Seminars

Colletotrichum orbiculare (syn. C. lagenarium) is the causal agent of anthracnose disease on cucurbitaceous plants. The pathogen also has an ability to infect Nicotiana benthamiana distantly related to cucurbitaceous plants.

C. orbiculare forms dome-shaped structure called appressorium that is darkly pigmented with melanin. Melanization is known to be important for functionality of appressorium for cuticle penetration.

The penetration peg emerging from melanized appressorium develops bulbous biotrophic hyphae in living host cells before switching to a destructive necrotrophic mode.

We are continuously studying on molecular mechanism for host infection by C. orbiculare. To understand how this fungal pathogen suppresses its host immunity, we recently initiated effector studies on C. orbicular.

To date, we identified several virulence-related effectors of C. orbiculare, including necrosis-inducing secreted protein 1 (NIS1) expressed at biotrophic phase.

We revealed that the effectors accumulate in a novel biotrophic interface at the neck region of primary hypha under melanized appressorium, pointing out the presence of spatial and temporal regulatory strategy of effector secretion in the pathogen.

The effector NIS1 has an ability to suppress cell death induced by the pathogen-associated molecular pattern (PAMP)-like secreted protein INF1 in N. benthamiana. Interestingly, NIS1 interacts with a component of PAMP receptor complex, suggesting that NIS1 likely targets plant machineries required for pathogen recognition. 

Further studies on the virulence-related effectors will be also presented.