Various abiotic stresses cause the appearance of reactive oxygen species (ROS) in plant cells, which seriously damage the cellular structures. The engineering of transgenic plants with higher production of ROS-scavenging enzyme in plant cells could protect the integrity of such a fine intracellular structure as the cytoskeleton and each cellular compartment. We analyzed the morphological changes in root tip cells caused by the application of iso-osmotic NaCl and Na₂SO₄ solutions to tomato plants harboring an introduced superoxide dismutase gene. To study the roots of tomato plants cultivar Belyi Naliv (WT) and FeSOD-transgenic line, we examined the distribution of ROS and enzyme-linked immunosorbent detection of α-tubulin. In addition, longitudinal sections of the root apexes were compared. Transmission electronic microscopy of atypical cytoskeleton structures was also performed. The differences in the microtubules cortical network between WT and transgenic plants without salt stress were detected. The differences were found in the cortical network of microtubules between WT and transgenic plants in the absence of salt stress. While an ordered microtubule network was revealed in the root cells of WT tomato, no such degree of ordering was detected in transgenic line cells. The signs of microtubule disorganization in root cells of WT plants were manifested under the NaCl treatment. On the contrary, the cytoskeleton structural organization in the transgenic line cells was more ordered. Similar changes, including the cortical microtubules disorganization, possibly associated with the formation of atypical tubulin polymers as a response to salt stress caused by Na₂SO₄ treatment, were also observed. Changes in cell size, due to both vacuolization and impaired cell expansion in columella zone and cap initials, were responsible for the root tip tissue modification.

ROS-dependent induction of oxidative damage can be used as a trigger initiating genetically determined non-specific protection in plant cells and tissues. Plants are potentially able to withstand various specific (toxic, osmotic) factors of abiotic effects, but do not have sufficient or specific sensitivity to form an adequate effective response. In this work, we demonstrate one of the possible approaches for successful cold acclimation through the formation of effective protection of photosynthetic structures due to the insertion of the heterologous FeSOD gene into the tobacco genome under the control of the constitutive promoter and equipped with a signal sequence targeting the protein to plastid. The increased enzymatic activity of superoxide dismutase in the plastid compartment of transgenic tobacco plants enables them to tolerate the oxidative factor of environmental stresses scavenging ROS. On the other hand, the cost of such resistance is quite high and, when grown under normal conditions, disturbs the arrangement of the intrachloroplastic subdomains leading to the modification of stromal thylakoids, probably significantly affecting the photosynthesis processes that regulate the efficiency of photosystem II. This is partially compensated for by the fact that, at the same time, under normal conditions, the production of peroxide induces the activation of ROS detoxification enzymes. However, a violation of a number of processes, such as the metabolism of accumulation, and utilization and transportation of sugars and starch, is significantly altered, which leads to a shift in metabolic chains. The expected step for further improvement of the applied technology could be both the use of inducible promoters in the expression cassette, and the addition of other genes encoding for hydrogen peroxide-scavenging enzymes in the genetic construct that are downstream in the metabolic chain.

The identification of reliable physiological and biochemical indicators for assessing tomato salt tolerance can increase the efficiency of plant breeding to create new varieties and lines. The purpose of our study was to identify available physiological and biochemical relevant characteristics for assessing the sensitivity to sodium chloride salinity of different tomato genotypes at the seedling stage. A complex analysis was carried out based on indicators such as biomass growth, water content of plant tissues, content of readily soluble salts, sodium and chlorine ions, photosynthetic pigments, carotenoids, phenolic compounds and flavonoids. Additionally, the stomata area of the upper and lower epidermis was taken into account. The comprehensive assessment carried out made it possible to reliably divide the eight studied tomato varieties into two groups: sensitive (Belyij Naliv, Geya, YaLF, Paradigma) and tolerant (Recordsmen, Yuryevskij, Bych’e Serdce, Astrakhanskij). Tomato genotypes that can be classified as sensitive (in order of increasing sensitivity to high concentrations of NaCl (150 mM)) were Belyij Naliv > Geya > YaLF ≥ Paradigma. Tomato genotypes that can be classified as resistant to salt stress (in order of increasing tolerance to high concentrations of NaCl (150 mM)) were Recordsmen < Yuryevskij < Bych’e Serdce < Astrakhanskij. The advisability of only using complex physiological and biochemical indicators to obtain relevant assessments for salinity tolerance at the early stages of tomato plant development has been demonstrated.

The study was devoted to morphological and cytoembryological analysis of disorders in the anther and pollen development of transgenic tomato plants with a normal and abnormal phenotype, which is characterized by the impaired development of generative organs. Various abnormalities in the structural organization of anthers and microspores were revealed. Such abnormalities in microspores lead to the blocking of asymmetric cell division and, accordingly, the male gametophyte formation. Some of the non-degenerated microspores accumulate a large number of storage inclusions, forming sterile mononuclear pseudo-pollen, which is similar in size and appearance to fertile pollen grain (looks like pollen grain). It was discussed that the growth of tapetal cells in abnormal anthers by increasing the size and ploidy level of nuclei contributes to this process. It has been shown that in transgenic plants with a normal phenotype, individual disturbances are also observed in the development of both male and female gametophytes. The reason for the developmental arrest of some ovules was the death of endosperm at different stages of the globular embryo. At the same time, noticeable hypertrophy of endothelial cells performing a secretory function was observed. In the ovules of transgenic plants with abnormalities, the endothelium forms a pseudo-embryo instead of the embryo sac, stimulating the development of parthenocarpic fruits. The data obtained in this study can be useful for a better understanding of the genetic and molecular mechanisms of cytoplasmic male sterility and parthenocarpic fruit development in tomatoes.

Understanding the mechanisms of plant salt tolerance as a complex trait is an integral part of many studies, the results of which have been used in the breeding process. The aim of this study was to compare the root response of two tomato (Solanum lycopersicum L.) genotypes (breeding line YaLF and cultivar Recordsmen) differing in salt tolerance. Rhizogenesis was induced in tomato shoots in vitro with different concentrations of NaCl in the culture medium. A number of morphobiological and cytological parameters were evaluated at the organ, tissue, and cellular levels for possible use in a comprehensive assessment of genotypes for salt tolerance. The influence of NaCl caused disruption of the cell cycle and redistribution of cells in the phases of the cell cycle. An increase in the degree of vacuolization was shown in cv Recordsmen at 75 and 150 mM NaCl and in the YaLF line at 150 mM NaCl. Under salt action, an increase/decrease in the length of cells such as columella cells (both genotypes) and epidermal cells (in cv Recordsmen at 75 and 150 mM NaCl) was shown. Differences between genotypes were demonstrated by changes in the area of the central cylinder and primary root cortex cells, as well as by changes of the S_nucleolus/S_nucleus ratio in these cells. Transmission electron microscopy (TEM) showed the modification of the chromatin structure in the root cells of these genotypes. Various cytoskeletal disorders were revealed in interphase cells of the tomato root of cv Recordsmen and the YaLF line by immunofluorescent staining under saline conditions. These morphometric and cytological parameters can be used for a comparative evaluation of genotypes differing in salt tolerance in a comprehensive assessment of varieties.

The integumentary tissues of plant seeds protect the embryo (new sporophyte) forming in them from unfavorable external conditions; therefore, comprehensive knowledge about the structural and functional specificity of seed covers in various plants may be of both theoretical and practical interest. As a result of our study, additional data were obtained on the morphological and ultrastructural features of the formation of a multilayer skin of wheat (Triticum aestivum L.) kernel (caryopsis). The ultrastructure research analysis showed that differentiation of the pericarp and inner integument of the ovule leads to the formation of functionally different layers of the skin of mature wheat grain. Thus, the differentiation of exocarp and endocarp cells is accompanied by a significant thickening of the cell walls, which reliably protect the ovule from adverse external conditions. The cells of the two-layer inner integument of the ovule differentiate into cuticular and phenolic layers, which are critical for protecting daughter tissues from various pathogens. The epidermis of the nucellus turns into a layer of mucilage, which apparently helps to maintain the water balance of the seed. Morphological and ultrastructural data showed that the formation of the kernel’s skin occurs in coordination with the development of the embryo and endosperm up to the full maturity of the kernel. This is evidenced by the structure of the cytoplasm and nucleus, characteristic of metabolically active protoplasts of cells, which is observed in most integumentary layers at the late stages of maturation. This activity can also be confirmed by a significant increase in the thickness of the cell walls in the cells of two layers of the exocarp and in cross cells in comparison with the earlier stages. Based on these results, we came to the conclusion that the cells of a majority in the covering tissues of the wheat kernel during its ontogenesis are transformed into specialized layers of the skin by terminal differentiation.