We investigated the subcelluler localization of tryptamine in sl mutant of rice infected with M. grisea. Under the light condition, tryptamine accumulation was observed in the cytosolic fraction prepared from leaves infected with M. grisea, but not in chloroplast fraction. However, no accumulation was observed in the both fractions prepared from M. grisea-inoculated leaves kept in the dark. This result suggested that tryptamine was light-dependently biosynthesized in cytosol of sl mutant of rice infected by M. grisea.