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

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Metabolic Engineering for Stress Tolerance 265 trade-off between increased stress tolerance and unwanted physiological effects on plant growth needs to be considered. In a recent example, Garg et. al., (2002) expressed bacterial genes (otsA and otsB) in rice using tissue-specific and stress-dependent promoters. Transgenic rice plants were not stunted and accumulated trehalose 3-10 times that of the non-transgenic controls and exhibited tolerance to salt, drought and low-temperature stress. Increased trehalose accumulation correlates with higher soluble carbohydrate levels and an elevated capacity for photosynthesis under both stress and non-stress conditions, consistent with a suggested role in modulating sugar sensing and carbohydrate metabolism. These findings demonstrate the feasibility of engineering rice for increased tolerance of abiotic stress and enhanced productivity through tissue-specific or stressdependent overproduction of trehalose (Garg et. al., 2002). This made the authors suggest that stress inducible transgene expression is important in recovering trehalose-accumulating transgenics without deleterious effects. However, in a similar study where a bacterial gene encoding both trehalose-6-phosphate synthase and trehalose- 6-phosphate phosphatase activities was expressed in rice under the control of a maize ubiquitin promoter (Jan et. al., 2002), stress tolerant transgenic rice with no growth abonormalities, was recovered, suggesting that rice may be more tolerant to trehalose pathway modification than dicots. It will be instructive therefore to engineer plants for novel osmoprotectants with and without stress inducible promoters and to use both monocots and dicots to evaluate the technology. 3.1.3. Fructans Fructans are polyfructose molecules synthesized by many plants and bacteria mainly as a storage carbohydrate (Hendry, 1993; Pilon-Smits et. al., 1995). Fructans play an important role in root branching, thus helpful in increasing root surface area and water uptake by the plant. Transgenic plants overexpressing gene sacB exhibited higher capacity for osmotic adjustment. The additional gain in carbohydrate storage may direct deeper rooting and enhanced water uptake (Sharp et. al., 1996; Pilon-Smits et. al., 1995; Schellenbaum et. al., 1999). 3.1.4. Proline and Proline Betaines Proline accumulation has been shown to be linked with drought and salinity stresses in plants (Delauney and Verma, 1990) and is caused by activation of proline biosynthesis and inhibition of proline degradation. Glutamate and ornithine are both precursors of proline. Proline is synthesized from glutamate via two intermediates, glutamic-Qsemialdehyde (GSA) and Ä- 1 pyrroline-5-carboxylate (P5C), catalyzed by two enzymes, P5C synthase (P5CS) in the first step and P5C reductase (P5CR) in the final step. Overproduction of proline in transgenic tobacco (10-18 folds) (Kavi Kishor et. al., 1995), rice (Zhu et. al., 1998), wheat (Sawahel and Hassan 2002) and hybrid larch, Laria
266 B. Rathinasabapathi and R. Kaur leptoeuropaea (30 folds) (Gleeson et. al., 2005) with the Ä- 1 pyrroline-5-carboxylate synthetase (P5CS) gene improved root biomass and flower development under water and salt stress. Further work on transgenic soybean (De Ronde et. al. 2000) and Arabidopsis (Nanjo et. al., 1999a) plants transformed with the antisense gene for Ä- 1 pyrroline-5-carboxylate reductase and the gene for proline dehydrogenase (ProDH) (Nanjo et. al., 1999b) showed additional evidence that proline accumulation is positively correlated with stress tolerance in the plants. The P5CS, Ä- 1 pyrroline-5-carboxylate synthase is subject to feedback inhibition by proline, thus is a rate-limiting enzyme in proline biosynthesis. Transgenic plants expressing a mutated form of the enzyme (P5CSF129A) whose feedback inhibition by proline was removed by site-directed mutagenesis accumulated about 2-fold more proline than the plants expressing Vigna aconitifolia wild-type P5CS (Hong et. al., 2000). Transgenic lines overexpressing ornithine-d-aminotransferase (d-OAT) showed increase in d-OAT enzyme activity, resulted in higher proline production than the control plants and demonstrated a higher biomass as well as higher germination rate under osmotic stress conditions (Roosens et. al., 2002). Yonamine et. al., (2004) observed that overexpression of NtHAL3 genes isolated from Saccharomyces cerevisae conferred increased levels of proline biosynthesis in cultured tobacco cells and enhanced salt tolerance. Proline is also a precursor for proline betaine and hydroxyproline betaines, excellent osmoprotectants found in certain members of the plant families Aizoaceae, Leguminosae, Rutaceae and Plumbaginaceae (Rathinasabapathi, 2002). The genes involved in proline betaine and hydroxyproline betaine synthesis routes have not yet been characterized and utilized in metabolic engineering. 3.1.5. Glycine Betaine Glycine betaine is a significant compatible solute commonly distributed among plants. It is synthesized by a two-step oxidation of choline via betaine aldehyde. Choline oxidation in plants is catalyzed by choline monooxygnease while microbes employ either choline dehydrogenase or choline oxidase. Diverse plant species have variable capability to synthesize and accumulate glycine betaine. Relatively high levels of glycine betaine are found in plants like, spinach and barley as compared to plants that do not synthesize or accumulate it (e.g. Arabidopsis and tobacco). Metabolic engineering has been used to introduce genes for glycine betaine synthesis from both microorganisms and higher plants into betaine-deficient plants (Sakamoto and Murata, 2002). Numerous plant species have been engineered to synthesize elevated levels of glycine betaine. Many examples of recovery of stress tolerant transgenic plants have been reported (McNeil et. al., 1999, Chen and Murata, 2002). This technology has also been extended to several crops to recover stress-tolerant transgenic crops (Chen et. al., 2000; Huang et. al., 2000; Mohanty et. al., 2002; Prasad et. al., 2000a and 2000b., Sakamoto et. al., 1998; Shen et. al., 2002). In general, the transgenic plants engineered to produce glycine betaine made only small amounts of the osmoprotectant - much less than what
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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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Page 226 and 227: 219 CHAPTER 8 HEAVY METAL STRESS KS
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Page 252 and 253: Heavy Metal Stress 245 7. CONCLUSIO
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Page 256 and 257: Heavy Metal Stress 249 Kägi, J.H.R
Page 258 and 259: Heavy Metal Stress 251 Murphy, A.,
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Page 262 and 263: 255 CHAPTER 9 METABOLIC ENGINEERING
Page 264 and 265: Metabolic Engineering for Stress To
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316 A.K. Tyagi, S. Vij and N. Saini
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Table 3. Continued... Source Resour
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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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