Abstract
Environmental stresses generate reactive oxygen species (ROS) which might be detrimental to the plants when produced in an uncontrolled way. However, the plants ameliorate such stresses by synthesizing antioxidants and enzymes responsible for the dismutation of ROS. Additionally, the dehydrins were also able to protect the inactivation of the enzyme lactate dehydrogenase against hydroxyl radicals (OH⋅) generated during Fenton’s reaction. SbDhn1 and SbDhn2 overexpressing transgenic tobacco plants were able to protect against oxidative damage. Transgenic tobacco lines showed better photosynthetic efficiency along with high chlorophyll content, soluble sugar and proline. However, the malonyl dialdehyde (MDA) content was significantly lower in transgenic lines. Experimental evidence demonstrates the protective effect of dehydrins on electron transport chain in isolated chloroplast upon methyl viologen (MV) treatment. The transgenic tobacco plants showed significantly lower superoxide radical generation () upon MV treatment. The accumulation of the H2O2 was also lower in the transgenic plants. Furthermore, in the transgenic plants the expression of ROS scavenging enzymes was higher compared to non-transformed (NT) or vector transformed (VT) plants. Taken together these data, during oxidative stress dehydrins function by scavenging the () directly and also by rendering protection to the enzymes responsible for the dismutation of () thereby significantly reducing the amount of hydrogen peroxides formed. Increase in proline content along with other antioxidants might also play a significant role in stress amelioration. Dehydrins thus function co-operatively with other protective mechanisms under oxidative stress conditions rendering protection in stress environment.
Highlights
Several environmental situations such as drought, salinity, temperature variation are the major stress factors, which hamper plant growth throughout their life cycle
Generation of reactive oxygen species (ROS) during oxidative conditions leads to damaging effect to the membranes and biomolecules
The hydroxyl radicals are more reactive compared to the superoxides and hydrogen peroxide (H2O2), thereby readily attacking the lipids, nucleic acids, and proteins at, or close to, the site of their formation (Halliwell and Gutteridge, 1990; Asada, 1994)
Summary
Several environmental situations such as drought, salinity, temperature variation are the major stress factors, which hamper plant growth throughout their life cycle. In order to ward off the oxidative damage in plants, a number of mechanisms orchestra together to handle the oxidative stress conditions This is generally achieved by production of antioxidants and radical scavengers along with an increase in enzymes responding to dismutation of free radicals. Previous reports showed an increase in SOD, POX, and CAT activity in overexpressed dehydrin plants which showed enhanced tolerance under oxidative stress conditions (Liu et al, 2017). In this current study two dehydrin genes, SbDhn Overexpression of dehydrin genes in transgenic tobacco plants showed better physiological conditions as compared to that of NT and VT plants
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