The fatty acid composition of polar lipids, which are the structural and functional bases of cell membranes in the bud of Betula pendula Roth birch, growing under the conditions of the cryolithozone, was studied for the first time. The important role played by lipid metabolism in the winter–spring period, when the apical meristem is at the stage of intrarenal development, was established. It was shown that, during this period, unsaturated fatty acids prevail over saturated in phospholipids and glycolipids in silver birch buds. However, under the conditions of extremely low air temperatures (–40°C and below), the lowest values of double bond index (DBI) and fatty acid unsaturation coefficient (U/S) were recorded. The rise of negative temperatures under the conditions of the cryolithozone (in March) to values usually observed during the winter period throughout the range of silver birch (–20°C and higher) contributed to an increase in the level of membrane lipid unsaturation. It was found that diene fatty acids predominate in phospholipids, and diene and triene acids predominate in glycolipids, the latter reaching maximum values (80.7% of the amount of unsaturated fatty acids) by the beginning of budding. It was hypothesized that, in order to preserve the viability of the apical meristem in buds of silver birch trees under the specific conditions of the cryolithozone, various interrelated adaptive mechanisms were formed. These mechanisms are aimed not only at protecting the rudimentary organs from the effects of sharp fluctuations in daily temperatures during spring, but also at protecting them during winter under conditions of extremely low temperatures (down to –60°С), which do not occur in other parts of its range. One of these mechanisms appeared to be nonspecific, and it was associated with an increase in the unsaturation of the fatty acid composition corresponding to the liquid-crystalline state of membrane lipids. Another adaptive mechanism is probably aimed at protecting cells from dehydration with the involvement of dehydrin proteins, as well as a number of other hydrophilic cryoprotective compounds against the background of increased viscosity of membrane lipids.

The composition and seasonal dynamics of stress proteins-dehydrins in the buds of the main birch species (downy birch ( Betula pubescens Ehrh.), silver birch ( B. pendula Roth)) and its varieties (Karelian birch ( B. pendula var. carelica (Mercklin) Hämet-Ahti)), growing in northwest Russia (on the example of the Republic of Karelia) were investigated for the first time. It was shown that the level of low-molecular dehydrins, mainly with a molecular mass of 17 kD, is subjected to major seasonal changes, regardless of the specific features of the birch. The maximal level of 17 kD dehydrin was formed during the autumn preparation of plants to dormancy and was persistently preserved during the cold period of the year. The content of medium-molecular weight dehydrins of 66–69 kD was almost at the same level all year round. Significant inter-and intraspecific polymorphism of the major dehydrins of 17 and 66–69 kD in the buds of downy birch, silver birch, and Karelian birch during dormancy was not found. The significant similarity in the composition of total proteins and dehydrins, as well as the uniform nature of their seasonal changes, mainly 17 kD dehydrin, indicates the phylogenetic proximity and similar mechanisms of adaptation of the main species of the genus Betula L. to the temperate continental climate of Karelia.

The peculiarities of the changes in the composition of dehydrin Betula pendula in the conditions of the cold regions of Eurasia (Yakutia, Karelia) are studied.When comparing dehydrins of this species of birch with those of B. pendula var.carelica and B. pubescens, growing in Karelia, revealed a significant similarity in the composition and nature of seasonal changes.In all types of birch, a high level of dehydrin was achieved in the winter.It is assumed that stress proteins-dehydrins participate in the formation of low-temperature resistance of plants.

Обобщен многолетний опыт изучения генетической системы гороха посевного (Pisum sativum L.), контролирующей развитие азотфиксирующего симбиоза и арбускулярной микоризы, полученный коллективом авторов и другими исследователями. Представлена обновленная фенотипическая классификация мутантов гороха. Отражены успехи в идентификации и клонировании симбиотических генов. Продемонстрирована возможность практического использования двойной инокуляции для увеличения продуктивности растений за счет мобилизации потенциала тройной симбиотической системы: горох – клубеньковые бактерии – грибы арбускулярной микоризы.

It is shown that dinitrosyl-iron complexes (DNIC) with glutathione can reduce oxoferrylmyoglobin forming on interaction of tert-butyl hydroperoxide and metmyoglobin. A rapid decrease in the DNIC concentration was observed under the conditions of production of tert-butyl free radicals; however, destruction of DNIC in the presence of oxoferrylmyoglobin alone was negligible. It is demonstrated that DNIC reduces oxoferrylmyoglobin more than an order more efficiently than S-nitrosoglutathione and glutathione. DNIC also inhibits formation of the thiyl radicals of glutathione in a medium containing metmyoglobin and tert-butyl hydroperoxide. A mechanism of the antioxidant action of DNIC based on regeneration of the nitrosyl complexes from the products of their interaction with oxoferrylheme is proposed.

The effects of exogenous nitrate on the number of developing nodules and their leghemoglobin content in the original pea (Pisum sativumL.) line and its symbiotic mutants were studied. Mutation in the Sym31gene conferred the tolerance to nitrate in the corresponding pea line and manifested itself as the number of nodules independent of the nitrate concentration. Thus, the Sym31gene was identified as the only known symbiotic gene involved in both the differentiation of symbiotic compartments and the nitrate-dependent process of nodule formation. The presence of leghemoglobin in double mutants (sym13, sym31) indicates the possibility of the complementary contribution of these genes in the control of leghemoglobin synthesis.

Metleghemoglobin reductases from nodules of yellow and blue lupines and garden pea were obtained in homogeneous state, some of their properties were studied. Presence of two isoforms of enzyme in nodules of both lupine species was shown. The comparison of properties of studied metleghemoglobin reductases from different legume plants was made. Possible mechanisms of their functioning in nodules are discussing.

Screening of different mutant traits with respect to nodule structure and function has shown that three of 20 legume plant symbiotic genes should be treated as crucial ones for the determination of the fate of bacteria inside the nodule. The identification of those genes in the model legume symbiotic systems and characterization of them at molecular level looks to be very promising for understanding the molecular mechanisms of their action.

Leghemoglobin content and metleghemoglobin reductase activity were determined in root nodules of the original pea line SGE and mutants SGEFix(-)-1 (gene Sym40) and SGEFix(-)-2 (gene Sym33) that produce ineffective nodules with defects of infection thread formation and bacteroid differentiation. The content of leghemoglobin in root nodules of SGEFix(-)-2 and SGEFix(-)-1 mutants was 5 and 150 times lower than in the original pea line. The activity of metleghemoglobin reductase was similar in nodules of all lines tested. The data are discussed in relation to the ultrastructural analysis of nodules and classification of mutants.

The review sums up the long experience of the authors and other researchers in studying the genetic system of garden pea (Pisum sativum L.), which controls the development of nitrogen-fixing symbiosis and arbuscular mycorrhiza. A justified phenotypic classification of pea mutants is presented. Progress in identifying and cloning symbiotic genes is adequately reflected. The feasibility of using double inoculation as a means of increasing the plant productivity is demonstrated, in which the potential of a tripartite symbiotic system (pea plants-root nodule bacteria-arbuscular mycorrhiza) is mobilized.

Already known mechanisms and models are presented to describe the function of diffusion barriers in legume nodules and the conditions under which these mechanisms operate. The control over oxygen influx to nodules is related to nodule structure. Four types of controls, which are set apart for regulating the barrier function with distinct periods and mechanisms of functioning, satisfactorily match the experimental evidence. The general pattern of the oxygen concentration gradient is put forward to describe oxygen flow from the rhizosphere to infected nodule cells.

Regulation of stress-affected oxygen exchange and operation of leghemoglobin in nitrogen-fixing nodules of legumes are considered. The classical conception of stress and the general adaptation syndrome can be applied to the analysis of environmental effects on plants and their responses to them.