Abstract
Antioxidant enzymes play a significant role in eliminating toxic levels of reactive oxygen species (ROS), generated during stress from living cells. In the present study, two different antioxidant enzymes namely copper-zinc superoxide dismutase derived from Potentilla astrisanguinea (PaSOD) and ascorbate peroxidase (RaAPX) from Rheum austral both of which are high altitude cold niche area plants of Himalaya were cloned and simultaneously over-expressed in Arabidopsis thaliana to alleviate cold stress. It was found that the transgenic plants over-expressing both the genes were more tolerant to cold stress than either of the single gene expressing transgenic plants during growth and development. In both single (PaSOD, RaAPX) and double (PaSOD + RaAPX) transgenic plants higher levels of total antioxidant enzyme activities, chlorophyll content, total soluble sugars, proline content and lower levels of ROS, ion leakage were recorded when compared to the WT during cold stress (4°C), besides increase in yield. In the present study, Confocal and SEM analysis in conjunction with qPCR data on the expression pattern of lignin biosynthetic pathway genes revealed that the cold stress tolerance of the transgenic plants might be because of the peroxide induced up-regulation of lignin by antioxidant genes mediated triggering.
Highlights
Abiotic stresses such as cold, drought, metal and salt stress are the major factors adversely affecting development and productivity in plants
It is commonly known that lignin evolved together with the plants adaptation to a terrestrial life to provide them with the structural support needed for an erect growth habit
Plasmid construction and plant transformation Full length cDNAs of Copper-Zinc Superoxide Dismutase (PaSOD) and Ascorbate Peroxidase from high altitude plants Potentilla atrosanguinea and Rheum australe (Rohtang Pass in Himachal Pradesh: altitude 4000 m; 32u 229 190 N; 077u 149 460 E), respectively, from Western Himalaya, were cloned in Arabidopsis thaliana as described earlier by Gill et al [14]
Summary
Abiotic stresses such as cold, drought, metal and salt stress are the major factors adversely affecting development and productivity in plants. Metabolic activities in various cellular compartments lead to the production of reactive oxygen species (ROS) such as superoxide anion (O22), hydrogen peroxide (H2O2), hydroxyl radical (OH?), and singlet oxygen (O2) [1]. These ROS are highly toxic, and are taken care of by the antioxidant system in the living cells. SOD (EC1.15.1.1) is the first enzyme in the plant’s antioxidative defense mechanism that converts superoxide anion radicals (O2.-) to hydrogen peroxide (H2O2) and water, thereby imparting protection against the harmful effects of highly reactive superoxide radical (O2.-).
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