Synergistic effects of heat and diatomaceous earth treatment for the control of Plodia interpunctella (Lepidoptera: Pyralidae)

Plodia interpunctella is a major economic pest that commonly infests most stored and processed agricultural products. Currently, heating at 50–60°C for at least 48 h is applied in facilities for disinfestation. However, this condition requires a great deal of time and expense. To improve the control efficiency of this system, we conducted combined treatments with heating and diatomaceous earth (DE), which is known to be toxic to pest insects. The DE effect was compared to heating at 25°C or 40°C to wandering fifth instar larvae, which is the stage most tolerant to heat. When larvae were brushed with DE powder, mortality was only 15.0–18.3% at 25°C for 10 days, but rapidly increased to 100% at 40°C within 4 h post‐treatment. In addition, when larvae were kept in a plastic cage with DE [4 mg/L (w/v)], their mortality was 100% in 24 h at 40°C post‐treatment; otherwise mortality was only 8.8% without DE. Thus, the control efficiency of heating significantly improved with the combination of DE. These effects increased further at higher temperatures and with longer exposure. Our results clearly showed that DE treatment showed synergistic effects with heating systems for the control of P. interpunctella.     

Cloning and expression of heat shock protein genes in two whitefly species in response to thermal stress

Two whitefly species, Trialeurodes vaporariorum and Bemisia tabaci biotype B were shown to have different temperature tolerance and seasonal dynamics. To determine whether this variation in thermal tolerance is related to different expression patterns of heat shock protein (hsp) genes during temperature stress, we obtained complete cDNA sequences for hsp90, hsp70 and hsp20, and analysed their expression profiles across temperature gradients by real‐time quantitative polymerase chain reaction (PCR). Six full‐length cDNAs were cloned and sequenced from these two species. The full‐length cDNAs of hsp90s contain 2166 and 2157 bp open‐reading frames (ORF) which encode proteins with calculated molecular weights of 83 013 and 82 857 Da in T. vaporariorum and B. tabaci, respectively. The 1947 and 1959 bp ORFs of whitefly hsp70s comprise 649 and 653 amino acids with the calculated masses of 70 885 and 71 008 Da in T. vaporariorum and B. tabaci, respectively. Both complete cDNAs of hsp20 of T. vaporariorum and B. tabaci contain 585 bp ORFs and deduced amino acid sequences had molecular weights of 21 559 and 21 539 Da, respectively. The hsp expression profile results showed that temperatures for onset (T_on) or maximal (T_max) induction of hsp expression in T. vaporariorum were generally 2–6°C lower than those in B. tabaci. These results suggest that the T_on (or T_max) of hsps can represent the differences in temperature tolerance of these two whitefly species, and may be used to determine their natural geographical distribution and natural population seasonal dynamics. Significant upregulation of most hsps were observed when temperature stress was lifted, except that hsp70 and hsp20 of B. tabaci did not respond to the cold stress, indicating that response to heat and cold stress may have a different genetic and physiological basis in two whitefly species. These results highlight the importance of understanding the complexity of the heat shock response across multiple isoforms while attempting to link them to whole‐organism traits such as thermal tolerance.     

Effects of heat shock on ovary development and hsp83 expression in Tribolium castaneum (Coleoptera: Tenebrionidae)

Heat shock affects reproductive performance in insects including Tribolium castaneum. In this study, the effects of heat shock on ovary development and hsp83 expression in T. castaneum were investigated. Two lines of T. castaneum, H line and C line, from the same base population were established and maintained for five successive generations. In each generation, the newly hatched beetles (within 3 h after eclosion) in the H line were treated with a heat shock at 40°C for 1 h, and those in the C line were raised at normal temperature (30°C) as control treatment. Four traits related to ovary development were measured for the beetles of the fifth generation: days from eclosion to laying the first eggs (T_o), days from eclosion to laying the first hatchable eggs (T_h), ovariole size on the third day after eclosion, and pupal mass of their offspring. The results showed that the beetles of the H line had a significantly longer pre‐oviposition period (0.6 more days) and smaller ovariole size than those of the C line. No significant difference in pupal mass was observed. Applying heat shock to the offspring of the fifth generation of both lines led to significantly higher hsp83 expression in offspring of the C line than in offspring of the H line. Within each line, the hsp83 expression level in offspring with heat shock was significantly higher than that of offspring without heat shock, but the difference in the C line was much larger than that in the H line. We infer from these results that a tradeoff between heat resistance, registered as hsp83 expression, and ovarian development operates under heat stress in T. castaneum. 2009 Wiley Periodicals, Inc.     

Cloning of heat shock protein genes from the brown planthopper,Nilaparvata lugens,and the small brown planthopper,Laodelphax striatellus,and their expression in relation to thermal stress

Three heat shock protein (HSP) genes (hsp70, hsc70, hsp90) were partially cloned from the brown planthopper Nilaparvata lugens and the small brown planthopper Laodelphax striatellus (Homoptera: Delphacidae), which are serious pests of the rice plant. Sequence comparisons at the deduced amino acid level showed that the three HSPs of planthoppers were most homologous to corresponding HSPs of dipteran and lepi‐dopteran species. Identities of both heat shock cognate 70 and HSP90 were higher than HSP70 in both species. Identity of the HSP70 between the two planthopper species was only 81%, a value much lower than seen among fly and moth groups. Effects of heat and cold shocks were demonstrated on expression of the three hsp genes in the two planthopper species. Heat shock (40 °C) upregulated the hsp90 level but did not change the hsc70 level in either the nymph and adult stages of either species. On the other hand, the hsp70 level was only upregulated in L. striatellus. This heat shock response was prompt and lasted only for 1 h after treatment. In contrast, cold shock at 4°C did not change the expression levels of any hsp in either species.     

Toxicity of cypermethrin: hsp70 as a biomarker of response in transgenic Drosophila

Heat shock protein induction is often associated with a cellular response to a harmful environment or to adverse life conditions. The main aims of our study were (1) to evaluate the cytotoxic potential of cypermethrin; and (2) to investigate the suitability of stress-induced heat shock protein Hsp70 as a biomarker for environmental pollutants in transgenic Drosophila melanogaster (Hsp70-lacZ)Bg⁹. Different concentrations of cypermethrin (0.002, 0.2, 0.5 and 50.0 p.p.m.) were mixed with food. Third instar larvae of transgenic Drosophila melanogaster were allowed to feed on these mixtures for different time intervals (2, 4, 6, 12, 24 and 48h). Following feeding, hsp70 induction and tissue damage were evaluated. In the highest concentration treatment group (50 p.p.m.), 100% larval mortality was recorded after 12 h exposure. Hsp70 was found to be induced even at the lowest concentration (0.002 p.p.m.) of the insecticide, while tissue damage was observed in the larvae exposed for 48 h. While an insignificant decline in hsp70 expression was observed in the larvae exposed to cypermethrin at a dietary concentration of 0.002 p.p.m. after 48 h compared with those exposed for 24 h, in the next two higher concentrations of the toxicant, a similar but significant decline in hsp70 expression was evident in the exposed larvae after 48 h. The present study reveals the cytotoxic potential of cypermethrin and further proposes that hsp70 induction in transgenic Drosophila melanogaster could be used as a sensitive biomarker in risk assessment.     

Atmospheric CO2, plant nitrogen status and the susceptibility of plants to an acute increase in temperature

Abstract. Elevated levels of CO₂ in the atmosphere are expected to affect plant performance and may alter global temperature patterns. Changes in mean air temperatures that might be induced by rising levels of CO₂ and other greenhouse gases could also be accompanied by increased variability in daily temperatures such that acute increases in air temperature may be more likely than at present. Consequently, we investigated whether plants grown in a CO₂ enriched atmosphere would be differently affected by a heat shock than plants grown at ambient CO₂ levels. Plants of a C₃ annual (Abutilon theophrasti), a C₃ annual crop (Sinapis alba) and a C₄ annual (Amaranthus retroflexus) were grown from seed in growth chambers under either 400 or 700cm³ m^?3 CO₂, and were fertilized with either a high or low nutrient regime. Young seedlings of S. alba, as well as plants of all species in either the vegetative or reproductive phase of growth were exposed to a 4-h heat shock in which the temperature was raised an additional 14–23°C (depending on plant age). Total biomass and reproductive biomass were examined to determine the effect of CO₂, nutrient and heat shock treatments on plant performance. Heat shock, CO₂, and nutrient treatments, all had some significant effects on plant performance, but plants from both CO₂ treatments responded similarly to heat shocks. We also found, as expected, that plants grown under high CO₂ had dramatically decreased tissue N concentrations relative to plants grown under ambient conditions. We predicted that high-CO₂-grown plants would be more susceptible to a heat shock than ambient-CO₂-grown plants, because the reduced N concentrations of high-CO₂ grown plants could result in the reduced synthesis of heat shock proteins and reduced thermotolerance. Although we did not examine heat shock proteins, our results showed little relationship between plant nitrogen status and the ability of a plant to tolerate an acute increase in temperature.     

IAA synthesis and root induction with iaa genes under heat shock promoter control

We have devised a heat shock-inducible indole-3-acetic acid (IAA) synthesis system for plant cells, which is based on the iaa genes of the Agrobacterium tumefaciens T-DNA and the heat shock promoter hsp70 of Drosophila melanogaster.Two DNA constructs were tested: one contains the iaaM gene linked to the hsp70 promoter (hsp 70-iaaM) and encodes the production of indoleacetamide (IAM), the other contains hsp 70-iaaM and the wild-type iaaH gene which codes for the conversion of IAM into IAA (hsp 70-iaaM/iaaH). Heat shock-controlled IAM and IAA synthesis was tested on two levels: biochemically by measuring IAM and IAA levels in Kalanchoe stem segments infected with the two constructs, and morphologically by IAA-dependent root formation on Kalanchoe plants, on carrot discs and on tobacco leaf fragments. At both levels the responses were found to be controlled by the heat shock promoter. IAM levels of segments infected with hsp 70-iaaM increased 6-fold upon heat shock induction to 240 pmol IAM per stem segment. The accumulation of IAA in segments infected with hsp 70-iaaM/iaaH and heat-shocked was found to be more variable, possibly due to IAA transport and metabolism. Heat shock treatment of Kalanchoe plants and tobacco leaf fragments infected with hsp 70-iaaM/iaaH led to a strong increase in root formation. On carrot discs, heat shock-specific root induction was also demonstrated, but the responses differed between individual carrots.     

Effect of Putrescine on Low-Temperature Acclimation in <i>Chlamydomonas reinhardtii</i>

Putrescine is reported to be necessary for cold acclimation under low-temperature stress. In this study, the effect of low-temperature on some physiological and biochemical parameters has been investigated using the green algae Chlamydomonas reinhardtii. The lipid peroxidation rate, amount of Rubisco protein, activities of antioxidant enzymes and gene expression of polyamine biosynthesis (odc2, and spd1), heat shock proteins (hsp70c, hsp90a, and hsp90c), and PSII repair mechanisms (psba, rep27, and tba1) were determined to understand the low-temperature response. Exogenous putrescine application significantly increased Rubisco protein concentration and catalase enzyme activities under low-temperature stress. Moreover, real-time RT-PCR results and gene expression analysis showed that polyamine metabolism induced gene expression at low-temperatures in the first 24 h. In the same way, the gene expression of heat shock proteins (hsp70c, hsp90a, and hsp90c) decreased under low-temperature treatment for 72 h; however, application of putrescine enhanced the gene expression in the first 24 h. The results obtained indicated that molecular response in the first 24 h could be important for cold acclimation. The psba and tba1 expressions were reduced under low-temperatures depending on the exposure time. In contrast, the exogenous putrescine enhanced the expression level of the psba response to low-temperature at 24 and 72 h. The results obtained in this study indicate that putrescine could play a role in the PS II repair mechanisms under low-temperature stress.     

NPR1-dependent salicylic acid signaling is not involved in elevated CO2-induced heat stress tolerance in Arabidopsis thaliana

Elevated CO₂ can protect plants from heat stress (HS); however, the underlying mechanisms are largely unknown. Here, we used a set of Arabidopsis mutants such as salicylic acid (SA) signaling mutants nonexpressor of pathogenesis-related gene 1 (npr1-1 and npr1-5) and heat-shock proteins (HSPs) mutants (hsp21 and hsp70-1) to understand the requirement of SA signaling and HSPs in elevated CO₂-induced HS tolerance. Under ambient CO₂ (380 µmol mol⁻¹) conditions, HS (42°C, 24 h) drastically decreased maximum photochemical efficiency of PSII (Fv/Fm) in all studied plant groups. Enrichment of CO₂ (800 µmol mol⁻¹) with HS remarkably increased the Fv/Fm value in all plant groups except hsp70-1, indicating that NPR1-dependent SA signaling is not involved in the elevated CO₂-induced HS tolerance. These results also suggest an essentiality of HSP70-1, but not HSP21 in elevated CO₂-induced HS mitigation.     

Ethanol treatment triggers a heat shock-like response but no thermotolerance in soybean (Glycine max cv. Kaohsiung No.8) seedlings

Non‐lethal heat‐shock (HS) treatment has previously been shown to induce thermotolerance in soybean (Glycine max cv. Kaohsiung No.8) seedlings. This acquired thermotolerance correlates with the de novo synthesis of heat‐shock proteins (HSPs). Interestingly, we found that ethanol treatments also elicited HS‐like responses in aetiolated soybean seedlings at their normal growth temperature of 28 °C. Northern blot analyses revealed that the expression of HS genes hsp17.5, hsp70 and hsc 70 was induced by ethanol. Radioactive amino acids were preferentially incorporated into high molecular weight (HMW) HSPs rather than class I low molecular weight (LMW) HSPs during non‐lethal ethanol treatments. Immunoblot analysis confirmed that no accumulation of class I LMW HSPs occurred after non‐lethal ethanol treatment. Pre‐treatment with a non‐lethal dose of ethanol did not provide thermotolerance, as the aetiolated soybean seedlings could not survive a subsequent heat shock of 45 °C for 2 h. In contrast, non‐lethal HS pre‐treatment, 40 °C for 2 h, conferred tolerance on aetiolated soybean seedlings to otherwise lethal treatments of 7·5% ethanol for 8 h or 10% ethanol for 4 h. These results suggest that plant class I LMW HSPs may play important roles in providing both thermotolerance and ethanol tolerance.     

Comparative toxic potential of market formulation of two organophosphate pesticides in transgenic Drosophila melanogaster (hsp70-lacZ)

This study investigated the working hypothesis that two widely used organophosphate pesticides; Nuvan and Dimecron, exert toxic effects in Drosophila. Transgenic D. melanogaster (hsp70-lacZ) was used as a model for assaying stress gene expression and AchE activity as an endpoint for toxicity and also to evaluate whether stress gene expression is sufficient to protect against toxic insult of the chemicals and to prevent tissue damage. The study was extended to investigate the effect of the pesticides on the life cycle and reproduction of the organism. The study showed that Nuvan affected emergence of the exposed flies more drastically than Dimecron and the effect was lethal at the highest tested concentration (0.075 ppm). While Nuvan at 0.0075 and 0.015 ppm concentrations affected reproduction of the flies significantly, the effect of Dimecron was significant only at 0.015 and 0.075 ppm. Nuvan-exposed third-instar larvae exhibited a 1.2-fold to 1.5-fold greater hsp70 expression compared to Dimecron at concentrations ranging from 0.0075 to 0.075 ppm following 12 and 18 h exposure. While maximum expression of hsp70 was observed in Nuvan-exposed third-instar larval tissues following 18 h exposure at 0.075 ppm, Dimecron at the same dietary concentration induced a maximum expression of hsp70 following 24 h exposure. Further, concomitant with a significant induction of hsp70, significant inhibition of AchE was observed following chemical exposure and temperature shock. Concurrent with a significant decline in hsp70 expression in Nuvan-exposed larvae after 48 h at 0.075 ppm, tissue damage was evident. Dimecron-exposed larvae exhibited a plateau in hsp70 induction even after 48 h exposure and moderate tissue damage was observed in these larvae. The present study suggests that Nuvan is more cytotoxic than Dimecron in transgenic Drosophila melanogaster.     

The heat shock protein hsp70 binds in vivo to subregions 2-48BC and 3-58D of the polytene chromosomes ofDrosophila hydei

Multiple interactions of members of the hsp70 family with cellular components have already been described. We present, however, the first evidence that upon heat shock treatment hsp70 molecules interact with specific chromosomal subdivisions of the polytene chromosomes ofDrosophila hydei. After a heat shock treatment of 20 min the protein binds to subdivision 3-58D₁ and to the heat shock inducible subdivisions 2-48B_3–6 and 2-48C_1–2. Hsp70 molecules were also observed in subdivision 3-58D₁ during recovery at 25°C but not in subdivisions 2-48B_3–6 and 2-48C_1–2. Our data suggest that this interaction is stress specific. DNase and RNase experiments suggest, moreover, that the hsp70 molecules bind to RNA from ribonucleoproteins (RNPs) in subdivisions 2-48B_3–6 and 2-48C_1–2 and to DNA in subdivision 3-58D₁. The DNA sequences in subdivision 3-58D₁ seem to have the potential to adopt the Z-DNA conformation.     

Impact of modified atmospheres on respiration of last instar larvae of the rice moth,Corcyra cephalonica (Lepidoptera: Pyralidae)

Abstract

Effect of modified atmospheres (MAs) containing CO₂ at 20, 40, 60 and 80% or containing N₂ at 97 and 98% on the mortality of Corcyra cephalonica Stainton (Lepidoptera: Pyralidae) sixth instar larvae was studied to determine the LT values at 30?°C. The respiration rates of untreated and treated larvae with 60% CO₂ and/or 98% N₂ at LT₅₀ were measured using Q-Box RP1LP low range respirometry package. Total protein and triglycerides of treated and untreated larvae were assayed. Complete larval mortality was recorded after 72 and 144?h of treatment with 60% CO₂ and 98% N₂, respectively. Calculated LT₅₀ values were 39.3 at 60% CO₂ and 87.5?h at 98% N₂ MAs. Respiration quotient (RQ) in the light of consumed O₂ and produced CO₂ of untreated larvae was 1.0 while it was 0.85 at 60% CO₂ and 0.72 at 98% N₂. Duration time necessary for produced CO₂ curve to reach the maximum point (2000?ppm) was significantly shorter at untreated larvae (27.64?min) in comparison with that recorded at CO₂ (35.48?min) which also significantly less than that obtained at N₂ (98.54?min). At all treatments, total protein was decreased while triglycerides were increased in comparison with control.