Lecture 18: Plant Biotechnology Flashcards
highly effective method have been developed to
transform plants & for plant tissue culture & regeneration
Golden rice
- milled rice doesn’t contain BETA-CAROTENE
- vitamin A deficiency afflicts over 200million children&woman
- ~500,000children go blind
- 2million children under 5 years die each year
Isopentenyl pathway
metabolite that gives rise to all colour in plants
Golden Rice: pathway
Isopentenyl pathway –>Geranyl geranyl pyrophosphate –phytoene synthase (plant)–>Phytoene–carotene desaturate (bacterial)–>Lycopene–>carotene—>Vitamin A
Understanding plant & bacterial biochemistry combined with GM tech allows manipulation of carotene biosynthesis in rice
Timeline Golden Rice:
1984: initial research on transgenic rice
(1992:First GMO plant approved for consumption)
1996: First Golden Rice prototype
2004: First field trials
2004: Intellectual property rights agreed
2005: Golden rice 2
Bill&Melinda Gates Foundation Funding
2013: ongoing field trials trashed in the philippines
after 30yrs Golden Rice is still not acc being used
Example of GM crops: Bt toxin
- Bt toxin used as commercial insecticide since 1960’s
- natural toxin produced by Bacillus thuringiengis
- 1990s: Bt gene transferred into crop plants (maize, cotton)
Example of GM crops:
herbicide tolerant plants
in plants pathway where NO3–>NO2–>NH4–glutamine synthetase–>glutamine–>amino acids
Phosphinothricin - herbicide (ACITVE) inhibits Glutamin synthetase enzyme
PAT converts Phosphinothricin (active) to Acetyl-Phosphinothricin (inactive)
resistant plants have PAT so inactivates Active herbicide
Phosphinothricin tolerant plants: - herbicide Phosphinothricin & non-transgenic (e.g. weed)
GROWTH
Phosphinothricin tolerant plants: -herbicide Phosphinothricin & transgenic with PAT gene
GROWTH e.g. maize
Phosphinothricin tolerant plants: + herbicide Phosphinothricin & non-transgenic (e.g.weed)
NO GROWTH
Phosphinothricin tolerant plants: +herbicide Phosphinothricin & transgenic with PAT gene (e.g. maize)
GROWTH
Glyphosate tolerant plants
-Glyphosate inhibits aromatic amino acid biosynthesis
in the chloroplast
-Bacterial mutant EPSP synthase retains affinity for PEP substrate but does not bind glyphosate
-ROUNDUP READY SOYBEANS
— Facilitates no-till agriculture
—But yields have not usually increased and new weed species have emerged
using transgenics to provide resistance to pathogens: Phytophera infestans
- potato blight
- S. tuberous (sensitive)
- S. bulbocastanum
- -sexual crossing no longer possible
-inoculate with fungus s.b = resistant
__% crop loss/year due to disease
30-40
wheat stem rust:
•A new, highly pathogenic strain emerged in Uganda in 1999 – it is called Ug99.
•Most wheat has no resistance to this strain.
•Without resistance and chemical control, a rust
outbreak can lead to loss of 90% of the crop
-spores can easily spread all over world
plant growth is often limited by
drought stress.
- Mild drought stress reduces the rate of photosynthesis and growth, whereas extreme drought stress is lethal.
a plant drought tolerance can be altered by a
single gene.
-HDG11 encodes a transcription factor.
Overexpressing the transcription factor leads to drought tolerance in Arabidodopsis
wheat yield 1961-200 __% increase but has come at a cost
300
-All the chemicals we put on the crops. Bt-cotton can lead to >50% decrease in pesticide use but glyphosate resistant weeds are increasing
GM plant could allow us to grow plants in __ climates.
or develop resistance __ to novel pathogens
drier
quickly
all crops are the result of selective breeding: (maize)
- ancient maize (teosinte)
- modern maize (Zea mays)
fertiliser is an _____ resource
energy-demanding limiting
- Crops need fertilizer – potassium, phosphate, nitrogen, and other nutrients
- Potassium and phosphate are non- renewable, mined resources
- Synthesis of nitrogen fertilizers requires huge amounts of energy
- Need to get agriculture to work more efficiently
many of the solution to increasing yield sustainability require an…
understanding of plant development.
- roots and N2
- changing leaf structure to enable more efficient photosynthesis (C4)
Rhizobium infection leads to N2 fixation
Nodules are formed - bacteria take over programme for lateral root formation
-Requires a specific host- derived
structure, the nodule. -Developmentally related to lateral root.
C3 vs C4 plants
C3
- Chloro in M cells
- LARGE distance between BS
- SMALL proportion of BS tissue
C4
- Chloro in BS cells
- SMALL distance between BS
- LARGE proportion of BS tissue
