PAMP triggered Immunity

Question 1

Step by Step PAMP triggered immunity

Answer 1

• receptors on the cell surface recognize conserved microbial structures (PAMPs/ MAMPs)
• this triggers a whole suite of different defense responses
• defense responses differ in amplitude and spatio-temporal distribution

Question 2

PAMP triggeres immunity response: dynamic, cellular responses

Answer 2

Re-organisation of the cytoskeleton, organell translocation, vesicle transport

Question 3

PAMP triggered immunity: Signal –Transduction Chains

Answer 3

Ca2+-Influx, MAP-Kinase-signalling, Phosphorylation

Question 4

PAMP triggered immunity: Transcriptional responses

Answer 4

Induction of defense-related genes (e.g. PR-genes)

Question 5

PAMP triggered immunity: Chemical responses

Answer 5

Production of reactive O2-species (ROS), Hormones

Question 6

PAMP triggered immunity: Synthesis of antimicrobial compounds

Answer 6

Phytoalexins

Question 7

PAMP triggered immunity: reinforcement of the cell wall

Answer 7

callose deposition, Papillae

Question 8

Early cellular responses upon pathogen recognition

Answer 8

-Calcium (Ca2+) Influx
-Reactive Oxygen Species
(ROS) Production
-Activation of MAP Kinase
Signaling
-Expression of
defense genes

Question 9

Intermediate cellular responses upon pathogen recognition

Answer 9

Closing of stomata to

prevent bacterial entry

Question 10

Later cellular responses upon pathogen recognition

Answer 10

Accumulation of Salicylic Acid

Accumulation of Phytoalexins

Question 11

Cell wall reinforcement by

Answer 11

deposition of callose
Callose, made out of b-1,3-Glucan of
glucose

Callose detection using fluorescence microscopy after anilin blue staining

Question 12

Vesicles carrying antimicrobial compounds can be observed

Answer 12

under the microscope

Question 13

Some facts about PAMPs and MAMPs

Answer 13

• Structural motifs/molecules characteristic for abroad spectrum of pathogens/microbes, e.g. cell wall components (chitin, ergosterol, lipopolysaccharides); typical sugars, peptides, nucleicacids
• A typical PAMP is highly conserved and essential for the survival of the microorganism
• Not present in the host (non-selfrecognition)
• A rerecognized by surface receptors (pattern recognition receptors; PRRs)
• induce basal defense responses (PAMP-triggered immunity(PTI))

Question 14

MAMPs recognized by plants

Answer 14

• Flagellin, fgl22 gramnegative bacteria At+Tomato
• elongation factor elf18, gram-negative bacteria At+brassiacea
• xylanase TKLGE pentapeptide in fungi tomato+tabacco are sensitive

Question 15

Among the conserved molecules in bacteria and fungi triggering defense are

Answer 15

EF-Tu, flagellin, lipopolysaccharides (LPS), peptidoglycane(PGN) and chitin

Question 16

Bacterial PAMPs -Flagellin

Answer 16

•Flagella are essential for mobility and pathogenicity
•composed of several thousand flagellin subunits
•Flagellin highly conserved among different bacterial species
•ideal PAMP recognized by different organisms(not only plants, but also byanimals)
filament consits of 10 000 flagellin molcules
conserved,variable,conserved

flg22 is strongly conserved in a range of pathogens

Question 17

flg22 induces

Answer 17

defense responses and inhibits growth

Reduced growth of A. thalianaCol-0, Ler
Induction of callose deposition

Induction of PR-gene expression

Question 18

PAMPs are recognized by pattern recognition receptors

Answer 18

• recognition in animals throughtoll-like receptors
• belong to the leucine rich repeat(LRR) family of transmembrane proteines
• plants do not possessTLR homologs
• instead their genomes encode large gene families of receptor-like kinases(RLKs) orreceptor-like proteins(RLP); ca. 600 genes in A. thaliana
• FLS2 (flg22) is the best characterized PRR in plants

Question 19

Identification of FLS2 by

Answer 19

EMS Mutagenesis of A. thaliana

LRR Domäne, TM Domäne, Ser/Thr Proteinkinase

Question 20

Flagellin-Signalling

Answer 20

flg22 binds to FLS2 (receptor), this receptor binds to other receptor: BAK1 -> defense program

The cytoplasmic kinase BIK1 associates with the FLS2/ BAK1 receptor complex and is required for activation of the signaling complex
(complex foming, BIK2 phosphorylation, thransphosphorylation, activation of MAMP signalling
Ubiquitination of FLS2 shuts down signaling

Question 21

Plants rapidly close their stomata

Answer 21

to prevent bacterial ingress (triggered by flg22)

Question 22

FLS2 plays a major role in stomatal immunity

Answer 22

fls2 mutant plants cannot close their stomata in response to P. syringae

fls2 mutant plants support higher bacterial growth upon spray inoculation

Question 23

Chronological order off lg22-responses

Answer 23

Immediate early responses (1-5min)
Calcium influx
ROS production
Activation of MAP Kinase-signalling

Early responses
(5-30 min)
Activation of transcription factors (e.g. WRKY) (5-10min)
Changes in gene expression (30 min: induction of ca. 100 genes)
Stomatal closing

Lateresponses
(hours, days)
Cell wall reinforcement and callosedeposition
Synthesis of antimicrobial compounds
Growth inhibition
Hormone synthesis (e.g. ethylene and SA)