Exogenous proline and glycinebetaine increase antioxidant enzyme activities and confer tolerance to cadmium stress in cultured tobacco cells

Up-regulation of antioxidant and glyoxalase systems by exogenous glycinebetaine and proline in mung bean confer tolerance to cadmium stress

“…3g). Decreases in CAT activity due to Cd stress were also reported in various plant species (Romero-Puertas et al 2006;Hu et al 2009;Islam et al 2010). But both proline-and betaine-supplemented Cdstressed seedlings also had decreased CAT activity indicating that both are unable to increase CAT activity under severe Cd stress condition.…”

“…However, the mechanisms by which proline and betaine protect plant cells under heavy metal stress have remained unsolved. Recent studies in plants have demonstrated that exogenous application of betaine or proline at high concentration (1-20 mM) enhance tolerance to abiotic oxidative stress (Park et al 2006;Hoque et al 2007;Huang et al 2009;Islam et al 2010;Hossain and Fujita 2010). Extensive research findings support the idea that coordinated induction and regulation of the antioxidant and glyoxalase pathway enzymes are necessary to obtain substantial tolerance against oxidative stress.…”

“…At the cellular level, Cd interacts with biomolecules such as protein and nucleic acids, is known to affect the enzyme activities and causes alterations in membrane permeability (Smeets et al 2008). In addition, Cd stress is known to disturb redox homeostasis in plant cells and induce a burst of reactive oxygen species (ROS) (Hsu and Kao 2007a, b;Popova et al 2009;Nouairi et al 2009;Islam et al 2010). ROS are necessary for inter-and intracellular signalling but at high concentrations they seriously disrupt normal metabolism leading to irreparable metabolic dysfunction and death (Gechev et al 2006).…”

“…The natural accumulation of proline/ betaine, however, is not high enough to protect plants from stress-induced damage (Subbarao et al 2001;Okuma et al 2002;Tamura et al 2003;Tamas et al 2008). Under such condition their exogenous application may help to reduce the adverse effects of various environmental stresses including Cd stress (Yang and Lu 2005;Kumar and Yadav 2009;Huang et al 2009;Islam et al 2010;Hossain and Fujita 2010). In addition to their roles as osmoprotectants, proline and betaine contribute to the protection of membranes, proteins and enzymes from the damaging effect of various stresses (Ashraf and Foolad 2007;Hossain and Fujita 2010).…”

“…Furthermore, betaine and proline provide protection against oxidative stress by maintaining redox homeostasis Hossain and Fujita 2010). Recently, it has been reported that betaine and proline alleviates Cd toxicity by detoxifying ROS and increasing antioxidant activity and GSH content in Solanum and tobacco BY-2 cells (Xu et al 2009;Islam et al 2010). To our knowledge, currently there is no information available on the possible beneficial effects of exogenous application of betaine and proline on MG detoxification system in plants grown under Cd stress.…”