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B3.0 > Legume-Rhizobium Symbiosis I > Flashcards

Legume-Rhizobium Symbiosis I Flashcards

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1
Q

Structure

A

1.
2.
3.

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2
Q

legumes

A
  • Fabaceae/Leguminosaea
  • Eurosid I clade
  • FaFaCuRo
  • 3rd largest plant Family (19,400sp.)
  • not all nodulate
  • evolved once
  • multiple losses
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3
Q

FaFaCuRo

A
  • Fabales
  • Fagales
  • Cucurbitales
  • Rosales
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4
Q

FaFaCu

A
  • nodule w/ actinorhizzal bacteria (Frankia)
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5
Q

Fabales

A
  • 95% Fabaceae
  • 5% milkweed
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6
Q

legume subfamilies

A
  1. Mimosoideae
  2. Caesalpinoidaea
  3. Faboideae (Papilionoideae)
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7
Q

Give a non-nodulating clade

A

rare in the Caesalpinioideae

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8
Q

1x non-legume host

A
  • Parasponia, Rosales
  • recent
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9
Q

Glycine max

A
  • soybean
  • typical agricultural legume
  • 1.1Gb polyploid
  • nodulates w/ Bradyrhizobium japonicum
  • pea-sized nodules
  • twice as much protein/acre as any other major vegetable/grain crop
  • 5-10x ^ protein/acre than land for grazing animals to make milk
  • 15x ^ protein.acre than land set aside for meat production
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10
Q

Arabidopsis

A
  • Brassica
  • does not nodulate
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11
Q

Medicago truncatula

A
  • model indeterminate plant
  • 375Mb
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12
Q

Lotus japonica

A
  • model determinate plant
  • 470Mb
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13
Q

Give the advantages of M. truncatula and L. japonica

A
  • small, diploid genomes
  • tractable for genetics
  • easy to transform
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14
Q

Pisum sativum

A
  • HUGE diploid genome
  • hundreds of accessions sequenced
  • syteny mapping
  • nodulation mutants in M. truncatula already exist in pea
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15
Q

Rhizobiaciae

A
  • alpha + betaproteobacteria
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16
Q

Rhizobiaciae alpha-proteobacteria

A

1) Rhizobium
2) Bradyrhizobium
3) Azorhizobium
4) Ensifer
5) Mesorhizobium

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17
Q

Rhizobiaciae beta-proteobacteria

A

1) Burkholderia
2) Cupriavidus

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18
Q

Rhizobium leguminosarum

A
  • 5Mb chromosome
  • 6x large plasmids
  • pRL10 (sym)
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19
Q

sym

A
  • nod
  • nif
  • fix
  • unique to the symbionts
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20
Q

Bradyrhizobium

A
  • 8.7Mb large chromosomes
  • sym island
  • no plasmids
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21
Q

Detection of plant signal

A

i) plant releases flavonoid inducers from the isoprenoid pathway
ii) NoDR produces nod TA

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22
Q

flavonoids

A
  • class name for flavones, isoflavones and flavanones
  • species specific
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23
Q

NoDR

A

LysR family

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24
Q

nod

A
  • Nod factor
  • lipochitooligosachharide (LCO) synthesis
  • 1,4-acetylglucosamine backbone + species specific modifications
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25
Nodulating counter-signal
- R. leguminosarum pRL10 Nod gene activation - NodD binds Nod box promoter region - species specific, complementary recognition
26
pRL10 Nod genes
- NmLEFDABCIJ - gene products: nodABCD
27
plant host range
- depends on nod genes - broad (NGR234) - narrow (b.v. trifolii)
28
NGR234
- cyanobacterium - suite of Nod factors - >200 genera - T3SS - mutation of effector proteins causes infection of different legumes
29
b.v. microfolii
clover
30
biovars
- sym transplantation: changes nodulation specificity - genomic equivalence, different ecology
31
LCOs
- up to 14 sugars - saturation positions: substitutable - chitin-like amino sugars - aka Nod factors - basic structure: long chain lipid - sulphate group addition - 4/5 sugar decoration provides complementation - + P/O - insufficient for sp. TF production
32
R. leguminosarum b.v. viciae
- different saturation - carbonyl groups
33
A. caulinodans
- rare - tropical tree legume - 2 sugars on reducing end
34
pea + red/white clover
- Nod factor differ @ a single saturation point
35
Host-plant recognition
i) plant detects LCOs ii) bacteria attach @ root hair Zone II iii) deformation: curling iv) cell nucleus aligns closely w/ infected bacteria; moves ahead of growing IT v) PITs form ahead of IT vi) topological extracellularity
36
attachment
stimulates nodule formation opposite protaoxylem pole
37
curling
- characteristic - flavonoid reduction - traps bacteria: infection foci - closed pocket: plant cell wall disruption - hole changes vascular turgour pressure; sealed cap - modified to form infection thread
38
PITs
- pre-infection threads - root hair tip in growth
39
Once the bacteria reach the epidermal cell
i) IT moves into cortical cells beneath epidermis ii) ramification, branching and distribution; multiple ITs spread thru cortex iii) nuclear alignment moves down, just behind IT; signal transmission
40
nuclear alignment
controlled by axial actin cables
41
Describe nuclear signal transmission behind the IT
- epidermis -> cortical layer -> inner cortex - formation of the discrete nodule primordial
42
Cellular components of infection
- Ca2+ gradient - small G proteins - dynamic F actin and microtubules
43
Ca2+ gradient in infection
- spiking - Golgi-derived vesicle fusion - deliver cell wall and matrix materials as well as signalling components - cell wall flexibility
44
small G proteins in infection
- localise to the apex - determine growth
45
dynamic F actin and microtubules
- subapical - vesicle deliver - PM protein turnover
46
LCORs
- allow signal transmission
47
LjLCORs
- NFR1/5
48
LjNFR1
- specific receptor kinase - Lysm EC domain - heterodimerisation
49
LysM
- PRR - detects chitin
50
LjNFR5
- DEAD domain
51
Common symbiosis pathway - the basics
- mutating early genes prevents both
52
Common symbiosis pathway - how does it work?
i) Nod + Myc factors activate LRR-kinase pairs, cation channels and nucleoproteins ii) Ca2+ spiking iii) CCaMK activation iv) specific TFs activate either nod or myc
53
CCaMK
- calcium and calmodulin dependent kinase - e.g. SYM RK
54
The full mechanism of infection
1) LCO activates NFR5 2) Mevalonate initiates nuclear signalling 3) Castor/Pollux activation 4) CNGC15 activation 5) Dmi3 activation; phosphorylates Cyclops 6) Cyclops activates NSP1/2 7) NSP1/2 activate ERN + NIN 8) MCA8 rebalanced Ca2+
55
mevalonate
- secondary messanger - soluble - initiates nuclear signalling
56
Castor/Pollux
- K+ channel - membrane hyperpolarisation
57
CNGC15
- large, voltage-gated C2+ channel - complexes with Castor/Pollux - NE into nucleus - flood cell
58
Dmi3
- CCaMK - takes hours to activate
59
NSP1/2
- TFs - dimerise
60
ENODs
- early nodulation genes - ERN + NIN
61
NIN
- master nodulation regulator - constitutive oe in strawbs (Rosales): nodule-like structures
62
MCA8
Ca2+ ATPase
63
cortical signalling
- cytokinin - near protaoxylem pole
64
epidermal signalling
2x parallel pathways for bacterial infection and nodule formation
65
lhk, cre1
- GOF mutants - activate NSP1/2, ERN + NIN - nodulate (initial sinals) - cytokinin Rs
66
NSP1/2, ERN + NIN
- inhibit PAT; accumulation
67
Genes involved in bacterial infection
- Cerberus - RPG - FLOT2/4
68
Genes invalid in signalling
- SYMRK - NUP85, 133 - Castor/Pollux - CCaMK - Cyclops - NSP1/2
69
Genes involved in induction
- ERN1 - NIN
70
genes involved in nodule organogenesis
ERF1
71
Nodules
- modified lateral roots - derived from cortical cells - distinct hormonal signals - common regulators
72
lateral roots
derived from dividing pericycle cells
73
Give some common regulators of nodule and lateral root organogenesis
- YUCCA - LBD16
74
nodule number is inhibited by
- CEP - CLE
75
CEP
- soil nitrate
76
CLE
- shoot - existing nodule bacteria
77
CLE-RSI/2
- Clea pepotides - respond to Rhizobia presence and nitrate levels
78
CLE R
- LRR - root - inhibits miRNA 2111
79
miRNA 2111
- inhibits TML
80
TML
- too much love - inhibits nodulation
81
N starvation?
- increased SEP - binds CRA2 - stimulates miRNA 2111
82
competition
- inoculants against residents - 150year "effectiveness" problem

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