Development Of Frost Resistance Research Articles

Характеристика суспензионных культур клеток Arabidopsis thaliana (L.) Heynh с изменённой экспрессией гена альтернативной оксидазы митохондрий АOX1a и анализ их морозоустойчивости

The enzyme alternative cyanide-resistant oxidase (AOX) localized in mitochondria is involved in the processes of plant adaptation to various unfavorable biotic and abiotic factors. Transfer of electrons from ubiquinone to oxygen by alternative oxidase has a nonprotonmotive character and, by bypassing two sites of H+ pumping in complexes III and IV, lowers the energy efficiency of respiration and energy of electron flow through AOX is released as heat. In this work, we characterized heterotrophic suspension cultures of Arabidopsis thaliana (L.) Heynh cells obtained from seeds of plants with altered (reduced (AS-12 line) and increased (XX-2 line)) expression of the alternative oxidase gene AOX1a and studied their viability under subzero temperature (-10 °С for 3, 6, 9 hours). Cell viability and reactive oxygen species (ROS) production were assessed using fluorescence microscopy with fluorescein diacetate (FDA) and propidium iodide (PI) for cell viability measurement and H2DCF-DA for ROS measurement. The proportion of living cells was calculated as the proportion of FDApositive and PI-negative cells. Differences between the studied lines were determined in the content of mitochondrial proteins of the respiratory chain (AOX, COXII, NDB) and uncoupling protein (UCP), as well as in the intensity of formation of ROS and frost resistance. The obtained results confirmed the higher content of the AOX protein and its high contribution to mitochondrial respiration in line XX-2. Suspension culture cells of the AS-12 line showed a decrease in the AOX protein content and its contribution to mitochondrial respiration, compared to the wild type (Col-0) and line XX-2. Simultaneously with a decrease in the AOX protein content in the AS-12 cell culture, an increase in the content of the uncoupling protein UCP and subunit II of cytochrome oxidase (COXII) was observed. ROS generation was reduced in cell cultures of both XX-2 and AS-12. The obtained results indicate that the cells of the wildtype (Col-0) suspension culture were subjected to the most significant effect of subzero temperature. Long-term exposure (for 9 h) under -10 °С revealed significant differences in the viability of wild-type culture cells and lines with altered AOX1a gene expression. Cells of line XX-2 with an increased content of AOX turned out to be more resistant to subzero temperature compared to wild-type and AS-12 cells. However, while the proportion of living cells in the culture of the AS-12 line 48 h after exposure remained at the same level as immediately after it, in the suspension culture of the wild type cell death developed over time. The obtained results indicate the importance of alternative oxidase in the development of frost resistance in plant cell.

Dehydrins associated with the development of frost resistance of Asian white birch

Seasonal changes in the content of dehydrins in Asian white birch (Betula platyphylla Sukacz.) growing under extreme cold conditions of Eastern Siberia (Central Yakutia) were studied for the first time by SDS-PAGE and immunoblotting. Several polypeptides, including putative storage proteins, which content was higher in winter than in other periods, were observed. Intraspecies polymorphism of dehydrins was detected during plant dormancy. The two groups of dehydrins were found: dehydrins with mol wts of 56-73 kD, which were present year-round, and dehydrins with mol wts of 15–21 kD, evidently related to the development of frost resistance because they were absent in summer but present in large amounts in winter. Under low winter temperatures, the highest level of dehydrins coincided with the lowest content of water in buds, which was accompanied by increased plant frost resistance to the highest values.

FROST HARDINESS OF PEACH AND APRICOT FLOWER BUDS

The determination of the frost resistance and winter hardiness of peach and apricot varieties is an important task in Hungary, as production can only be competitive if the location and variety are wisely chosen. Various overwintering organs of trees have very different levels of frost resistance, and this resistance also varies greatly over time. During dormancy flower buds are the most frost sensitive organs of peach and apricot trees. From the practical point of view frost resistance and winter hardiness of the flower buds deserve detailed study. The development rate of the overwintering organs of peach and apricot varieties and changes in their frost resistance during the dormancy period have been regularly investigated in recent years in the gene bank collection of Corvinus University of Budapest. The present paper provides an analysis of frost hardiness of flower buds based on the results obtained in three consecutive winters with very diverse weather conditions. The hardening processes of overwintering organs are fundamentally determined by environmental factors, particularly by temperature. Thus, even at the same location, the development rate of the flower buds and the development of frost resistance may differ from year to year. The determination of the maximum frost resistance genetically attainable and the description of changes in frost resistance are only possible in a series of experiments over several years.

Involvement of Oligosaccharides in Adaptation of Winter Wheat Seedlings to Subzero Temperatures

We studied the dynamics of endogenous content of biologically active oligosaccharides in the roots of winter wheat seedlings. Previously, these oligosaccharides proved to mediate the development of frost resistance during the first days of hardening (Zabotinaet al., 1998). The changes in their endogenous content can be described by a curve with a single peak observed 6 h after the onset of frost hardening. The capacity of these polysaccharides to increase frost resistance (LT50was evaluated by leakage of electrolytes) when added to growth medium did not depend on the pretreatment duration (from 1.5 to 18 h) but decreased if they were introduced in the course of the adaptive response. Inhibition of the adaptive response by inhibitors of RNA and protein synthesis ceased in the presence of the oligosaccharides. We believe that the oligosaccharides that are products of metabolism of the cell wall polysaccharides are involved in adaptation to low temperature.

Accumulation and characterization of the 75 kDa protein induced by low temperature in barley

The hardening-triggered accumulation of a barley cold-regulated protein of 75kDa (COR 75) has been investigated in several genotypes featuring contrasting frost tolerance capacity. COR 75 is accumulated at low temperatures, suggesting its involvement in the development of frost resistance. COR 75 is accumulated faster during the first days at low temperature in frost resistant varieties when compared with extremely sensitive varieties; nevertheless after 7 days of hardening, COR 75 is expressed at the same level in all genotypes tested despite their differences in frost tolerance. Besides low temperature, COR 75 can also be induced by ABA or drought stress indicating that this protein may be a general response to variation in tissue moisture status. Using a polyclonal antibody raised against COR 75, it has been demonstrated that this protein is immunologically related to two wheat cold-regulated proteins of 160 and 200 kDa. The role of COR 75 in the development of hardening is discussed.

Influence of soil substrate and ozone plus acid mist on the frost resistance of young Norway spruce

The needles of clonal Norway spruce grown in environmental chambers on two different soils (an acidic soil 1 and a calcareous soil 2) and exposed to two levels of ozone fumigation (a low level combined with neutral mist = control, and an elevated one combined with acid mist = treatment) were analyzed for their frost hardiness. No effect of ozone was observed on either the development of frost resistance during the hardening phase or on the decrease in frost resistance during the dehardening phase. The preliminary results of Brown et al. (1987) and Barnes and Davidson (1988), which indicated that ozone treatment predisposes plants to winter injury, could thus not be confirmed. Frost resistance was, however, distinctly influenced by the content of the mineral nutrients of the soils. The pronounced K + deficiency of the needles of the trees growing on the neutral soil (Alps) had less effect on the development of frost resistance than did the Ca ++ and Mg ++ deficiency of the needles of the trees grown on the acidic soil 1 (Bavarian Forest). The variability of frost resistance between the different clones on soil 1 was partly attributed to fluctuations in the mineral nutrient content of the needles, rather than to a genetic predisposition.

Frost Resistance in Spruce (Picea abies (L.) Karst.): V. Influence of Photoperiod and Temperature on the Membrane Lipids of the Needles

Summary Frost resistance of spruce needles is regulated by the environmental factors temperature and photoperiod. The frost resistant stage of spruce needles is characterized i.a. by a high content of cell membrane lipids containing a high proportion of unsaturated fatty acids. To investigate the possibility of a causal relationship between the extent of frost resistance and a characteristic lipid composition of cell membranes, the needles of small spruce trees which had been cultivated under different combinations of photoperiod and temperature at least for 3 years were analyzed with respect to their frost resistance and membrane lipids and compared to the data obtained from needles of a spruce tree growing under natural conditions. An increase in the content of the membrane lipids and in the degree of unsaturation of their fatty acids could never be separated from the development of frost resistance, even when the regulating environmental factors were combined in an artificial manner. Changes in lipid metabolism took place in an at least two-step process, corresponding to successive phases of frost hardening. A first, short day length-dependent step was characterized by an augmentation of membrane lipids, in particular of phospholipids. A second step induced by subzero temperatures featured a preferential incorporation of polyunsaturated fatty acids into the membrane lipids. The regulation of the metabolism of membrane lipids on the basis of phytohormone balance is discussed.