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Midterm 2 Flashcards

1
Q

How do herbicides (in general) kill plants?

A

plants = autotrophs -> attack any pathways -> guaranteed knockout of any nutrients -> guaranteed death
Target any chloroplast pathways -> photodisruption

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2
Q

How does glyphosate kill plants?

A

Inhibition of EPSP Synthase activity, preventing amino acid synthesis or auxin growth hormones

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3
Q

How are crops GMO’d to survive glyphosate exposure

A

Transgenic EPSP genes
Transgenic EPSP mutant
provide detoxification pathway

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4
Q

Transgenic EPSP

A

counteract glyphosate inhibition by overexpressing EPSP

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5
Q

Mutated EPSP

A

provide CP4 gene (mutant)
Place under constitutive euk promoter (35S or NOS)
Agrobacterium delivery

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6
Q

glyphosate detoxification

A

method of providing glyphosate resistance by inserting transgenic glyphosate oxidases (sourced from soil bacterium)

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7
Q

GATs

A

glyphosate acetyltransferases - enzymes for glyposate detox by acetylation. Naturally occuring bacterial GATs are too weak to make plants HT to glyphosate -> required hybridization of several GAts to achieve a 200x-400x strength super GAT for crop use

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8
Q

What is ALS

A

acetolactate synthase - responsible for synthesis of branched AAs (eg isoleucine)

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9
Q

what can inhibit ALS

A

Suphonylureases

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10
Q

PPT

A

phosphinothricin (herbicide) - targets broadleaf plants. Inhibits glutamine synthase, leading to toxic NH3 accumulation

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11
Q

what detoxifies PPT

A

Can be neutralized phosphinothricin acetyltransferase (acetylation)

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12
Q

BT

A

B.thurigiensis endotoxin (pesticide) - encoded by “Cry” genes
Kills pests by binding to intestinal membranes -> gut breakdown -> septicemia

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13
Q

Transgenic BT

A

required heavy sequence modification of teh cry genes -> 21% base mods, 60% codons changed
Required chimeric/hybridized BT genes to achieve enough toxicity to kill pests

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14
Q

Importance of low pesticide GMO expression crops (a reservoir)

A

maintains a population of low resistance pests -> dilutes the overall pesticide tolerance in the pest population therefore preventing/slowing evolution of complete immunity to the pesticide

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15
Q

3 types of plant-bacteria interactions

A

necrotrophs -eat dead tissue
biotrophs - eat live tissue
hemitroph - eats both

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16
Q

2 types of disease resistances

A

host resistance - organism specific (a novel mutation)
non-host resistance - species wide resistance to the disease

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17
Q

Disease resistance by physical methods

A

cuticles/max to seal the exterior
bark (thick layers of dead cells)

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18
Q

Disease resistance by proteins/chems

A

antimicrobics (eg SN1 peptide)
defensins

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19
Q

Disease resistance by inducible pathways

A

usually protein synthesis in response to a disease
Pathogen -> plant cells die -> plant detects cell fragments -> cascade -> response protein synthesis (eg SN1 peptide antimicrobic)

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20
Q

MAPK disease response pathway

A

Antigen on the pathogen is detected –> binding to cell -> kinase activation -> MAPK phosphorylation -> MAPK cascade -> stromal closure (prevent further pathogen entry)

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21
Q

chitinases

A

recognize pathogen -> tagging the pathogen membrane
tagged membrane is targeted by lethal phenolic compounds –> kills the pathogen

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22
Q

Fungal/mould infections

A

usually oomycetes
eg A. flavus -> produces aflatoxin (carcinogen)

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23
Q

How is A.flavus infection countered

A

GMO a mutant of A.flavus with deactivated aflatoxin genes -> expose to plants -> occupy niches -> therefore teh natural (lethal) bacterium can’t infect that plants

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24
Q

Race specific responses

A

each pathogen is recognized based on a unique gene it carries (avirulence (avr) gene)
the plant carries a corresponding resistance gene (R gene) to match

if an avr is recognized by a present R gene -> defence response occurs

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25
Systemic Acquired Response
Method of plant-plant comms for disease spread pathogen -> detection -> plant excretes salicyclic acid -> ethylene + jasmonic acid production -> warning signal to other plants
26
what proportion of plant virusses are ssRNA
~70%
27
Tobacco mosaic virus (TMV)
used in biotech due to self-assembly capability ssRNA genome is replicated into a (-) sense RNA -> (-) sense used as template for genome replication subgenomic RNA (sgRNA) used to regulate viral spread
28
Cowpea mosaic virus (CPMV)
carries 2 ssRNAs icosahedral capsid --> potential for nanoparticle delivery vesicle
29
Coat Proteins vs ArMV
Arabis mosaic virus (ArMV) resistance coat proteins (CP) used for capsid synthesis -> overexpress CP = infecting virus reforms capsid -> therefore prevents machinery from expressing the viral genome CP overexpression -> reform capsid -> can't replicate virus
30
why is overexpression of CP genes bad?
overexpresison of CP rna --> PTGS effects --> negates the resistance
31
Pathogen derived resistance (PDR) using satellite virusses
satellite virus = virus that requires a helper virus to replicate infection w/satellite forms dsRNA with helper virus -> RISC PTGS
32
how do virusses counter PDR?
virus carries antisense RNA to hybridize with the satellite virus --> forms siRNA -> RISC complex -> PTGS of the satellite virus
33
non-PDR resistance against viral infection
introduce transgenic protein kinase to disable eIF2a (translation factor) --> disable viral protein translation (Ideally place under wound-induced control)
34
benefit of non-PDR method?
disabled the eIF2a --> affects many virusses broad-range resistance
35
Geminiviruses
DNA viruses rolling replication relies on Ren + Rep + TrAP genes transgenic Ren/Rep/TrAP antisense -> RISC -> PTGS therefore disabling geminivirus replication
36
Define water potential
the tendency for water to move from A to B higher water potential = easier to move the water
37
env factors affecting water stress
T [salts] wind soil porosity
38
how do plants control water flow?
water moves towards higher salt concentrations (osmosis) --> therefore concentrate salts in tissues with low water
39
water stress vs turgor pressure
more water = more turgor pressure if turgor drops -> stroma closes to prevent water loss by transpiration
40
shell of hydration
proteins are surrounded by H2O --> prevents oxidation from O2 contact therefore if SoH breaks -> proteins denatured
41
osmolytes/osmoprotectants
used to maintain the shell of hydration (may be natural or transgenic)
42
osmoprotectant examples (6 types) remember POSM
pinitol ononitol sorbitol manitol zwiterions oligosaccharides
43
why is high salinity soil bad
due to osmosis, water will prefer to stay in the saline soil (reduced water potential)
44
halophyte adaptations
use sodium transports to intake salt -> cause osmosis into the plant use sodium antiports to detox from the high salt intake
45
glycophytes
use high expression of osmolytes/osmoprotectants to maintain SoH llimited salt tolerance due due to Na/Cl toxicity they cope with the salt, not deal with it
46
ROS
oxidative stresses --> ROS --> free radicals --> damage to NA + proteins
47
types of counters to ROS
antioxidants enzymatic free radical reduction
48
examples of antioxidants
glutathione Beta carotene vit C Vit E
49
examples of enzymatic free radical reduction
superoxidase dismutase catalase peroxidase
50
Cold response genes (CDL acronym)
C-repeat element (CRT) dehydration response element (DRE) low T response element (LRTE)
51
transgenic cold response genes
transgenic cold genes + constitutive expression --> plants dont need to acclimatize to cold weather
52
Tomato ripening
ethylene -> ripening signal -> over expression of ripening leads to rot
53
ripening genes
pTOM5 = red pigment pTOM6 = polygalacturonase (ripening) -> also affects pectin methylesterase pTOM13 = ethylene synthesis
54
FlavrSavr Tomato GMO
goal: delay rotting to extend shelf life method: antisense pTOM6 -> some PTGS of polygalacturonase (not full antisense expression, allow some PG) less PG -> less pectin methylesterase -> less pectin degradation
55
effects of antisense other tomato ripening genes
antisense pTOM5 -> no red pigments --> yellow + impacted photosynthesis (dwarfism) antisense pTOM13 -> no ethylene synth -> VERY slow rotting (2x shelf life)
56
Golden rice - VitA
rice normally = low vitA golden rice -> modified with bacterial + daffodil enzymes -> able to synthesize vitA -> fix vitA deficiencies
57
Golden rice - treating diarrhea
transgenic lactoferrin -> antimicrobic + antiinflammatory -> decrease diarrhea for low hygeine regions
58
Golden rice - improving photosynthesis
attempted to replace photosynthetic rubisco enzyme with cyanobacterial analog (to get more efficient PS) -> not much better -> concerns of HGT into weeds -> worsening weed growth/spread -> risk not worth the marginal PS increase
59
using plants for biosynthetics - Why are chloroplast transgenes so important
- chl genes are constitutively expressed - chl genes are better conserved + less likely to be mutated (eg by infections) - chl gene are maternally inherited --> can be used for tracking gene lines
60
carbohydrate biosynthetics - starch composition
20-30% linear amylose + 70-80% branched amylopectin
61
high starch barley GMO
want more linear amylose for berewing -> introduce ssRNA for amylopectin -> form dsRNA hairpin -> RISC -> PTGS of branched amylopectin. This forces teh barley to only produce the linear amylose
62
bioplastics synthesis
cellulose or starch -> nitrocellulose -> cellulose acetate -> cellulose acetate phthalate (bioplastic) or starch -> thermoplastic starch -> starch polycarbonate -> starch-modified cellulose -> starch vinyl alcohol
63
significance of PLA
it can be naturally biodegraded over 3-6 months into various byproducts -> useful as a packaging material
64
protein synthesis from GMOs
transgene expression of proteins -> Use see-specific promoters -> 36x more expression chloroplast expression (more effective) products: proteins, antibody domains, enzymes
65
plantibodies
plant-produced antibodies

Biol 433 (custom) (1 decks)

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