Transgenic Tobacco Overexpressing Glyoxalase Pathway Enzymes Grow and Set Viable Seeds in Zinc-Spiked Soils

• Published in: Plant physiology (Bethesda) Vol. 140; no. 2; pp. 613 - 623
• Main Authors: Singla-Pareek, Sneh L, Yadav, Sudesh K, Pareek, Ashwani, Reddy, M.K, Sopory, S.K
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01.02.2006; American Society of Plant Physiologists
• Subjects: biochemical pathways; Biological and medical sciences; biosynthesis; Brassica juncea; Cadmium; Cadmium - toxicity; carbon-sulfur ligases; Environmental Stress and Adaptation to Stress; Enzymes; flowering; Flowers - anatomy & histology; Flowers - growth & development; Fundamental and applied biological sciences. Psychology; gene overexpression; Genetic Engineering; Germination and dormancy; glutathione; Glutathione - biosynthesis; Glutathione - metabolism; glyoxalase; Heavy metals; homeostasis; Lactoylglutathione Lyase - metabolism; Lead - toxicity; Lipid Peroxidation; metal tolerance; methyl glyoxal; Molecular Sequence Data; Nicotiana - genetics; Nicotiana tabacum; Oryza sativa; Oxidative stress; Phytochelatins; plant biochemistry; Plant growth; plant physiology; Plant physiology and development; Plant Proteins - metabolism; Plant Roots - chemistry; Plant Roots - growth & development; Plants; Plants, Genetically Modified - drug effects; Plants, Genetically Modified - enzymology; Plants, Genetically Modified - growth & development; Pyruvaldehyde - metabolism; rice; seed development; Seedlings; Seeds; Seeds - drug effects; Seeds - physiology; Soil Pollutants - toxicity; source-sink relationships; Thiolester Hydrolases - metabolism; tobacco; transgenes; Transgenic plants; Up-Regulation; Zinc; Zinc - analysis; Zinc - toxicity; Flower; Seeds; Root; Enzyme; Growth; Homeostasis; Tolerance; Lipids; Lyases; Nicotiana tabacum; Survival; Stress; Heavy metal; Salinity; Gene; Dicotyledones; Angiospermae; Carbon-sulfur lyases; Spermatophyta; Transgenic plant; Solanaceae; Lactoylglutathione lyase; Peroxidation
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.105.073734

We reported earlier that engineering of the glyoxalase pathway (a two-step reaction mediated through glyoxalase I and II enzymes) enhances salinity tolerance. Here we report the extended suitability of this engineering strategy for improved heavy-metal tolerance in transgenic tobacco (Nicotiana tabacum). The glyoxalase transgenics were able to grow, flower, and set normal viable seeds in the presence of 5 mM ZnCl₂ without any yield penalty. The endogenous ion content measurements revealed roots to be the major sink for excess zinc accumulation, with negligible amounts in seeds in transgenic plants. Preliminary observations suggest that glyoxalase overexpression could confer tolerance to other heavy metals, such as cadmium or lead. Comparison of relative tolerance capacities of transgenic plants, overexpressing either glyoxalase I or II individually or together in double transgenics, evaluated in terms of various critical parameters such as survival, growth, and yield, reflected double transgenics to perform better than either of the single-gene transformants. Biochemical investigations indicated restricted methylglyoxal accumulation and less lipid peroxidation under high zinc conditions in transgenic plants. Studies employing the glutathione biosynthetic inhibitor, buthionine sulfoximine, suggested an increase in the level of phytochelatins and maintenance of glutathione homeostasis in transgenic plants during exposure to excess zinc as the possible mechanism behind this tolerance. Together, these findings presents a novel strategy to develop multiple stress tolerance via glyoxalase pathway engineering, thus implicating its potential use in engineering agriculturally important crop plants to grow on rapidly deteriorating lands with multiple unfavorable edaphic factors.