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Physiology and Molecular Biology of Stress ... - KHAM PHA MOI

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Metabolic Engineering for <strong>Stress</strong> Tolerance<br />

271<br />

Table 4. Examples for metabolic engineering for providing tolerance against heavy<br />

metal stress<br />

Metals Transgenic plant Gene engineered Source <strong>of</strong> gene References<br />

Cadmium Tobacco, Metallothionein Mus musculus Pan et. al.,<br />

1994<br />

Mercury Arabidopsis Mercury Escherichia Rugh et. al.,<br />

reductase (merA) coli 1996<br />

Aluminum Tobacco Citrate synthase Pseudomonas de la Fuente<br />

aeruginosa et. al., 1997<br />

Cadmium B. oleracea Metallothionein Sacchromyces Hasegawa et.<br />

cerevisiae al., 1997<br />

Mercury Liriodendron Modified merA E. coli Rugh et. al.,<br />

tulipifera 1998<br />

Cadmium Tobacco Metallothionein Nicotiana Suh et. al., 1998<br />

glutinosa<br />

Lead, Tobacco Cation channel N. tabacum Arazi et. al.,<br />

Nickel (NtCBP4) 1999<br />

Mercury Arabidopsis MerB E. coli Bizily et. al.,<br />

1999<br />

Selenium B. juncea ATP sulfurylase Arabidopsis Pilon-Smits et.<br />

(APS1) al., 1999<br />

Zinc Arabidopsis Zn transporter A. thaliana Van der Zaal<br />

ZAT1 et. al., 1999<br />

Cadmium Brassica juncea Glutathione E. coli Zu et al.,<br />

synthetase<br />

1999a,b<br />

Cadmium Tobacco Cysteine Rice Harada et. al.,<br />

synthase gene 2001<br />

3.2.3. Glutathione <strong>and</strong> Phytochelatins<br />

The tripeptide glutathione is the most common thiol. It is a striking target for engineering<br />

stress tolerance in plants (Kunert <strong>and</strong> Foyer, 1993). Primarily, heavy metal sequestration<br />

by plants involves the formation <strong>of</strong> complexes with cysteine- rich peptides –<br />

glutathione derivatives called phytochelatins (PCs) (Figure 5). Cadmium forms a com-<br />

plex with phytochelatins in the cytosol <strong>and</strong> transported to the vacuole (Rauser, 1995)

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