Grainy head signaling regulates epithelium development and ecdysis in Blattella germanica

The transcription factor grainy head(Grh)functions in the protection of the epithelium against the external environment by generating strongly adhesive layers,and this function is conserved in vertebrates and invertebrates.In Drosophila,the top model for holometabolous insects,Grh is necessary during embryonic development,epidermal differentiation,central nervous system specification and epithelial repair.However,the function of this gene in hemimetabolous insect epithelia remains unknown.To examine the function of Grh signaling in regulating epithelium development in Hemimetabola,we focused on the Blattella germanica epidermal layer using a gene knockdown strategy.The spatiotemporal expression pattern of BgGrh was detected,and knockdown of Bg-Grh and BgCad96ca,which provide positive feedback to BgGrh,caused severe defects in new epithelium development and impeded the molting process required to discard the old integument.Knockdown of the expression of BgGrh and BgCad96ca caused increased expression of chitin synthase gene{BgCHSl)and chitinase gene{BgCht5),the upregulations of which should be mediated by the higher level of hormone receptor 3{BgHr3)gene.In conclusion,epithelium development is regulated by Grh signaling,which might represent a potential target for the control of urban pest cockroaches.

Ecdysis triggering hormone peptide in the African malaria mosquito Anopheles gambiae:The peptide structure for receptor activation

Infections by mosquito-borne diseases represent one of the leading causes of death in third world countries.The rapid progression of resistance to conventional insecticide causes a significant threat to the highly efficient preventive methods currently in place.Insect neuropeptidergic system offers potential targets to control the insect vectors.The essential roles of the neuropeptide ecdysis triggering hormone(ETH)in insect development and reproduction led us to attempt understanding of the fundamentals of the biochemical interaction between ETH and its receptor in the African malaria mosquito Anopheles gambiae.One of two ETH peptides of the African malaria mosquito(AgETH1),a small peptide hormone with 17 amino acid residues(SESPGFFIKLSKSVPRI-NH2),was studied to elucidate its molecular structure.N-termini deletions and mutations of conserved amino acids in the ligand revealed the critical residues for the receptor activation.The solution structure of AgETH1 using 2D 1H-1H nuclear magnetic resonance(NMR)spectroscopy and nuclear overhauser effect(NOE)derived constraints revealed a short alpha helix between residues 3S and 11S.The NMR solution structure of AgETH1 will be of significant assistance for designing a new class of insecticidal compounds that acts on the AgETH receptor aiming for in silico docking studies.

Knockdown of Na,K-ATPase β-subunits in Oncopeltus fasciatus induces molting problems and alterations in tracheal morphology

The ubiquitously expressed transmembrane enzyme Na,K-ATPase(NKA)is vital in maintaining functionality of cells.The association of α-and β-subunits is believed to be essential for forming a functional enzyme.In the large milkweed bug Oncopeltus fasciatus fourα1-paralogs and four β-subunits exist that can associate into NKA complexes.This diversity raises the question of possible tissue-specific distribution and function.While the α1-subunits are known to modulate cardenolide-resistance and ion-transport efficiency,the functional importance of the β-subunits needed further investigation.We here characterize all four different β-subunits at the cellular,tissue,and whole organismal scales.A knockdown of different β-subunits heavily interferes with molting success resulting in strongly hampered phenotypes.The failure of ecdysis might be related to disrupted septate junction(SJ)formation,also reflected in β2-suppression-induced alteration in tracheal morphology.Our data further suggest the existence of isolated β-subunits forming homomeric or β-heteromeric complexes.This possible standalone and structure-specific distribution of the β-subunits predicts further,yet unknown pump-independent functions.The different effects caused byβknockdowns highlight the importance of the various β-subunits to fulfill tissue-specific requirements.

RNA interference targeting ecdysone receptor blocks the larval-pupal transition in Henosepilachna vigintioctopunctata

Henosepilachna vigintioctopunctata is a serious insect pest which attacks a large number of nightshades and cucurbits in Asian countries,Brazil and Australia.Prolonged application of traditional pesticides has caused environmental pollution and exerted deleterious effects on human health.Finding new approaches with high target specificity and low environmental contamination has become an urgent task.RNA interference(RNAi)induced by double-stranded RNA(dsRNA)is expected to be applicable to managing this pest.Here we evaluated the effects of Escherichia co/Z-expressed dsRNAs targeting ecdvsone receptor(EcR)gene via dietary delivery in laboratory and foliar spraying in a greenhouse.The target transcript was successfully knocked down when the 4th-instar larvae had fed on potatofoliage dipped with dsEcR in a laboratory bioassay.Around 85%of the HvEcR RNAi larvae remained as prepupae or became abnormal pupae,and failed to emerge into adults.Ingestion of ds£c7?-immersed foliage by the 3rd-instar larvae effectuated a comparable RNAi response and brought about more severe defects:all the resultant larvae arrested development,remained as prepupae and finally died.For assay in the greenhouse,a ds£c7?-contained E.coli suspension was directly sprayed to the foliage of greenhouse-growing potato plants and the 3rd-and 4th-instar larvae were transferred to the leaves.High RNAi efficacy was obtained and identical RNAi phenotypes were observed in treated larvae.In addition,spraying dsEcR reduced leaf damage.Our results indicate a possibility of practical application of dsEcR as an environmentally friendly RNA pesticide to control H.vigintioctopunctata larvae.