THE BACTERIAL PIGMENT XANTHOMONADIN OFFERS PROTECTION AGAINST PHOTODAMAGE

Xanthomonas oryzae pv. oryzae is a bacterial pathogen that causes leaf blight, a serious disease of rice. Most members of the genus Xanthomo nas produce yellow, membrane bound, brominated aryl polyene pigments c alled xanthomonadins whose functional role is unclear. We find that pi gment-deficient mutants of X. oryzae pv. oryzae exhibit hypersensitivi ty to photobiological damage. A clone containing the xanthomonadin bio synthetic gene cluster alleviates the hypersensitivity of the pigment- deficient mutant. Extracts containing xanthomonadin provide protection against photodynamic lipid peroxidation in liposomes. These results l ead us to suggest a role for the pigment, namely protection against ph otodamage. (C) 1997 Federation of European Biochemical Societies.