Low temperature acclimation

Cyanobacteria, prokaryotic algae that perform oxygenic photosynthesis, respond to a decrease in ambient growth temperature by desaturating the fatty acids of membrane lipids to compensate for the decrease in the molecular motion of the membrane lipids at low temperatures. During low-temperature acclimation of cyanobacterial cells, the desaturation of fatty acids occurs without de novo synthesis of fatty acids [110, 111]. All known cyanobacterial desaturases are intrinsic membrane proteins that act on acyl-Hpid substrates. 

Phenolic compounds may be involved in plant responses to cold stress and in plant acclimation to low temperature. Acclimation of apple trees to cold climates was found to be associated with a seasonal accumulation of chlorogenic acid [102]. Strengthened frost tolerance in a variety of plants were attributed to thicker cell-wall lignification or suberization [102]. Thickening of cell walls and increased production of suberin-type lipids were observed in cold-acclimated winter rye leaves [103]. The presence of suberin in cell walls may favour membrane cell-wall adhesion, a major factor in the resistance of plant cells to freezing [104]. 

Huner, N.P.A. Macdowall, F.D.H. (1979). The effects of low temperature acclimation on the catalytic properties of its ribulose bisphosphate carboxylase-oxygenase. Canadian Journal of Biochemistry 57, 1036-41. 

Kushad, M.M. Yelenosky, G. (1987). Evaluation of polyamine and proline levels during low temperature acclimation of citrus. Plant Physiology 84, 692-5. 

Lang, V., Heino, P. Palva, E.T. (1989). Low temperature acclimation and treatment with exogenous abscisic acid induce common polypeptides in Arabidopsis thaliana (L.) Heynh. Theoretical and Applied Genetics 77, 729-34. 

RNA concentration increases in the white muscle of fish following low temperature acclimation have been reported (Goolish et al. 1984 Foster etal. 1990b). The former authors hypothesised that increased muscle RNA concentration in cold acclimated fish compensated for a reduction in RNA activity with low water temperatures. Some tissues of rainbow trout (Fauconneau and Arnal 1985) and cod (Foster et al. 1990b) show reduced RNA activities at low temperatures suggesting a thermal compensatory mechanism. RNA activities of mammals are higher than those reported for ectotherms (e.g. Bates et al. 1987). There is therefore support for the idea that increased RNA concentrations in tissues act as a compensatory mechanism for low temperature acclimation. 

Huner NPA, Oquist G, Hurry VM, Krol M, Falk S, and Griffith M. Photosynthesis, photoinhibition and low temperature acclimation in cold tolerant plants. Photosynth Res. 1993 37 19-39. 

As an increasing number of reports appear on the subject of low temperature acclimation in plants, it becomes more and more apparent that a variety of lipid compositional changes are effected. The principal ones include 1) altered levels of fatty acid unsaturation, 2) altered molecular species composition within lipid classes, and 3) altered proportions of the different lipid classes. These three categories of change will be discussed separately. 

Lynch, D.V., and G.A. Thompson, Jr. Plant Physiology 74 198-203 (1984a). Chloroplast phospholipid molecular species alterations during low temperature acclimation in Dunaliella. 

Repression of cspA after acclimation at low temperatures appears to be mediated by the cold box region and is a possible target site for repressor binding [138]. In addition, CspA itself negatively regulates its own gene expression through the cold box [138, 139]. 

Verhoeven, A.S., Adams, III, W.W., Demmig-Adams, B., Croce, R., and Bassi, R. 1999. Xanthophyll cycle pigment localization and dynamics during exposure to low temperatures and light stress in low and high light-acclimated in vinca major. Plant Physiol 120 1-11. 

Before discussing the role of proteins in cold acclimation the physical effects caused by low temperature are briefly considered. A decrease of temperature leads to altered rates of enzymatic catalysis. Formation of hydrogen bonds and electrostatic interactions are thermodynamically more stable at a lower temperature whereas hydrophobic interactions are... 

Many physiological studies established a correlation between cold acclimation and increasing ABA levels in plant tissues (Chen etal., 1983). Furthermore, exogenous ABA application can induce cold-hardening to the same degree as a low temperature treatment does (Chen Gusta, 1983) while plant species which do not show a hardening capacity at low temperature do not harden even after ABA treatment. 

Despite many studies on the effect of ABA on plant tissues there is no demonstration that ABA can regulate the level of enzyme activities and specially of those involved in cold acclimation. On the other hand, ABA certainly induces modifications in gene expression and many genes are modulated by ABA (Skriver Mundy, 1990). Indeed several in vivo protein-labelling and in vitro translation experiments have demonstrated that the level of certain proteins or mRNAs increased in response to both low temperature and exogenous ABA applications (Robertson et al., 1987 Mohapatra et al., 1988 Ling et al., 1989). 

The property of cold acclimation resulting in freezing tolerance has evolved in many temperate plants. The metabolic pathways of this complex process are mostly unknown. However, from recent work it is clear that gene activation is involved. By means of molecular biology some cold-regulated transcripts have been isolated and have become amenable to further analysis. The cDNA clones so far available probably correspond to only a small number of the transcripts which are affected by low temperature. One may therefore expect that the number of cDNA clones and genomic clones available for characterisation will increase in the near future. 

Rome, L.C., Loughna, P.T. and Goldspink, G. (1985). Temperature acclimation improved sustained swimming performance in carp at low temperatures. Science, New York 228,194-1%. 

Figure 7.20. Effects of temperature on phase and static order of the membrane bilayer. Reductions in temperature from the physiological temperature of the organism (cell), that is, temperatures near those of adaptation or acclimation, lead to formation of gel-phase regions, which may separate from lipids that remain in the liquid-crystalline phase, the phase characteristic of most of the bilayer at physiological temperatures. At sufficiently low temperatures, the bulk of the membrane phospholipids enter the gel phase.

Temperature Most industrial wastes tend to be on the warm side. For the most part, temperature is not a critical issue below 37°C if wastewaters are to receive biological treatment. It is possible to operate thermophilic biological wastewater-treatment systems up to 65°C with acclimated microbes. Low-temperature operations in northern climates can result in very low winter temperatures and slow reaction rates for both biological treatment systems and chemical treatment systems. Increased viscosity of wastewaters at low temperatures makes solid separation more difficult. Efforts are generally made to keep operating temperatures between 10 and 30°C if possible. 

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