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  • 1
    Electronic Resource
    Electronic Resource
    Juhani Lehtonen (2000)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 110 (2000), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2000.110201.x
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  • 2
    Electronic Resource
    Electronic Resource
    Antifreeze proteins in winter rye (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 100 (1997), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Six antifreeze proteins, which have the unique ability to adsorb onto the surface of ice and inhibit its growth, have been isolated from the apoplast of winter rye leaves where ice forms at subzero temperatures. The rye antifreeze proteins accumulate during cold acclimation and are similar to plant pathogenesis-related proteins, including two endoglucanase-like, two chitinase-like and two thaumatin-like proteins. Immunolocalization of the glucanase-like antifreeze proteins showed that they accumulate in mesophyll cell walls facing intercellular spaces, in pectinaceous regions between adjoining mestome sheath cells, in the secondary cell walls of xylem vessels and in epidermal cell walls. Because the rye antifreeze proteins are located in areas where they could be in contact with ice, they may function as a barrier to the propagation of ice or to inhibit the recrystallization of ice. Antifreeze proteins similar to pathogenesis-related proteins were also found to accumulate in closely-related plants within the Triticum group but not in freezing-tolerant dicotyledonous plants. In winter wheat, the accumulation of antifreeze proteins and the development of freezing tolerance are regulated by chromosome 5. Rye antifreeze proteins may have evolved from pathogenesis-related proteins, but they retain their catalytic activities and may play a dual role in increasing both freezing and disease resistance in overwintering plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb04790.x
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrastructural changes induced by sub-zero temperatures in the plasma membrane of protoplasts from winter rye (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 100 (1997), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Freezing of nonacclimated protoplasts close to lethal temperatures induces alterations in the macromolecular organization of the plasma membrane but the significance of these structural changes in freezing injury is still uncertain. We therefore cooled non-acclimated protoplasts isolated from cultivars of winter rye (Secale cereale L.) to two sub-zero temperatures using two different cooling rates and analyzed freeze-induced plasma membrane changes by freeze-fracture electron microscopy. When a high cooling rate was used a lipid phase transition was observed in 34% of the total membrane fracture faces of the protoplasts, while with a slow cooling rate it occurred only to a very small extent. Smooth, aparticulate lamellae were approximately three times more frequent at low than at high cooling rate. Lipid phase transition from lamellar to hexagonalII (HII) phase occurred at high cooling rate more frequently at −10°C than at −30°C in three cultivars. The results suggest that the greatly increased proportion of phase transition from bilayer to non-bilayer phase is an artifact caused by too fast a cooling rate of protoplasts. Furthermore, lateral phase separation of the plasma membrane with segregation of intramembrane particles and the appearance of membrane associated stacks of lipid lamellae, may cause cellular death by retarding the flow of intracellular water towards extracellular ice crystals formed during freezing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb04791.x
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of cold exposure on cortical microtubules of rye (Secale cereale) as observed by immunocytochemistry (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 93 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The responses of cortical microtubules to sub-zero temperatures were examined in non-acclimated (NA) and cold-acclimated (CA) rye (Secale cereale L. cv. Voima) leaf and root cells, and in protoplasts isolated enzymatically from leaves. Responses of leaf and root cells to hypertonic solutions equivalent to the dehydration response of freezing (P. L. Steponkus and D. V. Lynch 1989. J. Bioenerg. Biomembr. 21: 21–41) were also examined. At the respective growth temperatures both NA and CA leaf and root cells had typical organization and abundance of cortical microtubules as observed by indirect immunofluorescence (IIF) staining. Unchanged microtubule arrays were still present in CA leaf cells after -4°C treatment, while in leaf cells of NA plants and in the root cells of both NA and CA plants microtubules were shorter and less abundant. After -10°C treatment the cortical microtubules were almost totally depolymerized in both types of root cells and in leaf cells of NA plants, while CA leaf cells still had abundant cortical microtubule arrays. Semiquantitative analyses of cortical microtubules (MTs) of protoplasts confirmed the findings with intact leaf cells. Hypertonic treatment of NA and CA leaf cells gave similar effects as exposure of cells to sub-zero temperatures. However, after the hypertonic treatment, more microtubules remained present in the CA root cells than in the NA root cells, suggesting that also in root cells cold acclimation increases the dehydration stability of MTs. In conclusion, cold acclimation induces both greater frost stability and greater osmotic tolerance in the cortical microtubules of the leaf cells, and greater osmotic tolerance in the microtubules of the root cells in winter rye.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb06859.x
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  • 5
    Electronic Resource
    Electronic Resource
    Genes encoding chitinase-antifreeze proteins are regulated by cold and expressed by all cell types in winter rye shoots (2001)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 112 (2001), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: One group of antifreeze proteins (AFPs) is composed of two chitinases that accumulate in the apoplast of winter rye leaves during cold acclimation. In this study, the 28- and 35-kDa chitinase-AFPs were localized in nonacclimated and cold-acclimated rye leaves by immunoelectron microscopy with an antiserum produced against the purified winter rye 35-kDa chitinase-AFP. In cold-acclimated winter rye leaves, labelled chitinase-AFPs were abundant in the walls of epidermal, parenchymal sheath and mesophyll cells and xylem vessels, while less label was present in walls of vascular parenchyma cells. In contrast, chitinase labelling was essentially absent in the nonacclimated cells except in xylem vessels. As shown by RNA blotting, the transcripts of chitinase-AFPs accumulated to a high level in rye leaves during cold acclimation, to a lesser extent in crowns and were not detectable in roots. mRNA transcripts of the 28-kDa chitinase-AFP were localized in rye leaves by in situ hybridization. The chitinase-AFP transcripts were found in the same cell types as the protein itself. We conclude that all metabolically active cell types in cold-acclimated winter rye leaves and crowns are able to synthesize chitinase-AFPs and secrete them into adjacent cell walls, where they may interact with ice to delay its propagation through the plant and modify its growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2001.1120309.x
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  • 6
    Electronic Resource
    Electronic Resource
    Antifreeze proteins are secreted by winter rye cells in suspension culture (2003)
    Oxford, UK : Munksgaard International Publishers
    Physiologia plantarum 118 (2003), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: During cold-acclimation, winter rye (Secale cereale L) leaves secrete antifreeze proteins (AFPs) into the apoplast. The AFPs bind to ice and modify its growth, which is easily observed in vitro. However, it is not yet known whether in planta AFPs interact with ice or whether they exert cryoprotective effects. These experiments are difficult to conduct with intact plants, so the aim of this work was to determine whether AFPs are produced in response to cold temperature in cell culture and to examine their function by using suspension cells. We showed that suspension cells secreted three of the six known winter rye AFPs into the culture medium during acclimation at 4°C. These AFPs were not present in washed suspension cells, thus indicating that they are not firmly bound to the cell walls. In order to examine the function of extracellular AFPs, non-acclimated (NA) winter rye suspension cells and protoplasts isolated from NA winter rye leaves were then frozen and thawed in the presence of AFPs extracted from cold-acclimated winter rye leaves. The AFPs had no effect on the survival of NA protoplasts after freezing; however, they lowered the lethal temperature at which 50% of the cells are killed by freezing (LT50) of NA suspension cells by 2.5°C. We conclude that low above-zero temperatures induce winter rye suspension cells to secrete AFPs free in solution where they can protect intact suspension cells, but not protoplasts, from freezing injury, presumably by interacting with extracellular ice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2003.00110.x
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