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Biol 433 (custom) > Midterm 2 > Flashcards

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
Q

Systemic Acquired Response

A

Method of plant-plant comms for disease spread
pathogen -> detection -> plant excretes salicyclic acid -> ethylene + jasmonic acid production -> warning signal to other plants

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26
Q

what proportion of plant virusses are ssRNA

A

~70%

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27
Q

Tobacco mosaic virus (TMV)

A

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
Q

Cowpea mosaic virus (CPMV)

A

carries 2 ssRNAs
icosahedral capsid –> potential for nanoparticle delivery vesicle

29
Q

Coat Proteins vs ArMV

A

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
Q

why is overexpression of CP genes bad?

A

overexpresison of CP rna –> PTGS effects –> negates the resistance

31
Q

Pathogen derived resistance (PDR) using satellite virusses

A

satellite virus = virus that requires a helper virus to replicate
infection w/satellite forms dsRNA with helper virus -> RISC PTGS

32
Q

how do virusses counter PDR?

A

virus carries antisense RNA to hybridize with the satellite virus –> forms siRNA -> RISC complex -> PTGS of the satellite virus

33
Q

non-PDR resistance against viral infection

A

introduce transgenic protein kinase to disable eIF2a (translation factor) –> disable viral protein translation
(Ideally place under wound-induced control)

34
Q

benefit of non-PDR method?

A

disabled the eIF2a –> affects many virusses
broad-range resistance

35
Q

Geminiviruses

A

DNA viruses
rolling replication relies on Ren + Rep + TrAP genes
transgenic Ren/Rep/TrAP antisense -> RISC -> PTGS therefore disabling geminivirus replication

36
Q

Define water potential

A

the tendency for water to move from A to B
higher water potential = easier to move the water

37
Q

env factors affecting water stress

A

T
[salts]
wind
soil porosity

38
Q

how do plants control water flow?

A

water moves towards higher salt concentrations (osmosis) –> therefore concentrate salts in tissues with low water

39
Q

water stress vs turgor pressure

A

more water = more turgor pressure
if turgor drops -> stroma closes to prevent water loss by transpiration

40
Q

shell of hydration

A

proteins are surrounded by H2O –> prevents oxidation from O2 contact
therefore if SoH breaks -> proteins denatured

41
Q

osmolytes/osmoprotectants

A

used to maintain the shell of hydration (may be natural or transgenic)

42
Q

osmoprotectant examples (6 types) remember POSM

A

pinitol
ononitol
sorbitol
manitol
zwiterions
oligosaccharides

43
Q

why is high salinity soil bad

A

due to osmosis, water will prefer to stay in the saline soil (reduced water potential)

44
Q

halophyte adaptations

A

use sodium transports to intake salt -> cause osmosis into the plant
use sodium antiports to detox from the high salt intake

45
Q

glycophytes

A

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
Q

ROS

A

oxidative stresses –> ROS –> free radicals –> damage to NA + proteins

47
Q

types of counters to ROS

A

antioxidants
enzymatic free radical reduction

48
Q

examples of antioxidants

A

glutathione
Beta carotene
vit C
Vit E

49
Q

examples of enzymatic free radical reduction

A

superoxidase dismutase
catalase
peroxidase

50
Q

Cold response genes (CDL acronym)

A

C-repeat element (CRT)
dehydration response element (DRE)
low T response element (LRTE)

51
Q

transgenic cold response genes

A

transgenic cold genes + constitutive expression –> plants dont need to acclimatize to cold weather

52
Q

Tomato ripening

A

ethylene -> ripening signal -> over expression of ripening leads to rot

53
Q

ripening genes

A

pTOM5 = red pigment
pTOM6 = polygalacturonase (ripening) -> also affects pectin methylesterase
pTOM13 = ethylene synthesis

54
Q

FlavrSavr Tomato GMO

A

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
Q

effects of antisense other tomato ripening genes

A

antisense pTOM5 -> no red pigments –> yellow + impacted photosynthesis (dwarfism)
antisense pTOM13 -> no ethylene synth -> VERY slow rotting (2x shelf life)

56
Q

Golden rice - VitA

A

rice normally = low vitA
golden rice -> modified with bacterial + daffodil enzymes -> able to synthesize vitA -> fix vitA deficiencies

57
Q

Golden rice - treating diarrhea

A

transgenic lactoferrin -> antimicrobic + antiinflammatory -> decrease diarrhea for low hygeine regions

58
Q

Golden rice - improving photosynthesis

A

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
Q

using plants for biosynthetics - Why are chloroplast transgenes so important

A
  • 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
Q

carbohydrate biosynthetics - starch composition

A

20-30% linear amylose + 70-80% branched amylopectin

61
Q

high starch barley GMO

A

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
Q

bioplastics synthesis

A

cellulose or starch -> nitrocellulose -> cellulose acetate -> cellulose acetate phthalate (bioplastic)
or
starch -> thermoplastic starch -> starch polycarbonate -> starch-modified cellulose -> starch vinyl alcohol

63
Q

significance of PLA

A

it can be naturally biodegraded over 3-6 months into various byproducts -> useful as a packaging material

64
Q

protein synthesis from GMOs

A

transgene expression of proteins -> Use see-specific promoters -> 36x more expression
chloroplast expression (more effective)
products: proteins, antibody domains, enzymes

65
Q

plantibodies

A

plant-produced antibodies

Biol 433 (custom) (1 decks)

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