Herbicide resistance, Herbicide resistance gene, reportor genes

2. why herbicide tolerance plants?
• Weeds are unwanted and useless plants that grow with the
crops these are compete with crops for light, place, food
resulting reducing crop quantity
• Approximately 20% of production lost through weeds
infestation per annum
• Weeds are controlled either mechanically or culturally tisuse are
expensive and cause damage to crops and soil.

3. Herbicides:
• The chemical compounds which kills the weeds
• these are 2types 1) Narrow spectrum 2) broad spectrum
• Mostly used herbicides are broad spectrum they kills broad range
Ideal herbicide have the fallowing characters :
1. Killing weeds without affecting crops
2. No toxic to animals and MOS
3. Rapidly translocate in trangent plants
4. Rapidly degraded in soil.

4. Glyphosate resistance
• Glyphosate is glycine derivative
• It is a broad spectrum herbicide it acts on shikimate pathway
• Glyphosate acts as competitive inhibitor of 5-enoyl pyruvate
shikimate 3-phaspate synthase(EPSPS) it is a key enzyme in
shikimate pathway
• which is important for production of aromatic aminoacids
phenylalanine, tryptophan, and tyrosine

5. • The enzyme EPSP synthase catalyses the
synthesis of 5-enoylpyruvateshikimate 3-
phospate from shikimate 3-phospate &
phosphoenolpyruvate
• Glyphosate more tightly bind with EPSP
synthase
• Because glyphosate has structural similarity
with substrate phosphoenoyl pyruvate
• So blocks the shikimate pathway

6. + Glyphosate
X
X
X
Shikimic acid + Phosphoenol pyruvate
3-Enolpyruvyl shikimic acid-5-phosphate
(EPSP)
Plant
EPSP synthase
Aromatic
amino acidsWithout amino acids,
plant dies
X

7. Detoxification in trangent plants
• The aroA gene convert glyphosate into non herbicidal
compound
• So the shikimate pathway is continue and produce amino acids
• These genes are characterized from Salmonella species
• Introduced into plant system it become resistant to glyphosate

8. PHOSPHINOTHRICIN
RESISTANCE(Glufosinate)
• Mechanism:
• phosphinothricin acts as competitive inhibitor of enzyme glutamine
synthase
• Glutamine synthase is an enzyme which convert ammonium into
glutamine
• when Glufosinate is spry It blocks the Glutamine synthase
• SO NH3 levels increase in plant it leads to death of plant.
• NH3 Glutamic acid Glutamine
GS
PPT

9. Detoxification in trangent plants
• The bar genes codes for phosphinothricin acityle transferase
enzyme it converts the phosphinothricin into non herbicidal
compound by transferring acityle group.
• So the plant will be resistant to PPT.
• These genes are charectarised from Streptomysis species
• and introduced into plant system by using CaMv 35s promoter.
NH3 glutamic acid glutamine
GS
PPT

10. Bromoxyline
• It is also most widely used herbicide
• Its acts on PS-II
• Bromoxyline is binds to Quinone complex of PS-II it inhibits the
electron transfer
• It leads to death of plant

11. Detoxification in trangent plants
• The bxn gene codes for nitrilase
• It convert the bromoxyline into 3,5 di bromo 4 hydroxyl benzoic
acid & ammonia which is non herbicide compound
• These genes are characterized from klbsepsella
• nitrilase
NH3