Oligochitosan inhibits Phytophthora capsici by penetrating the cell membrane and putative binding to intracellular targets

The mechanism of action of oligochitosan, which hasshown great antifungal activity against Phytophthora capsici in vitro, was studied using 2-aminoacridone-labeled oligoclutosan (2-AMAC-oligochitosan) and a gel-retardation experiment. Internalization of 2-AMAC-oligochitosan in cysts, gernitubes and sporangia of P. capsici was confirmed by confocal laser scan microscopy (CLSM), and the degree of uptake depended on the incubation concentration. 2-AMAC-oligochitosan localized mainly in the cytoplasm and showed no binding to both cell wall and cell membrane. Mannose, an inhibitor for oligochitosan uptake by macrophages, could not inhibit the internalization of oligochitosan in P. capsici. The gel-retardation experiment showed that oligochitosan bound strongly to DNA and RNA of P. capsici. These results indicate that oligochitosan exerts its antifungal activity by penetrating the cell membrane and putative binding to intracellular targets such as DNA and RNA. (c) 2006 Elsevier Inc. All rights reserved.