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

Liliya R Bogoutdinova,Ludmila V Kurenina,Tatyana Dilovarova,Elena M Lazareva,Neonila V Kononenko,Ekaterina N Baranova,Marat R Khaliluev,Elena A Smirnova,Alexander A Gulevich,Inna A Chaban

doi:10.3390/biology9090297

Abstract

Simple SummaryWe 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 and FeSOD-transgenic line, we examined the distribution of reactive oxygen species and immunodetection of α-tubulin. The differences in the microtubules cortical network between wild type and transgenic plants without salinity were detected. The differences were found in the cortical network of microtubules between control and transgenic plants in the absence of salt stress. While an ordered microtubule network was revealed in the root cells of wild type tomato, no such degree of ordering was detected in transgenic line cells. The signs of microtubule disorganization in root cells of wild type plants were manifested under the NaCl and Na2SO4 treatment. On the contrary, the cytoskeleton structural organization in the transgenic line cells was more ordered. In addition, the formation of atypical tubulin polymers was observed in response to salt stress. 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.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.

Highlights

Plant protection from the damaging effects of oxidative stress is an urgent problem of plant physiology and biotechnology
The root tips of the tomato plants cv Belyi Naliv (WT) and the transgenic line 19 obtained on this variety basis corresponded to the type of structural organization typical for tomatoes (Figure 1)
The root meristem has a clear-cut structure that makes it easy to identify the cells of the developing tissues of the exoderm, cortex, pericycle and stele with a common for normal conditions, reduced level of vacuolization in small cells with large nuclei and nucleoli located in the center of the cells (Figure 1)

Summary

Introduction

Plant protection from the damaging effects of oxidative stress is an urgent problem of plant physiology and biotechnology. Many abiotic and biotic factors cause a stress response in plants, during which the production level of reactive oxygen species (ROS) in cells increases, causing a state of oxidative stress [1]. A ROS homeostasis violation induces a reorganization of the microtubule cytoskeleton, which leads to impaired mitosis and cytokinesis [2,3]. This process at first caused the microtubules disassembly, and the formation of abnormal tubulin polymers (macrotubules and paracrystalline aggregates) [2]. Similar changes in the tubulin cytoskeleton were demonstrated under the various abiotic stresses [4]

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Conclusion