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B3.0 > Surviving The Deluge: Flooding Stress > Flashcards

Surviving The Deluge: Flooding Stress Flashcards

1
Q

Plants and submergence

A
  • Water excess, relatively common stress
  • several wild species, but few crops thrive in such an environment
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2
Q

Water logging

A

Only the below-ground part is under water saturating conditions

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3
Q

Flooding

A

Partial and complete submergence

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4
Q

Partial submergence

A

Root system and portion of shoot underwater

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5
Q

Complete submergence

A

Whole plant covered

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6
Q

Economic impact of crop flooding

A

Largest stressor!

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7
Q

Dynamics of flooding events

A
  • intensity, timing, duration = changing
  • frequent: UK, CE, Balkan area
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8
Q

Why is submergence a stress to plants?

A
  • anoxia
  • anaerobic activity of roots and rhizosphere
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9
Q

ROS

A
  • affect mitochondria and chloroplasts
  • < photosynthesis
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10
Q

Submergence process:

A
  1. Soil redox potential «
  2. Accumulation of toxic compounds (Mn2+, Fe2+, H2S)
  3. Gases diffuse 10^4 slower in water than air (severely &laquo_space;O2, CO2 availability; ethylene entrapment)
  4. Fermentation
  5. Carbon starvation
  6. &laquo_space;photosynthesis
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11
Q

Anaerobic metabolism

A
  • fermentations necessary to replenish glycolysis NAD+
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12
Q

Fermentation process

A
  1. Starch -> soluble sugars
  2. Soluble sugars -(glycolysis)-> pyruvate (NAD+ -> NADH; ADP -> ATP)
  3. Pyruvate -lactate dehydrogenase-> lactate (toxic! Acidifies, damages cell) (NADH -> NAD+)
    OR
  4. Pyruvate -pyruvate decarboxylase-> acetylaldehyde (toxic!)
  5. Acetylaldehyde -alcohol dehydrogenase-> ethanol (preferred!) (NADH -> NAD+)
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13
Q

Phytoglobins

A
  • plant Hbs
  • v high O2 affinity
  • no long distance transport
    • nitrate reductase: NAD+ regeneration
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14
Q

Nitrite

A

Alternative e- acceptor in mETC

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15
Q

A. thaliana ERFVIIs TFs

A
  • 5x total
  • 2x hypoxia-inducible (relative expression level across hypoxia time course)
  • transient/permanent up regulation
  • v conserved N terminus
  • cysteine residue followed by 2x glycines
  • very rare feature of proteins
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16
Q

N-degron pathway

A

Determines protein (in)stability depending on exposed aas

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17
Q

Oxygen-dependent oxidation of N-terminal cysteine (+R)

A

Prepares proteins for degradation

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18
Q

Cysteine in 2nd position

A
  • dangerous!
  • exposure R residue; degradation signal
  • PTM + R
  • 4x possible pathways
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19
Q

N-degron 4x pathway 1

A
  1. MC -MetAP-> C
  2. C -> *C
  3. *C -> RC
  4. RC -NO-> degradation
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20
Q

N-degron pathway 2

A
  1. MC -> NQ
  2. NQ -NTAN/NTAQ-> DE
  3. DE -ART6/VBR1-> R
  4. R-Ub-> degradation
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21
Q

N-degron pathway 3

A
  1. MC -endoproteolytic cleavage-> DE
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22
Q

N-degron pathway 4

A
  1. MC -> R
23
Q

Hiding from N-degron?

A

Mask/decorate

24
Q

N-degron ERFVII regulation

A
  • priming effect
25
Q

N-degron mutant analysis

A
  • mimic hypoxia
  • ate1/ate2, prt6 -> mutant genes are core hypoxia responders
26
Q

RAP2.12

A

wt = degraded
wt (hypoxia) = stabilised
ate1ate2 = stabilised
erfr11 = less DEGs under hypoxia (1% O2)

27
Q

High O2

A
  1. O2 + HIF-1α tags with Pro
  2. PH tags with OH
  3. pVHL targets for degradation
28
Q

Low O2 sensing in mammals

A

No PH

29
Q

PH

A
  • prolyl hydroxylase
  • transcriptionally regulated by HIF-1α
30
Q

Summarising O2 sensing in mammals

A
  • O2 dependent enzymatic proline residue hydroxylation in HIF-1α TF stimulates proteasomal degradation
  • stabilised HIF-1α induces metabolic + developmental genes (e.g. angiogenesis)
31
Q

For O2 sensing, both plants and animals rely on

A

aerobic degradation of a constitutively produced TF

32
Q

Can N-cysteine oxidation be enzymatically catalysed in plants?

A
  • localise in cytosol + nucleus (GFP localisation)
  • 2x hypoxia inducible
  • regulate other nuclear proteins?
33
Q

Cysteine oxidase in planta

A

Oxygen sensors! PCOs

34
Q

Oxygen sensing

A

Cysteine -O2 dependent cysteine oxidase- cysteine sulfunic acid

35
Q

HUP29, 43

A

Cysteinyl dioxygenase activity; PCOs

36
Q

PCO biochemical characterisation

A

Mass spectrometry analyses have confirmed that PCO can add 2x O2 atoms to ERFVII N-termini

37
Q

ERFVII interacting proteins

A
  • RAP2.12 interacts with ACBPs in PM
  • shown by biomolecular fluorescence complementation assay; photoconvertible + UV
38
Q

RAP2.12

A

Constitutive ERFVII

39
Q

RAP2.12 behaviour under hypoxia

A

Nuclear localisation

40
Q

HRPE

A
  • ERFVII enhancer
  • compare hypoxia promotors for signature
  • trim + luciferase fusion construct: measure expression under hypoxia
  • C9 motif KO: necessary
  • 32nt 3x repeat KI: sufficient
41
Q

ERFVII TF

A

Relocalisation and stabilisation in buckets to activate hypoxia genes

42
Q

Can we target ERFVIIs in plant breeding? Logic

A
  • modulating N-degron pathway (prt6) ; does this enhance plant flooding survival ??
  • hypoxia tolerance assays in vitro
  • submergence assays in soil
43
Q

Can we target ERFVIIs in plant breeding? Results

A
  • HRE1 hyper-expression = +ve
  • hyperstability (masking N-terminal cysteine) severely compromises plant development
  • silencing / spontaneous mutation = +ve
44
Q

Hormone homeostasis under submergence

A
  • phytohormone biosynthesis -> require O2 (+ATP) cosubstrate(s)
  • hormone metabolism depends on enzyme oxygen affinity
45
Q

Ethylene

A
  • gaseous
  • biosynthesis enzymes induced in hypoxia in several sp.
  • ACS, ACO
46
Q

Ethylene biosynthesis

A

Methionine -AdoMet synthetase-> S-Ado-Met -ATS-> amino-cyclopropanone carboxylic acid -ACO (O2->CO2) -> ethylene

47
Q

Acclimation

A
  • ethylene pretreatment = increased hypoxia tolerance
  • ethylene + hypoxia-induced phytoglobin can scavenge NO (uses O2 as substrate)
48
Q

How are phytoglobins induced?

A

By ethylene

49
Q

Ethylene induces ERFVII stabilisation

A
  • CPTIO = NO scavenging partner
  • does not accumulate in ethylene treated A. thaliana roots
  • stabilises RAP2.13
50
Q

ANACO13

A
  • early response TF
  • hypoxia-induced via promotors
  • homologs: -16, -17
51
Q

Membrane-associated NAC-TFs

A
  • ANACO13: ER-localised
  • cleaved under mitochondrial stress
  • goes to nucleus
52
Q

What cleaves ANACO13?

A
  • chemical mutagenesis analysis
  • rhomboid proteases cleave substrates inside membranes
  • rbl6/rbl2: no ANACO13 nuclear relocalisation
53
Q

Does ANACO13 contribute to hypoxia tolerance?

A

silencing/ inhibiting ER release using artificial miRNAS results in < hypoxia tolerance + bleaching

B3.0 (23 decks)

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