Differential oxidative stress responses in castor semilooper, Achaea janata

Ozone reduces lifespan and alters gene expression profiles in Rhyzopertha dominica (Fabricius)

Rhyzopertha dominica is one of the most important stored grain pests that seriously damage rice and wheat. At present, the method of controlling stored grain pests mainly relies on insecticide fumigation. However, the excessive use of pesticides not only leaves pesticide residues, with harmful effects on human health and the environment, but also induces insect resistance. Ozone is a strong oxidant with the characteristics of easy decomposition and without residue. Although ozone has been widely used in the food industry in recent years, research on the control of stored grain pests is limited. In this research, we used ozone treatment to control R. dominica adults and explore the molecular mechanisms that affect them. Here, we found that ozone treatment on R. dominica adults could decrease life span and increase malondialdehyde (MDA) content, as well as reduce activity of total superoxide dismutase (SOD) and catalase (CAT). Using RNA-seq technology, we identified 641 genes that were differentially expressed between ozone-treated and control R. dominica adults [fold-change of ≥ 2 (q-value < 5%)]. When comparing ozone treatment with control R. dominica adults, 330 genes were significantly upregulated and 311 were downregulated. RT-qPCR confirmed that 11 genes were differentially expressed in ozone-treated and control R. dominica adults. These genes were involved in insect cuticle protein and antioxidant system. This research showed that ozone treatment could reduce the lifespan of R. dominica through antioxidant system. It is an environmentally benign method for the control of stored grain pests and has great development potential.

Comparative response of Spodoptera litura challenged per os with Serratia marcescens strains differing in virulence

Host plays an important role in influencing virulence of a pathogen and efficacy of a biopesticide. The present study was aimed to characterize the possible factors present in Spodoptera litura that influenced pathogenecity of orally ingested S. marcescens strains, differing in their virulence. Fifth instar larvae of S. litura responded differently as challenged by two Serratia marcescens strains, SEN (virulent strain, LC₅₀ 7.02 10³ cfu/ml) and ICC-4 (non-virulent strain, LC₅₀ 1.19 10¹² cfu/ml). Considerable increase in activity of lytic enzymes protease and phospholipase was recorded in the gut and hemolymph of larvae fed on diet supplemented with S. marcescens strain ICC-4 as compared to the larvae treated with S. marcescens strain SEN. However, a significant up-regulation of antioxidative enzymes SOD (in foregut and midgut), CAT (in the midgut) and GST (in the foregut and hemolymph) was recorded in larvae fed on diet treated with the virulent S. marcescens strain SEN in comparison to larvae fed on diet treated with the non-virulent S. marcescens strain ICC-4. Activity of defense related enzymes lysozyme and phenoloxidase activity were also higher in the hemolymph of larvae fed with diet treated with S. marcescens strain SEN as compared to hemolymph of S. marcescens strain ICC-4 treated larvae. More number of over-expressed proteins was observed in the gut and hemolymph of S. marcescens strains ICC-4 and SEN treated larvae, respectively. Identification of the selected differentially expressed proteins indicated induction of proteins involved in insect innate immune response (Immunoglobulin I-set domain, Apolipophorin III, leucine rich repeat and Titin) in S. marcescens strain SEN treated larvae. Over-expression of two proteins, actin related protein and mt DNA helicase, were noted in S. marcescens treated larvae with very high levels observed in the non-virulent strain. Up-regulation of homeobox protein was noted only in S. marcescens strain ICC-4 challenged larvae. This study indicated that ingestion of non-virulent S. marcescens strain ICC-4 induced strong immune response in insect gut while there was weak response to the virulent S. marcescens strain SEN which probably resulted in difference in their virulence.

Utilization of microRNAs and their regulatory functions for improving biotic stress tolerance in tea plant [Camellia sinensis (L.) O. Kuntze]

MicroRNAs play a central role in responses to biotic stressors through their interactions with their target mRNAs. Tea plant (Camellia sinensis L.), an important beverage crop, is vulnerable to tea geometrid and anthracnose disease that causes considerable crop loss and tea production worldwide. Sustainable production of tea in the current scenario to biotic factors is major challenges. To overcome the problem of biotic stresses, high-throughput sequencing (HTS) with bioinformatics analyses has been used as an effective approach for the identification of stress-responsive miRNAs and their regulatory functions in tea plant. These stress-responsive miRNAs can be utilized for miRNA-mediated gene silencing to enhance stress tolerance in tea plant. Therefore, this review summarizes the current understanding of miRNAs regulatory functions in tea plant responding to Ectropis oblique and Colletotrichum gloeosporioides attacks for future miRNA research. Also, it highlights the utilization of miRNA-mediated gene silencing strategies for developing biotic stress-tolerant tea plant.

Role of Modified Atmosphere in Pest Control and Mechanism of Its Effect on Insects

Pests not only attack field crops during the growing season, but also damage grains and other food products stored in granaries. Modified or controlled atmospheres (MAs or CAs) with higher or lower concentrations of atmospheric gases, mainly oxygen (O₂), carbon dioxide (CO₂), ozone (O₃), and nitric oxide (NO), provide a cost-effective method to kill target pests and protect stored products. In this review, the most recent discoveries in the field of MAs are discussed, with a focus on pest control as well as current MA technologies. Although MAs have been used for more than 30 years in pest control and play a role in storage pest management, the specific mechanisms by which insects are affected by and adapt to low O₂ (hypoxia) and high carbon CO₂ (hypercapnia) are not completely understood. Insect tolerance to hypoxia/anoxia and hypercapnia involves a decrease in aerobic metabolism, including decreased NADPH enzyme activity, and subsequently, decreases in glutathione production and catalase, superoxide dismutase, glutathione-S-transferase, and glutathione peroxidase activities, as well as increases in carboxyl esterase and phosphatase activities. In addition, hypoxia induces energy and nutrient production, and in adapted insects, glycolysis and pyruvate carboxylase fluxes are downregulated, accompanied with O₂ consumption and acetate production. Consequently, genes encoding various signal transduction pathway components, including epidermal growth factor, insulin, Notch, and Toll/Imd signaling, are downregulated. We review the changes in insect energy and nutrient sources, metabolic enzymes, and molecular pathways in response to modified O₂, CO₂, NO, and O₃ concentrations, as well as the role of MAs in pest control. This knowledge will be useful for applying MAs in combination with temperature control for pest control in stored food products.

Cu,Zn Superoxide Dismutase Genes in Tribolium castaneum: Evolution, Molecular Characterisation, and Gene Expression during Immune Priming

The production of reactive oxygen species (ROS) is a normal consequence of the aerobic cell metabolism. Despite their high and potentially detrimental reactivity with various biomolecules, the endogenous production of ROS is a vital part of physiological, immunological, and molecular processes that contribute to fitness. The role of ROS in host-parasite interactions is frequently defined by their contribution to innate immunity as effectors, promoting parasite death during infections. In vertebrates, ROS and antioxidant system enzymes, such as superoxide dismutase (SOD) are also involved in acquired immune memory, where they are responsible for T-cell signalling, activation, proliferation, and viability. Based on recent findings, ROS are now also assumed to play a role in immune priming, i.e., a form of memory in invertebrates. In this study, the potential involvement of Cu,Zn SODs in immunity of the red flour beetle Tribolium castaneum is described for the first time, applying an approach that combines an in silico gene characterisation with an in vivo immune priming experiment using the Gram-positive entomopathogen Bacillus thuringiensis. We identified an unusually high number of three different transcripts for extracellular SOD and found that priming leads to a fine-tuned modulation of SOD expression, highlighting the potential of physiological co-adaptations for immune phenotypes.

Genome-wide identification of microRNAs responsive to Ectropis oblique feeding in tea plant (Camellia sinensis L.)

The tea plant (Camellia sinensis L.) is vulnerable to the geometrid Ectropis oblique; although microRNAs (miRNAs) are important for plant growth, development and stress response, the function of miRNAs in the response of C. sinensis to stress from E. oblique is unclear. To identify E. oblique stress-responsive miRNAs and their target genes in tea plant, three small RNA libraries were constructed from leaves subjected to mechanical wounding (MW), geometrid attack (GA) and from healthy control (CK) leaves. Using high-throughput sequencing, 130 known miRNAs and 512 novel miRNAs were identified; of these, differential expression under GA stress was observed for 36 known and 139 novel miRNAs. Furthermore, 169 GA-responsive and 173 MW-responsive miRNAs were detected by miRNA microarray. The expression patterns of six GA-responsive miRNAs were validated by qRT-PCR. Several target genes for these miRNAs encode various transcription factors, including ethylene-responsive transcription factors and squamosa promoter-binding-like proteins, which suggests that these miRNAs may regulate stress-responsive transcriptional processes in tea plant. The present findings provide novel insights into miRNA-mediated regulatory mechanisms underlying the response to GA stress, and also offer valuable information for development of pest resistance using RNA interference-based strategies in tea plants.

Comparisons of Transcriptional Profiles of Gut Genes between Cry1Ab-Resistant and Susceptible Strains of Ostrinia nubilalis Revealed Genes Possibly Related to the Adaptation of Resistant Larvae to Transgenic Cry1Ab Corn

A microarray developed on the basis of 2895 unique transcripts from larval gut was used to compare gut gene expression profiles between a laboratory-selected Cry1Ab-resistant (R) strain and its isoline susceptible (S) strain of the European corn borer (Ostrinia nubilalis) after the larvae were fed the leaves of transgenic corn (MON810) expressing Cry1Ab or its non-transgenic isoline for 6 h. We revealed 398 gut genes differentially expressed (i.e., either up- or down-regulated genes with expression ratio ≥2.0) in S-strain, but only 264 gut genes differentially expressed in R-strain after being fed transgenic corn leaves. Although the percentages of down-regulated genes among the total number of differentially expressed genes (50% in S-strain and 45% in R-strain) were similar between the R- and S-strains, the expression ratios of down-regulated genes were much higher in S-strain than in R-strain. We revealed that 17 and 9 significantly up- or down-regulated gut genes from S and R-strain, respectively, including serine proteases and aminopeptidases. These genes may be associated with Cry1Ab toxicity by degradation, binding, and cellular defense. Overall, our study suggests enhanced adaptation of Cry1Ab-resistant larvae on transgenic Cry1Ab corn as revealed by lower number and lower ratios of differentially expressed genes in R-strain than in S-strain of O. nubilalis.