Nod-like receptors

The NLRs are a large family of cytosolic proteins activated by intracellular PAMPs

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An effector molecule is

made by a pathogen to enhance the pathogen’s colonizing

abilities.

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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;

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Hemibiotrophs have an initial period of biotrophy followed by necrotrophy.

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Biotrophs are Specialised (‘obligate’) pathogens

Possess appressoria or haustoria

Narrow host range

Controlled by salicylate-dependent host-defence pathways

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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.