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

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Metabolic Engineering for Stress Tolerance 273 role in metal homeostasis and tolerance. Arabidopsis plants overexpressing ZAT1 or AtMTP1, encoding a putative zinc transporter in the CDF family of membrane transporters, accumulated higher zinc concentrations in their roots and also displayed better root growth in comparison to controls, when grown in a hydroponic media containing 200 ìM zinc. (Van der Zaal et. al., 1999; Maser et. al., 2001). Overexpression of PtdMTP1 (Populus trichocarpa x deltoids metal tolerance protein), in Arabidopsis conferred Zn tolerance (Blaudez et. al., 2003). Figure. 5. Glutathione mediated sequestration of Cadmium (Modified from Cobbett et al., 2000). Phytochelatin synthesis shown in the cytoplasm is a 3-step pathway. LMWPC-Cd refers to low molecular weight complex of PC and Cd and HMW PC-Cd shown in the vacuole refers to high molecular weight complex 3.2.6. Citrate Synthesis and Other Metabolic Targets Some plants have a capacity to tolerate Al toxicity by the process of exclusion of uptake from the root. These plants release organic acids such as citric acid, which chelates Al 3+ outside the plasma membrane. Transgenic tobacco, papaya and Arabidopsis that overexpressed a citrate synthase gene (CSb) from Pseudomonas aeruginosa in their cytoplasm showed higher tolerance against Al toxicity (de la Fuente et. al., 1997; Koyama et. al., 2000; Lopez-Bucio et. al., 2000; Guerinot, 2001). In alfalfa, overexpression of two genes encoding enzymes phosphoenolpyruvate carboxylase (PEPC) and malate dehy-
274 B. Rathinasabapathi and R. Kaur drogenase (MDH) displayed higher synthesis of citric acid and Al tolerance (Tesfaye et al., 2001). Transgenic Arabidopsis plants expressing MerA gene showed significantly enhanced tolerance to Hg (II) and volatilized elemental mercury (Rugh et. al., 1996). Also, transgenic MerB Arabidopsis plants were significantly more tolerant to methylmercury and other organomercurials (Bizily et. al., 1999). Transgenic tobacco and yellow poplar expressing both MerA and MerB genes also showed enhanced mercury tolerance (Rugh et. al., 2000). Transgenic tobacco overexpressing NtCBP4 (Nicotiana tabacum calmodulinbinding protein) demonstrated enhanced tolerance to Ni 2+ and hypersensitivity to Pb 2+ due to reduced Ni 2+ accumulation and Pb 2+ accumulation respectively (Arazi et. al., 1999). Furthermore, expression of a truncated tobacco NtCBP4 channel in transgenic plants and disruption of the homologous Arabidopsis CNGC1 gene conferred improved tolerance to Pb 2+ (Sunkar et. al., 2000). In an approach to enhance Se assimilation by plants, the plastidic Arabidopsis APS1 cDNA encoding ATP sulfurylase, was expressed in B. juncea under the control of a 35S promoter. Transgenic plants displayed a little increase in Se tolerance, and accumulated about 2-fold more Se in their shoots (Pilon- Smits et. al., 1999). Grichko et. al. (2000) found that the overexpression of 1- aminocyclopropane-1-carboxylic acid (ACC) deaminase led to an enhanced accumulation of a variety of metals, as well as higher metal tolerance. 3.2.7. Arsenic Hyperaccumulation Arsenic is a toxic carcinogen. In many areas of the world, the soil and ground water are contaminated with arsenic both due to natural and human activities. Current methods used to remediate arsenic contaminated water and soil are expensive. Recent research has uncovered the extraordinary ability of the Chinese brake fern (Pteris vittata) to hyperaccumulate arsenic (Ma et al. 2001), leading to phytoremediation technology to remediate arsenic contaminated environment. Arsenic exists most commonly in two forms, As V and As III, the latter being more reactive and toxic to cells. To understand how the Chinese brake fern hyperaccumulates arsenic, the roots were exposed to As V in a nutrient solution medium and the total arsenic and the species of As were analyzed in the plants’ fronds and roots. About 90% of the arsenic accumulated in the fern occurred in the form of As III and the accumulation was more in the shoots than in the roots (Tu et al., 2002; Figure 6). This shows that the fern has an efficient arsenic uptake system in its roots, and the fren’s tissue reduces As V to As III and arsenic hyperaccumulation occurs in the fronds. The mechanisms involved in arsenic hyperaccumulation in this fern are actively researched in many laboratories in the world including that of the authors. P.vittata genes involved in arsenic uptake, arsenate reduction, translocation, vacuolar transport
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PHYSIOLOGY AND MOLECULAR BIOLOGY OF
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A C.I.P. Catalogue record for this
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About the Editors K.V. Madhava Rao
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LIST OF CONTRIBUTORS K. AKASHI Grad
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List of Contributors xiii NAVINDER
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PREFACE Increasing agricultural pro
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2 K.V. Madhava Rao Abiotic stresses
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4 K.V. Madhava Rao SOME O THE PROMI
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6 K.V. Madhava Rao 2. WATER STRESS
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8 K.V. Madhava Rao 5. FREEZING STRE
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10 K.V. Madhava Rao of these pathwa
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12 K.V. Madhava Rao Bray, E.A. (199
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14 K.V. Madhava Rao Rao, K.V. Madha
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16 A. Yokota, K. Takahara and K. Ak
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41 CHAPTER 3 SALT STRESS ZORA DAJIC
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Salt Stress 43 activities (mainly i
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Salt Stress 45 In summary, mechanis
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Salt Stress 47 tolerance research i
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Salt Stress 49 need to rely on sodi
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Salt Stress 51 (Echeverria, 2000).
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Salt Stress 53 Therefore, the capac
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Salt Stress 55 Reduced plant growth
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Salt Stress 57 Table 3. Salt tolera
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Salt Stress 59 6.2. Nitrogen Fixati
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Salt Stress 61 A significant number
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Salt Stress 63 macromolecules, irre
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Salt Stress 65 8.2. Ion Homeostasis
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Salt Stress 67 1997), is speculated
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Salt Stress 69 together with the At
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Salt Stress 71 important role in si
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Salt Stress 73 Figure 5. Determinan
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Salt Stress 75 9.1.Transgenic Plant
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Salt Stress 77 tolerance from halop
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Salt Stress 79 sponse and yield (Su
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Salt Stress 81 Table 5. Possible ut
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Salt Stress 83 monitored with fluor
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Salt Stress 85 Func. Plant Biol. 29
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Salt Stress 87 Dajic, Z., Stevanovi
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Salt Stress 89 Gouia, H., Ghorbal,
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Salt Stress 91 Larcher, W. (1995).
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Salt Stress 93 Munns, R. and James,
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Salt Stress 95 Rausell, A., Kanhono
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Salt Stress 97 durum wheat crops gr
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Salt Stress 99 Yoshida, K. (2002).
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102 T.D. Sharkey and S.M. Schrader
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131 CHAPTER 5 FREEZING STRESS: SYST
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Freezing Stress 133 Whereas, in the
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Freezing Stress 135 genes at the tr
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Freezing Stress 137 with physiologi
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Freezing Stress 139 (1997). However
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Freezing Stress 141 (Barnett et al.
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Freezing Stress 143 (dehydrin) prot
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Freezing Stress 145 in cytosolic Ca
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Freezing Stress 147 Phospholiphase
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Freezing Stress 149 Accumulation of
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Freezing Stress 151 Ideker, T., Gal
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Freezing Stress 153 ellin acid on f
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Freezing Stress 155 Yoshida, S. and
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158 A.R. Reddy and A.S. Raghavendra
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188 K. Janardhan Reddy constitution
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190 K. Janardhan Reddy World nitrog
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192 K. Janardhan Reddy nitrogen def
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194 K. Janardhan Reddy endoplasmic
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196 K. Janardhan Reddy drought cond
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198 K. Janardhan Reddy Manganese-de
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200 K. Janardhan Reddy zinc deficie
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202 K. Janardhan Reddy Table 12 . E
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204 K. Janardhan Reddy Table 14. Ef
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206 K. Janardhan Reddy Table 15. Th
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208 K. Janardhan Reddy Table 17. Co
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210 K. Janardhan Reddy 18. MOLECULA
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212 K. Janardhan Reddy Bush, D.S.,
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214 K. Janardhan Reddy and Cobbett,
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216 K. Janardhan Reddy 143, 109-111
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219 CHAPTER 8 HEAVY METAL STRESS KS
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Heavy Metal Stress 221 porter) and
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Page 238 and 239: Heavy Metal Stress 231 a precursor
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Page 242 and 243: Table 1. Proposed specificity and l
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Page 248 and 249: Heavy Metal Stress 241 5. HYPERACCU
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Page 252 and 253: Heavy Metal Stress 245 7. CONCLUSIO
Page 254 and 255: Heavy Metal Stress 247 controlled b
Page 256 and 257: Heavy Metal Stress 249 Kägi, J.H.R
Page 258 and 259: Heavy Metal Stress 251 Murphy, A.,
Page 260 and 261: Heavy Metal Stress 253 through xyle
Page 262 and 263: 255 CHAPTER 9 METABOLIC ENGINEERING
Page 264 and 265: Metabolic Engineering for Stress To
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324 A.K. Tyagi, S. Vij and N. Saini
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336 Index Auxins, 146 Avena sativa
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338 Expressed sequence tags (ESTs),
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340 Index Magnesium, 195 Mairiena s
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342 Index Processes less sensitive
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344 Index Sunflecks, 104 Sunflower,
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