Summary
MBY365 Theme 4 summary
- Course
- MBY365 (MBY365)
- Institution
- University Of Pretoria (UP)
Full summary of theme 4 (mutualist and pathogenic interactions) made using lecture notes and class notes.
[Show more]
Content preview
PLANT AND MICROBE INTERACTIONSINFECTION PROCESS
- Entrance through
- Stomata
- Wounds
- Enzymatic disruption - cellulases, cutinases and pectinases
- Appressoria (fungi)
- Present in apoplast
- Microorganisms do not have to enter the live cells
- Could also grow into the apoplast - space between the junction of two
pavement cells
- This could delay recognition by the plant’s immunity system
OBLIGATE ENDO-PARASITIC PLANT PATHOGENS
- Oomycetes - Pythium and Phytophothora
- Plasmodiophorids - Phytomyxea (brassicas)
- Fungi - rusts and downy mildew
EXTRACELLULAR PLANT PATHOGENS
- Plant pathogens can be classified as biotrophs, hemi-biotrophs and
necrotrophs
- Necrotrophs
- Kill the living tissue and feed off of damaged and dead tissue
- Results in expanding necrotrophic spots
- Have a broad host range
, - Virulence factors
- Plant cell wall-degrading enzymes
- Cutinases
- Host-selective toxins
- Enzymes to detoxify phytoalexins
- Common use of T2SS
- Role of quorum sensing
- Results in tissue maceration, cell killing (host specific) and degradation
of plant cuticle
- Host response is activated by oligogalacturonate products (DAMPS)
- Biotrophs
- Feed on living cells and do not kill them
- E.g. the rust fungi Basidiomycota and the powdery mildew fungi
Ascomycota
- Hemi-biotrophs feed on living tissue but in the latter stage of their life
cycle kill the host tissues - behave as both biotrophs and necrotrophs
- Pseudomonas syringae is a hemi-biotroph
- Often have a high degree of host specificity
- Virulence factors
- Cytoplasmic effectors (avirulence proteins)
- Linked to secretion systems (T3SS) and global regulators
- Have a high level of redundancy
- Plant defence system uses two branches of defence
- First one uses trans-membrane pattern recognition receptors (PRRs)
activated by PAMPs or MAMPs
- Second one uses the protein products encoded by most R genes
- Zig-zag model
- First phase - PAMPs sensed by plant PRRs causing PAMP-triggered
immunity (PTI)
- Helps in further invasion of the pathogen
- Second phase - pathogens that succeeded to overcome the plant basal
defence release their effector molecules that supports pathogen
virulence
- Effector molecules can impede PTI resulting in effector-triggered
susceptibility (ETS)
- Third phase - pathogen effector molecules are recognised by one of
the plant NB-LRR proteins leading to effector-triggered immunity (ETI)
- Fourth phase - selection helps pathogens avoid ETI either by
modification in recognised effector gene or by shedding the surface
coating of lipid and/or protein - makes plants unable to recognise them
- Natural selection can add new specificities to R genes to trigger
accelerated ETI again
, PAMP-TRIGGERED IMMUNITY
- Is the basal defence system that activates after virulent pathogen infection on
susceptible hosts
- PAMPs or MAMPs - pathogen/microbial associated molecular patterns
- Flagellin
- LPS and peptidoglycan (bacteria)
- Chitin (fungi)
- Elongation factor Tu
- Cold shock protein
- Recognition by pattern recognition receptors (PRRs) - large gene family
- Transmembrane receptor kinases
- Transmembrane receptor-like proteins
- Response
- Localised cell death
- Induced systemic resistance (ISR) - ethylene and jasmonic acid
- Localised cell wall thickening
- Release of reactive oxygen
- Successful pathogen has effectors to overcome PTI
JASMONIC ACID
- Transmits signals both locally and systemically
- Triggers
- Necrotrophic pathogens
- Wounding or insect attack
- Response
- Signal molecules (ROS; RNS)
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through EFT, credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying this summary from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller ejnotes. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy this summary for R60,00. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
75632 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy summaries for 14 years now