Identification and characterization of virulence-related effectors in the cucumber anthracnose fungus Colletotrichum orbiculare

• Virulence effectors such as NIS1 and DN3 were identified in Colletotrichum orbiculare.
• NIS1 induces HR-like cell death in susceptible Nicotiana benthamiana.
• DN3 suppresses NIS1-induced cell death.
• mCherry-tagged effectors accumulate in a novel pathogen–host interface.
• C. orbiculare SEC4 and SEC22 are involved in effector secretion to the interface.

The anthracnose fungus Colletotrichum orbiculare invades hosts and establishes biotrophy, later switching to necrotrophy, together with the secretion of an arsenal of effectors. In this review, we describe current progress in the study of pathogen effectors. We identified three virulence-related effectors in C. orbiculare, and revealed part of the strategy for effector-mediated infection, including suppression of immunity triggered by particular effectors. The virulence-related effectors accumulate in a unique interfacial region between C. orbiculare and cucumbers around the neck of primary biotrophic invasive hyphae. We found that the secretion of effectors toward the interface involves exocytosis and SEC22-dependent ER-Golgi traffic.