Effects of acclimation temperature on thermal tolerance and membrane phospholipid composition in the fruit fly Drosophila melanogaster

Adaptative responses of ectothermic organisms to thermal variation typically involve the reorganization of membrane glycerophospholipids (GPLs) to maintain membrane function. We investigated how acclimation at 15, 20 and 25 degrees C during preimaginal development influences the thermal tolerance and the composition of membrane GPLs in adult Drosophila melanogaster. Long-term cold survival was significantly improved by low acclimation temperature. After 60 h at 0 degrees C, more than 80% of the 15 degrees C-acclimated flies survived while none of the 25 degrees C-acclimated flies survived. Cold shock tolerance (1h at subzero temperatures) was also slightly better in the cold acclimated flies. LT50 shifted down by ca 1.5 degrees C in 15 degrees C-acclimated flies in comparison to those acclimated at 25 degrees C. In contrast, heat tolerance was not influenced by acclimation temperature. Low temperature acclimation was associated with the increase in proportion of ethanolamine (from 52.7% to 58.5% in 25 degrees C-acclimated versus 15 degrees C-acclimated flies, respectively) at the expense of choline in GPLs. Relatively small, but statistically significant changes in lipid molecular composition were observed with decreasing acclimation temperature. In particular, the proportions of glycerophosphoethanolamines with linoleic acid (18:2) at the sn-2 position increased. No overall change in the degree of fatty acid unsaturation was observed. Thus, cold tolerance but not heat tolerance was influenced by preimaginal acclimation temperature and correlated with the changes in GPL composition in membranes of adult D. melanogaster.     

Complexity of the cold acclimation response in Drosophila melanogaster

Insects can increase their resistance to cold stress when they are exposed to non-lethal conditions prior to the stress; these plastic responses are normally described only in terms of immediate effects on mortality. Here we examine in Drosophila melanogaster the short- and longer-term effects of different conditions on several measures of cold resistance, but particularly chill coma recovery. Short-term exposure to sublethal temperature (cold hardening) did not decrease chill coma recovery times even though it decreased mortality. Exposure to 12 degrees C for 2 days (acclimation) decreased chill coma recovery times for a range of stressful temperatures when flies were cultured at 25 degrees C, but did not usually affect recovery times when flies were cultured at 19 degrees C. In contrast, 2-day exposure to 12 degrees C decreased mortality regardless of rearing temperature. Rearing at 19 degrees C decreased mortality and chill coma recovery time relative to rearing at 25 degrees C. Acclimation increased the eclosion rate of eggs from stressed females, but did not affect development time or size of the offspring. These results indicate that plastic responses to cold in D. melanogaster are complex when resistance is scored in different ways, and that effects can extend across generations.     

Extended alternating-temperature cold acclimation and culture duration improve pear shoot cryopreservation

Meristems of many pear genotypes can be successfully cryopreserved following 1 week of cold acclimation, but an equal number do not survive the process or have very little regrowth. This study compared commonly used cold acclimation protocols to determine whether the cold acclimation technique used affected the cold hardiness of shoots or the regrowth of cryopreserved meristems. In vitro-grown pear (Pyrus L.) shoots were cold acclimated for up to 16 weeks, then either the shoot tips were tested for cold hardiness or the meristems were cryopreserved by controlled freezing. Cold acclimation consisted of alternating temperatures (22 degrees C with light/-1 degrees C darkness with various photo- and thermoperiods) or a constant temperature (4 degrees C with an 8-h photoperiod or darkness). Compared with nonacclimated controls, both alternating- and constant-temperature acclimation significantly improved postcryopreservation regrowth of P. cordata Desv. and P. pashia Buch. -Ham. ex D. Don meristems. Alternating-temperature acclimation combined with either an 8-h photoperiod or darkness was significantly better than constant-temperature acclimation. Alternating-temperature shoot acclimation for 2 to 5 weeks significantly increased postcryopreservation meristem regrowth, and recovery remained high for up to 15 weeks acclimation. Postcryopreservation meristem regrowth increased with 1 to 5 weeks of constant-temperature acclimation and then declined with longer acclimation. Shoot cold hardiness varied with the acclimation procedure. The LT(50) of shoots acclimated for 10 weeks with alternating temperatures was -25 degrees C; that with constant temperature was -14.7 degrees C; and that of the nonacclimated control was -10 degrees C. Less frequent transfer of cultures also improved acclimation of shoots. Shoots grown without transfer to fresh medium for 6-12 weeks had higher postcryopreservation recovery with shorter periods of acclimation than shoots with a 3-week transfer cycle.     

Cold acclimation strategy is highly variable among the sunfishes (Centrarchidae)

We tested the hypothesis that the physiological strategy for acclimating to low body temperature is similar among closely related fish. Largemouth bass (Micropterus salmoides), green sunfish (Lepomis cyanellus), bluegill sunfish (Lepomis macrochirus), black crappie (Pomonix nigromaculatus), and white crappie (Pomonix annularis), all members of the family Centrarchidae, were acclimated to 5 degrees and 25 degrees C. Morphometric variables (total mass, total length, organ masses) and enzyme activities (hexokinase; lactate dehydrogenase; and cytochrome oxidase in heart, liver, and muscle) were measured in 5 degrees C- and 25 degrees C-acclimated fish at 5 degrees and 25 degrees C assay temperatures. Each species displayed a distinct physiological response to cold acclimation that differed among tissues. These data suggest that the response to cold acclimation is highly variable within families. Our findings are consistent with other studies suggesting that acclimation responses are labile and may evolve independently even among closely related species.     

A comparison of Hsp70 expression and thermotolerance in adults and larvae of three Drosophila species

Heat shock proteins (Hsps) and other molecular chaperones perform diverse physiological roles. One is to facilitate, in part, organismal thermotolerance, of which the functional consequences depend on Hsp70 concentration and developmental stage in Drosophila melanogaster. To test whether an Hsp70-thermotolerance relationship is a general phenomenon within Drosophila, I assayed Hsp70 concentration at a range of temperatures in intact larvae and adults of three species, D. melanogaster, D. simulans, and D. mojavensis, and compared those results to the increase in survival to heat shock that occurs after an Hsp70 inducing pretreatment. Larvae of D. melanogaster and D. simulans responded similarly to heat; they expressed Hsp70 maximally at 36-37 degrees C, and their tolerance of 1 h heat shocks increased by 1.5-2 degrees C. By contrast, D. mojavensis, which tolerates higher temperatures than do D. melanogaster and D. simulans, expressed Hsp70 only at higher temperatures, although the 36 degrees C pretreatment still increased thermotolerance. Critically, the temperature that maximally induced Hsp70 was a poor inducer of thermotolerance in D. mojavensis and may have harmed larvae. Results for Drosophila adults, which tolerated heat poorly compared to larvae, likewise suggest that a close link between peak Hsp70 expression and maximal induction of thermotolerance is a feature of D. melanogaster, and not of the other species. Neither D. simulans nor D. mojavensis adults increased tolerance after exposure to the temperatures that maximally induced Hsp70.     

Effect of low temperatures on mortality and oviposition in conjunction with climate mapping to predict spread of the root weevil Diaprepes abbreviatus and introduced natural enemies

The tropical root weevil, Diaprepes abbreviatus (L.), has been a pest of citrus and ornamental plants since its introduction into Lake County, FL, in 1964. Since then, it has colonized the Florida peninsula to the south of its point of introduction but has not expanded its range to the north. A lower threshold for oviposition by D. abbreviatus was estimated as 14.9 degrees C. Eggs were highly susceptible to cold, with 95% mortality (LTime95) occurring in 4.2 d at 12 degrees C. Relative susceptibility of life stages to cold was eggs > pupae > larvae > adults. Archived weather data from Florida were examined to guide a mapping exercise using the lower developmental threshold for larvae (12 degrees C) and the lower threshold for oviposition (15 degrees C) as critical temperatures for mapping the distribution of D. abbreviatus and the potential for establishment of egg parasitoids. Probability maps using the last 10 yr of weather data examined the frequency of at least 10, 15, 20, 25, or 30 d per winter when soil temperature was 相似文献   

Respiratory response to temperature and hypoxia in the zebra mussel Dreissena polymorpha

The effects of temperature acclimation, acute temperature variation and progressive hypoxia on oxygen consumption rates (VO2) were determined for the zebra mussel Dreissena polymorpha. In the first experiment, after acclimation to 5, 15 or 25 degrees C for at least 2 weeks, VO2 was determined at 5 degrees C increments from 5 to 45 degrees C. VO2 increased in all three acclimation groups from 5 to 30 degrees C, corresponding to the normal ambient temperature range for this species. Mussels displayed imperfect temperature compensation at temperatures above 15 degrees C, but exhibited little acclimatory ability below 15 degrees C. In the hypoxia experiment, VO2 was determined over the course of progressive hypoxia, from full saturation (oxygen tension [PO2]=160 Torr [21.3 kPa]) to a PO2 at which oxygen uptake ceased (<10 Torr [1.3 kPa]). Mussels were acclimated to either 5, 15 or 25 degrees C for at least 2 weeks and their respiratory response to progressive hypoxia was measured at three test temperatures (5, 15 and 25 degrees C). The degree of oxygen regulation increased with increasing test temperature, particularly from 5 to 15 degrees C, but decreased with increasing acclimation temperature. The decreased metabolic rate observed for warm-acclimated animals, particularly in the upper portion of the temperature range of the zebra mussel, may allow for conservation of organic energy stores during warm summer months. Compared to other freshwater bivalves, D. polymorpha is a relatively poor oxygen regulator, corresponding with its preference for well-oxygenated aquatic habitats. In addition, a new quantitative method for determining the degree of oxygen regulation is presented.     

Viability and rate of development at different temperatures in Drosophila: a comparison of constant and alternating thermal regimes

Populations belonging to the sibling species Drosophila melanogaster and D. simulans were collected in Southwestern France and Southern Spain, and investigated under constant (CT) and alternating (AT) temperature regimes. Development under CT was possible between 11 and 32 degrees C and egg-to-adult viability curves were almost 'rectangular', with a sharp decrease below 14 and above 29 degrees C. Rate of development followed a complex non-linear curve. A model described the curve as an exponential below a critical temperature (T(C)), and above T(C) as the difference between this function and another exponential which is assumed to show deleterious effects of heat. Developmental rates under two daily 12-h phases with various mid-temperatures and thermal amplitudes were compared to expected rates calculated from the above model. Acceleration effects were observed at four AT (in increasing order: 12-30, 9-21, 11-21, 16-26 degrees C); retardation occurred at three other ones (in increasing order, 7-21, 5-15, 7-29 degrees C). When expressed by the ratio observed/expected, the effects could be predicted using a multiple regression, as a positive function of the thermal amplitude and a negative one of the mid-temperature. Viability under AT was analysed considering an equivalent developmental temperature (EDT), that is the CT which would produce the same rate or development. Very low viabilities occurred under broad amplitude regimes, but the deleterious effects of some extreme temperatures, that would be lethal under CT, could be recovered by daily return to a moderate temperature. The two species exhibited slight but significant differences in their characteristic temperatures: developmental zero, critical temperature, temperature of maximum rate, upper developmental limit. All data may be interpreted by considering that D. simulans compared to D. melanogaster is more tolerant to cold but less tolerant to heat.     

Heat- and cold-shock responses and temperature adaptations in subtropical and temperate species of Drosophila

Accumulation of Hsp70 mRNA was investigated with relation to heat and cold tolerance in adult males of three Drosophila species. The subtropical lowland species (D. watanabei) and the cool-temperate species (D. triauraria) were more tolerant to heat than the subtropical highland species (D. trapezifrons), and the cool-temperate species were much more tolerant to cold than the two subtropical species. Thus, heat and cold tolerance was related to temperature conditions in the habitats. The threshold temperatures for the induction of Hsp70 mRNA at heat and cold were higher in D. watanabei than in D. trapezifrons or D. triauraria, but were not different between the latter two species in spite of the difference in their heat and cold tolerance. In D. trapezifrons, exposures to 0 degrees C for 12h and 6 degrees C for 24h killed about 40% of individuals, but the former treatment induced Hsp70 mRNA while the latter one did not. Thus, the relation between the heat- and cold-shock responses and temperature tolerance was not rigid in the species studied. In D. triauraria, the threshold temperatures for the induction of Hsp70 mRNA at heat and cold were lower when reared at a lower temperature.     

Cold shock and cold acclimation proteins in the psychrotrophic bacterium Arthrobacter globiformis SI55.

The psychrotrophic bacterium Arthrobacter globiformis SI55 was grown at 4 and 25 degrees C, and the cell protein contents were analyzed by two-dimensional electrophoresis. Cells subjected to cold shocks of increasing magnitude were also analyzed. Correspondence analysis of protein appearance distinguished four groups of physiological significance. Group I contained cold shock proteins (Csps) overexpressed only after a large temperature downshift. Group II contained Csps with optimal expression after mild shocks. Group III contained proteins overexpressed after all cold shocks. These last proteins were also overexpressed in cells growing at 4 degrees C and were considered to be early cold acclimation proteins (Caps). Group IV contained proteins which were present at high concentrations only in 4 degrees C steady-state cells and appeared to be late Caps. A portion of a gene very similar to the Escherichia coli cspA gene (encoding protein CS7.4) was identified. A synthetic peptide was used to produce an antibody which detected a CS7.4-like protein (A9) by immunoblotting two-dimensional electrophoresis gels of A. globiformis SI55 total proteins. Unlike mesophilic microorganisms, this CS7.4-like protein was still produced during prolonged growth at low temperature, and it might have a particular adaptive function needed for balanced growth under harsh conditions. However, A9 was induced at high temperature by chloramphenicol, suggesting that CS7.4-like proteins have a more general role than their sole implication in cold acclimation processes.     

Can the cold tolerance of C4 photosynthesis in Miscanthus x giganteus relative to Zea mays be explained by differences in activities and thermal properties of Rubisco?

The previous investigations show that the amount and activity of Rubisco appears the major limitation to effective C(4) photosynthesis at low temperatures. The chilling-tolerant and bioenergy feedstock species Miscanthus x giganteus (M. x giganteus) is exceptionally productive among C(4) grasses in cold climates. It is able to develop photosynthetically active leaves at temperatures 6 degrees C below the minimum for maize, and achieves a productivity even at 52 degrees N that exceeds that of the most productive C(3) crops at this latitude. This study investigates whether this unusual low temperature tolerance can be attributed to differences in the amount or kinetic properties of Rubisco relative to maize. An efficient protocol was developed to purify large amounts of functional Rubisco from C(4) leaves. The maximum carboxylation activities (V(max)), activation states, catalytic rates per active site (K(cat)) and activation energies (E(a)) of purified Rubisco and Rubisco in crude leaf extracts were determined for M. x giganteus grown at 14 degrees C and 25 degrees C, and maize grown at 25 degrees C. The sequences of M. x giganteus Rubisco small subunit mRNA are highly conserved, and 91% identical to those of maize. Although there were a few differences between the species in the translated protein sequences, there were no significant differences in the catalytic properties (V(max), K(cat), and E(a)) for purified Rubisco, nor was there any effect of growth temperature in M. x giganteus on these kinetic properties. Extracted activities were close to the observed rates of CO(2) assimilation by the leaves in vivo. On a leaf area basis the extracted activities and activation state of Rubisco did not differ significantly, either between the two species or between growth temperatures. The activation state of Rubisco in leaf extracts showed no significant difference between warm and cold-grown M. x giganteus. In total, these results suggest that the ability of M. x giganteus to be productive and maintain photosynthetically competent leaves at low temperature does not result from low temperature acclimation or adaptation of the catalytic properties of Rubisco.     

Relationship between supercooling point and mortality at low temperatures in Indianmeal moth (Lepidoptera: Pyralidae)

Indianmeal moth, Plodia interpunctella (Hübner), is classified as a freeze-intolerant organism and one of the most cold-tolerant stored-product pests. The objective of this study was to determine the relationship between mortality at low temperatures after minimum exposure and the supercooling point (SCP) for laboratory-reared P. interpunctella at different stages of development. This relationship also was analyzed for field-collected, cold-acclimated fifth instars. Mean SCP of laboratory-reared larvae (i.e., feeding stage) was consistently above approximately -16 degrees C. Mean SCP of laboratory-reared pupae and adults (i.e., nonfeeding stages) and field-collected, cold-acclimated fifth instars was consistently below approximately -21 degrees CP seemed to be the boundary between survival and death for larvae. However, it seemed that a 1-min exposure was not sufficient to cause larval mortality at the SCP. Alternatively, for both pupae and adults, the SCP seemed not to play an important role in their survival at low temperatures, with significant mortality observed at temperatures higher than the mean SCP. Adults were the most susceptible to low temperatures with no survival occurring at -20 degrees C, > 3 degrees C above its mean SCP. Results of this investigation demonstrate that P. interpunctella has a different response to low temperatures depending on stage of development and cold acclimation. Classifying P. interpunctella only as a freeze-intolerant organism disregards the occurrence of prefreeze mortality in this species. Therefore, a reclassification of this species (e.g., chill tolerant or chill susceptible) based on the extent of prefreeze mortality and the temperature and time of exposure at which it occurs is suggested.     

The effects of acclimation on thermal tolerance, desiccation resistance and metabolic rate in Chirodica chalcoptera (Coleoptera: Chrysomelidae)

Despite much focus on species responses to environmental variation through space and time, many higher taxa and geographic areas remain poorly studied. We report the effects of temperature acclimation on thermal tolerance, desiccation rate and metabolic rate for adult Chirodica chalcoptera (Coleoptera: Chrysomelidae) collected from Protea nerifolia inflorescences in the Fynbos Biome in South Africa. After 7 days of acclimation at 12, 19 and 25 degrees C, critical thermal maxima (mean+/-s.e.: 41.8+/-0.2 degrees C in field-fresh beetles) showed less response (<1 degrees C change) to temperature acclimation than did the onset of the critical thermal minima (0.1+/-0.2, 1.0+/-0.2 and 2.3+/-0.2 degrees C, respectively). Freezing was lethal in C. chalcoptera (field-fresh SCP -14.6 degrees C) and these beetles also showed pre-freeze mortality. Survival of 2 h at -10.1 degrees C increased from 20% to 76% after a 2 h pre-exposure to -2 degrees C, indicating rapid cold hardening. Metabolic rate, measured at 25 degrees C and adjusted by ANCOVA for mass variation, did not differ between males and females (2.772+/-0.471 and 2.517+/-0.560 ml CO2 h(-1), respectively), but was higher in 25 degrees C-acclimated beetles relative to the field-fresh and 12 degrees C-acclimated beetles. Body water content and desiccation rate did not differ between males and females and did not respond significantly to acclimation. We place these data in the context of measured inflorescence and ambient temperatures, and predict that climate change for the region could have effects on this species, in turn possibly affecting local ecosystem functioning.     

Triggering of cryoprotectant synthesis in the woolly bear caterpillar (Pyrrharctia isabella Lepidoptera: Arctiidae)

Isabella tiger moths (Pyrrharctia isabella) overwinter as caterpillars (i.e., woolly bears) that can survive freezing at moderate subzero temperatures. We observed an increase in hemolymph osmolality for field-collected woolly bears during October (325 +/- 47 to 445 +/- 27 mOsmol/liter) and tested the influence of temperature and moisture levels on cryoprotectant production. Laboratory acclimation was done at 5 degrees C in moist conditions and at 25 degrees C acclimation in both dry and moist conditions. Body water contents were diminished by dehydration at 25 degrees C for 4 days (57 +/- 4%). Caterpillars collected in early October did not alter their hemolymph osmolality during cold acclimation, but caterpillars increased by 45% (to 647 +/- 90 mOsmol/liter) after 4 days at 5 degrees C following their collection in late October. Hemolymph composition was markedly changed in caterpillars experiencing dehydration at 25 degrees C (1042 +/- 200 mOsmol/liter; 507 +/- 225 mmol glycerol/liter), whereas caterpillars showed no change in their hemolymph composition when kept moist at 25 degrees C. Our experiments reveal that both dehydration and cold acclimation rapidly induce cryoprotectant synthesis in P. isabella caterpillars. J. Exp. Zool. 286:367-371, 2000.     

Cold hardiness in summer and winter diapause and post-diapause pupae of the cabbage armyworm, Mamestra brassicae L. under temperature acclimation

Cold hardiness and biochemical changes were investigated in winter and summer pupae of the cabbage armyworm Mamestra brassicae at the diapause and post-diapause stages under temperature acclimation. Diapause pupae were successively acclimated to 25, 20 and then 10 degrees C (warm-acclimated group). Pupae at the diapause and post-diapause stages were successively acclimated to 5, 0, -5 and then -10 degrees C (cold-acclimated groups). Supercooling point values in winter and summer pupae remained constant regardless of the diapause stages and acclimated temperatures. Warm-acclimated pupae at the diapause stage did not survive the subzero temperature exposure, whereas, cold-acclimated pupae achieved cold hardiness to various degrees. Winter pupae were more cold hardy than summer pupae, and pupae at the post-diapause stage were more cold hardy than those at the diapause stage. Trehalose contents in winter pupae rose under cold acclimation. Summer pupae accumulated far lower trehalose contents than winter pupae, with the maximal level occurring in winter pupae at the post-diapause stage. Glycogen content remained at a high level in diapause pupae after warm acclimation, whereas it decreased after cold acclimation. Alanine, the main free amino acid in haemolymph after cold acclimation, increased at lower temperatures in both diapause and post-diapause pupae, but the increase was greater in the diapause pupae. These results suggest that cold hardiness is more fully developed in winter pupae than in summer pupae, and cold acclimation provides higher cold hardiness in winter pupae at the post-diapause stage than at the diapause stage.     

Induction of rapid cold hardening by cooling at ecologically relevant rates in Drosophila melanogaster

Over a decade ago it was hypothesized that the rapid cold hardening process allows an organism's overall cold tolerance to track changes in environmental temperature, as would occur in nature during diurnal thermal cycles. Although a number of studies have since focused on characterizing the rapid cold hardening process and on elucidating the physiological mechanisms upon which it is based, the ecological relevance of this phenomenon has received little attention. We present evidence that in Drosophila melanogaster rapid cold hardening can be induced during cooling at rates which occur naturally, and that the protection afforded in such a manner benefits the organism at ecologically relevant temperatures. Drosophila melanogaster cooled at natural rates (0.05 and 0.1 degrees C min(-1)) exhibited significantly higher survival after one hour of exposure to -7 and -8 degrees C than did those directly transferred to these temperatures or those cooled at 0.5, or 1.0 degrees C min(-1). Protection accrued throughout the cooling process (e.g., flies cooled to 0 degrees C were more cold tolerant than those cooled to 11 degrees C). Whereas D. melanogaster cooled at 1.0 degrees C min(-1) had a critical thermal minimum (i.e., the temperature at which torpor occurred) of 6.5+/-0.6 degrees C, those cooled at an ecologically relevant rate of 0.1 degrees C min(-1) had a significantly lower value of 3.9+/-0.9 degrees C.