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Plant - pathogen coevolution - Coggle Diagram
Plant - pathogen coevolution
Dodds and Thrall 2009: recognition events and host - pathogen coevolution in GFG
plants have multilayered defense system
General: recognize conserved structural components (= pathogen associated molecular patterns = PAMPs) using cell-surface receptors (PAMP-triggered immunity)
pathogens counter with effector proteins (= avr genes) that get into host cells (e.g. via Type III secretion system) and manipulate signalling processes
e.g. degrade specific host proteins, or influence gene transcription
Classic GFG model (Flor 1971), now called effector-triggered immunity (ETI): Plant R (resistance) genes recognize pathogen avr genes
more ion flux
extracellular oxidative burst
transcriptional response at infection site
localized cell death (= hypersensitive response)
2 classes of R proteins
recognition outside cell:
extracellular LRR domain, sometimes intracellular kinase domain
recognition inside cell
LRR domain and NBS domain (related to Nod proteins in animals)
many R proteins also have TIR domain (related to intracellular signalling domain of Drosophila Toll protein)
Flax rust model system was basis for GFG concept
haustorium - host cell interface mediates dynamic interactions: penetrate cell wall, traffick nutrients, signalling and defense molecules from plant
direct R-Avr protein interation is the basis for recognition specificity
both resistance and interaction specificities are controlled by LRR domain
overall, LRR region seems highly flexible in evolutionary sense with cappacity to recognise diverse pathogen ligands by direct interaction when coupled with NBS domain
Jones 2019: reflections on plant cell classics
long known that many plant genes for resistance are dominant suggesting they encode receptors (what do dominance and receptors have to do with one another??)
genes for virulence (evading recognition) are recessive
recognition thought to be solely specified by LRRs, but in flax/rust system, TIR domain also contributes to specific recognition
Ellis and Dodd showed how NLR proteins convert recognition of effectors into defense activation...