The SbMT-2 Gene from a Halophyte Confers Abiotic Stress Tolerance and Modulates ROS Scavenging in Transgenic Tobacco

Abstract

Heavy metals are common pollutants of the coastal saline area and Salicornia brachiata an extreme halophyte is frequently exposed to various abiotic stresses including heavy metals. The SbMT-2 gene was cloned and transformed to tobacco for the functional validation. Transgenic tobacco lines (L2, L4, L6 and L13) showed significantly enhanced salt (NaCl), osmotic (PEG) and metals (Zn++, Cu++ and Cd++) tolerance compared to WT plants. Transgenic lines did not show any morphological variation and had enhanced growth parameters viz. shoot length, root length, fresh weight and dry weight. High seed germination percentage, chlorophyll content, relative water content, electrolytic leakage and membrane stability index confirmed that transgenic lines performed better under salt (NaCl), osmotic (PEG) and metals (Zn++, Cu++ and Cd++) stress conditions compared to WT plants. Proline, H2O2 and lipid peroxidation (MDA) analyses suggested the role of SbMT-2 in cellular homeostasis and H2O2 detoxification. Furthermore in vivo localization of H2O2 and O2 −; and elevated expression of key antioxidant enzyme encoding genes, SOD, POD and APX evident the possible role of SbMT-2 in ROS scavenging/detoxification mechanism. Transgenic lines showed accumulation of Cu++ and Cd++ in root while Zn++ in stem under stress condition. Under control (unstressed) condition, Zn++ was accumulated more in root but accumulation of Zn++ in stem under stress condition suggested that SbMT-2 may involve in the selective translocation of Zn++ from root to stem. This observation was further supported by the up-regulation of zinc transporter encoding genes NtZIP1 and NtHMA-A under metal ion stress condition. The study suggested that SbMT-2 modulates ROS scavenging and is a potential candidate to be used for phytoremediation and imparting stress tolerance.

Metabolic profiling and scavenging activities of developing circumscissile fruit of psyllium (Plantago ovata Forssk.) reveal variation in primary and secondary metabolites

“…Reactive oxygen species (ROS) are generated in response to stress, causing oxidative damage to the cell; therefore, plants exhibit robust defence mechanisms against ROS-induced oxidative stress [7,25,44,60].…”

Non-targeted metabolomics and scavenging activity of reactive oxygen species reveal the potential of Salicornia brachiata as a functional food

“…Some species of Salicornia have shown important biological properties, such as antioxidant, anti-inflammatory, hypoglycemic and cytotoxic activities (Isca, Seca, Pinto, & Silva, 2014). Furthermore, Salicornia is being widely explored for abiotic stress-responsive genes and promoters to develop transgenic plants that can withstand adverse environmental conditions (Chaturvedi, Mishra, Tiwari, & Jha, 2012;Chaturvedi, Patel, Mishra, Tiwari, & Jha, 2014;Jha, Sharma, & Mishra, 2011;Singh, Mishra, & Jha, 2014a, 2014bUdawat, Mishra, & Jha, 2014). No information is available, so far, on the metabolomics of this important succulent halophytic plant.…”

Transgenic peanut overexpressing mtlD gene confers enhanced salinity stress tolerance via mannitol accumulation and differential antioxidative responses

“…Graph represents the mean ± SE (n = 3) followed by similar lower case letter are significantly not different according to Tukey's multiple range at P B 0.05 (this is the same for Figs. 3, MDA concentration in T lines at higher salt treatment (3 dS m -1 ), compared to WT, suggested that T plants had balanced ROS formation and suffered less oxidative lipid injury than WT lines(Tang et al 2005;Rai et al 2013).Similarly, lower in situ accumulation of O 2 -and H 2 O 2 was reported in SbMT-2 tobacco(Chaturvedi et al 2014), AhAREB1 Arabidopsis(Li et al 2013), and lower MDA content in mtlD tomato(Khare et al 2010) and MuNAC4…”

“…This includes lowmolecular-mass non-enzyme antioxidant metabolites, such as ascorbic acid and various antioxidant enzymes such as SOD, CAT, APX, GR and POD (Bhatnagar-Mathur et al 2009;Miller et al 2010;Chaturvedi et al 2014). Ascorbic acid (AsA) is both a secondary metabolite and an antioxidant which interacts enzymatically and non-enzymatically and detoxifies the ROS (Upadhyaya et al 2011).…”