Vol 65, No 2 (2018)

The dim1⁺ gene family is essential for G2/M transition during mitosis and encodes a small nuclear ribonucleoprotein that functions in the mRNA splicing machinery of eukaryotes. However, the plant homolog of DIM1 gene has not been defined yet. Here, we identified a gene named GmDim1 positioned on chromosome 9 of soybean (Glycine max (L.) Merr.) with 80% homology to other eukaryotic dim1⁺ family genes. A domain of soybean DIM1 protein was primarily conserved with U5 snRNP protein family and secondarily aligned with mitotic DIM1 protein family. The GmDim1 gene was expressed constitutively in all soybean organs. The transgenic Arabidopsis thaliana (L.) plants overexpressing GmDim1 showed early flowering and stem elongation, produced multiple shoots and continued flowering after the post-flowering stage. DIM1 proteins transiently expressed in onion cells were localized in the nucleus with dense deposition in the nucleolus. Therefore, we propose that the soybean GmDim1 gene is a component of plant U5 snRNP involved in mRNA splicing and normal progress of plant growth.

The peculiarities of root growth and stress tolerance of transgenic tobacco plants with constitutive expression of NtEXPA1 and NtEXPA5 genes, as well as plants with reduced expression of NtEXPA4 gene encoding α-expansins of Nicotiana tabacum, were studied during prolonged cultivation under conditions of drought, salinity, and low positive temperatures. Increased expression of expansin genes led to an increase in the growth rate and root length both under normal plant growth conditions and at 12°C and 50 mM NaCl. Increased expression of expansin genes influenced the changes in the fresh and dry mass of a shoot, leading to an increase in their exposure to hypothermia. Transgenic plants with a reduced level of NtEXPA4 expansin gene expression were characterized by a reduction in the fresh and dry weight of a shoot due to drought and low positive temperatures. The totality of the data obtained may indicate the involvement of NtEXPA1, NtEXPA4, and NtEXPA5 tobacco expansin genes in the regulation of growth under hypothermia, drought, and salinity.

Verticillium wilt (V. wilt), a notorious wilt disease caused by Verticillium dahliae, often leads to the reduction of eggplant (Solanum melongena L.) production. MiRNAs, as a class of small RNAs, can regulate gene expression and then affect growth and development in plants. MiR395 has been proven to respond to sulfate-deficient stress in Arabidopsis thaliana and sulfate is well known to have a close relationship with plant disease resistance. To explore the function of eggplant miR395, we examined its expression in V. dahliae-infected eggplant by qRT-PCR and found miR395 exhibited a gradual reduction trend with time after infection. We then expressed pre-miR395 from Arabidopsis thaliana in Suqi eggplant and resistance analysis showed that miR395 overexpressed plants were hypersensitive to V. dahliae infection. We further measured the content of GSH and activities of POD and SOD and the results indicated that the index of GSH/POD/SOD in the overexpressed plants was lower than that of the wild-type control under V. dahliae infection. These results suggest that miR395 plays a negative role in eggplant response to V. dahliae infection.

Nitric oxide (NO) effects on heat resistance of wheat (Triticum aestivum L.) coleoptiles induced by 24-epibrassinolide (24-EB) have been investigated. Coleoptiles’ survival after damaging heating (43°С, 10 min) increased when they were treated preliminarily with 5–200 nM of 24-EB. After 24-EB treatment, transient amplification of nitric oxide (NO) and also ROS (superoxide anion-radical (O₂^•−) and hydrogen peroxide) generation by coleoptiles was noted. Coleoptiles pretreatment with inhibitors of nitrate reductase and an enzyme similar to animal NO-synthase partially removed the increase of NO content caused by the action of 24-EB. Amplification of superoxide anion-radical generation caused by 24-EB was depressed under the influence of imidazole (NADPH-oxidase inhibitor). Calcium antagonists (EGTA and neomycin) largely neutralized the 24-EB-induced increase in generation of both O₂^•− and NO. The increase in NO content in coleoptile tissues caused by 24-EB was almost completely leveled by antioxidants and partly by imidazole. 24-EB-induced enhancement of the superoxide anion-radical generation was partially suppressed by the action of NO scavenger PTIO (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) and the inhibitors of nitrate reductase and an enzyme similar to animal NO-synthase. Positive 24-EB effect on the heat resistance of wheat coleoptiles was leveled by PTIO, inhibitors of enzymes that generate NO, antioxidants, an inhibitor of NADPH-oxidase imidazole, and calcium antagonists. A conclusion was made on the role of NO in brassinosteroid signal transduction inducing heat resistance development of coleoptiles and on the functional interaction between NO, ROS, and calcium ions as the signal mediators.

greenhouse experiment with factorial arrangement based on randomized complete block design with four replications was conducted in 2015 to evaluate the effects of salicylic acid (SA) (1 mM) and jasmonic acid (JA) (0.5 mM) on oil accumulation and fatty acid composition of soybean oil (Glycine max L.) under salt stress (Non-saline, 4, 7, and 10 dS/m NaCl). Oil percentage of soybean seeds declined, while oil content per seed enhanced with increasing seed filling duration. Foliar application of SA improved oil content per soybean seed at different stages of development under all salinity levels. Although JA treatment enhanced seed oil percentage, oil yield of these plants decreased as a result of reduction in seed yield per plant. In contrast, the highest oil yield was recorded for SA treated plants, due to higher seed yield. Salinity had no significant effects on percentage of palmitic acid and stearic acid, but treatment with JA significantly reduced stearic acid percentage. Oleic acid content of seeds increased, but percentages of linoleic acid, linolenic acid and unsaturation index (UI) of soybean oil decreased with increasing salinity. Foliar application of SA and JA improved oil quality of soybean seeds by reducing oleic acid and enhancing linoleic acid, linolenic acid contents and UI. Exogenous application of SA had the most beneficial effects on soybean seeds due to enhancing oil yield and quality under saline and non-saline conditions.

Seedling stage is a critical period for survival and growth under drought stress. In the current study, we determined effects of drought stress on physiological and biochemical parameters of leaves and roots of Lycium ruthenicum Murr. seedling. The variables measured were lipid peroxidation (in terms of malondialdehyde (MDA) content), osmotic substances (free proline, soluble protein, and soluble sugar), and antioxidative enzymes (peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT)). Free proline, soluble sugar, and MDA of leaves and roots increased with increasing stress level. Leaves displayed higher accumulations of free proline and MDA than roots. However, roots showed higher total soluble sugar than leaves. Under drought stress, soluble proteins in leaves and roots decreased initially and then increased. Meanwhile, measured proteins were higher in leaves. Under drought stress, SOD, POD, and CAT activities in leaves increased initially and then decreased but increased with increasing drought stress level in roots. Under drought the level of accumulation of osmotics was higher in the leaves than in the roots, while increased activity of antioxidant enzymes persisted in the stressed roots longer that in the leaves.

We studied the effect of cadmium and nickel on Sinapis alba L. plants inoculated with endophytic strains of Bacillus subtilis. It was shown that treatment of S. alba seeds with endophytic strains of bacteria B. subtilis improves plant resistance to the toxic effect of cadmium and nickel and reduces manifestation of oxidative stress in the presence of higher levels of metal ions in the above-ground part of plants. Anti-stress effect and the ability of endophytic strains of B. subtilis to intensify uptake of cadmium and nickel ions by S. alba plants may be used for phytoextraction of heavy metals and stimulation of plant growth in contaminated areas.

We investigated the response of chilling-sensitive plants of cucumber (Cucumis sativus L.) to prolonged permanent (6 days) (PLT) and short-term (3 h) daily exposures to low non-freezing temperatures (9 and 12°С) (DROP) lying on different sides of the critical value (10°С) corresponding to a phase transition of membrane lipids in chilling-sensitive plants from a liquid-crystalline to a solid gel structure. Effects and aftereffects of DROP treatments at temperatures of 9 and 12°С (DROP9 and DROP12, respectively) were identical. They caused a reduction in linear dimensions of plants (as compared with control plants) and enhanced chilling tolerance of leaves but did not influence photosynthetic activity and water relations. However, when exposure to these temperatures was permanent (PLT9 and PLT12), their effects on plants were different. PLT9 almost entirely suppressed plant growth and development, inactivated photosynthetic apparatus (PSA), increased relative electrolite leakage (REL), and boosted lipid peroxidation (LPO). PLT12 also considerably reduced plant height and leaf area and suppressed (but did not inactivate) PSA; it did not boost POL or increased REL. It is important that, after the termination of chilling, PLT9 plants (unlike PLT12 plants) could not quickly resume growth and restore photosynthetic activity. Thus, considerable differences in plant responses to various patterns of chilling (long permanent or short-term daily) are probably due to the fact that, in the case of DROP treatments, relatively short-term (3 h) chilling of plants is followed in the diurnal cycle by a prolonged period (21 h) of optimal temperature when possible deviations and/or disturbances of PSA are restored and toxic substances that could accumulate in the course of chilling metabolized and/or neutralized. Pronounced differences in plant response to permanent exposure to temperatures of 9 and 12°С probably depend on the fact that these temperatures lie on different sides of a critical value (10°С) below which chilling-sensitive plants suffer grave physiological disturbances due to cooling. In addition, we showed that different responses of plants to PLT and DROP treatments are not determined by a usual dose-effect relationship but depend in many respects on the pattern of temperature influence (prolonged or short-term, single or recurring). As a result, the number of DROP spans experienced by plants in the experiments proved to be more important than their duration (at least, within a time interval from 2 to 12 h).

Strigolactones (SLs) are signal molecules of a butenolide nature from the apocarotenoids family that are synthesized by plant organisms. They are widely propagated in nature and control different aspects of plant development, which allows us to consider them as phytohormones. It is known that SLs production and release into the rhizosphere are enhanced under a deficit of basic elements of plant nutrition. In addition, these compounds carry out the signaling function in the course of establishing supraorganismal relationships upon parasitism and symbiosis. In this review, the role of SLs in the formation of arbuscular mycorrhiza (AM), which provides a symbiotic pathway of P_i uptake by plants and partly nitrogen-fixing legume nodules, is examined. The data on SLs impact on AM fungi (AMFs) development at presymbiotic and symbiotic stages of plant growth were generalized. The main peculiarities of SLs structure providing their efficiency as “branching factors” of AMF hyphae and basic mechanisms of the possible influence of SLs on AMFs, including stimulation of mitochondria biogenesis, were described. Analysis of these data and phenotypes of plant mutants with disturbances in SLs biosynthesis and its regulation and also SLs perception and transport leads to the conclusion that their role in AM development is predominantly revealed in induction of AMF hyphae branching at the presymbiotic plant growth stage and is associated with plant response to P_i deficit. Analysis of the role these components of common symbiotic signaling cascade play in the regulation of SLs biosynthesis in the course of AM development and nitrogen-fixing legumes nodules was carried out. An important role of SLs in nodule development likely caused by their endogenous influence on its organogenesis was demonstrated. A possibility of the presence of different pathways usable by a plant upon AM and nodule development for activation of common symbiotic transcriptional factors, NSP1 and NSP2, participating in the regulation of SLs biosynthesis is discussed. The data concerning structural specificity of SLs and the results of phylogenetic analysis of genes encoding different components of SLs biosynthesis and signaling pathways and also symbiotic signaling cascade in plants provide evidence for the possible transformation of SLs signaling function from the hormonal one manifested inside the plant into the communicative one providing the establishment of interorganismal relations.