, 1. 2. 2-1. 2-2. 2-3. 3. 3-1. 3-2. 3-3. 3-4. Proteolysis, protein folding and prosthetic group aquisition 3-5. Inhibitory environments 3-6. Side- reactions of new compounds 4. 4-1. Production of osmoprotective compounds 4-2. Improved membrane flexibility 4-3. Stress - induced proteins 4-4. Scavenging reactive intermediates 5. Future prospects 6.
1.,,,. (biotic), (abiotic) ( 1)...,.. ( 2). avoidance tolerance ( 3).,..... [1]..
1. Environmental stress factors that increase the concentrations of reactive oxygen species in plant cells. 2. Many factors determine how plants respond to environmental stress. the genotype and developmental circumstances of the plant, the duration and severity of the stres s, the number of times the plants is subjected to stress, and any additive or synergistic effects of multiple stresses. Plants respond to stress throught a variety of mechanisms. Failure to compensate for a severe stress can result in plant death.
3. Stress resistance can involve tolerating the stressfull condition or avoiding it. Some resistance mechanisms are constitutive and are active before exposure to stress. In other case, plants exposed to stress alter their physiology in response, thereby acclimating themselves to an unfavorable environment. 2..,,.,.... [2].. [3], superoxide peroxides [4].,, osmoprotection [1], persxidase, superoxide dismutase.
2-1.,.., stem elongation, leaf expansion stomatal aperture. 2 [5] [6]. xylem ABA, ABA [7]. ABA, signal [8, 9, 10, 11].,,. Hsiao [12] 5. 1. Reduction of w ater potential or activity of cellular w ater. 2. Decrease of cell turgor pressure. 3. Concentration of small molecules and macromolecules as cell volume decreases with reduced turgor. 4. Alteration of spatial relations in the plasmalemma, tonoplast, and organelle membr anes by volume changes. 5. Change in structure or configuration of macromolecules by removal of w ater of hydration or through modification of structure of adjacent w ater. 2-2. 0 15 [13, 14]., [13], [15, 16].. 1. Cellular ch an g e s -,, 2. A ltere d m et ab olis m -,, anaerobic respiration metabolites 3. Redu c ed plant g row th an d de ath - wilted leaves, necrotic area 4. S urf ace le s ion s - surface pitting, large sunken areas, discoloration
5. W ater- s oaking of th e tis s u e - cellular breakdown, loss of membrane integrity 6. Intern al dis c oloration - pulp, seeds often turn brown 7. A c c elerate d s en e s c enc e - loss of chlorophyll, loss of cellular integrity 8. Incre as ed s u s ceptibility to dec ay - pathogen 9. F ailure to ripen n orm ally 10. Lo s s of v ig or -. primary event ' secondary event ' ( 4). primary event critical, secondary event primary event. (Reversible) (Irreversible) [17, 18, 19, 20]. 4. Schematic representation of the relationship between the 'primary event ' and 'secondary event ' of chilling injury.
2-3. Na + Cl - hyperionic & phyerosmotic [21, 22, 23]. cell division expansion death [23, 24]. membrane disorganization,, metabolic toxicity, [25, 26, 27]. 3. 6 ( 5). ( 1),. 3-1. electroporation, polyethylene glycol- mediated gene transfer, microinjection, particle bombardment A g robacterium - mediated gene transfer [28].,, A. tum ifaciens - mediated gene transfer,,, particle bombardment [29].. 3-2.. promoter. CaMV 35S promoter [30]. promoter., atsa (A rabidop s is Rubisco small subunit gene) promoter [31], granule- bound starch synthase G28 promoter [32] patatin type I promoter [33] tubers. osmotin promoter [34] salinity, drought, ABA, glyceraldehyde- 3- phosphate dehydrogenase 4 promoter [35] anoxia
. promoter. 5. Strategy for creating a more stress- tolerant plant using genetic engineering
1. Potential pitfalls when expressing foreign genes in higher plants 1. Tra nsformation. Techniques for tra nsforming the host pla nt a re ava ila ble in most case, but there are exceptions 2. Adequate express ion. Adequate express ion of the gene is esse ntial, with high express ion at the right time. 3. Ce llula r loca lization. Express ion in s pecific tiss ues a nd orga ne lles is ofte n esse ntia l for achiveving the des ired res ults. 4. Post- trans lationa l modifications. Correct process ing and folding a re often prerequis ites for function. 5. Prosthetic- group acquis ition. Limitations in prosthetic group acquis ition may inactivate fore ign enzymes. 6. Precursor ava ilability. Precursor s hortage will place limitations on product formation. 7. Inhibitory e nvironments. Suboptima l enzyme activity may be because of abnormal ph, temperature or salt concentrations. 8. Side- reactions of new compounds. Endogenous enzyme activities may deplete the product pool or form toxic compounds. 3-3....... transit peptide [36, 37]. 3-4. Prote oly s is, protein folding an d pros thetic g roup aqui s ition.. S tap hy loccocal protein A (Spa) [38]. Spa IgG. chaperone disulphide chaperone.
prosthetic group.,,,. 3-5. Inhibitory env ironm ent s ph,, redox potential, ionic strength,.. 3-6. S ide - re action s of n ew c om poun ds. side- reaction. 4. 2. 4-1. Produ ction of o s m oprotectiv e com poun ds Osmoprotectant osmolyte(quaternary amines, amino acids, sugar alcohols).,,, osmoprotective glycine betaine.
2. Foreign genes expressed in transgenic plants Ge ne O rig in Ho s t S tre s s Re fs BetA E. coli Sa linity 16 coda A rthrobacter globiformis Arabidops is Sa linity & Drought 17 p5cs Vigna aconitifolia Drought 18 Mltd E. coli Arabidops is Sa linity 19 Mltd E. coli Sa linity 20 TPS 1 S accharomy ces cere visiae Drought 2 1 SacB Bacillus s ubtilis Drought 22 fad7 A rabidop sis Chilling 23 Des9 Anacys tis nidulans Chilling 24 HVA 1 Ba rley Rice Sa linity & Drought 6 Afp Winte r flounde r Freezing 26 afa3 Winte r flounde r Tomato Freezing 18 Mn- S od Nicotiana plumbaginifolia Alfa lfa Drought & Freezing 15 Mn- S od N. plum baginifolia Oxidative 30 Fe- S od A rabidop sis Oxidative 3 1 Gr/ Cu,Zn- S od E. coli/rice Oxidative 33 vhb Vitreoscilla s tercoraria Hypoxia & Anoxia 35 Choline glycine betaine E. coli Choline dehydrogenase beta salt- tolerant freezing - tolerant [39], choline oxidase coda A rabidop s is salt- tolerant freezing- tolerant [40]. proline glycine betaine osmoprotective. p5cs drought- stress proline 10 18 [41]. proline overexpression salt stress.. osmolyte overexpression. A rabidop s is m ltd sugar alcohol mannitol salt stress [42, 43]. TP S1 trehalose drought - tolerance, desiccation- tolerance [44]. sacb fructan. fructan [45].
4-2. Im prov ed m em brane flex ibility unsaturation [46]. cis - double bond phase- transition 0. A rabidop s is cis - double bond [47, 48]. 4-3. S tre s s - indu c ed protein s Abiotic LEA (late- embryogenesis- abundant ).. LEA H VA 1 LEA, [29]. LEA antifreeze (AFPs). AFP neutralize ice nucletors ice recrystallization. AFP [38, 39]. ice recrystallization [38], cold specific [49]. 4-4. S c av en g in g re activ e interm e di ate s salt, freezing, drought stress.,, [48] oxidative stress [4]. abiotic stress antioxidant - defence system [50]. antioxidant system SOD, peroxidase, catalases, glutathione reductase [4]. antioxidant defencedptj SOD Cu/ Zn - SOD, Mn- SOD, Fe- SOD 3 [51]. [52, 53, 54, 55]. Fe- SOD leaf- disc chilling- induced photoinhinition, salt stress.
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