P-128 - Identification of a novel Colletotrichum higginsianum effector candidate protein structurally similar to bacterial toxins.

Colletotrichum higginsianum is a hemibiotrophic fungal pathogen causing anthracnose in cruciferous crops. Effectors play a crucial role in its infection process, but their functional roles are still poorly understood. In this study, we identified a novel effector candidate protein in C. higginsianum that shares structural similarity with bacterial toxins. The gene was isolated from a previously unannotated region of the C. higginsianum genome and was specifically expressed during plant infection. Structural prediction analysis suggested that the protein shared similarity with bacterial toxin proteins containing ADP-ribosyltransferase domain. Transient expression of the protein induced a severe cell death in both Nicotiana benthamiana and Brassica rapa. This cell death was attenuated by the addition of nicotinamide, a compound that may competitively interfere with NAD⁺ metabolism. Furthermore, a single amino acid substitution within the putative catalytic domain of the protein resulted in a significant decrease in cell death-inducing activity. These results suggest that the novel effector candidate protein promotes C. higginsianum infection via ADP-ribosylation to host target factors.