Genetic engineering of the glyoxalase pathway in tobacco leads to enhanced salinity tolerance

Abstract

The glyoxalase pathway involving glyoxalase I (gly I) and glyoxalase II (gly II) enzymes is required for glutathione-based detoxification of methylglyoxal. We had earlier indicated the potential of gly I as a probable candidate gene in conferring salinity tolerance. We report here that overexpression of gly I؉II together confers improved salinity tolerance, thus offering another effective strategy for manipulating stress tolerance in crop plants. We have overexpressed the gly II gene either alone in untransformed plants or with gly I transgenic background. Both types of these transgenic plants stably expressed the foreign protein, and the enzyme activity was also higher. Compared with nontransformants, several independent gly II transgenic lines showed improved capability for tolerating exposure to high methylglyoxal and NaCl concentration and were able to grow, flower, and set normal viable seeds under continuous salinity stress conditions. Importantly, the double transgenic lines always showed a better response than either of the single gene-transformed lines and WT plants under salinity stress. Ionic measurements revealed higher accumulation of Na ؉ and K ؉ in old leaves and negligible accumulation of Na ؉ in seeds of transgenic lines as compared with the WT plants. Comparison of various growth parameters and seed production demonstrated that there is hardly any yield penalty in the double transgenics under nonstress conditions and that these plants suffered only 5% loss in total productivity when grown in 200 mM NaCl. These findings establish the potential of manipulation of the glyoxalase pathway for increased salinity tolerance without affecting yield in crop plants.

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

“…The accumulation of MG is indicative of abiotic stress conditions including heavy metals (Yadav et al 2005a, b;Singla-Pareek et al 2003;). MG causes a dose-and time-dependent depletion of GSH and increased GSH oxidation or formation of GSSG.…”

“…Higher Gly I and Gly II activities might protect plants against MG that is formed during abiotic stresses (Veena et al 1999;Jain et al 2002;Saxena et al 2005;. Overexpression of Gly I and Gly II in transgenic plants inhibits an increase in MG level under Zn and salt stress condition and confers tolerance to heavy metal and high salt by increasing the GSH based detoxification system and decreasing lipid peroxidation (Veena et al 1999;Singla-Pareek et al 2003;Yadav et al 2005a, b). A proteomic study of salt-tolerant barley also showed higher Gly I protein expression under salinity stress conditions (Witzel et al 2009).…”

Glutathione in plants: biosynthesis and physiological role in environmental stress tolerance

“…glyoxalase I (Gly I) and glyoxalase II (Gly II). Research findings have demonstrated that GSH acts as a methylglyoxal detoxifier that confers salt stress tolerance (Singla-Pareek et al 2003). An experiment by El-Shabrawi et al (2010) conducted with Pokkali (salt tolerant) and IR64 (salt sensitive) rice cultivars, indicated that the GSH level and both Gly I and II activities were significantly higher in Pokkali than in IR64.…”

The Human Hydroxyacylglutathione Hydrolase (HAGH) Gene Encodes Both Cytosolic and Mitochondrial Forms of Glyoxalase II

“…Thus in A. thaliana five genes have been identified, three that appear to encode mitochondrial proteins (GLX2-1, GLX2-4, and GLX2-5), one that encodes a cytosolic protein (GLX2-2), and one whose function is currently uncharacterized (GLX2-3) (10,13). An apparent homologue of one of the mitochondrial forms (AY054407 from Oryza sativa) has been overexpressed in tobacco and increases resistance to salinity (14).…”