Response to temperature stress of reactive oxygen species scavenging enzymes in the cross-tolerance of barley seed germination

A number of studies have shown the existence of cross-tolerance in plants, but the physiological mechanism is poorly understood. In this study, we used the germination of barley seeds as a system to investigate the cross-tolerance of low-temperature pretreatment to high-temperature stress and the possible involvement of reactive oxygen species （ROS） scavenging enzymes in the cross-tolerance. After pretreatment at 0 ℃ for different periods of time, barley seeds were germinated at 35 ℃, and the content of malondialdehyde （MDA） and the activities of ROS scavenging enzymes were measured by a spectrophotometer analysis. The results showed that barley seed germinated very poorly at 35 ℃, and this inhibitive effect could be overcome by pretreatment at 0 ℃. The MDA content varied, depending on the temperature at which seeds germinated, while barley seeds pretreated at 0 ℃ did not change the MDA content. Compared with seeds germinated directly at 35 ℃, the seeds pretreated first at 0 ℃ and then germinated at 35 ℃ had markedly increased activities of superoxide dismutase （SOD）, ascorbate peroxidase （APX）, catalase （CAT）, and glutathione reductase （GR）. The SOD and APX activities of seeds germinated at 35 ℃ after 0 ℃-pretreatment were even substantially higher than those at 25 ℃, and GR activity was similar to that at 25 ℃, at which the highest germination performance of barley seeds was achieved. These results indicate that low-temperature pretreatment can markedly increase the tolerance of barley seed to high temperature during germination, this being related to the increase in ROS scavenging enzyme activity. This may provide a new method for increasing seed germination under stress environments, and may be an excellent model system for the study of cross-tolerance.

The effects of selection for cold tolerance on cross-tolerance to other environmental stressors in Drosophila melanogaster

Cross tolerance, whereby tolerance to one environmental stress is correlated with tolerance to other stressors, is thought to be widespread in insects. We used lines of Drosophila melanogaster Meigen （Diptera： Drosophilidae） selected for survival at a 1-h exposure to -5℃ to examine the extent to which this selection results in increased tolerance to other stresses, including high and low temperatures, desiccation and starvation. While selection improved tolerance to acute cold exposure and survival at -5℃, there was little effect of selection regime on tolerance to other stressors. There was no correlation between tolerances to any of the stressors, suggesting different mechanisms of tolerance. This supports arguments that correlations between stress tolerances during selection experiments with D. melanogaster may be coincidental. The magnitude of heat-hardening was apparently constrained by basal tolerance among lines, but the magnitude of the rapid cold-hardening response was not correlated with basal cold tolerance, implying that the relationship between inducible and basal tolerances differs at high and low temperatures.

The central nucleus of amygdala is involved in tolerance to the antinociceptive effect of NSAIDs

Aim: Repeated microinjections of non-opioid an-algesics into the midbrain periaqueductal gray matter and rostral ventro-medial medulla induce antinociception with development of tolerance. Antinociception following systemic administra-tion of non-steroidal anti-inflammatory drugs (N SAIDs) also exhibit tolerance. Presently our aim was to investigate the development of tolerance to the antinociceptive effects of NSAIDs analgine, ketorolac, and xefocam microinjected into cen-tral nucleus of amygdala (Ce) in rats. Methods: Under anesthesia with thiopental a stainless steel guide cannula was stereotaxically implanted uni- laterally or bilaterally into the Ce using stereo-taxic atlas coordinates, and anchored to the cra- nium by dental cement. Five days after surgery, 3 μl of these NSAIDs were injected via the injec-tion cannula while the rat was gently restrained. Twenty min post microinjection, i.e. 10-min be-fore the peak of the drugs’ effect is normally rea- ched, animals were tested with tail flick (TF) and hot plate (HP) tests. On the 5th experimental day all animals received a Ce microinjection of mor-phine. Results: Daily microinjection of NSAIDs into the Ce uni- or bilaterally, produced antino-ciception with development of complete toler-ance over a 5-day period. Following the treat-ment period, morphine microinjection into the Ce failed to elicit antinociception, indicating cro- ss-tolerance to the antinociceptive effect of N SAIDs. In other words, the “non-opioid tolerant” rats showed cross-tolerance to morphine. Con-clusions: Our data confirmed the suggestion that NSAIDs interact with endogenous opioid systems, which likely play a key role in the development of tolerance to the antinociceptive effects of NSA IDs.

UV-B has larger negative impacts on invasive populations of Triadica sebifera but ozone impacts do not vary

Aims Abiotic stresses may interact with each other to determine impacts on plants so that their combined impact is less than or more than additive.Increasing UV-B radiation and surface ozone(O3)are two major components of global change that may have such interactive impacts.Moreover,invasive and native populations of plants may respond differently to stresses as they can vary in primary and secondary metabolism.Methods Here,we conducted a factorial field experiment with open-top chambers assigned to an ozone treatment(ambient,100 ppb,or 150 ppb)and UV-B treatment(ambient or increased 20%).We grew seedlings of native and invasive populations of Triadica sebifera in these chambers for one growing season.Important Findings Invasive plants grew faster than native plants in ambient UV-B but they did not differ significantly in elevated UV-B.Litter production of invasive plants was especially sensitive to UV-B in a way that increased with UV-B for native plants but decreased for invasive plants which may be important for nutrient cycling.In ambient UV-B,total mass decreased as ozone increased.Total mass was lower with elevated UV-B but there was no additional impact of increasing ozone.Leaf area did not decrease with UV-B so SLA and LAR were lowest at ambient ozone levels.These results suggest that the effects of ozone will depend on UV-B conditions perhaps due to changes in foliar traits.The traits that allow invasive populations of plants to be successful invaders may make them especially sensitive to UV-B which may reduce their success in future climatic conditions.

Context-dependent effects of cold stress on behavioral, physiological,and life-history traits of the red flour beetle

Animals are exposed in nature to a variety ofstressors.While stress is generally harmful,mild stress can also be beneficial and contribute to reproduction and survival.We studied the effect of five cold shock events versus a single cold shock and a control group, representing three levels of stress (harsh,mild,and no stress),on behavioral,physiological, and life-history traits of the red flour beetle (Tribolium castaneum,Herbst 1797).Beetles exposed to harsh cold stress were less active than a control group:they moved less and failed more frequently to detect a food patch.Their probability to mate was also lower. Beetle pairs exposed to harsh cold stress frequently failed to reproduce at all,and if reproducing,females laid fewer eggs,which were,as larvae in mid-development,smaller than those in the control group.However,harsh cold stress led to improved female starvation tolerance,probably due to enhanced lipid accumulation.Harsh cold shock also improved tolerance to an additional cold shock compared to the control.Finally,a single cold shock event negatively affected fewer measured response variables than the harsh cold stress, but also enhanced neither starvation tolerance nor tolerance to an additional cold shock. The consequences of a harsher cold stress are thus not solely detrimental but might even enhance survival under stressful conditions.Under benign conditions,nevertheless,harsh stress impedes beetle performance.The harsh stress probably shifted the balance point of the survival-reproduction trade-off,a shift that did not take place following exposure to mild stress.

Context-dependent integrated stress resistance promotes a global invasive pest

In nature,insects concurrently face multiple environmental stressors,a sce-nario likely increasing with climate change.Integrated stress resistance(ISR)thus often improves fitness and could drive invasiveness,but how physiological mechanisms influ-ence invasion has lacked examination.Here,we investigated cross-tolerance to abiotic stress factors which may influence range limits in the South American tomato pinworm a global invader that is an ecologically and socially damaging crop pest.Specifically,we tested the effects of prior rapid cold-and heat-hardening(RCH and RHH),fasting,and desiccation on cold and heat tolerance traits,as well as starvation and desiccation sur-vivability between T.absoluta life stages.Acclimation effects on critical thermal minima(CT_(min))and maxima(CT_(max))were inconsistent,showing significantly deleterious effects of RCH on adult CT_(max) and CT_(min) and,conversely,beneficial acclimation effects of RCH on larval CT_(min).While no beneficial effects of desiccation acclimation were recorded for desiccation tolerance,fasted individuals had significantly higher survival in adults,whereas fasting negatively affected larval tolerances.Furthermore,fasted and desiccation acclimated adults had significantly higher starvation tolerance,showing strong evidence for cross-tolerance.Our results show context-dependent ISR traits that may promote T.absoluta fitness and competitiveness.Given the frequent overlapping occurrence of these divergent stressors,ISR reported here may thus partly elucidate the observed rapid global spread of T.absoluta into more stressful environments than expected.This information is vital in determining the underpinnings of multistressor responses,which are fundamental in forecasting species responses to changing environments and management responses.