Transcript Slide 1
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