuronidase (GUS) activity was used to identify elicitors with strong activity. Integrated bioassays were conducted to acquire chemical elicitors that induce resistance in rice to the brown planthopper Nilaparvata lugens and they are not direct toxic to the pest. Our results demonstrate that these compounds have the potential to serve as new kinds of environment-friendly plant protection agents in rice.

The Wrinkle-Lipped Free-Tailed Bat (Chaerephon plicatus Buchannan, 1800) Feeds Mainly on Brown Planthoppers in Rice Fields of Central Thailand

The brown planthopper (Nilaparvata lugens) is one of the major insect pests of rice fields in Southeast Asia. They have been widely acknowledged for causing significant rice yield losses. However, the wrinkle-lipped free-tailed bat (Chaerephon plicatus Buchannan, 1800) is a known agent of pest suppression for white-backed planthoppers (Sogatella furcifera), and may also suppress brown planthopper populations. Hence, it is important to investigate the diet of C. plicatus in areas where brown planthoppers are common to determine whether these bats feed on these insects. To accomplish this objective, we analyzed the diet of C. plicatus from two caves that differed in the percentage of surrounding land area occupied by rice fields (70% versus 22%). Bat fecal pellets were collected monthly for a year. A total of 720 fecal pellets were analyzed, and the results revealed that C. plicatus feeds on at least eight insect orders, including Coleoptera, Homoptera, Hemiptera, Diptera, Lepidoptera, Odonata, Hymenoptera and Orthoptera. Specifically, homopterans comprised the greatest diet volume in the rice growing season, whereas coleopterans were most abundant in the diet when rice fields were fallow. Moreover, most homopterans were identified as brown planthoppers. To estimate the relative numbers of brown planthoppers consumed during each month, the number of genitalia of male brown planthoppers was counted. We recorded the greatest numbers of genitalia during the rice planting period, with an average of four genitalia per fecal pellet. Examining both the percent volume and percent frequency of each insect order in the diet of C. plicatus revealed that the two study caves were no significantly different, even though the proportion of surrounding active rice fields was different. Our results suggest that tens of millions of brown planthoppers are consumed by this bat species each night. The similar diets of the two study colonies may be due to their high altitude foraging and preference for migratory insects. Our results indicate that the wrinkle-lipped freetailed bat is an important biological suppression agent of brown planthoppers in rice fields.

Schaftoside Interacts With NlCDK1 Protein: A Mechanism of Rice Resistance to Brown Planthopper, Nilaparvata lugens.

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.

Block of Kir channels by flonicamid disrupts salivary and renal excretion of insect pests

Flonicamid is a selective insecticide for the control of sap-sucking insects; it exerts toxic effects by inhibiting insect feeding. However, its molecular target remains elusive. In this study, we functionally characterized NlKir1 channels of the brown planthopper (Nilaparvata lugens) in HEK293 cells. Homomeric NlKir1 channels generated inward-rectifying K+ currents. Flonicamid inhibited NlKir1 channels at nanomolar concentrations. Furthermore, flonicamid inhibited honeydew and salivary secretions of planthoppers, and reduced the renal excretion of female mosquitoes in a dose-dependent manner. The inhibitory effect of flonicamid on fluid secretion of isolated Malpighian tubules from Culex pipiens pullens was comparable to that of the selective Kir1 inhibitor. The observed physiological alterations by flonicamid are likely mediated by Kir1 channels and could lead to the disruption of feeding behaviors and eventually lethality. Our study establishes the Kir1 channel as the target of flonicamid and provided new insights into the mode of action of flonicamid.

Molecular characterization and evolution of a chemosensory receptor gene family in three notorious rice planthoppers, Nilaparvata lugens, Sogatella furcifera and Laodelphax striatellus, based on genome and transcriptome analyses.

The white-backed planthopper (WBPH) Sogatella furcifera, the brown planthopper (BPH) Nilaparvata lugens, and the small brown planthopper (SBPH) Laodelphax striatellus (Hemiptera: Delphacidae) are rice pests that damage rice plants by sap-sucking and by transmitting viruses. Host-seeking behavior involves chemosensory receptor genes that include odorant receptors (ORs), ionotropic receptors (IRs) and gustatory receptors (GRs). We used genome and transcriptome data to identify 141 ORs, 28 GRs and 25 IRs in BPH; 135 ORs, 18 GRs and 16 IRs in WBPH; and 37 ORs, 14 GRs and 6 IRs in SBPH. A phylogenetic analysis identified several specific OR clades of rice planthoppers, the results indicating that these OR members might be used to respond to specific host volatiles. OR co-receptor (Orco) is the most conserved and essential OR gene among these species and RNA interference (RNAi) can decrease their mRNA expression level to <50%. RNAi knockdown rice planthoppers were anosmia and were unable to seek or locate rice plants in behavioral tests. The results demonstrate the importance of the planthopper Orco genes in locating rice plants. This information may aid in the development of RNAi-based transgenic rice and other pest management technologies. © 2018 Society of Chemical Industry.

The Commonly Used Bactericide Bismerthiazol Promotes Rice Defenses against Herbivores.

Chemical elicitors that enhance plant resistance to pathogens have been extensively studied, however, chemical elicitors that induce plant defenses against insect pests have received little attention. Here, we found that the exogenous application of a commonly used bactericide, bismerthiazol, on rice induced the biosynthesis of constitutive and/or elicited jasmonic acid (JA), jasmonoyl-isoleucine conjugate (JA-Ile), ethylene and H2O2 but not salicylic acid. These activated signaling pathways altered the volatile profile of rice plants. White-backed planthopper (WBPH, Sogatella furcifera) nymphs and gravid females showed a preference for feeding and/or oviposition on control plants: survival rates were better and more eggs were laid than on bismerthiazol-treated plants. Moreover, bismerthiazol treatment also increased both the parasitism rate of WBPH eggs laid on plants in the field by Anagrus nilaparvatae, and also the resistance of rice to the brown planthopper (BPH) Nilaparvata lugens and the striped stem borer (SSB) Chilo suppressalis. These findings suggest that the bactericide bismerthiazol can induce the direct and/or indirect resistance of rice to multiple insect pests, and so can be used as a broad-spectrum chemical elicitor.

Gut Bacterial Diversity of Insecticide-Susceptible and -Resistant Nymphs of the Brown Planthopper Nilaparvata lugens Stål (Hemiptera: Delphacidae) and Elucidation of Their Putative Functional Roles.

Knowledge about the gut bacterial communities associated with insects is essential to understand their roles in the physiology of the host. In the present study, the gut bacterial communities of a laboratory-reared insecticide-susceptible (IS), and a field-collected insecticide-resistant (IR) population of a major rice pest, the brown planthopper Nilaparvata lugens, were evaluated. The deep-sequencing analysis of the V3 hypervariable region of the 16S rRNA gene was performed using Illumina and the sequence data were processed using QIIME. The toxicological bioassays showed that compared with the IS population, IR population exhibited 7.9-, 6.7-, 14.8-, and 18.7-fold resistance to acephate, imidacloprid, thiamethoxam, and buprofezin, respectively. The analysis of the alpha diversity indicated a higher bacterial diversity and richness associated with the IR population. The dominant phylum in the IS population was Proteobacteria (99.86%), whereas the IR population consisted of Firmicutes (46.06%), followed by Bacteroidetes (30.8%) and Proteobacteria (15.49%). Morganella, Weissella, and Enterococcus were among the genera shared between the two populations and might form the core bacteria associated with N. lugens. The taxonomic-to-phenotypic mapping revealed the presence of ammonia oxidizers, nitrogen fixers, sulfur oxidizers and reducers, xylan degraders, and aromatic hydrocarbon degraders in the metagenome of N. lugens. Interestingly, the IR population was found to be enriched with bacteria involved in detoxification functions. The results obtained in this study provide a basis for future studies elucidating the roles of the gut bacteria in the insecticide resistance-associated symbiotic relationship and on the design of novel strategies for the management of N. lugens.

Enhancing the parasitism of insect herbivores through diversification of habitat in Philippine rice fields

The diversification of farming landscapes is proposed as a method to increase farm productivity while at the same time enhancing pest regulation services provided by the natural enemies of insect herbivores. In this study, areas of diversified and conventional rice fields (with 2–14 fields per area = 0.42–1.31 ha) were established at three sites in the Philippines. The diversified areas had a series (> 40 per hectare) of small (< 2 m2) vegetable patches interspersed along rice bunds (levees). The abundance of planthopper and lepidopteran pests in these areas was monitored during two consecutive cropping seasons using sweep nets with rice yield and damage recorded at the end of each season. Mortality of brown planthopper (Nilaparvata lugens) and yellow stemborer (Scirpophaga incertulas) eggs was monitored through field exposures of infested rice plants. There were no differences in rice yields between the conventional and diversified areas; however, a range of vegetables were produced as a supplementary product from the diversified rice areas. Diversification had no effect on planthopper or leaffolder (Cnaphalocrocis medinalis) abundance at the sites. Adult stemborers (Scirpophaga incertulas) were more abundant in the diversified areas; however, stemborer damage was similar between area treatments in both years. Vegetable patches did not increase parasitism of planthopper eggs; however, egg parasitism was highest close to the vegetable patches, suggesting that egg parasitoids interacted with the patches. Mortality of stemborer eggs was higher in the diversified areas than in the conventional areas. Parasitism due to Trichogramma japonicum and other egg parasitoids was also higher in the diversified areas. These results indicate the potential for vegetable patches to enhance the biological control services provided by egg parasitoids in rice fields; however, the study also indicates a need to carefully select vegetable crops that avoid any potential benefits for rice pests. We discuss the need for further research into diversified farms as a means of achieving sustainable rice production in Asia.

Current status of rice brown planthopper against insecticides in China (Abstract)

The brown planthopper (Nilaparvata lugens Stal) is one of the most destructive pest of rice crops throughout Asia, and this pest has developed high resistance to many groups of insecticides following their heavy and frequent application. In order to investigate the current status of resistance to frequently used insecticides, a total of fifty-three field populations of N. lugens were collected in nine Chinese provinces, and resistance to insecticides was monitored from 2013 to 2017. The result showed that field populations of N. lugens had developed susceptible to low resistance levels to sulfoxaflor (RR 0.8-8.0), susceptible to moderate resistance levels to etofenprox (RR 1.0-11.2), triflumezopyrim (RR 1.2-17.1) and nitenpyram (RR 1.2-17.3), low to moderate resistance levels to chlorpyrifos (RR 7.7-57.4), low to high resistance levels to clothianidin (RR 6.1-138.8) and dinotefuran (RR 6.4-187.0), and moderate to high resistance levels to isoprocarb (RR 15.4-113.9) and thiamethoxam (RR 25.9-1025.6). Furthermore, all fifty-three field populations of N. lugens had developed high resistance levels to imidacloprid (RR 220.4-6324.0) and buprofezin (RR 306.4-11573.2). Except etofenprox, nitenpyram and chlorpyrifos, the resistance ratio of N. lugens to other insecticides all showed an increasing trend from 2013 to 2017. The obvious increase in resistance to widely applied insecticides indicates that insecticide resistance management strategies are urgently needed to prevent or delay further increase of insecticide resistance in N. lugens.

Fitness cost of nitenpyram resistance in the brown planthopper Nilaparvata lugens

A resistant strain of Nilaparvata lugens has been continuously selected in the presence of nitenpyram for 27 generations under laboratory conditions in order to study the fitness cost of nitenpyram resistance. The resistance to nitenpyram in N. lugens was at a high level (resistance ratio = 144.7-fold). Life-tables of the nitenpyram-resistant strain and the susceptible strain (SS) of N. lugens were studied by using the age-stage, two-sex life-table approach. Compared to the SS, the relative fitness of the resistant strain of N. lugens was 0.55, with a lower intrinsic rate of increase (r) and net reproductive rate (R0). Changes in some life-history traits of the resistant strain were also observed. The duration of the egg stage, the development times of the first-, third- and fourth-instar nymphs, the adult preoviposition period and the total preoviposition period of the resistant strain were significantly increased, whereas the longevity, egg survival rate and fecundity (eggs/female) (absolute fitness) were significantly decreased in the resistant strain of N. lugens. The lower intrinsic rate of increase (r) and net reproductive rate (R0) seemed to be largely due to number of eggs laid, developmental time and egg survival rate. These results showed that the development of nitenpyram resistance may lead to significant fitness costs in resistant populations of N. lugens. This study provided valuable information for facilitating the development of nitenpyram-resistance management strategies.

The evolution of insecticide resistance in the brown planthopper (Nilaparvata lugens St\xe5l) of China in the period 2012\u20132016

The brown planthopper, Nilaparvata lugens, is an economically important pest on rice in Asia. Chemical control is still the most efficient primary way for rice planthopper control. However, due to the intensive use of insecticides to control this pest over many years, resistance to most of the classes of chemical insecticides has been reported. In this article, we report on the status of eight insecticides resistance in Nilaparvata lugens (Stål) collected from China over the period 2012–2016. All of the field populations collected in 2016 had developed extremely high resistance to imidacloprid, thiamethoxam, and buprofezin. Synergism tests showed that piperonyl butoxide (PBO) produced a high synergism of imidacloprid, thiamethoxam, and buprofezin effects in the three field populations, YA2016, HX2016, and YC2016. Functional studies using both double-strand RNA (dsRNA)-mediated knockdown in the expression of CYP6ER1 and transgenic expression of CYP6ER1 in Drosophila melanogaster showed that CYP6ER1 confers imidacloprid, thiamethoxam and buprofezin resistance. These results will be beneficial for effective insecticide resistance management strategies to prevent or delay the development of insecticide resistance in brown planthopper populations.

A new gene Bph33(t) conferring resistance to brown planthopper (BPH), Nilaparvata lugens (Stål) in rice line RP2068-18-3-5

The rice brown planthopper (BPH) Nilaparvata lugens (Stal) is one of the major pests of rice across Asia. Host-plant resistance is the most ecologically acceptable means to manage this pest. A rice breeding line RP2068-18-3-5 (RP2068) derived from the land race Velluthacheera is reported to be resistant to BPH populations across India. We identified a new R gene [Bph33(t)] in this line using advanced generation RILs derived from TN1 × RP2068 cross through phenotyping at two locations and linkage analysis with 99 polymorphic SSR markers. QTL analysis through IciMapping identified at least two major QTL on chromosome 1 influencing seedling damage score in seed box screening, honey dew excretion by adults and nymphal survival. Since no BPH R gene has been reported on chromosome 1, we designate this locus as a new gene Bph33(t) which accounted for over 20% of phenotypic variance. Scanning the region for candidate gene suggested two likely candidates a leucine rich repeat (LRR) gene and a heat shock protein (HSP) coding gene. Expression profiling of the two genes in the two contrasting parents and RILs showed induction of the HSP gene (LOC_Os01g42190.1) at 6 h after infestation while LRR gene did not show such induction. It is likely that the HSP represented Bph33(t).

Effectiveness of biopesticides against brown planthopper (Nilaparvata lugens) in paddy cultivation

The brown planthopper (BPH) causes serious damage to rice by sucking rice sap, ovipositing in rice tissues, and transmitting a number of rice diseases during its long-distance migration that severely affect the productivity of paddy. Thus, the aim of this study is to investigate the effectiveness of biopesticides against BPH population. BV500WS is used at the early stage of paddy cultivation for growth enhancement meanwhile BV612EC is used a week after the liberation of BPH for crop protection. Three conditions were adopted as follows which are T1 where the paddy was sprayed using BV500WS and BV612EC to study the effectiveness of both types of biopesticides, T2 where the paddy was sprayed using BV500WS only and C1 where the paddy was cultivated without any pesticide application as control. BPH was released twice on day 46 and 59 of paddy cultivation. Reduction of BPH population with up to 100% mortality rate was observed with the application of two types of biopesticides at T1 resulting in the highest number of remaining tillers with 68.56%. Although severely affected by BPH, T2 was able to has comparable number of remaining tillers as C1 which was 46.24% and 49.65% respectively. These results showed that two types of biopesticides were more effective in reducing BPH compared to one type of biopesticide.

Double-ambient CO2 concentration affects the growth, development and sucking behavior of non-target brown plant hopper Nilaparvata lugens fed on transgenic Bt rice.

In recent years, the two issues of climate change including elevated CO2 etc., and resistance of transgenic Bt crops against non-target insect pests have received widespread attention. Elevated CO2 can affect the herbivorous insects. To date, there is no consensus about the effect of elevated CO2 on the suck-feeding insect pests (non-target insect pests of transgenic Bt crops). Its effects on the suck-feeding behavior have rarely been reported. In this study, CO2 levels were set up in artificial climate chamber to examined the effects of ambient (400 μL·L-1) and double-ambient (800 μL·L-1) CO2 levels on the suck-feeding behavior, growth, development, and reproduction of the non-target insect pest of transgenic Bt rice, brown planthopper, Nilaparvata lugens. The results showed that CO2 level significantly affected the egg and nymph duration, longevity and body mass of adults, and feeding behavior of the 4th and 5th instar nymphs, while had no effect on the fecundity of N. lugens. The duration of eggs and nymphs, and the longevity of female adults were significantly shortened by 4.0%, 4.2% and 6.6% respectively, the proportion of the macropterous adults was significantly increased by 11.6%, and the body mass of newly hatched female adults was significantly decreased by 2.2% by elevated CO2. In addition, elevated CO2 significantly enhanced the stylet puncturing efficiency of the 4th and 5th instar nymphs of N. lugens. The duration ofphloem ingestion of the N4b waveform was significantly prolonged by 60.0% and 50.1%, and the frequency significantly was increased by 230.0% and 155.9% for the 4th and 5th instar nymphs of N. lugens by elevated CO2, respectively. It was concluded that double-ambient CO2 could promote the growth and development of N. lugens through enhancing its suck-feeding, shorten the generation life-span and increase the macropertous adults' proportion of N. lugens. Thus, it could result in the occurrence of non-target rice planthopper N. lugens and make the transgenic Bt crops face with harm risk due to migration and diffusion of N. lugens under elevated CO2.

Analysis of Homologs of Cry-toxin Receptor-Related Proteins in the Midgut of a Non-Bt Target, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae).

The brown planthopper (BPH) Nilaparvata lugens is one of the most destructive insect pests in the rice fields of Asia. Like other hemipteran insects, BPH is not susceptible to Cry toxins of Bacillus thuringiensis (Bt) or transgenic rice carrying Bt cry genes. Lack of Cry receptors in the midgut is one of the main reasons that BPH is not susceptible to the Cry toxins. The main Cry-binding proteins (CBPs) of the susceptible insects are cadherin, aminopeptidase N (APN), and alkaline phosphatase (ALP). In this study, we analyzed and validated de novo assembled transcripts from transcriptome sequencing data of BPH to identify and characterize homologs of cadherin, APN, and ALP. We then compared the cadherin-, APN-, and ALP-like proteins of BPH to previously reported CBPs to identify their homologs in BPH. The sequence analysis revealed that at least one cadherin, one APN, and two ALPs of BPH contained homologous functional domains identified from the Cry-binding cadherin, APN, and ALP, respectively. Quantitative real-time polymerase chain reaction used to verify the expression level of each putative Cry receptor homolog in the BPH midgut indicated that the CBPs homologous APN and ALP were expressed at high or medium-high levels while the cadherin was expressed at a low level. These results suggest that homologs of CBPs exist in the midgut of BPH. However, differences in key motifs of CBPs, which are functional in interacting with Cry toxins, may be responsible for insusceptibility of BPH to Cry toxins.

Viral infection induces different detoxification enzyme activities in insecticide-resistant and -susceptible brown planthopper Nilaparvata lugens strains.

This study aimed to describe the relationship between viral infection in Nilaparvata lugens (Stål), the brown planthopper (BPH), and different insecticide susceptibilities. BPH-resistant strains were selected using fenthion (an organophosphate) or etofenprox (a pyrethroid); a susceptible strain was used as the baseline colony before insecticide selection. All strains were infected with rice ragged stunt virus (RRSV) or rice grassy stunt virus (RGSV), after which the activities of three detoxification enzymes, cytochrome-P450-monooxygenase (P450), glutathione S-transferase (GST), and carboxylesterase (CE), were compared. Males of the strains selected for both insecticides showed high P450 and GST-CDNB activities. The activity of all enzymes was higher in males than in females, as a whole. However, males of the susceptible strain infected with RRSV showed decreased CE and GST-CDNB activities. BPH with low susceptibility to etofenprox showed a marked increase in P450 activity after RRSV infection; the GST-CDNB activity of females in the insecticide-resistant strain increased. RGSV infection induced high CE and P450 activities in etofenprox-selected females. The RRSV infection rate, but not the RGSV, decreased in etofenprox-selected strains.

الفلافونويدات المضادة للميكروبات ودورها في تفاعلات النبات والحيوان

الفلافونويدات عبارة عن: (("خلايا التخليق (التركيب الضوئي) الموجودة في كل مكان، والتي توجد عادة في الفواكه والخضراوات، والمكسرات، والبذور، والزهور، والشاي، والنبيذ، والعسل)). ولعدة قرون، كانت المستحضرات المحتوية على هذه المركبات من الناحية الفسيولوجية هي المكونات الرئيسة النشطة التي تستخدم لعلاج الأمراض التي تصيب الإنسان. إنّ إحدى الوظائف المسلّم بها للفلافونويدات متعددة الفينولات دورها المهم في حماية النباتات ضد الغـزو الميكروبيّ. وهـذا لا يتضمن فقط وجودها في النباتات بوصفها أساسية مضادة للفطريات المتكونة؛ بل تجمعها في صورة أكسين (سم) نباتي المصدر كاستجابة للهجوم الميكروبيّ. ونظراً لقدرتها الـواسعـة على منع النمو الجرثومي المسبب للمرض في النبات؛ فلقد اقترح أيضا استخدامها كمضادات لمسببات الأمراض الفطرية عند الإنسان. لقد أصبح مقبولاً في الوقت الحاضر اعتبار الفلافونويدات في بعض النباتات متعددة الفينولات ذات دور في حماية النباتات من الحشرات والحيوانات الآكلة للعشب. ففي السنوات الأخيرة تم التركيز على المركبات الفينولية أو على الفلافولانات البوليمرية أو على بروأنثوسيانيدينات؛ ولكن بعض هذه البحوث ركزت على فلافونات، فلافونولات وأيسوفلافونات ذات الوزن الجزيئي المنخفض. فعلى سبيل المثال، مركبات جليكوفلافونات الثلاثة، وهي سشافتوسيد، أيسوسشافتوسيد ونيوسشافتوسيد تم التعرف عليها في نسغ لحاء نبات الأرز، حيث تقوم هذه المركبات بامتصاص موانع الحشـرات الضارة وخاصة الحشرة النطاطة ذات اللون البنّي Nilaparvata lugens. إن الغرض من هذا البحث مناقشة التطورات الحديثة في الكيمياء الحيوية، والأوجه الطبية للفلافونويدات، حيث أثبت في الوقت الحاضر أن الفلافونويدات تساهم في مقاومة الأمراض، إما بوصفها عوامل مضادة للفطريات المتكونة، أو بوصفها مضادات للميكروبات التي تغزو جسم النبات. كما توجد دلائـل إضافية على أن الفلافونويدات وخاصة فلافولانات أو بروانثوسيانيدينات، توفر الحماية ضد العاشب (حيوان من العواشب أي الحيوانات المقتاتة بالأعشاب) وبعض التجارب الحديثة في النبات-الحيوان سوف يشار إليها في هذا البحث.

CRISPR/Cas9-mediated knockout of two eye pigmentation genes in the brown planthopper, Nilaparvata lugens (Hemiptera: Delphacidae)

The brown planthopper Nilaparvata lugens is one of the most destructive insect pests in Asia, demonstrating high fertility and causing huge crop losses by sucking sap of rice as well as transmitting viruses. However, functional genomic studies on N. lugens are seriously constrained by lack of genetic tools. Here, we employed two eye pigmentation genes to generate germ-line mutations in N. lugens using the CRISPR/Cas9 (clustered regularly interspaced palindromic repeats/CRISPR-associated) system. We showed that injection of single guide RNA of the cinnabar gene of N. lugens (Nl-cn) into pre-blastoderm eggs induced insertion and deletion (indels) in the founder generation (G0), which were heritably transmitted to the following G1 generation, leading to bright red compound eyes and ocelli. Mutations of N. lugens white (Nl-w) generated a high mutant rate of up to 27.3%, resulting in mosaic eyes consisting of white and lightly pigmented ommatidia in both G0 and G1 individuals. The specificity of CRISPR/Cas9-mediated mutagenesis was further bolstered by PCR and RNA interference-based knockdown analysis. These results show that CRISPR/Cas9-mediated gene editing is achievable in a hemipteran insect, offering a valuable tool for the study of functional genomics and pest management in this planthopper species.