Salt Stress-Induced Structural Changes Are Mitigated in Transgenic Tomato Plants Over-Expressing Superoxide Dismutase

Abstract

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.

Regulation of Reactive Oxygen Species and Antioxidant Defense in Plants under Salinity

“…Due to the close proximity to the saline-affected soil, salt-induced roots were seen to be hampered by the disrupted nuclei and nuclear membrane of T. aestivum [75]. Similar results were recorded in S. lycopersicum [76], where salinity changed the root structure through decreasing different layers of the columella, cortex cells and cell sizes and enlarging cell nucleoli, ultimately leading to transforming the cell shape and vacuoles. Interestingly, salt-induced Brassica napus roots were seen to produce an apoplastic barrier near the root apex to moderate the over-accumulated toxic ions [77].…”

Effect of Sodium Chloride Stress on the Adaptation of Zea mays Seedlings at the Expense of Growth

“…The data showed similar results, however, interestingly the chlorophyll content increased with the increasing salt concentration as the seedlings adapted to the salt stress. Similar results were reported by (Bogoutdinova et al, 2020), meanwhile, there is an opposite aspect obtained from the experiment that few surviving seedlings of maize had low electrolytic leakage and high-water content whereas salinity promotes the electrolytic leakage as concluded by Abdelaal et al, (2020). This low electrolyte leakage and retention of high water contents may be an adaptive edge of the maize cultivar (Hycorn 984) to the salinity stress that has induced survival instincts of the seedlings at the expense of vegetative growth.…”

Microtubule Dynamics Plays a Vital Role in Plant Adaptation and Tolerance to Salt Stress

“…ROS induces the MTs’ reorganization through MT disassembly and the formation of irregular MT polymers [ 19 ]. When ROS homeostasis is collapsed by salt stress, tubulin forms a modified structural state by assembling non-typical tubulin structures [ 22 ]. Propyzamide-hypersensitive 1 (PHS1), a mitogen-activated protein kinase phosphatase, phosphorylates α-tubulin and elevates MT depolymerization to salt stress [ 23 ].…”