Sterol and Fatty Acid Metabolism in Fusarium oxysporum

The effects of temperatures ranging from 10°C to 35°C on sterol and fatty acid production and hydroxymethylglutaryl CoA reductase (EC 1.1,1.34, HMGCoA reductase) activity have been examined. Growth, based on dry weight, was maximal at 25°C to 30°C. Sterol production and the reductase activity were highest at 15°C after 28~32 hr incubation when the total fatty acids were minimal. Fatty acid unsaturation generally increased with decrease in temperature.     

Heat shock induced proteins in plant cells

Tobacco (Nicotiana tabacum) and soybean (Glycine max) tissue culture cells were exposed to a heat shock and protein synthesis studied by SDS-polyacrylamide gel electrophoresis after labeling with radioactive amino acids. A new pattern of protein synthesis is observed in heat-shocked cells compared to that in control cells. About 12 protein bands, some newly appearing, others synthesized in greatly increased quantities in heat-shock cells, are seen. Several of the heat-shock proteins (HSPs) in both tobacco and soybean are similar in size. One of the HSPs in soybean (76K) shares peptide homology with its presumptive 25°C counterpart, indicating that the synthesis of at least some HSPs may not be due to activation of new genes. The optimum temperature for maximal induction of most HSPs is 39–40°C. Total protein synthesis decreases as heat-shock temperature is increased and is barely detectable at 45°C. The heat-shock response is maintained for a relatively short time in tobacco cells. After 3 hr at 39°C, a decrease is seen in the synthesis of the HSPs, and after 4 hr practically no HSPs are synthesized. After exposure to 39°C for 1 hr, followed by a return of tobacco cells to 26°C, recovery to the control pattern of synthesis requires greater than 6 hours. These results indicate that cells of flowering plants exhibit a heat-shock response similar to that observed in animal cells.     

Inhibition of the accumulation of viral polypeptides in the densonucleosis virus-infected midgut of the silkworm,Bombyx mori,reared at a supraoptimal temperature

Effect of a supraoptimal temperature on the accumulation of viral polypeptides in the midgut was examined by immunoblot analysis in the larvae of the silkworm, Bombyx mori, infected with Bombyx densonucleosis virus type 2. In the larvae reared continuously at 25°C, viral polypeptides were first detected in the midgut at 2 days postinfection (pi) and in the feces at 4 days pi. When the larvae inoculated per os with the virus for 24 hr at 25°C were immediately shifted to 35°C, there were no detectable viral polypeptides in both the midgut and feces throughout the experiment. In the infected larvae shifted from 25° to 35°C at 48 hr pi, viral polypeptides preexisting in the midgut decreased to an undetectable level within 48 hr after the temperature shift, and no viral polypeptides were detected thereafter. Viral polypeptides in the feces of these larvae became detectable at 48 hr (4 days pi) after the temperature shift, as in the larvae at 25°C, and disappeared by 96 hr (6 days pi). These results indicate that a supraoptimal temperature inhibits accumulation of viral polypeptides in the midgut. It is likely that inhibited production of viral polypeptides rather than enhanced discharge of the infected midgut cells is responsible for the inhibited accumulation of viral polypeptides in the midgut at 35°C.     

Variation in the content of free amino acids in body fluids of freshwater mollusk Lymnaea stagnalis during seasonal adaptation to low positive temperatures

The effect of autumn and winter decrease in environmental temperature on the content of free amino acids in body fluids has been studied in freshwater snail Lymnaea stagnalis. In autumn, when temperature drops to 4 and 0°C, the highest increase in alanine concentration was observed and its pool was almost three times that in summer. A less pronounced accumulation of glutamate, glycine, histidine, and serine was observed in the same temperature range. Cysteine was detected at 0°C. The accumulation of essential amino acids methionine, leucine, isoleucine, tyrosine, and phenylalanine took place at 0°C, while only traces of these amino acids were detectable at 4°C. At the same time, free lysine undetectable in summer has been revealed in autumn at 4°C and its concentration increased as temperature decreased to 0°C. In winter, when the mollusks were hypermetabolic for 2.5 months, the pools of all amino acids decreased 4–8 times, while essential amino acids (except lysine) were undetectable. The involvement of alanine and, possibly, lysine in L. stagnalis adaptation to near-zero temperature is proposed.     

Combined effects of CO2 enrichment and elevated growth temperatures on metabolites in soybean leaflets: evidence for dynamic changes of TCA cycle intermediates

Soybean (Glycine max [Merr.] L.) was grown in indoor chambers with ambient (38 Pa) and elevated (70 Pa) CO₂ and day/night temperature treatments of 28/20, 32/24 and 36/28 °C. We hypothesized that CO₂ enrichment would mitigate the deleterious effects of elevated growth temperatures on metabolites in soybean leaflets. Net CO₂ assimilation rates increased incrementally with growth temperature and were enhanced up to 24 % on average by CO₂ enrichment. Stomatal conductance about doubled from the lowest to highest temperature but this was partially reversed by CO₂ enrichment. Metabolites were measured thrice daily and 19 and 28 of 43 total leaf metabolites were altered by the 32/24 and 36/28 °C temperature treatments, respectively, in both CO₂ treatments. Polyols, raffinose and GABA increased and 23 nonstructural carbohydrates, organic acids and amino acids decreased when the temperature was increased from 28 to 36 °C under ambient CO₂. Citrate, aconitate and 2-oxoglutarate decreased over 90 % in the 36/28 °C compared to the 28/20 °C temperature treatment. Temperature-dependent changes of sugars, organic acids and all but three amino acids were almost completely eliminated by CO₂ enrichment. The above findings suggested that specific TCA cycle intermediates were highly depleted by heat stress under ambient CO₂. Mitigating effects of CO₂ enrichment on soybean leaflet metabolites were attributed to altered rates of photosynthesis, photorespiration, dark respiration, the anaplerotic pathway and to possible changes of gene expression.     

Effect of temperature and photoperiod on the induction of diapause in the mite Metaseiulus occidentalis

Diapause in a predaceous mite, Metaseiulus occidentalis, from a Californian vineyard population is a photoperiodically induced, facultative, adult reproductive diapause in females. The laboratory-determined critical photophase at 19°C was estimated at 11·2 hr. At 16°C, the critical photophase under laboratory conditions was approximately 11·6 hr. Temperature influenced the photoresponse of M. occidentalis so that diapause was entirely averted at temperatures of 22, 25, and 30°C. Aestival diapause at higher temperatures and long photophases was lacking. Development was continuous under constant darkness at all the temperatures tested. Diapause termination in laboratory-reared mites occurred spontaneously under the inductive conditions. Under constant 19°C temperatures, females responded to photophases so that diapause was terminated most rapidly under a 16 hr photophase (in 18·6 days); the 12 and 8 hr photophases, at this temperature, were next in their effectiveness, with 27·9 and 73·0 days, respectively, required for termination.     

Extracellular protease production fromXenorhabdus nematophilus, a symbiotic bacterium of entomopathogenic nematodes

Effects of nutrients and growth temperature on the production of an extracellular protease fromXenorhabdus nematophilus, a symbiotic bacterium of entomopathogenic nematodes were studied for batch culture. Tryptone and fructose were most effective nitrogen and carbon sources to produce high level of the protease within 24–28 hr of incubation. The stability of protease was poor during the incubation of the bacteria. The protease activity increased in parallel with cell growth then decreased significantly for extended culture periods of the bacteria over 48 hr at 22–30°C. Autolysis of the protease was not a major cause for the decreased protease activity since no decrease in the protease activity was observed for the whole culture broth of the bacteria which was stored up to 80 hr at 4°C.     

Development and Quality Evaluation of Hypoallergenic Bakery Products Suitable for Patients with Wheat-associated Allergy

The influence of growth temperature (21–41°C) and light intensity on compositions of four carotenoids, and of fatty acids from carotenoid glucoside ester (carotenoid K-G-FA) and from the cellular lipids in Rhodococcus rhodochrous RNMS1 were quantitatively investigated. Lowering the temperature increased the total carotenoid content and the proportion of carotenoid K-G-FA. It increased the proportion of unsaturated fatty acids in both carotenoid K-G-FA and the cellular lipids, decreased that of saturated ones, and slightly decreased that of branched-chain ones. This bacterium adapted itself to low temperature by desaturating its fatty acids. The light intensity affected neither the content and the composition of carotenoids nor the composition of the fatty acids in carotenoid K-G-FA and the cellular lipids. This bacterium was a scotochromogenic strain.     

Effect of growth temperature on lipid fatty acids of four fungi (Aspergillus niger,Neurospora crassa,Penicillium chrysogenum,andTrichoderma reesei)

The effect of growth temperature on the lipid fatty acid composition was studied over a temperature range from 35 to 10° C with 5° C intervals in four exponentially growing fungi: Aspergillus niger, Neurospora crassa, Penicillium chrysogenum, and Trichoderma reesei. Fatty acid unsaturation increased in A. niger, P. chrysogenum, and T. reesei when the temperature was lowered to 20–15, 20, and 26–20° C, respectively. In A. niger and T. reesei, this was due to the increase in linolenic acid content. In P. chrysogenum, the linolenic acid content increased concomitantly with a more pronounced decrease in the less-unsaturated fatty acid, oleic acid, and in palmitic and linoleic acids; consequently, the fatty acid content decreased as the temperature was lowered to 20° C. In T. reesei, when the growth temperature was reduced below 26–20° C, fatty acid unsaturation decreased since the mycelial linolenic acid content decreased. In A. niger and P. chrysogenum, the mycelial fatty acid content increased greatly at temperatures below 20–15° C. In contrast, in N. crassa, fatty acid unsaturation was nearly temperature-independent, although palmitic and linoleic acid contents clearly decreased when the temperature was lowered between 26 and 20° C; concomitantly, the growth rate decreased. Therefore, large differences in the effects of growth temperature on mycelial fatty acids were observed among various fungal species. However, the similarities found may indicate common regulatory mechanisms causing the responses. Received: 1 March 1995 / Accepted: 8 May 1995     

Influence of rearing temperature on triacylglycerol storage in the pea aphid,Acyrthosiphon pisum

Total fatty acids in the pea aphid reared at low temperatures increased significantly compared to that at high rearing temperatures. This change is reflected in a large increase of myristic acid, which occurs exclusively in triacylglycerols. When aphids were moved from 25°C to a lower rearing temperature at 10°C, saturated fatty acids accumulated over time, reaching a maximum at 16th day. When aphids were moved to 4°C, a temperature below the developmental threshold, those aphids did not accumulate saturated fatty acids. Similar results were observed when aphids were exposed to sequential decrease in rearing temperature. However, both total fatty acids and myristic acid in the aphids from the treatments of sequential decreasing rearing temperature were significantly higher compared to those in the aphids from the treatments of sudden decreasing rearing temperature. This result, therefore, supports the hypothesis that cold‐adapted aphids can survive under threshold temperature for a longer period of time than noncold‐adapted aphids. Acetyl‐CoA carboxylase activity in the aphids at 25°C was twofold higher than that in the aphids at 10°C, whereas fatty acid synthase activities in the aphids reared at 25 and 10°C are similar. Aphids reared at 10°C showed a threefold reduction in reproduction rates. This reduced production of new nymphs reduces energy demand and would allow for accumulation of energy in the form of triacylglycerols. Therefore, the increased level of saturated fatty acids in aphids reared at low temperature is probably related to lower utilization of fatty acids rather than increased rates of biosynthesis.     

EFFECTS OF LOWERING TEMPERATURE DURING CULTURE ON THE PRODUCTION OF POLYUNSATURATED FATTY ACIDS IN THE MARINE DIATOM PHAEODACTYLUM TRICORNUTUM (BACILLARIOPHYCEAE)1

The composition of fatty acids and contents of eicosapentaenoic acid (EPA) and polyunsaturated fatty acids (PUFAs) of the economically important marine diatom, Phaeodactylum tricornutum (Bohlin), were investigated to see whether reducing the culture temperature enhances the production of EPA and PUFAs. The contents of EPA and PUFAs of P. tricornutum were found to be higher at lower temperature when cultured at 10, 15, 20, or 25°C. When the cells grown at 25°C were shifted to 20, 15, or 10°C, the contents per dry mass of PUFAs and EPA increased to the maximal values in 48, 24, and 12 h, respectively. The highest yields of PUFAs and EPA per unit dry mass (per unit volume of culture) were 4.9% and 2.6% (12.4 and 6.6 mg·L^?1), respectively, when temperature was shifted from 25 to 10°C for 12 h, both being raised by 120% compared with the control. The representative fatty acids in the total fatty acids, when temperature was lowered from 25 to 10°C, decreased proportionally by about 30% in C_16:0 and 20% in C_16:1(n?7) but increased about 85% in EPA. It was concluded that lowering culture temperature of P. tricornutum could significantly raise the yields of EPA and PUFAs.     

Free amino acids in the late embryogenesis and pre-hatching stage of two coregonid fishes

Developing eggs of vendace (Coregonus albula L.) and whitefish (C. lavaretus L.) were experimentally delayed in hatching by incubation at low water temperature (1–2°). Some eggs were taken during this period to a water temperature which was gradually raised up to 8° to provoke mass hatching of embryos. The pattern of free amino acids was followed in eggs incubated at both temperatures. During a 56 days period, the content of several essential amino acids significantly decreased in eggs of both species. For instance, the lysine content dropped from 703 to 270 mg/g dry matter and the arginine content from 257 to 13.3 mg/100 g dry matter in whitefish eggs. A similar pattern of decreasing level of free amino acids in embryonated ova up to hatching was characteristic for essential amino acids and serine. Methionine was exceptional; its level remained approximately the same. On the other hand, non-essential amino acids showed a significant increase in concentration during the experimental period. For instance, the glycine level increased 4.9 and 2.1 times in whitefish and vendace eggs, respectively. Transfer of eggs to 8° accelerated the decrease of nearly all free amino acids before hatching. The consequence of such amino acid metabolism for newly hatched larvae is discussed.     

Effects of temperature and growth phase on lipid and biochemical composition of Isochrysis galbana TK1

The lipid and biochemical composition of the haptophyte Isochrysis galbana TK1 was examined. Cultures were grown at 15 °C and 30 °C, and harvested in the exponential and early stationary growth phases. Carbohydrate and protein content varied at the two culture temperatures and growth phases. The highest protein content was found at the exponential growth phase at 15 °C, and the highest carbohydrate content was found at the stationary phase at the same culture temperature. Lipid accumulated in the stationary growth phase and its content was higher at 30 °C than at 15 °C regardless of the growth phase. The neutral lipids were the major class of lipid found in all the cultures. The stationary phase culture had a higher proportion of neutral lipids than the exponential phase culture and the proportion decreased slightly when culture temperature was increased from 15 °C to 30 °C. Phospholipid levels remained constant at the two temperatures, but slightly decreased in the stationary phase. Glycolipids in the exponentially growing cells were higher than those from stationary growth phase and increased with temperature. Polyunsaturated fatty acids (PUFAs) predominated in glycolipids and phospholipids. Cells grown at 15 °C contained higher proportion of 18:3 (n–3) and 22:6 (n–3) with a corresponding decrease in 18:2 (n–6), monounsaturated and saturated fatty acids. This revised version was published online in August 2006 with corrections to the Cover Date.     

Influence de la température sur la biosynthèse des acides gras de deux champignons filamenteux, Aspergillus ochraceus et Mucor mucedo

The two moulds, Mucor mucedo and Aspergillus ochraceus, grow very rapidly at 22°; when transferred to 12°, Mucor shows a regular growth and sporulation while Aspergillus development is almost entirely inhibited. ¹⁴C Acetate was supplied to both fungi at 12° and 22°. In both, the total radioactivity of saturated fatty acids was less important at the lowest temperature. In contrast, C 18:1 radioactivity rose in Mucor while it was C 18:2 radioactivity which rose in Aspergillus at the lowest temperature. There was an increase in phosphatidylethanolamine (PE) and phosphatidylcholine (PC) radioactivities in Mucor while the phosphatidylserine (PS) radioactivity decreased at low temperature. By contrast, when Aspergillus was placed in the same cultural conditions, PE and PC radioactivities decreased while PS radioactivity increased. Based on these results, a tentative explanation of the improved cold-resistance of M. mucedo is presented.     

Effect of photoperiod and temperature on diapause in a Florida strain of the tropical warehouse moth Ephestia cautella

A photoperiodically-controlled diapause of the long-day, short-day type was identified in a brown-winged, yellow-eyed strain of Ephestia cautella (Walker). The proportion of larvae diapausing in very long photoperiods was less than in short photoperiods. The mean critical photoperiod, here defined as that photoperiod giving half the maximum percentage of insects that diapause in response to photoperiod at a given temperature, was between 12 and 13 hr for the long-day reaction at both 20 and 25°C. The principal sensitive phase occurred near the time of the last larval moult. The mean duration of diapause was 2–3 months at 20°C and slightly longer at 25°C. The optimum temperature for diapause development was near 15°C, all larvae pupating within 24 days after a 45-day exposure at this temperature. Diapause could be terminated whenever larvae diapausing at 20°C were exposed to as few as five long (15 hr) photoperiods at 25°C. Long photoperiods at 20°C, or short photoperiods (9 hr) at 25°C were less effective in terminating diapause.     

Photoperiodic and thermoperiodic interactions in the regulation of the larval diapause of Diatraea grandiosella

The effect of various combinations of photoperiod and temperature on the induction and termination of the mature larval diapause of a Missouri strain of the southwestern corn borer. Diatraea grandiosella, was examined. Larval exposure to regimes in which the low phase of a 30°:23°C thermoperiod coincided with a scotophase of 10 to 14 hr duration led to high incidence of diapause. Larval exposure to 30°:24°C, 33°:21°C, and 36°:18°C thermoperiods with half cycles of 12 hr in continuous darkness yielded a diapause incidence of 16%, 22%, and 59%, respectively, whereas exposure to a 30°:24°C thermoperiod in continuous illumination yielded a completely nondiapause generation. Larval exposure to one of a series of 36°:18°C thermoperiods in which the duration of the high phase was increased in 2 hr increments from 0 to 24 hr in continuous darkness showed that “short-day” thermoperiods yielded a high incidence of diapause. However, no clearly defined critical thermoperiod was observed. An examination of photoperiodic and thermoperiodic effects on diapause development showed that, in general, those combinations of temperature and light cycles which were diapause inductive also retarded diapause development. The relationship between seasonal photoperiods and thermoperiods in southeastern Missouri was examined.     

Effect of temperature upon heart preservation for transplantation.

In this work we studied the effect of three different temperatures (7 °, 15 °, and 30 °C) on heart preservation. The best temperature for 24 hr pulsatile perfusion of canine hearts was 7 °C. Hearts perfused at this temperature showed no evidence of abnormal preservation changes nor of histological damage immediately upon transplantation. If the temperature was increased to 15 ° or 30 °C, moderate to severe preservation and histological damage were observed, and only three out of 10 dogs survived upon heart implantation.     

Diapause termination in two species of damselflies

Larvae of two species of damselflies, Enallagma hageni and E. aspersum, were collected in southwestern North Carolina and subjected to different combinations of daylength (SD, 11 hr day; LD, 14 hr day) and temperature to determine the factor critical in the termination of diapause. Diapausing larvae were collected in September, and 15 comparable groups of each species were given pretreatments (SD, 10°C; LD, 10°C; or SD, 21°C) for 2, 4, or 8 weeks and then transferred to SD, 21°C or LD, 21°C until emergence. Control groups were maintained under both photoperiods at 21°C.Response times (days from collection to emergence) for both species showed that rapid development required transfer to LD, 21°C regardless of the type of pretreatment or length of exposure. Larvae transferred to LD, 21°C after exposure to any of the three types of pretreatment for equal lengths of time developed at similar rates. Pretreatments at 10°C, which were equally effective with SD or LD, stimulated subsequent rapid development at LD, 21°C to a greater extent than continuous exposure to LD, 21°C conditions, and the longer the exposure to 10°C, the faster the subsequent response. Pretreatments at SD, 21°C also resulted in rapid development, similar to that of larvae exposed to 10°C, upon transfer to LD, 21°C conditions. Long daylengths administered only during pretreatments did not effect rapid development, since all larvae responded slowly when transferred to SD, 21°C. Diapause termination, therefore, was effected by LD, 21°C conditions preceded by exposure to either low temperatures, during which the photoperiod was not important, or short daylengths at 21°C.     

Certain components of lettuce juice modify the thermoresponse of the ciliated protozoan Blepharisma japonicum

When the cells of Blepharisma cultured in lettuce juice were transferred to media containing lettuce juice with temperature gradient of 20–30°C, they accumulated in a region corresponding to about 25°C. The cells washed in a saline solution, however, accumulated in the region above 30°C. The results indicate that certain components contained in lettuce juice change the thermosensitivity of the cells. When the temperature was suddenly changed, a transient decrease or increase in the frequency of ciliary reversal was observed. The response of the cells incubated in a saline solution without lettuce juice was different from those in the saline solution containing lettuce juice above 25°C. Above 25°C, the cells incubated in a saline solution without lettuce juice responded by increased frequency of ciliary reversal only to step-down in temperature and by repression of ciliary reversal to a step-up in temperature, while the cells incubated in the same saline solution containing lettuce juice responded by increased frequency of ciliary reversal to a step-up in temperature and by repression of ciliary reversal to a step-down in temperature. The thermal response was examined in bisected fragments of the cells. The difference in response between the saline solution without lettuce juice and the solution containing lettuce juice was detected only in posterior fragments above 25°C. Above 25°C, the posterior fragments incubated in the solution without lettuce juice did not respond to sudden temperature changes, whereas the fragments kept in the medium containing lettuce juice responded (step-up thermophobic response and step-down repression of ciliary reversal) in the presence of lettuce juice.