Plant pathogens secrete effectors to manipulate their host and facilitate 
colonization. Fusarium oxysporum f. sp. lycopersici is the causal agent of 
Fusarium wilt disease in tomato. Upon infection, F. oxysporum f. sp. lycopersici 
secretes numerous small proteins into the xylem sap (Six proteins). Most Six 
proteins are unique to F. oxysporum, but Six6 is an exception; a homolog is also 
present in two Colletotrichum spp. SIX6 expression was found to require living 
host cells and a knockout of SIX6 in F. oxysporum f. sp. lycopersici compromised 
virulence, classifying it as a genuine effector. Heterologous expression of SIX6 
did not affect growth of Agrobacterium tumefaciens in Nicotiana benthamiana 
leaves or susceptibility of Arabidopsis thaliana toward Verticillium dahliae, 
Pseudomonas syringae, or F. oxysporum, suggesting a specific function for F. 
oxysporum f. sp. lycopersici Six6 in the F. oxysporum f. sp. lycopersici- tomato 
pathosystem. Remarkably, Six6 was found to specifically suppress I-2-mediated 
cell death (I2CD) upon transient expression in N. benthamiana, whereas it did 
not compromise the activity of other cell-death-inducing genes. Still, this I2CD 
suppressing activity of Six6 does not allow the fungus to overcome I-2 
resistance in tomato, suggesting that I-2-mediated resistance is independent 
from cell death.