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.