Antioxidant responses of the pest natural enemy Hylyphantes graminicola (Araneae: Linyphiidae) exposed to short-term heat stress

Disruption of midgut homeostasis by microplastics in Spodoptera frugiperda: Insights into inflammatory and oxidative mechanisms

Microplastics have evolved as widespread contaminants in terrestrial and aquatic environments, raising significant environmental concerns due to their persistence and bioaccumulation. In this study, we investigated the toxicity of polyethylene microplastics (PE-MPs) on the agricultural insect, Spodoptera frugiperda. Maize leaves containing three sizes (0.5 μm, 5 μm, and 50 μm) of PE-MPs were fed to fall armyworm larvae for 12 days at concentrations of 1.25 g/ L, 5 g/L, and 20 g/L. The results showed that smaller size and higher concentration of microplastics led to increased toxicity. Furthermore, different sizes and maximum concentrations of PE-MPs were selected for subsequent experiments to observe changes in histological and enzymatic biomarkers, midgut microbiome, and metabolic responses. Following PE-MPs exposure, inflammation signs and oxidative stress were detected in the midgut. Significant changes were also observed in midgut microbiota and metabolomes, most related with oxidative stress, inflammatory disorders, and energy metabolism. These results provide evidence of midgut damage and alterations in the microbiota and metabolome of S. frugiperda because of PE-MPs exposure, highlighting the harm that microplastics can inflict on agricultural insects. Additionally, the study lays a theoretical foundation for future research on the transmission of microplastics through the food chain in agricultural ecosystems.

Comparative transcriptome analysis provides comprehensive insight into the molecular mechanisms of heat adaption in Plutella xylostella

Plutella xylostella is one of the most destructive pests for cruciferous vegetables, and is adaptability to different environmental stressors. However, we still know little about the molecular mechanisms of how P. xylostella adapt to thermal stress. Here, the comparative transcriptome analysis was conducted from the samples of control (27 °C, CK) and heat treatment (40 °C, 40 T) P. xylostella. The results showed 1253 genes were differentially expressed, with 624 and 629 genes up- and down-regulated respectively. The annotation analysis demonstrated that "Energy production and conversion", "Protein processing in endoplasmic reticulum", "Peroxisome" and "Tyrosine metabolism" pathways were significantly enriched. Additionally, we found the expression levels of heat shock protein genes (Hsps), cuticle related genes and mitochondrial genes were significantly up-regulated in 40 T insects, suggesting their vital roles in improving adaption to heat stress. Importantly, the SOD activity and MDA content of P. xylostella were both identified to be increased under high temperature stress, indicating the elevated antioxidant reactions might be involved in response to heat stress. In conclusion, the present study offered us an overview of gene expression changes after 40 °C treatments, and found some critical pathways and genes of P. xylostella might play the critical roles in resisting heat stress.

Hotter days, stronger immunity? Exploring the impact of rising temperatures on insect gut health and microbial relationships

Climate change can generate cascading effects on animals through compounding stressors. As ectotherms, insects are particularly susceptible to variation in temperature and extreme events. How insects respond to temperature often occurs with respect to their environment, and a pertinent question involves how thermal stress integrates with insect capabilities to resolve interactions with gut microorganisms (microbiome and gut pathogens). We explore the impact of elevated temperatures and the impact of the host physiological response influencing immune system regulation and the gut microbiome. We summarize the literature involving how elevated temperature extremes impact insect gut immune systems, and how in turn that alters potential interactions with the gut microbiome and potential pathogens. Temperature effects on immunity are complex, and ultimate effects on microbial components can vary by system. Moreover, there are multiple questions yet to explore in how insects contend with simultaneous abiotic stressors and potential trade-offs in their response to opportunistic microbiota.

Three Heat Shock Protein Genes and Antioxidant Enzymes Protect Pardosa pseudoannulata (Araneae: Lycosidae) from High Temperature Stress

Pardosa pseudoannulata (P. pseudoannulata) is an essential natural predatory enemy in rice ecosystems. The fluctuating climate may cause them to experience heat stress, whereas heat shock proteins (HSPs) and antioxidant enzymes help resist heat damage. Herein, we cloned and characterized the full-length genes PpHSP27, PpHSP60, and PpHSC70 from P. pseudoannulata. Changes in gene expression levels and superoxide dismutase (SOD), catalase (CAT), and glutathione transferase (GST) activities in adult male and female P. pseudoannulata were measured at different stress exposure times and temperatures. We found that the abovementioned HSP genes belong to the sHSP, HSP60, and HSP70 families. The expression of the three HSP genes and the activities of SOD, CAT, and GST were significantly upregulated with the increasing stress temperature and time. The knockdown of the three HSP genes via RNA interference significantly decreased the survival rate of male and female P. pseudoannulata during high temperature stress. Thus, PpHSP27, PpHSP60, and PpHSC70 play an important role in the heat tolerance of P. pseudoannulata, and SOD, CAT, and GST enable recovery heat stress-induced oxidative damage. Their changes and regulation during high temperature stress can improve spiders' adaptability in the field and enhance the biological control of environmental pests.

Genome-wide characterization of homeodomain-leucine zipper genes reveals RsHDZ17 enhances the heat tolerance in radish (Raphanus sativus L.)

Homeodomain-leucine zipper (HD-Zip) transcription factors are involved in various biological processes of plant growth, development, and abiotic stress response. However, how they regulate heat stress (HS) response remains largely unclear in plants. In this study, a total of 83 RsHD-Zip genes were firstly identified from the genome of Raphanus sativus. RNA-Seq, RT-qPCR and promoter activity assays revealed that RsHDZ17 from HD-Zip Class I was highly expressed under heat, salt, and Cd stresses. RsHDZ17 is a nuclear protein with transcriptional activity at the C-terminus. Ectopic overexpression (OE) of RsHDZ17 in Arabidopsis thaliana enhanced the HS tolerance by improving the survival rate, photosynthesis capacity, and scavenging for reactive oxygen species (ROS). In addition, transient OE of RsHDZ17 in radish cotyledons impeded cell injury and augmented ROS scavenging under HS. Moreover, yeast one-hybrid, dual-luciferase assay, and electrophoretic mobility shift assay revealed that RsHDZ17 could bind to the promoter of HSFA1e. Collectively, these pieces of evidence demonstrate that RsHDZ17 could play a positive role in thermotolerance, partially through up-regulation of the expression of HSFA1e in plants. These results provide novel insights into the role of HD-Zips in radish and facilitate genetical engineering and development of heat-tolerant radish in breeding programs.

Antioxidant Enzymes and Heat-Shock Protein Genes of Green Peach Aphid (Myzus persicae) Under Short-Time Heat Stress

The management of insect pests under fluctuating temperatures has become an interesting area of study due to their ability to stimulate defense mechanisms against heat stress. Therefore, understanding insect’s physiological and molecular response to heat stress is of paramount importance for pest management. Aphids are ectothermic organisms capable of surviving in different climatic conditions. This study aimed to determine the effects of short-time heat stress on green peach aphid Myzus persicae under controlled conditions. In this study, short-time heat stress treatments at different temperatures 27, 30, 33, and 36°C with exposure times of 1, 3, 6, and 10 h, respectively, on the activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and oxidants, such as malondialdehyde (MDA) and hydrogen peroxide (H₂O₂), were determined. The results showed that the short-time heat stress significantly increased the content of MDA of M. persicae by 71, 78, 81, and 86% at 36°C for the exposure times of 1, 3, 6, and 10 h, respectively, compared with control. The content of H₂O₂ increased by 75, 80, 85, and 88% at 36°C for the exposure times of 1, 3, 6, and 10 h, respectively, compared with the control. The SOD, POD, and CAT activities increased by 61, 76, and 77% for 1 h, 72, 83, and 84% for 3 h, 80, 85, and 86% for 6 h, and 87, 87.6, and 88% for 10 h at 36°C, respectively, compared with control. Again, under short-time heat stress, the transcription levels of Hsp22, Hsp23, Hsp27, SOD, POD, and CAT genes were upregulated compared with control. Our results suggest that M. persicae increased the enzymatic antioxidant activity and heat-shock gene expression as one of the defensive mechanisms in response to heat stresses.

Elevated CO2 concentration affects survival, but not development, reproduction, or predation of the predator Hylyphantes graminicola (Araneae: Linyphiidae)

Elevated CO₂ concentrations can change the multi-level nutritional relationship of the ecosystem through the cascading effect of the food chain. To date, few studies have investigated the effects of elevated CO₂ concentration on the Araneae species through the tritrophic system. Hylyphantes graminicola (Araneae: Linyphiidae) is distributed widely in Asia and is a dominant predator in cotton fields. This study investigated chemical components in the food chain of cotton (Gossypium hirsutum)-cotton aphid (Aphis gossypii)-predator (H. graminicola) and compared the development, reproduction, and predation of H. graminicola under ambient (400 ppm) and elevated concentration of CO₂ (800 ppm). The results showed that the elevated CO₂ concentration increased the chemicals of cotton and cotton aphid, but it did not affect the nutrients, development, reproduction, and predation of the spider. However, the survival rate of the spider was significantly decreased in elevated CO₂. The results will further our understanding of the role of natural enemies in an environment with elevated CO₂ concentration.

Antioxidant Enzymes and Heat Shock Protein Genes from Liposcelis bostrychophila Are Involved in Stress Defense upon Heat Shock

Simple Summary

Liposcelis bostrychophila is one of the most serious pests of stored commodities among the psocids. Controlling psocids mainly relies on chemical insecticides and heat stress. In fact, L. bostrychophila has developed high levels of resistance or tolerance to heat treatment in grain storage systems. In this study, we evaluated the changes in malondialdehyde (MDA) concentration after different high temperatures. The result showed that MDA is increased slightly overall, but a drastic increase is detected at 42.5 °C for exposure of different times. To further explore the principles of L. bostrychophila in response to heat stress, we tested the changes of superoxide dismutase (SOD), catalase (CAT), peroxidases (POD) and glutathione-S-transferases (GST) activities under different heat treatments and identified four inducible LbHsp70 genes and one LbHsp110 gene. Enzyme activities and transcript levels changed drastically after different heat treatments. These findings contribute to our understanding of the mechanism of L. bostrychophila responding to heat stress and provide baseline information for further understanding the excellent targets of L. bostrychophila.

Abstract

Psocids are a new risk for global food security and safety because they are significant worldwide pests of stored products. Among these psocids, Liposcelis bostrychophila has developed high levels of resistance or tolerance to heat treatment in grain storage systems, and thus has led to investigation of molecular mechanisms underlying heat tolerance in this pest. In this study, the time-related effects of thermal stress treatments at relatively high temperatures on the activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), peroxidases (POD), glutathione-S-transferases (GST) and malondialdehyde (MDA), of L. bostrychophila were determined. Thermal stress resulted that L. bostrychophila had a significantly higher MDA concentration at 42.5 °C, which indicated that the heat stress increased lipid peroxidation (LPO) contents and oxidative stress in this psocid pest. Heat stress also resulted in significant elevation of SOD, CAT and GST activities but decreased POD activity. Our data indicates that different antioxidant enzymes contribute to defense mechanisms, counteracting oxidative damage in varying levels. POD play minor roles in scavenging deleterious LPO, while enhanced SOD, CAT and GST activities in response to thermal stress likely play a more important role against oxidative damage. Here, we firstly identified five LbHsps (four LbHsp70s and one LbHsp110) from psocids, and most of these LbHsps (except LbHsp70-1) are highly expressed at fourth instar nymph and adults, and LbHsp70-1 likely presents as a cognate form of HSP due to its non-significant changes of expression. Most LbHsp70s (except LbHsp70-4) are significantly induced at moderate high temperatures (<40 °C) and decreased at extreme high temperatures (40–45 °C), but LbHsp110-1 can be significantly induced at all high temperatures. Results of this study suggest that the LbHsp70s and LbHsp110 genes are involved in tolerance to thermal stress in L. bostrychophila, and antioxidant enzymes and heat shock proteins may be coordinately involved in the tolerance to thermal stress in psocids.