RNAi-based functional analysis of bursicon genes related to wing expansion in gypsy moths.

Bursicon is a heterodimeric neuropeptide composed of Burs-α and Burs-ß subunits that plays an important role in cuticle tanning and wing expansion in insects. In this study, full-length cDNAs of Burs-α (LdBurs-α) and Burs-ß (LdBurs-ß) genes were identified in gypsy moth (Lymantria dispar) and cloned. The 480 bp and 420 bp open reading frames (ORFs) encode 159 and 129 amino acid polypeptides, respectively. LdBurs-α and LdBurs-ß have 11 conserved cysteine residues, and LdBurs-α and LdBurs-ß genes were expressed during all developmental stages according to quantitative reverse transcription PCR (qRT-PCR), with highest expression in the egg stage. High expression levels were also detected in the haemolymph, cuticle and head. To explore the physiological functions of LdBurs-α and LdBurs-ß, the genes were knocked down in larvae and pupae using RNA interference (RNAi), and expression levels of LdBurs-α and LdBurs-ß were decreased by 42.26-80.09%. Wing defects were observed in L. dispar pupae following Ldbursion silencing, with a phenotypic percentage ranging from 10.17% to 15.00%. RNAi-mediated knockdown of Ldbursicon prevented the expansion of male and female L. dispar adult wings, with malformation rates ranging from 6.38% and 30.00% to 57.69% and 69.23%, but no cuticle tanning defects were observed in pupae or adults. The results indicate that bursicon plays a key role in wing expansion in L. dispar adults, making it a potentially novel molecular target for insecticide-based control of this pest species.

[Structure dynamics of insect communities in typical artificial and primeval forests during restoring stages in Xiaoxing'an Mountain, Northeast China].

In order to study the insect community structure of typical artificial and primeval forests during different restoring stages in Xiaoxing'an Mountains, we had systematically investigated the insect communities of four typical forests in Liangshui Natural Reserve. A total of 11712 specimens of 293 species were collected, which belonged to 81 families of 10 orders, with Hymenoptera, Diptera, and Coleoptera being the dominant groups. The community stability analysis on insect communities showed that the insect communities of Dahurian larch plantation and original broadleaved Korean pine forest were more stable than other forest types. The principal components analysis indicated that predatory and neutral insects played important roles in the community stability which increased with the increasing predatory insect species and quantities. Polar ordination analysis showed that there was little difference between the environmental factors of Korean pine plantation and the original Korean pine forest.

Purification, characterization, and sensitivity to pesticides of carboxylesterase from Dendrolimus superans (Lepidoptera: Lasiocampidae).

Through a combination of steps including centrifugation, ammonium sulfate gradient precipitation, sephadex G-25 gel chromatography, diethylaminoethyl cellulose 52 ion-exchange chromatography and hydroxyapatite affinity chromatography, carboxylesterase (CarE, EC3.1.1.1) from sixth instar larch caterpillar moth, Dendrolimus superans (Lepidoptera: Lasiocampidae) larvae was purified and its biochemical properties were compared between crude homogenate and purified CarE. The final purified CarE after hydroxyapatite chromatography had a specific activity of 52.019 µmol/(min·mg protein), 138.348-fold of crude homogenate, and the yield of 2.782%. The molecular weight of the purified CarE was approximately 84.78 kDa by SDS-PAGE. Three pesticides (dichlorvos, lambda-cyhalothrin, and avermectins) showed different inhibition to crude CarE and purified CarE, respectively. In vitro median inhibitory concentration indicated that the sensitivity of CarE (both crude homogenate and final purified CarE) to pesticides was in decreasing order of dichlorvos > avermectins > lambda-cyhalothrin. By the kinetic analysis, the substrates alpha-naphthyl acetate (α-NA) and beta-naphthyl acetate (ß-NA) showed lesser affinity to crude extract than purified CarE. The results also indicated that both crude homogenate and purified CarE had more affinity to α-NA than to ß-NA, and the Kcat and Vmax values of crude extract were lower than purified CarE using α-NA or ß-NA as substrate.

Toxicity and affecting factors of Bacillus thuringiensis var. israelensis on Chironomus kiiensis larvae.

Abstract Bacillus thuringiensis var. israelensis (Bti) is a suitable agent for controlling Chironomus kiiensis, a major pest polluting water. In this study, laboratory bioassays were used to study toxicity and affecting factors of Bti on C. kiiensis larvae. Tests were conducted using three commercial Bti formulations (oil miscible suspension, 1,200 ITU/mL; wettable power, 1,200 ITU/mg; technical material, 5,000 ITU/mg) of Bti. The toxicity of Bti formulations to third and fourth instar C. kiiensis larvae was in decreasing order of technical material, oil miscible suspension, and wettable powder, based on the 12 and 24 hour LC50 values. Increasing larval densities (from 10 to 30 per bioassay cup) increased the LC50 values for fourth instar C. kiiensis larvae. The LC50 values for fourth instar larvae reared in sand substrate were higher than those from soil substrate, and autoclaved substrates significantly increased the LC50 values. The technical material of Bti at 12 and 24 hours responded similarly to changes in temperature between 30° C and 15° C, but the LC50 values at a range of tested temperatures showed distinct differences in time points.

[Responses of biological markers of larval Propsilocerus akamusi to phenol].

Taking the 4th-instar larval Propsilocerus akamusi as test object, this paper studied the acute toxicity of phenol, and the body mass, pupation rate, protective enzyme activities, and detoxifying enzyme activities of the larvae under exposure to phenol. The LC50 value of phenol to the larvae after exposure for 6, 24, 48, 72, and 96 h was 222.52, 134.86, 67.74, 47.39, and 35.76 mg x L(-1), respectively, and the dry mass, fresh mass, and pupation rate of the larvae decreased under the exposure of 0. 4, 4, and 40 mg phenol x L(-1). During 72 h exposure to phenol, the larval catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), and carboxylesterase (CarE) activities responded to phenol in concentration- and time-dependent way, while the acid phosphatase (ACP) and alkaline phosphatase (ALP) activities responded slowly and were only inhibited significantly under the exposure to 40 mg x L(-1) of phenol for 48 and 72 h, respectively. It was suggested that the body mass, pupation rate, and CAT, SOD, GST, and CarE activities of 4th-instar larval P. akamusi could be used as the biological markers to monitor the phenol pollution of water body.

Response of the gypsy moth, Lymantria dispar to transgenic poplar, Populus simonii x P. nigra, expressing fusion protein gene of the spider insecticidal peptide and Bt-toxin C-peptide.

The response of the Asian gypsy moth Lymantria dispar (L.) (Lepidoptera: Lymantriidae) to a fusion gene consisting of the spider, Atrax robustus Simon (Araneae: Hexanthelidae) ω-ACTX-Ar1 sequence coding for an ω-atracotoxin and a sequence coding for the Bt-toxin C-peptide, expressed in transgenic poplar Populus simonii x P. nigra L. (Malphigiales: Salicaceae) was investigated. Individual performance, feeding selection, midgut proteinase activity and nutrition utilization were monitored. The growth and development of L. dispar were significantly affected by continually feeding on the transgenic poplar, with the larval instars displaying significantly shorter developmental times than those fed on nontransgenic poplar, but pupation was delayed. Mortality was higher in populations fed transgenic poplar leaves, than for larvae fed nontransgenic poplar leaves. The cumulative mortality during all stages of larvae fed transgenic leaves was 92% compared to 16.7% of larvae on nontransgenic leaves. The highest mortality observed was 71.7% in the last larval instar stage. A two-choice test showed that fifth-instar larvae preferred to feed on nontransgenic leaves at a ratio of 1:1.4. Feeding on transgenic leaves had highly significant negative effects on relative growth of larvae, and the efficiency of conversion of ingested and digested food. Activity of major midgut proteinases was measured using substrates TAME and BTEE showed significant increases in tryptase and chymotrypsinlike activity (9.2- and 9.0-fold, respectively) in fifth-instar larvae fed on transgenic leaves over control. These results suggest transgenic poplar is resistant to L. dispar, and the mature L. dispar may be weakened by the transgenic plants due to Bt protoxins activated by elevated major midgut proteinase activity. The new transgenic poplar expressing fusion protein genes of Bt and a new spider insecticidal peptide are good candidates for managing gypsy moth.