Download Round-up Ready - Howard University > Plant Biotechnology

Plant Biotechnology Workshop, July,2011
ROUNDUP and ROUNDUP READY Soybean
Weed management by plant biotechnology
Abul Basar
Graduate Student
Department of Biology,Howard
University
Washington, D.C
why do we need to manage weed while our desired crops is being
grown???
Crops
Weed
So you must weed out your field?
How?
1. Machine/Human:
2. Herbicide:
Problem:
Human/ Machine: weed can regrow, labor cost resulting high production cost
Herbicide: Most of the herbicides are used at the pre- emergence of the crop.
weed can regrow, and then you can’t use it again because it can kill your
desired plant.
Herbicide Modes of
Action
1.
Inorganic (contact)
•
Ex. Cu2SO4, NH4SO4
•
Plasmolysis
2. Auxin-like (systemic)
•Phenoxy-acids: 2,4-D; 2,4,5-T
•Rapid stem elongation
•Cells starve
2,4,5-T = agent orange - contam. W/ dioxin
Photosystem inhibitor
Diquat,
paraquat
Atrazine
Atrazine inhibits photolysis of water
3. Photosystem inhibitor: Atrazine
Fate in environment
•Moderate persistence
•7-9 mo. Half-life
•“dry-year carryover”
•Surface water
•1-70 ppb – rural creeks
•1000 ppb – agric. ditches etc.
4. Metabolic Inhibitors
•Dintrophenols – x electron transport
•“Round-Up”- Amino Acid Synthesis Inhibitor
Essential
Nonessential
Isoleucine
Alanine
Leucine
Arginine
Lysine
Aspartate
Methionine
Cysteine
Phenylalanine
Glutamate
Threonine
Glutamine
Tryptophan
Glycine
Valine
Proline
Histidine
Serine
Tyrosine
Asparagine
Selenocysteine
Pyrrolysine
Aromatic amino acid production pathway in plant
3-phosphoshikimate
+
Phosphoenolpyruvate
-----
3-phospho-5-enolpyruvylshikimate
synthase (ESPS)
3 phospho-5-enolpyruvylshikimate-
--
Phenylalaninie, Tyrosine (Aromatic a.a)

Glyphosate ‘kills’ EPSP enzyme; so no aromatic
a.a.
3-phosphoshikimate
-----
Glyophosphate/roundup
+
Phosphoenolpyruvate
3-phospho-5-enolpyruvylshikimate
synthase (ESPS)
3 phospho-5-enolpyruvylshikimate-
--
Phenylalaninie, Tyrosine (Aromatic a.a)

But the enzyme is same but how they made resistant to round up
Initial Goal:
1. Over production of the ESPS : Failed , though it can give some sort of
resistance but it can not withstand against the concentration used in
field to kill weed.
2. Introduction of glyphosphate degradation gene. Though it works but the
advanced study was not possible due to technological limitation, as it
does not work in cell free system.
3. Isolating Glyphosphate resistant ESPS.
Survival for the fittest………………………….
As the herbicide mixed up with the environment so the bacteria may evolve an
alternative pathway to survive like antibiotic resistant bacteria…..
Why Bacteria not Plant?????
High multiplication Rate , more mutation, better and rapid adaptation to environment
So the scientists began to look for the alternative form of ESPS enzyme that
will not be affected with the round up
E.coli……..Bacillus….Agrobacterium
How can we use this ESPS gene
Put it into the soybean plant so that when u use the herbicide they
can synthesize their aromatic amino acid and remain viable……………..
Construct: Clone it and put it into the plant……………..……but it will not
express until you put it under plant promoter and need terminator to
terminate it.
Plant DNA CMV 35s promoter CP4-ESPS gene
nos terminator plant DNA
==========================================================
Advantage:
•Wide spectrum weed control
•Increasing the ability to use need basis
•Offering less dependence on herbicide before plnating
•No till system, reduce soil erosion and fuel cost
•Cost effective because less number of herbicide used in their
herbicide control management system.
Disadvantage:
•Herbicide Resistant plant may appear
•Surfactant used with Glyophosphate is harmful to human