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Freeze Tolerance (freeze + tolerance)
Selected AbstractsFreeze tolerance of the yeast Torulaspora delbrueckii: cellular and biochemical basisFEMS MICROBIOLOGY LETTERS, Issue 1 2004Cecília Alves-Araújo Abstract The freeze stress responses to prolonged storage at ,20 °C in Torulaspora delbrueckii PYCC5323 were investigated. In this yeast, no loss of cell viability was observed for at least 120 days during freezing at ,20 °C, whereas a loss of 80% was observed in a commercial baker's yeast after 15 days. In the former strain, freeze resistance was dependent on an adaptation process. The primary cell target of freeze stress was the plasma membrane, preservation of its integrity being related with a lower increase of lipid peroxidation and with a higher resistance to H2O2, but not with the intracellular trehalose concentration. [source] Impacts of heavy metals, polyaromatic hydrocarbons, and pesticides on freeze tolerance of the earthworm Dendrobaena octaedraENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2009Anne-Mette Bindesbøl Abstract Previous studies have shown that the interactions between chemicals and climatic stressors can lead to synergistically increased mortality. In the present study, we investigated the effect of seven common environmental contaminants on survival at ,6 and 15°C as well as on reproduction at 15°C in the earthworm Dendrobaena octaedra. Three classes of chemicals were considered: Heavy metals (nickel, lead, and mercury), polycyclic aromatic hydrocarbons (pyrene and phenanthrene), and pesticides (abamectin and carbendazim). Phenanthrene interacted antagonistically with freezing temperatures, whereas no interaction was observed with any of the tested pesticides. Two of the three tested metals (nickel and mercury) reduced the freeze tolerance synergistically (mercury was especially potent). This suggests that traditional laboratory studies, in which organisms are exposed to increasing concentrations of a single compound under otherwise optimal conditions, may underestimate the toxicity of some metals to field populations living in cold areas. [source] Cold tolerance and cold hardening strategy of the Japanese pine sawyer Monochamus alternatus (Coleoptera: Cerambycidae)INSECT SCIENCE, Issue 4 2008Jing Tian Abstract The Japanese pine sawyer, Monochamus alternatus, is an important pine forest pest and vector transmitting the pine wilt nematode that causes pine wilt disease. Low temperatures in autumn, winter and spring often differentially affect mortality of M. alternatus larvae. In this paper, we mainly compared the differences of mortality and cold hardening of larvae from different seasons, based on supercooling point (SCP) and cumulative probability of individuals freezing (CPIF). The cold hardening of the larvae from autumn, winter and spring seasons were largely different. Correlations between mortality and CPIF of autumn and spring larvae were highest on day 1/4, and gradually decreased with prolonged exposure duration. This beetle's death mainly resulted from freezing in short exposure duration. However, the correlation between mortality and CPIF of winter larvae increased gradually with the prolonged exposure duration. Death did not mainly result from freezing in long exposure duration. Autumn larvae are more susceptible and adaptable than winter and spring larvae. Winter larvae have a slight freeze-tolerance trend. Our research showed that M. alternatus came into complex cold-hardening strategies under natural selection. Freeze avoidance is the primary strategy; with prolonged exposure duration to above SCP or < 0 °C, chill tolerance is more important; this is followed by freeze tolerance during harsh winters. [source] Adaptive evolution of baker's yeast in a dough-like environment enhances freeze and salinity toleranceMICROBIAL BIOTECHNOLOGY, Issue 2 2010Jaime Aguilera Summary We used adaptive evolution to improve freeze tolerance of industrial baker's yeast. Our hypothesis was that adaptation to low temperature is accompanied by enhanced resistance of yeast to freezing. Based on this hypothesis, yeast was propagated in a flour-free liquid dough model system, which contained sorbitol and NaCl, by successive batch refreshments maintained constantly at 12°C over at least 200 generations. Relative to the parental population, the maximal growth rate (µmax) under the restrictive conditions, increased gradually over the time course of the experiment. This increase was accompanied by enhanced freeze tolerance. However, these changes were not the consequence of genetic adaptation to low temperature, a fact that was confirmed by prolonged selection of yeast cells in YPD at 12°C. Instead, the experimental populations showed a progressive increase in NaCl tolerance. This phenotype was likely achieved at the expense of others traits, since evolved cells showed a ploidy reduction, a defect in the glucose derepression mechanism and a loss in their ability to utilize gluconeogenic carbon sources. We discuss the genetic flexibility of S. cerevisiae in terms of adaptation to the multiple constraints of the experimental design applied to drive adaptive evolution and the technologically advantageous phenotype of the evolved population. [source] Ice recrystallization inhibition proteins (IRIPs) and freeze tolerance in the cryophilic Antarctic hair grass Deschampsia antarctica E. Desv.PLANT CELL & ENVIRONMENT, Issue 4 2009ULRIK P. JOHN ABSTRACT Antarctic hair grass (Deschampsia antarctica E. Desv.), the only grass indigenous to Antarctica, has well-developed freezing tolerance, strongly induced by cold acclimation. Here, we show that in response to low temperatures, D. antarctica expresses potent recrystallization inhibition (RI) activity that, inhibits the growth of small ice crystals into potentially damaging large ones, is proteinaceous and localized to the apoplasm. A gene family from D. antarctica encoding putative homologs of an ice recrystallization inhibition protein (IRIP) has been isolated and characterized. IRIPs are apoplastically targeted proteins with two potential ice-binding motifs: 1,9 leucine-rich repeats (LRRs) and c. 16 ,IRIP' repeats. IRIP genes appear to be confined to the grass subfamily Pooideae and their products, exhibit sequence similarity to phytosulphokine receptors and are predicted to adopt conformations with two ice-binding surfaces. D. antarctica IRIP (DaIRIP) transcript levels are greatly enhanced in leaf tissue following cold acclimation. Transgenic Arabidopsis thaliana expressing a DaIRIP has novel RI activity, and purified DaIRIP, when added back to extracts of leaves from non-acclimated D. antarctica, can reconstitute the activity found in acclimated plants. We propose that IRIP-mediated RI activity may contribute to the cryotolerance of D. antarctica, and thus to its unique ability to have colonized Antarctica. [source] Leaf vascular dimensions associated with freeze tolerance in bahiagrass (Paspalum notatum)ANNALS OF APPLIED BIOLOGY, Issue 2 2009J.W. Breman Abstract Foliage damage as a result of individual freeze events is a major limitation to the expansion of bahiagrass (Paspalum notatum) pastures and hay production in Southeastern USA. Greater tolerance to such freeze events would allow production deeper into the fall and winter and allow expansion of this species into colder regions. While it has been reported that small cells are more tolerant to freeze damage, this possibility has not been explored in bahiagrass. Specifically, the hypothesis was examined that xylem vessels with smaller diameter in the midrib of leaves are associated with freeze tolerance among bahiagrass genotypes. Vascular bundle diameter was also measured as a possible index of xylem cell size. A total of eight bahiagrass genotypes were eventually studied representing four freeze-sensitive and four freeze-tolerant lines. There was a clear distinction in xylem cell size between the freeze-sensitive and the freeze-tolerant lines. The freeze-tolerant genotypes had xylem element cells that were significantly smaller than the freeze-sensitive genotypes. Averaged across three leaf positions and all genotypes, the xylem element diameter for the freeze-sensitive lines was 222 ,m and for the freeze-tolerant lines was only 164 ,m. A similar difference was observed in overall vascular bundle diameter with freeze-sensitive lines having a mean of 1168 ,m and the freeze-tolerant lines a mean of 917 ,m. These results indicated that the diameter of the xylem cells in the vascular midrib of bahiagrass may be an important variable influencing the sensitivity among genotypes to freeze damage. [source] Climatic variability and the evolution of insect freeze toleranceBIOLOGICAL REVIEWS, Issue 2 2003BRENT J. SINCLAIR ABSTRACT Insects may survive subzero temperatures by two general strategies: Freeze-tolerant insects withstand the formation of internal ice, while freeze-avoiding insects die upon freezing. While it is widely recognized that these represent alternative strategies to survive low temperatures, and mechanistic understanding of the physical and molecular process of cold tolerance are becoming well elucidated, the reasons why one strategy or the other is adopted remain unclear. Freeze avoidance is clearly basal within the arthropod lineages, and it seems that freeze tolerance has evolved convergently at least six times among the insects (in the Blattaria, Orthoptera, Coleoptera, Hymenoptera, Diptera and Lepidoptera). Of the pterygote insect species whose cold-tolerance strategy has been reported in the literature, 29% (69 of 241 species studied) of those in the Northern Hemisphere, whereas 85%(11 of 13 species) in the Southern Hemisphere exhibit freeze tolerance. A randomization test indicates that this predominance of freeze tolerance in the Southern Hemisphere is too great to be due to chance, and there is no evidence of a recent publication bias in favour of new reports of freeze-tolerant species. We conclude from this that the specific nature of cold insect habitats in the Southern Hemisphere, which are characterized by oceanic influence and climate variability must lead to strong selection in favour of freeze tolerance in this hemisphere. We envisage two main scenarios where it would prove advantageous for insects to be freeze tolerant. In the first, characteristic of cold continental habitats of the Northern Hemisphere, freeze tolerance allows insects to survive very low temperatures for long periods of time, and to avoid desiccation. These responses tend to be strongly seasonal, and insects in these habitats are only freeze tolerant for the overwintering period. By contrast, in mild and unpredictable environments, characteristic of habitats influenced by the Southern Ocean, freeze tolerance allows insects which habitually have ice nucleators in their guts to survive summer cold snaps, and to take advantage of mild winter periods without the need for extensive seasonal cold hardening. Thus, we conclude that the climates of the two hemispheres have led to the parallel evolution of freeze tolerance for very different reasons, and that this hemispheric difference is symptomatic of many wide-scale disparities in Northern and Southern ecological processes. [source] | |||||||||||||||||||