Biotic Stress

Question 1

Plant pathogen

Answer 1

An organism that completes part or all of its life cycle in a plant and has a negative effect

Question 2

Fungi biographic strat

Answer 2

Haustorium

Question 3

Effectors

Answer 3

Made by pathogens to enhance colonizing ability

Question 4

Plant preformed defenses

Answer 4

Cell wall
Secondary metabolites (target neurotrophs in vacuoles/organelles)
Glucosinolates

Question 5

Induced defenses

Answer 5

Zig-zag model of plant defenses
PTI: Pattern triggered immunity
ETI: Effector triggered immunity

Question 6

Glucosinolates

Answer 6

Sulfur glycosides stored in inactive form
Activated by myrosinase = subcellular compartmentalization
- Cell damage = glucosinolates mix with myrosinase
-toxic compounds released = protection against pathogen and insects

Question 7

PTI

Answer 7

Occurs when PRR (Pattern recognition receptors) recognize PAMPs (pathogen associated molecular patterns)
-activate defense

Question 8

ETS

Answer 8

Occurs when pathogen effectors suppress plant defenses

Question 9

ETI

Answer 9

• R gene mediated defense
  Occurs when R (plant resistance proteins) recognize pathogen effectors (Avr) and activate a strong resistance response
  -often hypersensitive response (self-sacrifice)

Question 10

Call wall fortification

Answer 10

Papilla (callose B-glucan)

Question 11

3 steps of defense

Answer 11

Recognition
Signaling
Response

Question 12

Gene-for-gene model

Answer 12

Resistance will occur only when plant has dominant resistance gene (R) and pathogen expresses complementary dominant recognized effector gene (Ree)

Question 13

2 resistance effector mechanisms

Answer 13

Resistance by direct interaction

Resistance by guarding (virulence target)

Question 14

Pathogenesis-related proteins

Answer 14

Induced defense response

Toxic to pathogens

Question 15

Limitations of breeding with R genes

Answer 15

Lengthy process
Boom and bust cycle
Many genes transferred with R gene (some undesirable)

Question 16

Advantages of breeding with R genes

Answer 16

Transfer genes between species
Many R genes isolated
Direct transfer into elite lines

Question 17

RNA silencing

Answer 17

Transfer of coat protein into plant Cell causes double stranded rna = silenced

Question 18

T3SS

Answer 18

Delivers effectors to suppress plant resistance
Coded for by hrp genes
Common for bacterial pathogens of plants and animals

Question 19

hrp gene

Answer 19

Hypersensitive response and pathogenicity gene

Question 20

Crown gall disease

Answer 20

T-DNA transfer
Synthesizes opines (bacteria food), auxin and cytokinins

Question 21

ssRNA virus

Answer 21

Tobacco mosaic virus

Question 22

dsDNA virus

Answer 22

Cauliflower mosaic virus

Question 23

Virus symptoms

Answer 23

Chlorosis
Necrosis
Mosaic pattern
Leaf rolling

Question 24

Pathogen survival mechanisms

Answer 24

High reproduction rate during main growing season of host
Efficient dispersal (wind, water insects )
Long term survival form
Generate high genetic diversity

Question 25

PRR

Answer 25

Pathogen recognition receptors

E.g. CERK (recognizes chitin)

Question 26

ROS

Answer 26

Reactive oxygen species
H2O2, O2-
Direct antimicrobial effect

Question 27

Tomato strat

Answer 27

PTI conferred by Elongation Factor Receptor in Arabidopsis
Tomato lacks EFR so it is transferred
Result: EFR+ —> more resistance

Question 28

Potato strat

Answer 28

Late blight overcomes most R genes introduced by traditional breeding
New R genes with broad spectrum resistance to late blight found in wild potato’s
Transfer R gene from wild to commercial (Desiree )
Result: resistance to phytophthora infestans

Question 29

Rice strat

Answer 29

Bacteria injects effectors that move into nucleus of rice
—> activates transcription of gene that transports sucrose to pathogen
Genome editing tool TALEN modifies gene to be resistance to effectors but still be expressed when needed
Result: Recessive resistance to bacteria created