An MD-2-related lipid-recognition protein is required for insect reproduction and integument development

The myeloid differentiation factor 2 (MD-2)-related lipid-recognition protein is involved in immune responses through recognizing bacteria lipopolysaccharide in mammals, arthropods and plants. However, the physiological roles of MD-2 in other biological processes are largely unknown. Here, we identified three homologue MD-2 genes ( NlML1 , NlML2 and NlML3 ) by searching the genome and transcriptome databases of the brown planthopper Nilaparvata lugens , a hemipteran insect species. Temporospatial analysis showed that the NlML1 gene was highly expressed in the fat body but much less so in the other tissues, while the NlML2 and NlML3 genes were highly expressed in the testis or digestive tract. RNA interference-mediated depletion of the NlML1 gene significantly downregulated the transcription of numerous integument protein genes. The NlML1 knockdown led to moulting failure and mortality at the nymph–adult transition phase, impaired egg laying and hatching, and reduced 20-hydroxyecdysone (20E) production in the nymphs. 20E could rescue the deficient moulting phenotypes derived from ds NlML1 RNAi. These novel findings indicate that NlML1 is required for nymphal moulting and female reproductive success as it plays an important role in regulating 20E synthesis, lipid and chitin metabolisms in N. lugens , thus contributing to our understanding of developmental and reproductive mechanisms in insects.

Characterization of the morphology and complete mitochondrial genomes of Eupteryx minusula and Eupteryx gracilirama (Hemiptera: Cicadellidae: Typhlocybinae) from Karst area, Southwest China

Background The hemipteran insect family Cicadellidae (leafhoppers) includes >2,600 valid genera and >22,000 valid species worldwide, including >2,000 species in China. Typhlocybinae, second largest subfamilies of Cicadellidae, is widely distributed in the six major zoogeographic regions of the world, including >4,000 species worldwide and >1,000 species in China. Previously, morphological analysis are often effective to the way of taxonomy, but it did not combine with molecular biology. Therefore, morphology and mitochondrial genomes (mitogenomes) of two leafhopper species, Eupteryx (Eupteryx) minuscula Lindberg, 1929 and Eupteryx (Stacla) gracilirama Hou, Zhang & Huang, 2016 were studied and analyzed. This study analyzed the morphological and molecular characteristics of the two leafhoppers, and showed whether the results of the two identifications were consistent. Methods Based on the method of comparison, mitogenomes and morphology were analyzed to prove the relationship between the two leafhoppers. Results Although two focal species are classified in two different subgenera of the same genus, they still share many morphological features, such as the moderately produced crown fore margin; the milky yellow apical part of scutellum; the pronotum, basal triangles of scutellum, and forewing are dark with several colorless patches on the surface; the light yellow face, without any spots or stripes, and so on. The circular mitogenomes are 16,944 bp long in E. minuscula (GenBank: MN910279) and 17,173 bp long in E. gracilirama (GenBank: MT594485). All of the protein-coding genes are starting with ATN, except for some in mitogenome, which has a single T or TAN as a stop codon. All tRNAs have the typical cloverleaf-shaped structure except for trnS1 (AGN) (E. minuscula) which has a reduced DHU arm. Moreover, these two mitogenomes have trnR with an unpaired base in the acceptor stem. The phylogenetic relationships between E. minuscula and E. gracilirama in respect to related lineages were reconstructed using Maximum likelihood and Maximum parsimony analyses. Discussion The result showed that the tribe Typhlocybini is a sister to the tribes Erythroneurini and Empoascini, and five genera, Bolanusoides, Typhlocyba, Eupteryx, Zyginella and Limassolla are forming a single clade. E. minuscula and E. gracilirama are clustered together, supporting the monophyly of the genus Eupteryx. The above conclusions are consistent with the traditional classification of the subfamily.

The Olfactory Chemosensation of Hematophagous Hemipteran Insects

As one of the most abundant insect orders on earth, most Hemipteran insects are phytophagous, with the few hematophagous exceptions falling into two families: Cimicidae, such as bed bugs, and Reduviidae, such as kissing bugs. Many of these blood-feeding hemipteran insects are known to be realistic or potential disease vectors, presenting both physical and psychological risks for public health. Considerable researches into the interactions between hemipteran insects such as kissing bugs and bed bugs and their human hosts have revealed important information that deepens our understanding of their chemical ecology and olfactory physiology. Sensory mechanisms in the peripheral olfactory system of both insects have now been characterized, with a particular emphasis on their olfactory sensory neurons and odorant receptors. This review summarizes the findings of recent studies of both kissing bugs (including Rhodnius prolixus and Triatoma infestans) and bed bugs (Cimex lectularius), focusing on their chemical ecology and peripheral olfactory systems. Potential chemosensation-based applications for the management of these Hemipteran insect vectors are also discussed.

Transmission, Tropism, and Biological Impacts of Torix Rickettsia in the Common Bed Bug Cimex lectularius (Hemiptera: Cimicidae)

The torix group of Rickettsia have been recorded from a wide assemblage of invertebrates, but details of transmission and biological impacts on the host have rarely been established. The common bed bug (Cimex lectularius) is a hemipteran insect which lives as an obligatory hematophagous pest of humans and is host to a primary Wolbachia symbiont and two facultative symbionts, a BEV-like symbiont, and a torix group Rickettsia. In this study, we first note the presence of a single Rickettsia strain in multiple laboratory bed bug isolates derived from Europe and Africa. Importantly, we discovered that the Rickettsia has segregated in two laboratory strains, providing infected and uninfected isogenic lines for study. Crosses with these lines established transmission was purely maternal. Fluorescence in-situ hybridization analysis indicates Rickettsia infection in oocytes, bacteriomes, and other somatic tissues. We found no evidence that Rickettsia infection was associated with sex ratio distortion activity, but Rickettsia infected individuals developed from first instar to adult more slowly. The impact of Rickettsia on fecundity and fertility resulted in infected females producing fewer fertile eggs. However, we could not find any evidence for cytoplasmic incompatibility associated with Rickettsia presence. These data imply the existence of an unknown benefit to C. lectularius carrying Rickettsia that awaits further research.

Transmission, tropism and biological impacts of torix Rickettsia in the common bed bug Cimex lectularius (Hemiptera: Cimicidae)

ABSTRACTThe torix group of Rickettsia have been recorded from a wide assemblage of invertebrates, but details of transmission and biological impacts on the host have rarely been established. The common bed bug (Cimex lectularius) is a hemipteran insect which lives as an obligatory hematophagous pest of humans and is host to a primary Wolbachia symbiont and two facultative symbionts, a BEV-like symbiont, and a torix group Rickettsia. In this study, we first note the presence of a single Rickettsia strain in multiple laboratory bed bug isolates derived from Europe and Africa. Importantly, we discovered that the Rickettsia has segregated in two laboratory strains, providing infected and uninfected isogenic lines for this study. Crosses with these lines established transmission was purely maternal, in contrast to previous studies of torix infections in planthoppers where paternal infection status was also important. Fluorescence in-situ hybridization analysis indicates Rickettsia infected in oocytes and bacteriomes, and other somatic tissues. There was no evidence that Rickettsia infection was associated with sex ratio distortion activity, but Rickettsia infected individuals developed from first instar to adult more slowly. The impact of Rickettsia on fecundity and fertility were investigated. Rickettsia infected females produced fewer fertile eggs, but there was no evidence for cytoplasmic incompatibility. These data imply the existence of an unknown benefit to C. lectularius carrying Rickettsia that awaits further research.

Beware the brown marmorated stink bug!

The brown marmorated stink bug (BMSB), Halyomorpha halys (Stål, 1855) is a hemipteran insect in the Pentatomidae family native to eastern Asia. This extremely polyphagous species is spreading rapidly worldwide. It is responsible for important economic damage to various agricultural crops, including wine grapes. Available data suggest that the current range of the BMSB is likely to expand in the near future which calls for more research and exploration of management options and biocontrol. Citizen science is a promising way forward on monitoring the BMSB expansion.

Natural infection by the protozoan Leptomonas wallacei impacts the morphology, physiology, reproduction, and lifespan of the insect Oncopeltus fasciatus

Trypanosomatids are protozoan parasites that infect thousands of globally dispersed hosts, potentially affecting their physiology. Several species of trypanosomatids are commonly found in phytophagous insects. Leptomonas wallacei is a gut-restricted insect trypanosomatid only retrieved from Oncopeltus fasciatus. The insects get infected by coprophagy and transovum transmission of L. wallacei cysts. The main goal of the present study was to investigate the effects of a natural infection by L. wallacei on the hemipteran insect O. fasciatus, by comparing infected and uninfected individuals in a controlled environment. The L. wallacei-infected individuals showed reduced lifespan and morphological alterations. Also, we demonstrated a higher infection burden in females than in males. The infection caused by L. wallacei reduced host reproductive fitness by negatively impacting egg load, oviposition, and eclosion, and promoting an increase in egg reabsorption. Moreover, we associated the egg reabsorption observed in infected females, with a decrease in the intersex gene expression. Finally, we suggest alterations in population dynamics induced by L. wallacei infection using a mathematical model. Collectively, our findings demonstrated that L. wallacei infection negatively affected the physiology of O. fasciatus, which suggests that L. wallacei potentially has a vast ecological impact on host population growth.

Identification of a female determinant gene for the sexual determination of a hemipteran insect, the brown planthopper

The sex determination mechanism for hemipteran species remains poorly understood. During the sex determination of the brown planthopper (BPH), Nilaparvata lugens, one species of Hemiptera, the functions of doublesex (Nldsx) and NlTra-2 (NlTra-2) genes were identified in our previous studies. Here, we identify an upstream gene for Nldsx in the sex determination cascade, NlFmd, which acts as female determinant gene for N. lugens. The sex-specific transcript of NlFmd (NlFmd-F) encodes an arginine/serine-, and proline-rich protein that is essential for female development. The knockdown of NlFmd resulted in the development of pseudomales, with sex-specific alternative Nldsx processing, and maternal RNA interference (RNAi) against NlFmd generates male-only progeny. Moreover, homologous genes for NlFmd have also been identified in two rice planthopper species, the white-backed planthopper (WBPH, Sogotalla furcifera) and the small brown planthopper (SBPH, Laodelphax striatellus), and these genes appear to be involved in the sex determination cascades for these species. Our data suggest that the sex determination cascade in Delphacidae is conserved.

Plant Nutrition: A tool for the management of hemipteran insect-pests-A review

Nutrition of plants has a substantial impact on the predisposition of plants to insect-pests. Regulated and balanced crop fertilization can be helpful in altering host plant susceptibility to sucking insect-pests. Hemipteran herbivores are sensitive to alteration in host plant nutrition. Primary pest defence of plants like biochemical, physical and mechanical properties can be enhanced by balanced fertilization with plant nutrients. All plant nutrients may affect plant health but two of them namely, nitrogen and potassium play a major role. The effect of other nutrients is less frequently mentioned. Most studies revealed that generally excessive use of nitrogen decreases crop resistance to pests whereas potassium increases the same. So, the agricultural practices like excessive, injudicious and unscientific use of fertilizers can result in nutrient imbalance and finally into increased attack of insect-pests. Careful consideration of present and future information on this topic can lead to better predictive capabilities in hemipteran insect-pest management.