Molecular cloning and characterization of the first caspase in the Striped Stem Borer, Chilo suppressalis

Changes in immune responses, gene expression, and life table parameters of Helicoverpa armigera Hübner fed on a diet containing the saponin of tea plant, Camellia sinensis

Saponins cause mortality in insects by reducing food absorption and movement in the gut, which may be used to exploit the control of insect pests. In the current study, tea seed saponin (TSS) was extracted and then added to the artificial diets of Helicoverpa armigera. Pre-ovipositional period of the TSS-treated individuals increased while longevity and fecundity decreased compared to control. There was a significant reduction of the treated individuals in the life table parameters of TSS-treated Individuals including net reproduction rate (R₀ ), intrinsic rate of population increase (r), finite rate of increase (λ), and gross reproduction rate (GRR). Also, we found that saponin suppressed the immune system by reducing the total hemocyte count, immune-related gene expression, and phenoloxidase activity. Our results demonstrated a lower expression of cecropin gene in the treated larvae with TSS while no significant differences were observed in attacin gene. Our results clearly showed that feeding of H. armigera larvae in the diet containing TSS significantly reduced demographic parameters, forced insects to obtain more time to complete one generation, and caused vulnerabilities against pathogens. These discrepancies alleviated nutrient uptake of the larvae and disrupted their feeding and growth. Hence, a proper formulation with a desirable concentration would be prepared and applied in the fields suffering H. armigera damage to monitor insecticidal efficiency of TSS.

The Bactrocera dorsalis caspase-1 gene is expressed throughout development and required for female fertility

BACKGROUND

The oriental fruit fly Bactrocera dorsalis is one of the most destructive pests of fruits and vegetables. The sterile insect technique (SIT) is an effective and environmentally friendly approach to the control of tephritid fruit flies. The pro-apoptotic gene head involution defective (hid) has been used as an effective lethal effector in SIT. It initiates an interaction cascade including activation of caspase-like proteases. However, the biological role of caspase activity in tephritid fruit flies has yet to be explored.

RESULTS

In this study, the B. dorsalis caspase-1 gene (Bdcp-1) was cloned and characterized. Sequence comparison showed that Bdcp-1 protein shared highly homology with Drosophila effector caspases Drice and Dcp-1. It is predicted to contain a short pro-domain because two proteolytic cleavage sites (Asp¹⁶ and Asp²²³ ) are present. Expression patterns indicated that Bdcp-1 is highly transcribed in embryos and expression was upregulated during metamorphosis and upon ultraviolet irradiation. RNA interference showed that Bdcp-1 is essential for ovarian development and female fertility. For example, knockdown of Bdcp-1 caused transcriptional downregulation of expression of the yolk protein-1 gene (Bdyp-1) and delayed ovarian development. The percentage of spawning females and female fecundity were significantly reduced.

CONCLUSION

This study illustrates the function of the Bdcp-1 gene and provides an attractive method to develop a biological way to control the oriental fruit fly through the control of caspases. © 2020 Society of Chemical Industry.

Effects of the Agglutinins Extracted From Rhizoctonia solani (Cantharellales: Ceratobasidiaceae) on Pieris brassicae (Lepidoptera: Pieridae)

Lectins are widespread proteins found in plants, fungi, bacteria, and vertebrates, and they play the critical roles in many physiological functions. Two lectin molecules (namely, RSAI and RSAII) were extracted from Rhizoctonia solani Kuhn and their effects on Pieris brassicae L. larvae were determined by larval survival rate, body mass, nutritional indices, digestive enzyme activities, and caspase-3 gene expression. The highest mortality caused by RSA treatment was recorded up to 80%, the larval weight decreased to 0.05 g and Similarly, RSAs significantly decreased nutritional indices including conversion efficiency of ingested food (ECI), conversion efficiency of digested food (ECD), approximate digestibility (AD), relative consumption rate (RCR), and relative growth rate (RGR) in a dose-dependent manner. Activities of α-amylase and α- and β-glucosidases significantly decreased in the larvae fed with RSA-treated diets. Also, activities of TAG-lipase and proteases significantly reduced after feeding with different concentrations of RSAs. Gene expression analysis of caspase-3 in control and treated larvae revealed significant increment of its expression in the larvae fed with RSAI and RSAII, respectively, 9.52- and 1.47-fold compared to control. These results clearly demonstrated insecticidal effects of R. solani lectins on P. brassicae via several physiological pathways, thus rendering RSA as a good target for furthering our knowledge and suggesting new strategies to overcome pesticide side effects.

Characterization of a Digestive α-Amylase in the Midgut of Pieris brassicae L. (Lepidoptera: Pieridae)

The current study deals with a digestive α-amylase in the larvae of Pieris brassicae L. through purification, enzymatic characterization, gene expression, and in vivo effect of a specific inhibitor, Acarbose. Although α-amylase activity was the highest in the whole gut homogenate of larvae but compartmentalization of amylolytic activity showed an equal activity in posterior midgut (PM) and anterior midgut (AM). A three step purification using ammonium sulfate, Sepharyl G-100 and DEAE-Cellulose Fast flow revealed an enzyme with a specific activity of 5.18 U/mg, recovery of 13.20, purification fold of 19.25 and molecular weight of 88 kDa. The purified α-amylase had the highest activity at optimal pH and temperature of 8 and 35°C. Also, the enzyme had V_max values of 4.64 and 3.02 U/mg protein and K_m values of 1.37 and 1.74% using starch and glycogen as substrates, respectively. Different concentrations of acarbose, ethylenediamine tetraacetic acid, and ethylene glycol-bis (β-aminoethylether) N, N, N′, N′-tetraacetic acid significantly decreased activity of the purified α-amylase. The 4th instar larvae of P. brassicae were fed on the treated leaves of Raphanus sativus L. with 0.22 mM of Acarbose to find in vivo effects on nutritional indices, α-amylase activity, and gene expression. The significant differences were only found in conversion efficiency of digested food, relative growth rate, and metabolic cost of control and fed larvae on Acarbose. Also, amylolytic activity significantly decreased in the treated larvae by both biochemical and native-PAGE experiments. Results of RT-PCR revealed a gene with 621 bp length responsible for α-amylase expression that had 75% identity with Papilio xuthus and P. polytes. Finally, qRT-PCR revealed higher expression of α-amylase in control larvae compared to acarbose-fed ones.

A COMPREHENSIVE STUDY ON APOPTOSIS INDUCTION BY AZADIRACHTIN IN Spodoptera frugiperda CULTURED CELL LINE Sf9

The induction of apoptosis by azadirachtin, a well-known botanical tetranortriterpenoid isolated from the neem tree (Azadirachta indica A. Juss) and other members of the Meliaceae, was investigated in Spodoptera frugiperda cultured cell line (Sf9). Morphological changes in Sf9 cells treated by various concentrations of azadirachtin were observed at different times under light microscopy. Morphological and biochemical analysis indicated that Sf9 cells treated by 1.5 μg/mL azadirachtin showed typical morphological changes, which were indicative of apoptosis and a clear DNA ladder. The flow cytometry analysis showed the apoptosis rate reached a maximum value of 32.66% at 24 h with 1.5 μg/mL azadirachtin in Sf9 cells. The inhibition of Sf9 cell proliferation suggested that the effect of azadirachtin was dose dependent and the EC50 at 48 and 72 h was 2.727 × 10(-6) and 6.348 × 10(-9) μg/mL, respectively. The treatment of azadirachtin in Sf9 cells could significantly increase the activity of Sf caspase-1, but showed no effect on the activity of Topo I, suggesting that the apoptosis induced by azadirachtinin Sf9 cells is through caspase-dependent pathway. These results provided not only a series of morphological, biochemical, and toxicological comprehensive evidences for induction of apoptosis by azadirachtin, but also a reference model for screening insect cell apoptosis inducers from natural compounds.