**1. Introduction**

Plant seeds are a unique object for studying the mechanisms of tolerance and adaptation to abiotic stresses. The seeds could not escape unfavorable environmental conditions but must

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adapt to overcome them, to retain a capability of germination and to fulfill their physiological destination, that is, species preservation and distribution. Furthermore, in seeds the develop‐ mental program of the individual plant is switched over from embryogenesis to germination; in the periods of seed development and germination, seed embryos, being subjected to the action of unfavorable conditions, must change cell activity on the level of gene expression and induce the synthesis of anti-stress proteins to protect themselves and overcome stress effects. On the other hand, embryos have to provide expression of genes for proteins required for further development, that is, germination *per se*.

Different environmental stresses to a plant may result in similar responses at the cellular and molecular level. This is due to the fact that the impacts of the stressors trigger similar strains and downstream signal transduction chains. Stressors such as drought (lack of environmental water), salinity (high osmolarity), and cold, especially frost (lack of liquid water), induce water deficiency [1]. All three forms of abiotic stress affect the water relations of a plant on the cellular as well as whole plant level, causing specific as well as unspecific reactions, damages and adaptation reactions. The stabilizing effect of liquid water on the membrane can be supported by compatible solutes and special proteins. At the metabolic level, osmotic adjustment by synthesis of low-molecular osmolytes (carbohydrates, betains, proline) can counteract cellular dehydration and turgor loss [1].

During the periods of dehydration, a wide variety of plants can express dehydration proteins (dehydrins), which are also members of the plant late embryogenesis abundant (LEA) protein family. For the first time, LEA proteins were characterized in ripening seeds [2]. But they are widely investigated now [3–5]. However, their precise role has not been clear yet. These proteins are supposed to protect cells from water loss; they can behave as molecular chaper‐ ones [2]. Now the expression of LEA proteins has been shown not only in ripen seeds but also in other plant (or animal) tissues. LEA proteins are induced by osmotic or cold stress, by exogenous ABA (abscisic acid) [6]. It is believed that LEA proteins are non-catalytic proteins. Practically, all LEA proteins are water-soluble hydrophilic heat-stable and unfolded proteins. LEA proteins are synthesized in orthodox seeds, and the development of which at the final stage is associated with genetically determined drying. Their amount can reach 4% of total cell proteins [7]. At the same time, LEA proteins are found in desiccation-sensitive recalcitrant seeds. That is why the study of recalcitrant seeds is of great interest. On the one hand, these seeds produce LEA proteins, and on the other hand, they are sensitive to desiccation. Therefore, a characterization of LEA proteins in recalcitrant seeds can help understanding their role, for example when plant cells are challenged by abiotic stress as cold or salt stress.

LEA proteins are classified into more than seven distinct groups [8]. Among the induced LEA proteins, dehydrins (group II of late embryogenesis abundant proteins) have been most commonly studied, but our knowledge of their fundamental role in the cell is incomplete.
