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Plant Physiology Preview Published on December 29, 2005; 10.1104/pp.105.073734
Received November 2, 2005 Transgenic Tobacco Overexpressing Glyoxalase Pathway Enzymes Grow and Set Viable Seeds in Zinc Spiked Soils
Plant Molecular Biology, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi-110 067, India * Corresponding author; email: sneh{at}icgeb.res.in.
We reported earlier that engineering of glyoxalase pathway (a two step reaction mediated through glyoxalase I and II enzymes) enhances salinity tolerance (Singla-Pareek et al., 2003). 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 also such as cadmium or lead. Comparison of relative tolerance capacities of transgenic plants, overexpressing either glyoxalase I or II individually or two 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 lesser lipid peroxidation under high zinc conditions in transgenic plants. Studies employing glutathione biosynthetic inhibitor, buthionine sulfoximine (BSO), suggested 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.
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