Elevated CO2 and temperature alter development and food utilization of Spodoptera litura fed on resistant soybean

Effects of elevated atmospheric CO₂ (elevated CO₂ vs. ambient CO₂) and temperature (+0.67–0.79°C vs. ambient temperature) on the developmental life cycle of Spodoptera litura and the food utilization of the fourth‐instar larvae fed on soybean (resistant cultivar Lamar vs. susceptible landrace JLNMH) grown in open‐top chambers were studied from 2013 to 2015. The results indicated that: (i) compared with ambient CO₂, elevated CO₂ significantly prolonged the duration of larva and pupa, and adult longevity; significantly decreased the pupation rate, pupal weight, fecundity, the relative growth rate (RGR), efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD); and increased the relative consumption rate (RCR) and approximate digestibility (AD). (ii) Compared with ambient temperature, elevated temperature significantly shortened the duration of larva and pupa; significantly decreased the pupal weight; and increased the RGR, RCR, ECD and ECI. (iii) Compared with the susceptible soybean accession JLNMH, the resistant soybean cultivar Lamar significantly prolonged the duration of larva and pupa; significantly decreased the pupation rate, pupal weight, adult longevity, fecundity and RGR, RCR and AD; and increased the indexes of ECD. (iv) At elevated temperature, S. litura fed on resistant vs. susceptible cultivars showed opposite trends in the RGR, RCR, AD, ECD and ECI. In addition, elevated temperature under elevated CO₂ significantly decreased the RGR (2014), ECD (2013 & 2014) and ECI (2013) and increased the AD (2013 & 2014) compared with other treatment combinations when S. litura fed on Lamar. Future climatic change of temperature and CO₂ concentration would likely affect growth and food utilization of S. litura, with increased food intake, but the reduced fecundity may compensate for the increased food consumption, resulting in no significant reduction in insect‐induced yield loss in soybean production. Nevertheless, use of insect resistant soybean cultivars will aid in ecological management of S. litura and reduce the insecticide load in soybean production.     

Flavonoid glycosides in Malabar spinach Basella alba inhibit the growth of Spodoptera litura larvae

Basella alba is a perennial plant of the Basellaceae and is known by various common names including Malabar spinach. There are few insects that cause damage to B. alba. In this study, we examined the effect of B. alba leaves on the growth of Spodoptera litura larvae. B. alba leaves and a methanolic extract of the leaves inhibited the growth of S. litura larvae. Half of the larvae reared on the leaves died within 1 week. We found that two flavonoids, vitexin, and vitexin-2″-O-arabinofuranoside, were abundant in the methanol extract of leaves. When larvae were reared on purified vitexin or vitexin-2″-O-arabinofuranoside, their growth was significantly impaired compared with larvae reared on control spinach leaves. These results suggested that the flavonoid glycosides in B. alba leaves act as deterrents to S. litura larvae.     

Biological response of S. littoralis larvae to feeding on diet mixed with neem product at different concentrations

Studies were carried out to determine the effect of the neem product, suneem oil, at two concentrations 10 and 100 ppm, on the second instar larvae of S. littoralis in the laboratory. Two sets of experiments were carried out, choice and no choice. Results showed that suneem oil has anti-feeding and repellency effects on the test insects and it markedly affects the longevity of larvae and pupae, impairs the normal development of larvae and has an effect on the weight of pupae, depending on the concentration used (100 or 10 ppm).     

The role of bacterial symbionts in suppressing the defence reaction in larval hemolymph of the cotton leafworm Spodoptera littoralis (Biosd.)

Abstract

Spodoptera littoralis hemolymph exhibited a decrease in phenoloxidase activity during the first hour of exposure to alive or dead Xenorhabdus nematophilus and Photorhabdus luminescens even in the presence or absence of laminarin and α-chymotrypsin. Also, as the bacterial numbers in the hemolymph of the larvae of S. littoralis increased, the suppression of the enzyme, phenoloxidase, activity in vivo increased. On the other hand, in the in vitro incubation of the infected hemolymph with X. nematophilus for 30 min with laminarin, the decrease in phenoloxidase activity reached 92% in the infection with the highest dose (1 × 10¹⁰ cells/ml) live bacteria, and reached 100% at the same dose in the infection with live bacteria in the absence of laminarin. A two-fold decrease in enzyme activity was recorded in the case of injection of (1 × 10⁶ cells/ml) dead X. nematophilus and the absence of laminarin compared with injection of the same dose in the presence of laminarin. The same trend was also observed by the end of incubation of X. nematophilus-treated hemolymph without α-chymotrypsin. The decrease in phenoloxidase activity was highly significantly different in injection of dead P. luminescens and the absence of laminarin during incubation. In the case of injection of (1 × 10⁸ cells/ml) live P. luminescens a higher degree in the reduction of enzyme activity was recorded in the absence of α-chymotrypsin, where it reached to nearly a two-fold decrease. The results of these studies indicated that both X. nematophilus and P. luminescens alive or dead suppress the phenoloxidase activity in the presence or absence of both laminarin and α-chymotrypsin but, the suppression in absence of both during the in vitro incubation was highly comparable.     

Role of Challenger pesticide and plant extracts on some physiological parameters of the cotton leafworm,Spodoptera littoralis (Boisd.)

Fourth instar larvae of cotton leafworm, Spodoptera littoralis (Boisd.), fed on castor bean leaves treated with sub-lethal concentrations of both alcohol and hexane extracts of Egyptian conyza and Challenger 36% SC insecticide as well to study their effects on mortality, food consumption and utilisation of food. The tested insecticides exhibited relatively high mortality in alcoholic extract of Egyptian conyza (5.0% concentration) followed by Challenger (1.0% concentration). Results showed a slight reduction in the consumption index for larvae treated with both alcoholic extract and Challenger at low concentrations, while hexane extract (5%) recorded significant increase. The approximate digestibility (AD) was reduced in all treatments of alcoholic extract and the relative growth rate insignificantly decreased at 5% concentration, whereas AD increased for larvae fed on Challenger 0.25% concentration. The lower concentration of alcoholic extract of conyza and all treatments of Challenger pesticides induced insignificant decrease in the efficiency of conversion of the ingested food, while hexane extract exhibited insignificant increase. Challenger at all tested concentrations achieved insignificant decrease in the efficiency of the conversion of digested food with respect to the control.     

Effect of Calcium Activated Factor on Properties of Actin and Myosin of Rabbit Skeletal Muscle

The effect of calcium activated factor (CAF) on enzymatic properties of actin and myosin was investigated. SDS polyacrylamide gel electrophoresis revealed that CAF did not degrade actin, but a slight degradation was found in myosin during CAF digestion, which might have been due to contaminated protease (s) in CAF preparation. No influence was found in EDTA ATPase of myosin and polymerization of G-actin during CAF digestion. However, heavy meromyosin (HMM) ATPase activating ability of actin was slightly decreased during CAF digestion. Although CAF digestion slightly decreased the biological activity of myofibrillar proteins, a single sarcomere prepared by CAF digestion is a useful model for studying muscle contraction because of its almost intact contractility.     

Insecticidal bacteria isolated from predatory larvae of the antlion species Myrmeleon bore (Neuroptera: Myrmeleontidae)

Various bacterial species were isolated from the crop (digestive organ) of the antlion species Myrmeleon bore and tested for their insecticidal activity against caterpillars by injection. Sixty-eight isolates from the antlion crop were grouped into twenty-four species based on homologies of 16S rRNA gene sequences and biochemical properties. Isolated Bacillus cereus, Bacillus sphaericus, Morganella morganii, Serratia marcescens and a Klebsiella species killed 80% or more cutworms when injected at a dose of 5x10(5)cells per insect. In addition, cutworms killed by these isolates resembled observations made of caterpillars attacked by antlions. A culture-independent analysis showed that the isolated bacterial species are likely to be frequently present in the antlion crop. These results suggest that insecticidal microorganisms associate with antlions, and may promote the death of prey.     

Crystal structure of the cofactor-binding domain of the human phase II drug-metabolism enzyme UDP-glucuronosyltransferase 2B7

Human UDP-glucuronosyltransferases (UGT) are the dominant phase II conjugative drug metabolism enzymes that also play a central role in processing a range of endobiotic compounds. UGTs catalyze the covalent addition of glucuronic acid sugar moieties to a host of therapeutics and environmental toxins, as well as to a variety of endogenous steroids and other signaling molecules. We report the 1.8-A resolution apo crystal structure of the UDP-glucuronic acid binding domain of human UGT isoform 2B7 (UGT2B7), which catalyzes the conjugative elimination of opioid, antiviral, and anticancer drugs. This is the first crystal structure of any region of a mammalian UGT drug metabolism enzyme. Designated UGT2B7 mutants at residues predicted to interact with the UDP-glucuronic acid cofactor exhibited significantly impaired catalytic activity, with maximum effects observed for amino acids closest to the glucuronic acid sugar transferred to the acceptor molecule. Homology modeling of UGT2B7 with related plant flavonoid glucosyltransferases indicates human UGTs share a common catalytic mechanism. Point mutations at predicted catalytic residues in UGT2B7 abrogated activity, strongly suggesting human UGTs also utilize a serine hydrolase-like catalytic mechanism to facilitate glucuronic acid transfer.