Salt Tolerance Assessment in Triticum Aestivum and Triticum Durum.

BACKGROUND: Salt stress is a multicomponent phenomenon; it includes many processes that directly or indirectly affect the plant. Attempts have been made to comprehensively consider the processes of salt stress in plants Triticum aestivum (variety Orenburgskaya 22) and Triticum durum (variety Zolotaya). METHODS: The study used methods of light and fluorescence microscopy, methods of immunofluorodetection, expression of DNA methyltransferase genes, genes of the ion transporter and superoxide dismutase families, as well as biochemical determination of total antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) reagent. RESULTS: According to morphometric indicators, the Orenburgskaya 22 variety showed greater tolerance to the action of 150 mM NaCl than the Zolotaya variety. The level of expression of genes of the HKT ion transporter family in the Orenburgskaya 22 variety is higher than in the Zolotaya variety. It was found that the expression of the DNA methyltransferase gene DRM2.1, which post-translationally methylates cytosine residues, is 22.3 times higher in Zolotaya compared to Orenburg 22 when exposed to salt. The accumulation of toxic ions is accompanied by an increase in reactive oxygen species (ROS) and increased damage to root tissue, especially in the Zolotaya variety. Using fluorescence microscopy using the Carboxy-H2DFF marker in the Orenburgskaya 22 variety at high NaCl concentrations, the highest fluorescence intensity was determined in the cap zone; in the Zolotaya variety-in the zones of the cap and root meristem. Excess ROS is more successfully removed in the Orenburgskaya 22 variety, which has a higher level of antioxidant activity (AOA), as well as the level of expression of the Cu/ZnSOD and MnSOD superoxide dismutase genes. Using programmed cell death (PCD) markers based on the release of cytochrome c from mitochondria into the cytoplasm, DNA breakage and the release of phosphatidylserine from mitochondria, the degree of damage to root cells was assessed in both wheat varieties. It has been proven that wheat cell death occurs through the mitochondrial pathway. It was noted that the salt-sensitive variety Zolotaya had a significant number of necrotic cells. CONCLUSION: Based on the data obtained, it was concluded that the Orenburgskaya 22 variety exhibits greater resistance to salinity than the Zolotaya variety. These data may be of practical importance for enhancing protective mechanisms under abiotic stress.

Mechanisms of Antioxidant Resistance in Different Wheat Genotypes under Salt Stress and Hypoxia.

Various stressors lead to an increase in ROS and damage to plant tissues. Plants have a powerful antioxidant system (AOS), which allows them to neutralize excess ROS. We detected an intense fluorescent glow of ROS in the cells of the cap, meristem, and elongation zones in the roots of wheat Triticum aestivum (Orenburgskaya 22 variety) and Triticum durum (Zolotaya variety). An increase in ROS was accompanied by DNA breaks in the nuclei of wheat root cells, the release of cytochrome c from mitochondria into the cytoplasm, and the translocation of phosphatidylserine into the outer layer of the plasma membrane under salt stress and hypoxia. The different resistances of the two wheat varieties to different abiotic stresses were revealed. The soft wheat variety Orenburgskaya 22 showed high resistance to salt stress but sensitivity to hypoxia, and the durum wheat variety Zolotaya showed tolerance to hypoxia but high sensitivity to salt stress. Different activations of AOS components (GSH, MnSOD, Cu/ZnSOD, CAT, PX, GPX, and GST) were revealed in different wheat genotypes. The basis for the tolerance of the Zolotaya variety to hypoxia is the high content of glutathione (GSH) and the activation of glutathione-dependent enzymes. One of the mechanisms of high resistance to salt stress in the Orenburgskaya 22 variety is a decrease in the level of ROS as a result of the increased activity of the MnSOD and Cu/ZnSOD genes. Identifying the mechanisms of plant tolerance to abiotic stress is the most important task for improving breeding varieties of agricultural plants and increasing their yield.

Molecular Mechanisms of Regulation of Root Development by Plant Peptides.

Peptides perform many functions, participating in the regulation of cell differentiation, regulating plant growth and development, and also involved in the response to stress factors and in antimicrobial defense. Peptides are an important class biomolecules for intercellular communication and in the transmission of various signals. The intercellular communication system based on the ligand-receptor bond is one of the most important molecular bases for creating complex multicellular organisms. Peptide-mediated intercellular communication plays a critical role in the coordination and determination of cellular functions in plants. The intercellular communication system based on the receptor-ligand is one of the most important molecular foundations for creating complex multicellular organisms. Peptide-mediated intercellular communication plays a critical role in the coordination and determination of cellular functions in plants. The identification of peptide hormones, their interaction with receptors, and the molecular mechanisms of peptide functioning are important for understanding the mechanisms of both intercellular communications and for regulating plant development. In this review, we drew attention to some peptides involved in the regulation of root development, which implement this regulation by the mechanism of a negative feedback loop.

Elongating Effect of the Peptide AEDL on the Root of Nicotiana tabacum under Salinity.

The overall survival of a plant depends on the development, growth, and functioning of the roots. Root development and growth are not only genetically programmed but are constantly influenced by environmental factors, with the roots adapting to such changes. The peptide AEDL (alanine-glutamine acid-asparagine acid-leucine) at a concentration of 10-7 M had an elongating effect on the root cells of Nicotiana tabacum seedlings. The action of this peptide at such a low concentration is similar to that of peptide phytohormones. In the presence of 150 mM NaCl, a strong distortion in the development and architecture of the tobacco roots was observed. However, the combined presence of AEDL and NaCl resulted in normal root development. In the presence of AEDL, reactive oxygen species (ROS) were detected in the elongation and root hair zones of the roots. The ROS marker fluorescence intensity in plant cells grown with AEDL was much lower than that of plant cells grown without the peptide. Thus, AEDL protected the root tissue from damage by oxidative stress caused by the toxic effects of NaCl. Localization and accumulation of AEDL at the root were tissue-specific. Fluorescence microscopy showed that FITC-AEDL predominantly localized in the zones of elongation and root hairs, with insignificant localization in the meristem zone. AEDL induced a change in the structural organization of chromatin. Structural changes in chromatin caused significant changes in the expression of numerous genes associated with the development and differentiation of the root system. In the roots of tobacco seedlings grown in the presence of AEDL, the expression of WOX family genes decreased, and differentiation of stem cells increased, which led to root elongation. However, in the presence of NaCl, elongation of the tobacco root occurred via a different mechanism involving genes of the expansin family that weaken the cell wall in the elongation zone. Root elongation of plants is of fundamental importance in biology and is especially relevant to crop production as it can affect crop yields.

Short Peptides Induce Development of Root Hair Nicotiana tabacum.

Root hairs absorb soil nutrients and water, and anchor the plant in the soil. Treatment of tobacco (Nicotiana tabacum) roots with glycine (Gly) amino acid, and glycilglycine (GlyGly) and glycilaspartic acid (GlyAsp) dipeptides (10-7 M concentration) significantly increased the development of root hairs. In the root, peptide accumulation was tissue-specific, with predominant localization to the root cap, meristem, elongation zone, and absorption zone. Peptides penetrated the epidermal and cortical cell and showed greater localization to the nucleus than to the cytoplasm. Compared with the control, tobacco plants grown in the presence of Gly, GlyGly, and GlyAsp exhibited the activation of WER, CPC, bHLH54, and bHLH66 genes and suppression of GTL1 and GL2 genes during root hair lengthening. Although Gly, GlyGly, and GlyAsp have a similar structure, the mechanism of regulation of root hair growth in each case were different, and these differences are most likely due to the fact that neutral Gly and GlyGly and negatively charged GlyAsp bind to different motives of functionally important proteins. Short peptides site-specifically interact with DNA, and histones. The molecular mechanisms underlying the effect of exogenous peptides on cellular processes remain unclear. Since these compounds acted at low concentrations, gene expression regulation by short peptides is most likely of epigenetic nature.

Wheat endonuclease WEN1 dependent on S-adenosyl-L-methionine and sensitive to DNA methylation status.

Ca(2+)-, Mg(2+)-dependent wheat endonuclease WEN1 with molecular mass of about 27 kDa was isolated from coleoptyles. Methylated DNA of lambda phage grown on E. coli dam(+), dcm(+) cells was hydrolyzed by WEN1 more effectively than DNA of phage grown on dam(-), dcm(-) cells. Two pH activity maxima (pH 6.5-7.5 and 9.0-10.5) were observed when double-stranded DNA was hydrolyzed. WEN1 is stable at elevated temperatures (65 degrees C ) and in wide range of pH values. WEN1 is activated by S-adenosyl-L-methionine, S-adenosyl-L-homocysteine and S-isobutyladenosine. It is a first case to show that higher eukaryote endonuclease discriminates between DNA of various methylation status and is modulated by S-AdoMet and its analogs.

N(6)-Adenine DNA-methyltransferase in wheat seedlings.

The N(6)-adenine DNA-methyltransferase was isolated from the vacuolar vesicle fraction of wheat coleoptiles. In the presence of S-adenosyl-L-methionine the enzyme de novo methylates the first adenine residue in the TGATCA sequence in the single- or double-stranded DNA substrates but it prefers single-stranded structures. Wheat adenine DNA-methyltransferase (wadmtase) is a Mg(2+)- or Ca(2+)-dependent enzyme with a maximum activity at pH 7.5-8.0. Wadmtase seems to be responsible for mitochondrial DNA modification that might be involved in the regulation of replication of mitochondria in plants.