Genetic Improvement of Crop Plants short version with animation links

Report
Development of Crop Plants - History
• Domestication of crops
• We have been modifying our crops
for 10,000 years through Selection.
• All crops we grow today have
undergone extensive genetic change
from their wild ancestors.
• Crops, strains and genes have
moved around the globe.
Domestication of
corn creating a
new species in the
process – Zea mays
Teosinte
Hybrids
Modern Corn
Thanks to C.S. Prakash for some of the pictures on this and the next couple of slides.
The domestication of animals has also been
accompanied by extensive human-directed
genetic modification. This is exemplified with the
domestic dog, Canis familiaris.
Modern genetics including genomics
indicates that all domestic dogs are
originally derived from the wolf,
Canis lupus. Thus the Siberian
Husky and Mexican Chihuahua are
derived from the same original specie
with the only difference being the
extent of the genetic modification!
Traditional Breeding
Crossing individuals with desirable
characteristics (e.g. yield) and selecting among
the progeny. Genes recombine in a random
fashion and finding superior progeny has been
as much art as science. Needs excellent
management since it’s a numbers game and
genotype often masked by environmental
influences.
For specific characteristics such as fatty acid % of oil, naturally
occurring mutants screened for and if not found induced by
chemical mutagenesis or irradiation.
Conventional:
Wide Hybridization introduces
20,000 to 100,000 potentially
negative genes in order to obtain
one desirable disease resistance
gene.
Induced mutagenesis has been
used for decades to create
genetic variants.
Genetic Engineering:
Introduce one (or a few) foreign
“good” genes into the best accepted
cultivar background.
Genetic Engineering:
Introduce one (or a few) foreign
“good” genes into the best accepted
cultivar background.
The main thing that is new with
genetic engineering is that species
barriers can now readily be bridged.
Genetic Engineering:
Introduce one (or a few) foreign
“good” genes into the best accepted
cultivar background.
The main thing that is new with
genetic engineering is that species
barriers can now readily be bridged.
This opens new opportunities and
depending on how it is used requires
new safeguards.
Recombinant
DNA?
DNA_Extraction.swf
Gene Cloning
Chromosomal
DNA
Ti plasmid
T-DNA
Chromosome
T-DNA
Crown
Gall
A. tumefaciens
Agrobacterium
tumefaciens
Plant chromosomes
containing T-DNA
Plant crown gall tissue
naturally transgenic
How Do You Introduce
a Foreign Gene into
a Recipient Organism?
Overview
Methods Used to Date for
Plant Transformation
Agrobacterium tumefaciens and rhizogenes
Gene Gun Microprojectiles (PDS)
Electroporation of protoplasts
Microinjection
Pollen Tube Pathway
Silica Carbide fibers
Microlaser
Viruses [some native genes replaced]
plasmid
Recombinant
plasmid
Desired DNA
Plant cell
inoculated with
A. tumefaciens
Regenerant
Plant cell containing Desired DNA
Agrobacterium
tumefaciens
containing Wt
Ti plasmid
Adult plant expressing
desired trait (DNA)
A. tumefaciens containing
engineered Ti plasmid
Cultured plant cells
Inserting foreign genes into plant cells. A plasmid containing DNA is cut with a restriction enzyme & DNA of
desired gene (red) inserted. Desired gene then inserted into Ti (tumor-inducing) plasmid naturally found in A.
tumefaciens. Plant cell inoculated with A. tumefaciens containing engineered Ti plasmid + the desired DNA
transfers desired DNA + t-DNA into plant chromosomes. Plantlets with desired trait then regenerated.
The Gene Gun
Helium chamber
Rupture disk
Macrocarrier
DNA coated
gold particle
Stopping screen
Focusing device
PDS1000 Microparticle Delivery System
Gene gun
Target tissue
From Collins lab
Biolistic Transformation
Before impact
DNA coated gold particle
During impact
Plant Cell Wall
?
After impact
How do Genes do Their Job?
GENE EXPRESSION
DNA
Transcription
mRNA
Translation
Protein
Structural Gene
Enzyme (Protein)
Product A
Product B
Roundup Ready Crops
Monsanto web page:
Roundup (Glyphosate) is a very strong inhibitor of EPSP1
Synthase.
PEP
Shikimate
3-phosphate
O
-
C
O
-
O
O
C
O
-
C
EPSP
O
+ Pi
+
C
CH2
Pi
O
OH
O
Pi
O
-
OH
Pi
C
O
OH
O
NH
Glyphosate
CH2
Pi
1EPSP =
5-ENOLPYRUVYLSHIKIMATE 3-PHOSPHATE
P h e, T rp , T y r
CH2
O
C
C
-
O
Sulfonylurea Tolerant Soybeans - STS These cultivars are resistant to certain sulfonyl ureas (SUs), a
family of herbicides which are most effective against broadleaf
weeds. STS herbicides used over soybean varieties that have the
STS gene offer the benefit of using broad spectrum sulfonylurea
broadleaf herbicides without injuring young soybean plants.
Labeled sulfonylurea herbicides include Synchrony STS¹, Reliance
STS¹, Classic¹, Pinnacle¹, Canopy¹, Canopy XL¹ and Concert¹.
The STS gene was incorporated into soybean germplasm using
conventional breeding methods.
SU tolerant gene induced by EMS mutagenesis (US patent #
5,084,082).
Bx breeding
Mechanism of action of SUs
SUs inhibit the essential plant enzyme acetolactate
synthase or ALS. Animals do not have ALS.
O
-keto butyrate
HC
O
HC
O
-
O
HC
CH2
H 3C
CH3
C
CH
CO2
O
HC
O
HC
O
CH3
H2
C
acetolactate
O
-
OH
O
O
CH3
-
pyruvate
H 3C
isoleucine
-
HC
O
HC
NH2
CH
CH2
CH3
+
+
Charles Darwin...
“
It is not the
strongest species
that survive, nor the
most intelligent, but
the ones most
responsive to change”
“I’m all for progress; it’s change I
don’t like” - Mark Twain
Slide from C.S. Prakash

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