20. Cladosporium Flashcards
What is the pathogen associated with the study of C. fulvum?
Cladosporium fulvum
It is a model pathogen that is asexual and has a clonal lineage.
Is C. fulvum an obligate biotrophic pathogen?
No, it is biotrophic but not obligate, allowing it to be grown in the lab.
What economic impact has C. fulvum had?
Serious losses in greenhouse-grown tomatoes
Losses were historically significant during summer months, addressed by selective breeding for R genes and improved ventilation.
What is a major symptom of C. fulvum infection on tomato leaves?
White/yellow patterns on the upper leaf and brown mycelium on the lower leaf.
How does C. fulvum spread its conidia?
By wind.
What triggers the Hypersensitive Response (HR) in plants?
Cf proteins.
What is the function of the Hypersensitive Response (HR)?
To kill C. fulvum and prevent further growth of the pathogen.
What is the relationship between avirulence factors (Avr) and resistance genes (R)?
Gene-for-gene relationship.
What maintains R-genes in nature?
Balancing selection.
What are Near Isogenic Lines (NILs)?
Classical plant breeding experiments found the introgression of Cf genes.
How many different Cf genes are known?
Cf-0, Cf-2, Cf-4, Cf-5, and Cf-9.
What does the gene-for-gene model allow researchers to do?
Match Avr genes with Cf lineages to understand the evolution of R genes.
What type of protein is Avr9?
A small, secreted protein (SSP).
What is the significance of the Cf9 NIL?
It confers resistance against Avr9.
What is the function of Avr4?
To protect and bind chitin.
What is the main structural feature of Avr4?
It is an SSP with 8 cysteines and 4 disulphide bridges.
What does the Decoy Hypothesis suggest?
Guarded host targets may act as co-receptors or ‘decoys’.
What is Pip1?
A broad range immune protease.
What is the role of Rcr3 in Cladosporium resistance?
It encodes a defence-related, secreted papain-like Cys protein.
What is the old ‘Guard’ hypothesis?
R proteins ‘guard’ the host target of matching effector proteins.
What is the function of Sobir1 in plant immunity?
Required for RLPs.
What does the term ‘gene stacking’ refer to?
Combining multiple R genes to confer durable resistance.
What is the significance of the Hcr9 gene cluster?
It contains RLPs like Cf4 and Cf9.
True or False: The endogenous function of Avr9 is fully understood.
False.
