improvement of drought tolerance through genetic engineering
TRANSCRIPT
Improvement of drought tolerance through Genetic Transformation
Improvement of drought tolerance through Genetic Transformation
Drought tolerance
Drought tolerance refers to the degree to which a plant is adopted to arid or drought conditions.
Desiccation tolerance is extreme degree of drought tolerance.
Drought tolerant plants typically make use of either C4 carbon fixation or crassulacean acid metabolism (CAM) to fix carbon during photosynthesis.
Many adaptations for dry conditions are structural, including the following:
Adaptations of the stomata to reduce water loss, such as reduced numbers or waxy surfaces.
Water storage in succulent above-ground parts or water-filled tubers.
Adaptations in the root system to increase water absorption.
Trichomes (small hairs) on the leaves to absorb atmospheric water.
Drought Tolerance – is it a Complex Trait?
Drought tolerance is a very complex trait.
However, both conceptually and functionally, drought tolerance is not a complex trait if one consider the following axioms:
1. Most of the crucial plant traits that control plant water status and plant production under drought are constitutive and not stress adaptive.
2. Plant water status, more than plant function, controls crop performance under drought.
Response of Plants to drought Response of Plants to drought
Constitutive Plant Traits Controlling Plant Water Status and Productivity under Drought
Phenology
Root traits
Plant and organ size
Leaf surface properties
Non -senescence
Stress Adaptive Plant Traits Controlling PlantProduction under Drought
Cellular compatible solutes
Anti oxidant agents
Heat shock proteins
Molecular chaperone proteins
Methods of crop Improvement for drought Methods of crop Improvement for drought
• Traditional Breeding Crossing two individuals from the same species; produces a new, improved variety; not a biotechnology procedure
• Genetic Transformation Adding a gene from another species; the essential biotechnology procedure to produce transgenics
Source: USDA
Source: USDA
Umezawa et al 2006, 17:113-122
Strategies for the genetic engineering
of drought tolerance.
Success of getting drought tolerant plants
Through…. Conventional breeding : Undesirable
linkage, time consuming and laborious. Molecular breeding : Improvement of
drought tolerance by this method overcomes the bottlenecks of traditional breeding.
Further molecular breeding may be of 2 Types they are :
Marker assisted selection :
Marker-assisted selection, are costly,
slow, require massive screening
labours to identify specific
quantitative traits, while linkage of
Agronomically important QTL´s to
undesirable traits can sometimes
occur.
Best OptionBest Option
Transgenics : A transgenic crop plant contains a
gene or genes which have been artificially inserted instead of the plant acquiring them through pollination.
The inserted gene sequence (known as the transgene) may come from another unrelated plant, or from a completely different species
What is a transgenic?What is a transgenic?
Transgene – A gene introduced in to an organism by means of genetic engineering. This gene may be from the same or a different organism or even a synthetic sequence
Ex. – Daffodil gene in golden rice
Transgenic – an organism containing a transgene introduced through genetic engineering and has become integrated in its genome.
Ex. – BT-COTTON
We can develop crops that express a “novel” trait not normally found in the existing plant
Why are Transgenics important?
Extended shelf-life tomato (Flavr-Savr)
Herbicide resistant soybean (Roundup Ready)
Steps in transgenic development
Nucleic acid extraction
Gene cloning
Gene design and packing
Transformation
Back cross breeding
Introducing the Geneor
Developing Transgenics
Steps
1. Create transformation cassette
2. Introduce and select for transformants
Transformation Cassettes
Contains
1. Gene of interest
• The coding region and its controlling elements
2. Selectable marker
• Distinguishes transformed/untransformed plants
3. Insertion sequences• Aids Agrobacterium insertion
Transformation Steps
Prepare tissue for transformation
Introduce DNA
Culture plant tissue
• Develop shoots• Root the shoots
Field test the plants
• Leaf, germinating seed, immature embryos• Tissue must be capable of developing into normal plants
• Agrobacterium or gene gun
• Multiple sites, multiple years
Plant Transformation Plant Transformation
• Plants are the easiest of higher organisms to transform
• Both physical and biological methods exist for transformation
• Until recently, only transgenic organisms in wide public release were plants
Plant Transformation Methods
Physical Chemical Biological
MicroinjectionBiolistics - gene gun/particle bombardment Electroporation Liposome mediated transformationSilica/carbon fibersmediated Transformation
PEGCalcium phosphate co-precipitationPolycation DMSO technique
A. Tum e fa c ie nsA. Rhiz o g e ne s
Virus-mediated
In planta
Microinjection This Electroporator is for low current applications such as those using small electrodes
Biolistic / Gene Gun
Biological Transformation
Agrobacterium tumefaciens Agrobacterium tumefaciens & & AgrobacteriumrhizogenesAgrobacteriumrhizogenes
Selection of transgenic plantsSelection of transgenic plants
May be of two type Negative selection : The transgenic cells acquire the ability to
survive on selective media while the non-transgenic cells are killed .
positive selection : Actively favours regeneration and growth of the transgenic cells while the non-transgenic cells are starved but not killed.
E. coli -glucuronidase gene has become the most frequently used reporter gene for the analysis of plant gene expression. Major advantage of this reporter is that it does not require DNA extraction, electrophoresis or autoradiography.
Drought Stress Genes Identified
Low temperature responsive genes/proteins in plants
Plant species Genes /ProteinsArabidopsis Rab 18, Kin 1,2
Brassica Oleracea 7K .Da proteins
Cucumis sativus Proteins of 25,50,70,80 K Da
Soyabean HSP 70
Oat 45,75 K Da
Tomato Proteins 27,35 K
Rice Proteins of 95,75,50,25, K Da
Wheat Wes 19, 120
Maize Adh-1
Water stress responsive genes/proteins in plants
Plant species Genes /Proteins
Sorghum BADH 1,15 clone
Cotton LEA Proteins
Sunflower Hsp 17
Soya bean P 5 CR Clone
Oat LEA Proteins
Rice Rab 16 A, Rab 16 B, Rab 16 C
Peas PPs B 12 Clone
Wheat Emla, lb WSP-23
Maize Rab 17,28,LEA Proteins
Expression of the Nicotiana protein kinase (NPK1) enhanced drought tolerance in transgenic maizeExpression of the Nicotiana protein kinase (NPK1) enhanced drought tolerance in transgenic maize
Huixia Shou, Patricia Bordallo and Kan Wang (2004)Huixia Shou, Patricia Bordallo and Kan Wang (2004)
Effect of drought on Apparent Photosynthesis (AP) rate of transgenic and non-transgenic maize plants
Events Apparent photosynthetic rate decrease (%)
Transgenic event
A4-1 19
A4-2 13.8
A4-9 5.3
P84 24.4
Non-transgenic control
Hi II 47Huixia e t a l (2004)
Effect of drought on final leaf number of transgenic and non-transgenic maize
Events Leaf number increases (%)
Transgenic event
A4-1 3.3
A4-2 9.6
A4-9 3.3
P84 3.1
Non-transgenic check
Hi II -2.2Huixia e t a l (2004)
Kernel appearance of transgenic (A4-1, A4-2, A4-9, P84-12) and non-transgenic (Hi II) plants under well-watered (WW)
and drought-stressed (DS) conditions.
Kernel appearance of transgenic (A4-1, A4-2, A4-9, P84-12) and non-transgenic (Hi II) plants under well-watered (WW)
and drought-stressed (DS) conditions.
Modulation of the polyamine biosynthetic pathway in transgenic rice confers tolerance to drought stress
Teresa Capell, Ludovic Bassie, and Paul Christou (2004)
Response of rice plants to drought stress
(A) Phenotype of 2-montholdwild-type (WT) and transgenic plants with adc gene of Datura stramonium (84-2 and 84-9 lineages) growing in soil after drought stress (6 days).
(B) Close-up of rice leaves (wild type on the left and 84-2 on the right)
Response of rice plants to drought stress
(A) Phenotype of 2-montholdwild-type (WT) and transgenic plants with adc gene of Datura stramonium (84-2 and 84-9 lineages) growing in soil after drought stress (6 days).
(B) Close-up of rice leaves (wild type on the left and 84-2 on the right)
Tolerance of Mannitol-Accumulating Transgenic Wheat to Water Stress and Salinity
Tilahun Abebe, Arron C. Guenzi, Bjorn Martin, and John C. Cushman(2003)
Effect of water stress and salinity on the growth of -mtlD and +mtlD plants.
A)The mannitol-accumulating transgenic wheat line P2-19-1 (-mtlD) and the non accumulating P1-13-1 (+mtlD) were stressed by withholding water. B) supplementing the nutrient solution with 150 mM NaCl (B) for 30 days
Effect of water stress and salinity on the growth of -mtlD and +mtlD plants.
A)The mannitol-accumulating transgenic wheat line P2-19-1 (-mtlD) and the non accumulating P1-13-1 (+mtlD) were stressed by withholding water. B) supplementing the nutrient solution with 150 mM NaCl (B) for 30 days
Phenotypes observed in transgenic wheat plants. LinesP2-16-1 and P2-19-1 were transformed with plasmid pTA2 for accumulation of mannitol in the cytosol (mtlD). Line P1-13-1 was transformed with pAHC20 (mtlD) and did not accumulate mannitol. In the fertile mtlD plants, mannitol content ranged from 0.4 to 0.7 micro mol/g fresh weight.
Phenotypes observed in transgenic wheat plants. LinesP2-16-1 and P2-19-1 were transformed with plasmid pTA2 for accumulation of mannitol in the cytosol (mtlD). Line P1-13-1 was transformed with pAHC20 (mtlD) and did not accumulate mannitol. In the fertile mtlD plants, mannitol content ranged from 0.4 to 0.7 micro mol/g fresh weight.
A novel cold-inducible zinc finger protein from soybean, SCOF-1, enhances cold tolerance in transgenic plants
Jong Cheol Kim, Sang Hyoung Lee, Yong Hwa Cheon, Cheol-Min Yo, Soo In Le, Hyun Jin Chun, Dae-Jin Yu. (2001)
Freezing tolerance of SCOF-1transgenic Arabidopsis plants . The transcription of SCOF-1 is specifically induced by low
temperature and absicsic acid.
WT-wild type
Cold tolerance of SCOF-1 transgenic tobacco plants
Wide range of substrate specificity
Highly conserved structure (NADH or NADPH binding region, catalytic tetrad)
Occurrence: from bacteria to Homo sapiens
polyol pathway
detoxification of reactive aldehydes
About the aldose reductase superfamily in general:
Development of first shoots on medium
Transgenic plantletsin soil
Role of ALR For Regeneration of the Transgenic wheat for drought tolerance
Fertile ALR spikes
ALR EXPRESSING TRANSGENIC WHEAT LINES WITH IMPROVED DROUGHT TOLERANCE
CTR
AL
R A
CT
. (A
. U
.)
10
50
ALR ACTIVITY IN LEAF EXTRACTS
20
30
40
TR304 TR288
CTR
(% D
RO
UG
HT
ST
R./
UN
ST
R.)
90
110
HARVEST INDEX(% DROUGHT STR./UNSTR.)
95
100
105
TR304 TR288
CTR
85
125
95
105
115
TR304 TR288
THOUSAND KERNEL WEIGHT(% DROUGHT STR./UNSTR.)
(% D
RO
UG
HT
ST
R./
UN
ST
R.)
Is there any commercial success for drought tolerance through Transgenics ?
Though research on developing transgenic crops has gained momentum across the world and producing commercial results, but they were restricted to biotic stresses only.
As most abiotic stresses are quantitative traits and commercial success for these traits specially for drought is still far from reality.
Agriculture Transgenics On the Market
Source: USDA
Insect resistant cotton – Bt toxin kills the cotton boll worm• Transgene = Bt protein
Insect resistant corn – Bt toxin kills the European corn borer• Transgene = Bt protein
Normal Transgenic
Virus resistance - Papaya resistant to papaya Ring spot virus• Transgene = virus coat protein
Source: Monsanto
Herbicide resistant crops Now: soybean, corn, canola Coming: sugar beet, lettuce, strawberry alfalfa, potato, wheat • Transgene = modified EPSP Synthase or Phosphinothricin-N-acetyltransferase
Next Generation of Ag Biotech Products
Source: Minnesota Microscopy Society
Golden Rice – increased Vitamin A content (but not without controversy)Transgene = three pathway enzymes
Sunflower – white mold resistanceTransgene = oxalate oxidase from wheat
Transgenics in world scenario
Top transgenic crop producers 2010
Ranking by million hectares in GM crops Ranking by % of farmland in GM crops1. USA 64 Paraguay 66% 12. Brazil 21.4 Argentina 65% 23. Argentina 21.3 Uruguay 35% 34. India 8.4 USA 32% 45. Canada 8.2 Brazil 23% 56. China 3.7 Canada 13% 67. Paraguay 2.2 South Africa 11% 78. South Africa 2.1 India 4% 89.= Uruguay 0.8 China 2% 99.= Bolivia 0.8
1. Source: ISAAA Brief 41-2010, www.isaaa.org/resources/publications/briefs/41/default.asp2. Source: Heinemann, Jack A. (2010) Hope Not Hype, Penang: Third World Network
ConclusionConclusion
The conventional breeding strategies have been useful in some cases for the improvement of the drought tolerance. But the success rate is few and far.
Hence Gene manipulations are being looked hopefully for raising the drought tolerant genotypes
Thank youThank you