ARS | Publication request: Secreted effectors of the tomato leaf mould fungus Cladosporium fulvum are virulence factors that target host defense

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 17, 2009
Publication Date: March 9, 2009
Repository URL: http://www.fgsc.net/25thFGC/FGC25.htm
Citation: Van Esse, P., De Jonge, R., Bolton, M.D., Thomma, B. 2009. Secreted Effectors of the Tomato Leaf Mould Fungus Cladosporium Fulvum are Virulence Factors that Target Host Defense [abstract.] 25th Fungal Genetics Conference, March 17-22, 2009, Asilomar, CA. p. 527.

Technical Abstract: Cladosporium fulvum is a biotrophic fungal pathogen that causes leaf mould of tomato. Inside the leaf, C. fulvum does not penetrate host cells or develop haustoria but remains confined to the intercellular space between mesophyll cells. Ten effector proteins that are secreted during host colonization have been identified so far. We have recently revealed virulence functions for a number of these effectors. It was previously shown that the Avr2 effector interacts with, and inhibits, the tomato cysteine protease Rcr3 which, in compliance with the guard hypothesis, is required for immunity mediated by the tomato resistance protein Cf-2. However, in compatible interactions Avr2 inhibits several additional extracellular host cysteine proteases that are required for host basal defense. Also the recently identified secreted effector Ecp6 is a true virulence factor, as RNAi-mediated gene silencing compromised fungal virulence on tomato. Intriguingly, all previously identified C. fulvum effectors are unique as no clear homologs have been identified in other organisms. Ecp6 is an exception to this rule, with clear homologs in many fungal species. Ecp6 contains LysM domains that have been implicated in carbohydrate binding and we speculate that Ecp6 plays a role to dampen host immune responses. A detailed characterization of the secreted effectors will be presented.