Sigma Region 3/4 linker mimics RNA

TLS Online TPP Program

#Id: 9485

#Unit 6. System Physiology – Plant

Plant pathogens are divided into three groups

Biotrophs derive energy from living cells, they are found on or in living plants, can have very complex nutrient requirements and do not kill host plants rapidly;

Necrotrophs derive energy from killed cells; they invade and kill plant tissue rapidly and then live saprotrophically on the dead remains;

TLS Online TPP Program

#Id: 9486

#Unit 6. System Physiology – Plant

Hemibiotrophs have an initial period of biotrophy followed by necrotrophy.

TLS Online TPP Program

#Id: 9487

#Unit 6. System Physiology – Plant

Biotrophs are Specialised (‘obligate’) pathogens

Possess appressoria or haustoria

Narrow host range

Controlled by salicylate-dependent host-defence pathways

TLS Online TPP Program

#Id: 9488

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 9489

#Unit 6. System Physiology – Plant

Biotrophic fungi usually penetrate the rigid cell wall via the formation of a specialized infection structure on the plant

surface called an appressorium. Then, the emerging penetration

peg breaches the rigid plant cell wall and provides entry into the plant cell. Finally, a haustorium forms upon entry into the plant cell.

TLS Online TPP Program

#Id: 9490

#Unit 6. System Physiology – Plant

Necrotrophs are Opportunistic, unspecialised (‘non-obligate’) pathogens and Host cells killed rapidly

Entry unspecialised via wounds or natural openings

Secrete copious cell-wall-degrading (lytic) enzymes and toxins

Appressoria/haustoria not normally produced

Wide host range

Easy to culture axenically

Survive as competitive saprotrophs

Controlled by jasmonate- and ethylene-dependent host-defence pathways