Brown Planthopper Nilaparvata Lugens Research Articles

Characterization of gustatory receptor 7 in the brown planthopper reveals functional versatility

Insect pests consume tastants as their necessary energy and nutrient sources. Gustatory receptors play important roles in insect life and can form within an extremely complicated regulatory network. However, there are still many gustatory genes that have a significant impact on insect physiology, but their functional mechanism is still unknown. Here, we purified and characterized a gustatory receptor (protein) coding gene, NlGr7, from the brown planthopper (BPH) Nilaparvata lugens, which is an important insect pest of rice. Our results revealed that NlGr7 has an active association with various ligands, such as lectins, lipids (phospho- and sphingolipid) and copper. The mass-spectrometry result showed that NlGr7 is a sugar receptor, and NlGr7 is validated by different types of insoluble polysaccharides and a varied range of tastants. Further, we observed that NlGr7-bound ATP hydrolysed on the ATPase activity assay, which indicated that NlGr7 may be associated with important biological functions in the BPH. Furthermore, an injection of NlGr7 (protein), into newly emerged female adults of BPH, showed the reduced vitellogenin in ovary. The important NlGr7 for chemoreception has now been characterized in the BPH. We showed that NlGr7 in the BPH is required for various protein-ligands, as well as protein-sugars interactions, and for regulation of fecundity marker to play crucial roles in this pest. This study will provide valuable information for further functional studies of chemoreception mechanisms in this important agricultural pest.

Genotypic Variation in Virulence Level of Several Brown Planthopper (Nilaparvata lugens Stål) Populations of Rice (Oryza sativa L.)

Genotypic Variation in Virulence Level of Several Brown Planthopper (Nilaparvata lugens Stål) Populations of Rice (Oryza sativa L.)

The performance of the brown planthopper (Nilaparvata lugens) population and predators on endemic lowland rice areas of Banten Province

Brown planthopper (BPH) are one of the main pests of rice plants, their abundance is influenced by biotic and abiotic factors such as the presence of predators (natural enemies). The aim of the study was to determine the relationship between the natural enemies’ performance and the BPH performance. The study was conducted in BPH endemic areas in Serang and Lebak Regencies from March to July 2017. Sampling was carried out directly through visual observations based on four replications, where each replication consisted of 10 observation units. Data were analyzed descriptively in the form of tables and graphs, BPH performance was calculated based on existing population and corrected population. While predators are calculated based on the exsiting population that at the time of observation. Observations were made for five weeks, from 21 days after planting (DAP) to 56 DAP. The BPH population performance in Serang Regency was highest at 42 DAP (8.05 individual/clump) and in Lebak Regency at 35 DAP (25.05 individual/clump). Paederus is a predator with the highest abundance in Serang District, while the highest abundance of predators in Lebak Regency is spiders.

Genetic dissection and identification of candidate genes for brown planthopper, Nilaparvata lugens (Delphacidae: Hemiptera) resistance in farmers’ varieties of rice in Odisha

Globally, rice production is severely affected by brown planthopper (Nilaparvata lugens) populations. Among the four different biotypes of N. lugens reported worldwide, biotype 4 is the most damaging and prevalent insect pest in South East Asian countries, especially in the Indian sub-continent. Management of this pest with resistant genotypes is effective and thus it has received considerable attention worldwide. In the present work, a total of 600 farmer's varieties (FVs) were screened against N. lugens and subsequently 104 panel populations were selected for genotyping. Marker-trait association and genetic diversity were worked out for 87 molecular markers linked to 34 different N. lugens resistance genes. The average content of polymorphism information was 0.354 for 34 genes with a threshold level 0.018 to 0.750. One hundred and four FVs were categorized into three main genetic groups according to cluster analysis and population structure. Resistant and moderately resistant FVs were separately distributed according to principal co-ordinate analysis. Analysis of molecular variance displayed maximum diversity (83%) within population and minimum diversity (17%) between populations. In both generalized linear model (GLM) and multi linear model (MLM), eight markers linked to Bph genes were found to be common for four different phenotypic parameters like honeydew excretion, nymphal survival, percent damage, and feeding mark. Our study suggests that presently available monogenic BPH resistant lines were not withstanding BPH biotype-4 pressure. Thus, the reported resistance genes either alone or in combination could be introgressed into elite varieties with genomic approach to develop robust resistant rice varieties against N. lugens biotype 4. Further, the identified FVs are useful for novel R genes identification, host–insect interaction, and genomic studies.

CRISPR/Cas9-mediated knockout of the NlCSAD gene results in darker cuticle pigmentation and a reduction in female fecundity in Nilaparvata lugens (Hemiptera: Delphacidae)

In insects, cuticular pigmentation genes have been exploited as potential visible markers for constructing genetic manipulation systems. Here, we cloned cysteine sulfinic acid decarboxylase (CSAD), an orthologue of melanin metabolism pathway genes, and performed RNAi experiments in the brown planthopper Nilaparvata lugens (Hemiptera: Delphacidae). The results showed that a decrease in the level of transcription of NlCSAD increased melanin deposition in the body compared to the control group, resulting in darker cuticle pigmentation. Female adults treated with dsNlCSAD and mated with wild-type males laid significantly fewer eggs than the dsGFP-treated group, and lower hatchability of the eggs was also observed. In addition, two melanic mutant N. lugens strains (NlCSAD−/+ and NlCSAD−/−) constructed by the CRISPR/Cas9 genome editing system showed darker cuticular melanisation and a reduced oviposition and hatching rate, but the homozygotes had a darker body colour, fewer eggs and lower hatchability than heterozygotes or individuals after RNAi. Thus, we have provided the first evidence that NlCSAD is required for normal body pigmentation in adults and has a role in the fecundity of females and hatchability of eggs in N. lugens via a combination of RNAi and knockout of target genes based on the CRISPR/Cas9 genome editing system. Our results suggest that NlCSAD is a candidate visual reference gene for genetic manipulation of this important crop pest.

Chromosome-level assembly of the brown planthopper genome with a characterized Y chromosome.

Hundreds of insect genome sequences have been reported; however, most sequencing projects have not determined the sex chromosomes, and no Y chromosomes from a heterometabolous insect have been identified and characterized to date. The brown planthopper (Nilaparvata lugens Stål) is the most economically damaging pest to rice and is also an ideal research subject for paddy ecology and functional genomics. We previously assembled a draft female genome mainly using second-generation sequencing technologies, with a contig N50 of only 24kb, due to the large size and excessive repetitive regions in the N.lugens genome. Here, we utilize third-generation sequencing technologies and Hi-C data to generate a high-quality male N.lugens assembly with a contig N50 of 1.01Mb, a scaffold N50 of 69.96Mb and more than 95.6% of the assembled bases located on 16 chromosomes. Fourteen autosomes and two sex chromosomes (X+Y) were identified, filling in the gap related to the Y chromosome in heterometabolous insects. A total of 18,021 protein-coding genes and 6423 long-noncoding RNAs were predicted with full-length cDNA sequencing data. All 315 of the Y chromosome genes (Y-genes) were derived from autosomal and X-chromosome duplications. Large-scale RNA interference (RNAi) experiments were conducted against the N.lugens Y-genes, demonstrating that 7 Y-genes were essential for normal BPH development or male organ development, suggesting the importance of Y-genes. The first identified Y chromosome in heterometabolous insects will help gain more insight into sex determination, fertility and chromosome evolution.

Evaluation of Light Trap System in Monitoring of Rice Pests, Brown Planthopper (Nilaparvata lugens)

Brown Planthopper (Nilaparvata lugens) is a major rice pest insect in Malaysia. Series of the outbreak has been recorded in 1991, 1909, 2011, and 2015 which caused heavy yield losses. The light trap is now commonly used to monitor the pest population to predict the outbreak. The population sampling was conducted based on the crop stage at a specific sampling point and area. It has been done manually through field observations using netting, sweeping, board tapping, or survey patrol. Those methods are laborious and time-consuming. Malaysia Agriculture Research and Development Institute (MARDI) has developed an early warning system for brown planthopper monitoring consisting of modular light traps and a weather database to provide earlier forecasts and more effective outbreak prediction. However, there is not much information about how effective the light trap operated in the open field to draw and trap the insects. The light trap's efficiency depends on a few factors like the trap design, type of light source, duration, and sampling time; all affect the trap's effectiveness. A 30W Compact fluorescence light (CFL) has been selected and used to build four operated light traps and placed at the appropriate selected location. Sampling works were conducted twice a week for three hours per night throughout the planting season (15 weeks). Comparative statistical analysis was conducted to evaluate the effectiveness of the light trap compared to the aerial netting method. The results showed that the difference is statistically significant between light trap and aerial netting with a value of 0.0167 at p <0.05. Therefore, brown planthopper population monitoring is more effectively done using the new design light trap.

Screening of Rice Varieties for Resistance to Major Insect Pests

Rice is attacked by several insect pests and of these the stem borers Scirpophaga incertulas (Walker), S. innotata (Walker), Sesamia inferens (Walker), leaf folder Cnaphalocrocis medinalis (Guenee) and plant hoppers viz. brown plant hopper Nilaparvata lugens (Stal), white backed plant hopper, Sogatella furcifera (Horvath) are the most destructive. This study was carried out at the PAU Regional Station, Gurdaspur during kharif seasons of 2017 and 2018 to evaluate performance of varieties viz. PR 121, PR 122, PR 123, PR 124, Pusa 44, PR 126, PR 115, PR 114 and HKR 127 against these pests. The incidence of stem borers, leaf folder and of plant hoppers/ hill were observed at 40, 60, 80 and 100 days after transplanting. It was observed that rice varieties PR 126, PR 115 were the least preferred whereas Pusa 44 was found highly preferred by these major insect pests.

Herbivore induced plant volatiles of paddy and their influence in the attraction of mirids Cyrtorhinus lividipennis reuter

In the present study, a popular rice variety IR 20 was selected to characterize volatile profile change due to the two major insect pest infestation (Brown plant hopper Nilaparvata lugens and Yellow stem borer Scirpophaga incertulas). Volatile collection was made using air entrainment method and were characterized using GCMS (Gas Chromatography Mass Spectrometry). Collected volatiles were checked for their attraction towards the predator of Brown plant hopper (BPH), Mirids Cyrtorhinus lividipennis (Reuter) using Y arm olfactometer. Terpenoids were identified as the major compounds differentiating from the healthy plants. Significant attraction was observed in the predators towards BPH infested volatiles. The results of the study suggested its usage for the management of the pest under field conditions.

Impact of climate change on pests of rice and cassava

Abstract Climate change is exacerbating food insecurity, and its negative impacts will worsen over time. This is happening via several pathways, among which plant pests are a leading cause. To contribute to more evidence-based decisions and policies, a team from the Food and Agriculture Organization of the United Nations (FAO) carried out a comprehensive literature review on rice ( Oryza sativa ) and cassava ( Manihot esculenta ), the major pests and diseases affecting them, and the impact of climate change on the latter. Rice is the major staple crop for about half the world’s population. Most studies conclude that pest pressure will increase on rice under future climate change. There are a lot of pests of rice, among which brown planthopper ( Nilaparvata lugens ) is the most important pest. Leaf blast disease caused by fungus Magnaporthe grisea is the most significant disease, with losses of up to USD 66 billion dollars per year that are equivalent to the amount needed to feed 60 million people. Cassava is the major staple crop and crucial for food security in many countries of the world. A study has shown that cassava production will vary from −3.5% to +17.5% within Africa under 2030 climate projections. Unfortunately, as other crops, cassava will be vulnerable to pests and diseases. Over a third of attainable cassava yield is lost every year to pests and disease alone.

KIF2A regulates ovarian development via modulating cell cycle progression and vitollogenin levels.

The kinesin superfamily of proteins (KIFs) are microtubule motor proteins that use the hydrolysis of ATP to power directional movement along microtubules. KIFs induce microtubule depolymerization to regulate the length and dynamics of microtubules in a variety of cell processes and structures, including the mitotic and meiotic spindles and centriole and interphase microtubules. KIF plays a significant role in the transport of organelles, protein complexes and mRNAs. The brown planthopper (Nilaparvata lugens) is a major insect pest in rice paddy fields. Ovarian development is regulated by multiple factors, including endocrine factors. The role of KIFs in brown planthopper ovarian development remains unknown. We found that downregulation of KIF2A significantly compromised the development and eclosion of the brown planthopper, delayed ovarian cell cycle progression, disrupted ovarian development, reduced the expression of MCM genes required for DNA replication and significantly reduced the number of nuclei in the follicles. We also found a significant reduction in Vg mRNA and protein levels. We conclude that downregulation of KIF2A disrupts the cell cycle progression of cells. Alternatively, the ovarian phenotype could be an indirect effect of a compromised trophic cord. In summary, KIF2A regulates ovarian development via modulating cell cycle progression and/or vitollogenin transportation.

PENGARUH INSEKTISIDA NABATI KAMANDRAH DAN AKAR TUBA TERHADAP WERENG BATANG COKLAT

[THE INFLUENCE OF BOTANICAL INSECTICIDES BASED ON CROTON OIL AND DERRIS ROOT AGAINST BROWN PLANTHOPPER]. Brown planthopper (BPH) (Nilaparvata lugens Stall) is a serious pest in rice. Using synthetic insecticide to control BPH is harmful for human health and can caused environmental pollution. The objective of this research is to find out ecofriendly insecticide to control BPH. Research has been conducted at Entomological laboratory, Indonesian Spice and Medicinal Crops Research Institute (ISMECRI), Bogor. It was designed with CRD, 16 treatments and 3 replications. Treatments consisted of botanical insecticides based on Croton tiglium and Derris elliptica. Each material was extracted by water, methanol, and xylene, and then tested by individually and combination, so there were 15 formulas and 1 control treatment (water). Third nymph BPH and IR64 rice variety were used in this research. Research was done in two methods, i.e. contact application and residual application. The result shows that there are 11 formulas which are prospective to be further developed i.e aqueous extraction (6 formulas) and combination extraction (aqueous with xylene and methanol (5 formulas). The aqueous extraction maybe the most prospective formulation since the technique could easily be adopted by farmers. Botanical pesticide based on Croton tiglium and Derris elliptica are very promising, therefore the research should be continued to find out the best formula of botanical insecticides for controlling BPH).

Sustainable control of the rice pest, Nilaparvata lugens, using the entomopathogenic fungus Isaria javanica.

The brown planthopper (Nilaparvata lugens) is an insect pest of rice (Oryza sativa) that is distributed worldwide and is responsible for significant crop yield losses. Of particular concern, N. lugens has developed high resistance to several commonly used insecticides. The entomopathogenic fungus, Isaria javanica, offers an alternative to insecticides for the control of rice plant pests. We show that I. javanica caused high mortality of N. lugens nymphs and reduced the survival and fecundity of newly emerged adults in I. javanica-treated insects. I. javanica persisted on plants up to 17 days after its inoculation under greenhouse conditions carried out in summer and autumn. Rice metabolites supported conidial germination and mycelia growth of I. javanica. A granular formulation of I. javanica conidia controlled N. lugens populations in a field experiment. The granular formulation promoted fungal survival and growth in the field up to 28 days post inoculation, resulting in increased fungal persistence and greater pest control coverage. These data indicate that a granular formulation of I. javanica is able to control N. lugens populations in rice fields. Therefore, this granular formulation can be an alternative to insecticides and can be used in organic fields. © 2020 Society of Chemical Industry.

Regulatory Functions of Nilaparvata lugens GSK-3 in Energy and Chitin Metabolism.

Glucose metabolism is a biologically important metabolic process. Glycogen synthase kinase (GSK-3) is a key enzyme located in the middle of the sugar metabolism pathway that can regulate the energy metabolism process in the body through insulin signaling. This paper mainly explores the regulatory effect of glycogen synthase kinase on the metabolism of glycogen and trehalose in the brown planthopper (Nilaparvata lugens) by RNA interference. In this paper, microinjection of the target double-stranded GSK-3 (dsGSK-3) effectively inhibited the expression of target genes in N. lugens. GSK-3 gene silencing can effectively inhibit the expression of target genes (glycogen phosphorylase gene, glycogen synthase gene, trehalose-6-phosphate synthase 1 gene, and trehalose-6-phosphate synthase 2 gene) in N. lugens and trehalase activity, thereby reducing glycogen and glucose content, increasing trehalose content, and regulating insect trehalose balance. GSK-3 can regulate the genes chitin synthase gene and glucose-6-phosphate isomerase gene involved in the chitin biosynthetic pathway of N. lugens. GSK-3 gene silencing can inhibit the synthesis of chitin N. lugens, resulting in abnormal phenotypes and increased mortality. These results indicated that a low expression of GSK-3 in N. lugens can regulate the metabolism of glycogen and trehalose through the insulin signal pathway and energy metabolism pathway, and can regulate the biosynthesis of chitin, which affects molting and wing formation. The relevant research results will help us to more comprehensively explore the molecular mechanism of the regulation of energy and chitin metabolism of insect glycogen synthase kinases in species such as N. lugens.

Chromosomal-level genomes of three rice planthoppers provide new insights into sex chromosome evolution.

The brown planthopper Nilaparvata lugens, white-backed planthopper Sogatella furcifera, and small brown planthopper Laodelphax striatellus are three major insect pests of rice. They are genetically close; however, they differ in several ecological traits such as host range, migration capacity, and in their sex chromosomes. Though the draft genome of these three planthoppers have been previously released, the quality of genome assemblies need to be improved. The absence of chromosome-level genome resources has hindered in-depth research of these three species. Here, we performed a de novo genome assembly for N.lugens to increase its genome assembly quality with PacBio and Illumina platforms, increasing the contig N50 to 589.46Kb. Then, with the new N.lugens genome and previously reported S. furcifera and L.striatellus genome assemblies, we generated chromosome-level scaffold assemblies of these three planthopper species using HiC scaffolding technique. The scaffold N50s significantly increased to 77.63Mb, 43.36Mb and 29.24Mb for N.lugens, S.furcifera and L.striatellus, respectively. To identify sex chromosomes of these three planthopper species, we carried out genome re-sequencing of males and females and successfully determined the X and Y chromosomes for N.lugens, and X chromosome for S.furcifera and L.striatellus. The gene content of the sex chromosomes showed high diversity among these three planthoppers suggesting the rapid evolution of sex-linked genes, and all chromosomes showed high synteny. The chromosome-level genome assemblies of three planthoppers would provide a valuable resource for a broad range of future research in molecular ecology, and subsequently benefits development of modern pest control strategies.

Overexpression of a Cytosolic 6-Phosphogluconate Dehydrogenase Gene Enhances the Resistance of Rice to Nilaparvata lugens.

The pentose phosphate pathway (PPP) plays an important role in plant growth and development, and plant responses to biotic and abiotic stresses. Yet, whether the PPP regulates plant defenses against herbivorous insects remains unclear. In this study, we cloned a rice cytosolic 6-phosphogluconate dehydrogenase gene, Os6PGDH1, which encodes the key enzyme catalyzing the third step in the reaction involving the oxidative phase of the PPP, and explored its role in rice defenses induced by brown planthopper (BPH) Nilaparvata lugens. Levels of Os6PGDH1 transcripts were detected in all five examined tissues, with the highest in outer leaf sheaths and lowest in inner leaf sheaths. Os6PGDH1 expression was strongly induced by mechanical wounding, infestation of gravid BPH females, and jasmonic acid (JA) treatment. Overexpressing Os6PGDH1 (oe6PGDH) decreased the height of rice plants and the mass of the aboveground part of plants, but slightly increased the length of plant roots. In addition, the overexpression of Os6PGDH1 enhanced levels of BPH-induced JA, jasmonoyl-isoleucine (JA-Ile), and H2O2, but decreased BPH-induced levels of ethylene. Bioassays revealed that gravid BPH females preferred to feed and lay eggs on wild-type (WT) plants over oe6PGDH plants; moreover, the hatching rate of BPH eggs raised on oe6PGDH plants and the fecundity of BPH females fed on these were significantly lower than the eggs and the females raised and fed on WT plants. Taken together, these results indicate that Os6PGDH1 plays a pivotal role not only in rice growth but also in the resistance of rice to BPH by modulating JA, ethylene, and H2O2 pathways.

Lipidomic analyses reveal enhanced lipolysis in planthoppers feeding on resistant host plants.

The brown planthopper (BPH) (Nilaparvata lugens Stål) is a highly destructive pest that seriously damages rice (Oryza sativa L.) and causes severe yield losses. To better understand the physiological and metabolic mechanisms through which BPHs respond to resistant rice, we combined mass-spectrometry-based lipidomics with transcriptomic analysis and gene knockdown techniques to compare the lipidomes of BPHs feeding on either of the two resistant (NIL-Bph6 and NIL-Bph9) plants or a wild-type, BPH susceptible (9311) plant. Insects that were fed on resistant rice transformed triglyceride (TG) to phosphatidylcholine (PC) and digalactosyldiacylglycerol (DGDG), with these lipid classes showing significant alterations in fatty acid composition. Moreover, the insects that were fed on resistant rice were characterized by prominent expression changes in genes involved in lipid metabolism processes. Knockdown of the NlBmm gene, which encodes a lipase that regulates the mobilization of lipid reserves, significantly increased TG content and feeding performance of BPHs on resistant plants relative to dsGFP-injected BPHs. Our study provides the first detailed description of lipid changes in BPHs fed on resistant and susceptible rice genotypes. Results from BPHs fed on resistant rice plants reveal that these insects can accelerate TG mobilization to provide energy for cell proliferation, body maintenance, growth and oviposition.

A Mechanosensory Receptor TMC Regulates Ovary Development in the Brown Planthopper Nilaparvata lugens.

Transmembrane channel-like (TMC) genes encode a family of evolutionarily conserved membrane proteins. Mutations in the TMC1 and TMC2 cause deafness in humans and mice. However, their functions in insects are is still not well known. Here we cloned three tmc genes, Nltmc3, Nltmc5, and Nltmc7 from brown planthoppers. The predicted amino acid sequences showed high identity with other species homologs and have the characteristic eight or nine transmembrane domains and TMC domain architecture. We detected these three genes in all developmental stages and examined tissues. Interestingly, we found Nltmc3 was highly expressed in the female reproductive organ especially in the oviduct. RNAi-mediated silencing of Nltmc3 substantially decreased the egg-laying number and impaired ovary development. Our results indicate that Nltmc3 has an essential role in the ovary development of brown planthoppers.

Field evaluation of novel insecticides against brown planthopper (Nilaparvata lugens) and white backed planthopper (Sogatella furcifera) in rice

A field experiment was conducted to evaluate the bioefficacy of novel insecticides against brown planthopper [Nilaparvatha lugens (Stal)] (BPH) and white backed planthopper [Sogatella furcifera (Hoverth)] (WBPH) on rice. The results revealed that field application of triflumezopyrim 10 SC @ 235 ml per ha was found superior and registered 1.88 and 1.26 hoppers per hill against BPH and WBPH followed bypymetrozine 50 WG @ 300g per ha with 2.12 and 1.26 hoppers of BPH and WBPH per hill, respectively. The response of these insecticides was also observed on the yield attributes, with highest grain yield of 55.58 q/ha in triflumezopyrim 10 SC @ 235 ml per ha followed by pymetrozine 50 WG @ 300 g per ha (53.79 q/ ha).

An InR/mir‐9a/NlUbx regulatory cascade regulates wing diphenism in brown planthoppers

Wing polymorphism significantly contributes to the ecological success of some insect species. For example, the brown planthopper (BPH) Nilaparvata lugens, which is one of the most destructive rice pests in Asia, can develop into either highly mobile long-winged or highly fecund short-winged adult morphs. A recent study reported a highly provocative result that the Hox gene Ultrabithorax (Ubx) is expressed in BPH forewings and showed that this wing development gene is differentially expressed in nymphs that develop into long-winged versus short-winged morphs. Here, we found that Ubx may be a mir-9a target, and used dual luciferase reporter assays and injected micro RNA (miRNA) mimics and inhibitors to confirm the interactions between mir-9a and NlUbx. We measured the mir-9a and NlUbx expression profiles in nymphs and found that the expression of these two biomolecules was negatively correlated. By rearing BPH nymphs on host rice plants with different nutritional status, we were able to characterize a regulatory cascade between insulin receptor genes, mir-9a, and NlUbx that regulate wing length in BPHs. When host quality was low, NlInR1 expression in the nymph terga increased and NlInR2 expression decreased; this led to a higher mir-9a level, which in turn reduced the NlUbx transcript level and ultimately resulted in longer wing lengths. Beyond extending our understanding of the interplay between host plant status and genetic events that modulate polymorphism, we demonstrated both the upstream signal and miRNA-based regulatory mechanism that control Ubx expression in BPH forewings.