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.

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 ß-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.

Effects of an extracted lectin from Citrullus colocynthis L. (Cucurbitaceae) on survival, digestion and energy reserves of Ectomyelois ceratoniae Zeller (Lepidoptera: Pyralidae).

Lectins are the heterogeneous proteins in plants that serve as storage proteins via defensive mechanisms against herbivores. In the current study, a lectin was extracted and purified from seeds of Citrullus colocynthis by Sepharose 4B-Galactose and DEAE-cellulose fast flow chromatographies. Different concentrations of the lectin were added to artificial diet of Ectomyelois ceratoniae larvae finding out its effect on some biological parameters, digestive physiology and amount of storage macromolecules. It was found that CCA (C. colocynthis Agglutinin) increased life span from 23.44 days in control to 28.59 days in the treated individuals. Survival of larvae on control and CCA diets were 93.3 and 66.6%, respectively. Different concentrations of CCA significantly affected α-amylase and general proteolytic activities except for TAG-lipase activity. Activities of all specific proteases decreased when larvae were fed on different concentrations of CCA except for aminopeptidase. Meanwhile, amount of storage macromolecules in the larvae fed on different concentrations of CCA statistically decreased vs. control. These results demonstrated that CCA could intervene in physiology of E. ceratoniae and survival of larvae. Therefore, it can be taken into consideration in IPM of the pest through plant breeding programs.

Enzymatic properties of alpha- and beta-glocusidases extracted from midgut and salivary glands of rice striped stem borer, Chilo suppressalis Walker (Lepidoptera: Pyralidae).

The study of digestive enzymes, especially in important pests like Chilo suppressalis Walker (Lepidoptera: Pyralidae), which are a key constraint on rice production in a wide area of the globe and also in Iran, could be a successful procedure in the development of a safe and useful control strategy. Glycosidase are a type of digestive enzymes which have a critical role in the final stages of carbohydrate digestion; they hydrolyze alpha-D-(1,4)-glucose linkage such as p-nitrophenyl-alpha-D-glucoside in di and oligosaccharide components. Laboratory reared 4th instar larvae were randomly selected; midgut and salivary gland were removed by dissection under a stereo microscope and glucosidase activities were assayed by Ferreira and Terra's procedures. The activities of alpha- and beta-glucosidase in the midgut and salivary gland were 0.009, 0.0063, 0.005 and 0.003 micromol/min/mg protein, respectively. The optimal pH and temperature for enzyme activity were determined to be 9 and 45 degrees C for the glucosidases measured, values which are in agreement with other reports, especially in lepidopteran insects, which give values between 8-12 and 20-50 degrees C. The enzyme activity increased with the addition of NaCl, MgCl(2) and CaCl(2) and decreased due to the use of different concentrations of KCl, Urea, EDTA, SDS and Urea both in midgut and the salivary glands. Control of pests by using resistant varieties is one of the most important practices that are dependent on inhibitors in plants. Hence, characterization of digestive enzymes, especially the effect of inhibitors on enzyme activity, could be useful, on the one hand for a better understanding of enzyme roles in the nutrition physiology of insects, and on the other hand to reach safe and useful controls of insect pests.