Improved tolerance of Cu/Zn superoxide dismutase and ascorbate peroxidase expressing transgenic tobacco seeds and seedlings against multiple abiotic stresses

Abstract

Reactive oxygen species (ROS) are produced during seed germination but remain under-control in optimum germination conditions. Seeds being germinated in single or multiple stress conditions such as drought, excessive salt and low-temperature may face burst of ROS, which leads to poor germination and weak seedling establishment. Enzymatic activities, germination rates and seedling growth of the seeds of transgenic tobacco plants simultaneously expressing Cu/Zn-superoxide dismutase (CuZnSOD) and ascorbate peroxidase (APX) in plastids (CA seeds) under various combinations of environmental stresses (drought, salt and low temperature) were investigated and compared with the non-transgenic seeds (NT seeds). CA seeds maintained higher CuZnSOD and APX activities during seed imbibitions than NT seeds. CA seeds depicted less ion leakage after salt stress than NT seeds providing the evidence of proper functioning of CuZnSOD and APX to keep ROS production under control. When germinated in stress conditions, CA seeds germinated earlier than NT seeds and this character was more profound under double or triple stress conditions. Moreover, CA seedlings accumulated more shoot and root dry weight as compared to NT seedlings under single, double and triple stress conditions. These investigations strongly suggest that overexpression of CuZnSOD and APX helped CA seeds to keep ROS under control by detoxifying superoxide radicals and H2O2, which paved the way for increased germination and seedling growth in various combinations of environmental stresses.