Infectivity, Speed of Kill, and Productivity of a Baculovirus Expressing the Itch Mite Toxin Txp-1 in Second and Fourth Instar Larvae of Trichoplusia ni

ABSTRACT Insect pathogens, such as baculoviruses, that are used as microbial insecticides have been genetically modified to increase their speed of action. Nontarget species will often be exposed to these pathogens, and it is important to know the consequences of infection in hosts across the whole spectrum of susceptibility. Two key parameters, speed of kill and pathogen yield, are compared here for two baculoviruses, a wild-type Autographa californica nucleopolyhedrovirus (AcNPV), AcNPV clone C6, and a genetically modified AcNPV which expresses an insect-selective toxin, AcNPV-ST3, for two lepidopteran hosts which differ in susceptibility. The pathogenicity of the two viruses was equal in the less-susceptible host, Mamestra brassicae, but the recombinant was more pathogenic than the wild-type virus in the susceptible species, Trichoplusia ni. Both viruses took longer to kill the larvae of M. brassicae than to kill those of T. ni. However, whereas the larvae of T. ni were killed more quickly by the recombinant virus, the reverse was found to be true for the larvae ofM. brassicae. Both viruses produced a greater yield inM. brassicae, and the yield of the recombinant was significantly lower than that of the wild type in both species. The virus yield increased linearly with the time taken for the insects to die. However, despite the more rapid speed of kill of the wild-type AcNPV in M. brassicae, the yield was significantly lower for the recombinant virus at any given time to death. A lower yield for the recombinant virus could be the result of a reduction in replication rate. This was investigated by comparing determinations of the virus yield per unit of weight of insect cadaver. The response of the two species (to both viruses) was very different: the yield per unit of weight decreased over time for M. brassicae but increased for T. ni. The implications of these data for risk assessment of wild-type and genetically modified baculoviruses are discussed.

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Infectivity of entomopathogenic nematodes against the legume pod-borer, Maruca vitrata Fabricius, infesting pigeon pea

Journal of Helminthology ◽

10.1017/s0022149x21000043 ◽

2021 ◽

Vol 95 ◽

Author(s):

R. Pervez ◽

U. Rao

Keyword(s):

Entomopathogenic Nematodes ◽

Agricultural Research ◽

Insect Pest ◽

Indian Agricultural Research Institute ◽

Pigeon Pea ◽

Fourth Instar ◽

Maruca Vitrata ◽

Pod Borer ◽

Legume Pod Borer ◽

Maximum Penetration

Abstract The legume pod-borer, Maruca vitrata Fabricius (Lepidoptera: Crambidae) (LPB), is an important insect pest of pigeon pea. Chemical pesticides are generally employed to manage this pest, but because of the soil residue issues and other environmental hazards associated with their use, biopesticides are also in demand. Another benign alternative is to use entomopathogenic nematodes (EPNs) to manage this vital pest. In the present study, the infectivity of ten native EPNs was evaluated against LPB by assessing their penetration and production in the LPB. The effectiveness of the promising EPNs against second-, third- and fourth-instar LPB larvae was also studied. Heterorhabditis sp. (Indian Agricultural Research Institute-Entomopathogenic Nematodes Rashid Pervez (IARI-EPN RP) 06) and Oscheius sp. (IARI-EPN RP 08) were found to be most pathogenic to LPB, resulting in about 100% mortality within 72 h, followed by Steinernema sp. (IARI-EPN RP 03 and 09). Oscheius sp. (IARI-EPN RP 04) was found to be the least pathogenic to LPB larva with 67% mortality. Maximum penetration was exhibited by Heterorhabditis sp. (IARI-EPN RP 06) followed by Oscheius sp. (IARI-EPN RP 08), whereas the lowest rate of penetration was exhibited by Oscheius sp. (IARI-EPN RP 01). The highest rate of production was observed with Oscheius sp. (IARI-EPN RP 08), followed by Oscheius sp. (IARI-EPN RP 04 and 10). Among the tested instars of the LPB larvae, second-instar larvae were more susceptible to EPNs, followed by third- and fourth-instar larvae. The results indicate that Heterorhabditis sp. (IARI-EPN RP 06) and Oscheius sp. (IARI-EPN RP 08) have a good potential to the manage LPB.

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Bacmid Expression of Granulovirus Enhancin En3 Accumulates in Cell Soluble Fraction to Potentiate Nucleopolyhedrovirus Infection

Viruses ◽

10.3390/v13071233 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1233

Author(s):

Adriana Ricarte-Bermejo ◽

Oihane Simón ◽

Ana Beatriz Fernández ◽

Trevor Williams ◽

Primitivo Caballero

Keyword(s):

Trichoplusia Ni ◽

Recombinant Virus ◽

Spodoptera Exigua ◽

Insect Cells ◽

Soluble Fraction ◽

Autographa Californica ◽

Insect Midgut ◽

Baculovirus Infection ◽

Occlusion Bodies ◽

Infected Cells

Enhancins are metalloproteinases that facilitate baculovirus infection in the insect midgut. They are more prevalent in granuloviruses (GVs), constituting up to 5% of the proteins of viral occlusion bodies (OBs). In nucleopolyhedroviruses (NPVs), in contrast, they are present in the envelope of the occlusion-derived virions (ODV). In the present study, we constructed a recombinant Autographa californica NPV (AcMNPV) that expressed the Trichoplusia ni GV (TnGV) enhancin 3 (En3), with the aim of increasing the presence of enhancin in the OBs or ODVs. En3 was successfully produced but did not localize to the OBs or the ODVs and accumulated in the soluble fraction of infected cells. As a result, increased OB pathogenicity was observed when OBs were administered in mixtures with the soluble fraction of infected cells. The mixture of OBs and the soluble fraction of Sf9 cells infected with BacPhEn3 recombinant virus was ~3- and ~4.7-fold more pathogenic than BacPh control OBs in the second and fourth instars of Spodoptera exigua, respectively. In contrast, when purified, recombinant BacPhEn3 OBs were as pathogenic as control BacPh OBs. The expression of En3 in the soluble fraction of insect cells may find applications in the development of virus-based insecticides with increased efficacy.

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The unusual structure of the PiggyMac cysteine-rich domain reveals zinc finger diversity in PiggyBac-related transposases

Mobile DNA ◽

10.1186/s13100-021-00240-4 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Marc Guérineau ◽

Luiza Bessa ◽

Séverine Moriau ◽

Ewen Lescop ◽

François Bontems ◽

...

Keyword(s):

Zinc Finger ◽

Dna Cleavage ◽

Trichoplusia Ni ◽

Catalytic Domain ◽

Structural Diversity ◽

Paramecium Tetraurelia ◽

Lysine Methylation ◽

Unusual Structure ◽

Rich Domain ◽

Cysteine Rich Domain

Abstract Background Transposons are mobile genetic elements that colonize genomes and drive their plasticity in all organisms. DNA transposon-encoded transposases bind to the ends of their cognate transposons and catalyze their movement. In some cases, exaptation of transposon genes has allowed novel cellular functions to emerge. The PiggyMac (Pgm) endonuclease of the ciliate Paramecium tetraurelia is a domesticated transposase from the PiggyBac family. It carries a core catalytic domain typical of PiggyBac-related transposases and a short cysteine-rich domain (CRD), flanked by N- and C-terminal extensions. During sexual processes Pgm catalyzes programmed genome rearrangements (PGR) that eliminate ~ 30% of germline DNA from the somatic genome at each generation. How Pgm recognizes its DNA cleavage sites in chromatin is unclear and the structure-function relationships of its different domains have remained elusive. Results We provide insight into Pgm structure by determining the fold adopted by its CRD, an essential domain required for PGR. Using Nuclear Magnetic Resonance, we show that the Pgm CRD binds two Zn2+ ions and forms an unusual binuclear cross-brace zinc finger, with a circularly permutated treble-clef fold flanked by two flexible arms. The Pgm CRD structure clearly differs from that of several other PiggyBac-related transposases, among which is the well-studied PB transposase from Trichoplusia ni. Instead, the arrangement of cysteines and histidines in the primary sequence of the Pgm CRD resembles that of active transposases from piggyBac-like elements found in other species and of human PiggyBac-derived domesticated transposases. We show that, unlike the PB CRD, the Pgm CRD does not bind DNA. Instead, it interacts weakly with the N-terminus of histone H3, whatever its lysine methylation state. Conclusions The present study points to the structural diversity of the CRD among transposases from the PiggyBac family and their domesticated derivatives, and highlights the diverse interactions this domain may establish with chromatin, from sequence-specific DNA binding to contacts with histone tails. Our data suggest that the Pgm CRD fold, whose unusual arrangement of cysteines and histidines is found in all PiggyBac-related domesticated transposases from Paramecium and Tetrahymena, was already present in the ancestral active transposase that gave rise to ciliate domesticated proteins.

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EFFECTS OF ECDYSONES, JUVENILE HORMONE ANALOGS, AND 6-OXOOCTANOIC ACID ON THE DEVELOPMENT OF THE MOSQUITO, CULEX TARSALIS (DIPTERA: CULICIDAE)

The Canadian Entomologist ◽

10.4039/ent10679-1 ◽

1974 ◽

Vol 106 (1) ◽

pp. 79-85 ◽

Cited By ~ 2

Author(s):

P. I. Ittycheriah ◽

M. S. Quraishi ◽

E. P. Marks

Keyword(s):

Juvenile Hormone ◽

Topical Treatment ◽

Adult Emergence ◽

Fourth Instar ◽

Culex Tarsalis ◽

Juvenile Hormone Analog ◽

Hormone Analog ◽

High Doses ◽

Hormone Analogs ◽

Very High

AbstractEggs, larvae, and pupae of Culex tarsalis Coquillett were treated with ecdysones, juvenile hormone analogs, and 6-oxooctanoic acid. Effects of these agents on mortality, induction of supernumerary stages, and adult emergence were determined. Topical treatment of eggs with CRD9499 (a juvenile hormone analog), β-ecdysone, and 22-isoecdysone caused a reduction in adult emergence. Treatment of fourth-instar larvae with these chemicals not only induced mortality but also caused the formation of supernumerary intermediate stages. Larvae of C. tarsalis were very susceptible to CRD9499, but pupae were resistant. The ecdysones caused some mortality but only at very high doses and would thus be of little use as larvicides. 6-Oxooctanoic acid caused high rates of mortality at 0.001 M concentrations.

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Expression of biologically active human butyrylcholinesterase in the cabbage looper (Trichoplusia ni)

Biotechnology and Applied Biochemistry ◽

10.1042/ba19990038 ◽

2000 ◽

Vol 31 (3) ◽

pp. 225 ◽

Cited By ~ 6

Author(s):

Peter L. Platteborze ◽

Clarence A. Broomfield

Keyword(s):

Trichoplusia Ni ◽

Biologically Active ◽

Cabbage Looper ◽

Human Butyrylcholinesterase

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Bacillus thuringiensis Bel Protein Enhances the Toxicity of Cry1Ac Protein to Helicoverpa armigera Larvae by Degrading Insect Intestinal Mucin

Applied and Environmental Microbiology ◽

10.1128/aem.00532-09 ◽

2009 ◽

Vol 75 (16) ◽

pp. 5237-5243 ◽

Cited By ~ 47

Author(s):

Shangling Fang ◽

Li Wang ◽

Wei Guo ◽

Xia Zhang ◽

Donghai Peng ◽

...

Keyword(s):

Bacillus Thuringiensis ◽

Helicoverpa Armigera ◽

Trichoplusia Ni ◽

Knockout Mutant ◽

Gene Encoding ◽

In Vitro Degradation ◽

Intestinal Mucin ◽

Helicoverpa Armígera ◽

Cry1ac Protein

ABSTRACT Bacillus thuringiensis has been used as a bioinsecticide to control agricultural insects. Bacillus cereus group genomes were found to have a Bacillus enhancin-like (bel) gene, encoding a peptide with 20 to 30% identity to viral enhancin protein, which can enhance viral infection by degradation of the peritrophic matrix (PM) of the insect midgut. In this study, the bel gene was found to have an activity similar to that of the viral enhancin gene. A bel knockout mutant was constructed by using a plasmid-free B. thuringiensis derivative, BMB171. The 50% lethal concentrations of this mutant plus the cry1Ac insecticidal protein gene were about 5.8-fold higher than those of the BMB171 strain. When purified Bel was mixed with the Cry1Ac protein and fed to Helicoverpa armigera larvae, 3 μg/ml Cry1Ac alone induced 34.2% mortality. Meanwhile, the mortality rate rose to 74.4% when the same amount of Cry1Ac was mixed with 0.8 μg/ml of Bel. Microscopic observation showed a significant disruption detected on the midgut PM of H. armigera larvae after they were fed Bel. In vitro degradation assays showed that Bel digested the intestinal mucin (IIM) of Trichoplusia ni and H. armigera larvae to various degrading products, similar to findings for viral enhancin. These results imply Bel toxicity enhancement depends on the destruction of midgut PM and IIM, similar to the case with viral enhancin. This discovery showed that Bel has the potential to enhance insecticidal activity of B. thuringiensis-based biopesticides and transgenic crops.

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