Journal of Thermal Biology 27 (2002) 55–60 Accumulation and disappearance of dehydrins and sugars depending on freezing tolerance of winter wheat plants at different developmental phases I.V. Stupnikova*, G.B. Borovskii, N.V. Dorofeev, A.A. Peshkova, V.K. Voinikov Siberian Institute of Plant Physiology and Biochemistry, Siberian Division of Russian Academy of Sciences, Irkutsk P.O.Box 1243, 664033, Irkutsk-33, Russia Abstract Several heat-stable dehydrins with mol. wts of 209, 196, 66, 50 and 41 kD characteristic of hardened winter wheat (Triticum aestivum L.) plants were detected by PAGE and Western blotting. These proteins together with sugars were accumulated under field conditions during low temperature adaptation and disappeared during spring. Their content depended on developmental phase and was connected with plant winter tolerance. Seemingly, more tolerant winter wheat plants have more effective mechanism of additive action of these protecting compounds. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Triticum aestivum L.; Heat-stable plant proteins; Dehydrins; Hardening; Deacclimation 1. Introduction Many plants increase in freezing tolerance upon exposure to low nonfreezing temperatures, a phenom- enon known as cold acclimation. It is provided by different biochemical mechanisms which are known to involve the induction of genes encoding stress proteins, increased levels of sugars, enhancement of antioxidative mechanisms, changes in lipid composition, etc. (Thoma- show, 1999; Borovskii et al., 1999; Storz and Imlay, 1999). These processes were activated by low temperature signal alone and in most cases low temperature dehydration that are deleterious for plants. It appears that dehydration in turn induce expression of dehydra- tion-inducible genes and production of plant hormone abscisic acid (ABA) which also triggers the transcription of ABA-inducible genes (Shinozaki and Yamaguchi- Shinozaki, 1997). Among the COR-proteins encoded by the COR-genes dehydrins family presents a particular interest because of they cryoprotective property. Dehy- drins (dhns) have unusually hydrophilic, heat stable nature. They have been hypothesized to function by stabilizing large-scale hydrophobic interactions such as membrane structures or hydrophobic patches of pro- teins, acting essentially as a surfactant (Close, 1997). A number of studies have established positive correlation between drought and cold stress tolerance and dehydrin accumulation in a different plant species (Labhilili et al., 1995; Close, 1996; Pelah et al., 1997). Also correlation was established between other cryoprotectants, for example water-soluble sugars, and frost tolerance in various plant species (Vagujfalvi et al., 1999). The carbohydrates as other cryoprotectants, such as amino acids, glycinebetaine, polyamines, are hypothe- sized to act synergistically to stabilize macromolecules, thereby stabilizing the protoplasm (Close, 1996). How- ever, available information about accumulation and disappearance of the protecting compounds is presented widely but is dispersed. Particularly, its observation concern with experiments conducted under field condi- tions, where all complex of nature factors acts. In this connection, the aim of the present work was to find proteins with immunochemical affinity to dehydrins *Corresponding author. Fax: +7-3925-510754. E-mail address: irina@sifibr.irk.ru (I.V. Stupnikova). 0306-4565/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII:S0306-4565(01)00015-8