The bacterial pigment xanthomonadin offers protection against photodamage

Abstract

Xanthomonas oryzae pv. oryzae is a bacterial pathogen that causes leaf blight, a serious disease of rice. Most members of the genus Xanthomonas produce yellow, membrane bound, brominated aryl polyene pigments called xanthomonadins whose functional role is unclear. We find that pigment-deficient mutants of X. oryzae pv. oryzae exhibit hypersensitivity to photobiological damage. A clone containing the xanthomonadin biosynthetic gene cluster alleviates the hypersensitivity of the pigment-deficient mutant. Extracts containing xanthomonadin provide protection against photodynamic lipid peroxidation in liposomes. These results lead us to suggest a role for the pigment, namely protection against photodamage.

Biological Role of Xanthomonadin Pigments in Xanthomonas campestris pv. Campestris

“…However, these results do not preclude the possibility that xanthomonadins may protect against indirect UV damage, mediated by an unknown photosensitizing agent on the leaf surface. Previous studies have indicated that xanthomonadins may protect against visible light damage in the presence of photosensitizers (11,18). In the first study, a single, chemically induced mutant strain of X. juglandis was more sensitive than its parent strain to photosensitizer-mediated photobiological damage.…”

“…The results of other studies suggest an association of xanthomonadins with protection against photobiological damage (11,18). However, these studies were not conducted using modern methods of single gene mutation and chromosomal restoration, from which definitive conclusions can be drawn.…”

“…DF extracellularly restored all of these traits to a pigB mutant strain (4, 15, 16), indicating that DF is needed for xanthomonadin and EPS production, as well as for epiphytic survival and host infection. These results suggest that DF acts as a signal for the initiation of xanthomonadin and EPS production and that xanthomonadins and EPS may play a role in host infection and/or epiphytic survival.The results of other studies suggest an association of xanthomonadins with protection against photobiological damage (11,18). However, these studies were not conducted using modern methods of single gene mutation and chromosomal restoration, from which definitive conclusions can be drawn.…”

Genetic Locus Encoding Functions Involved in Biosynthesis and Outer Membrane Localization of Xanthomonadin in Xanthomonas oryzae pv. oryzae

“…Pigment-deficient mutants of Xanthomonas juglandis (20), Xanthomonas oryzae pv. oryzae (37), and Xanthomonas campestris pv. campestris (33) are more susceptible to photooxidative damage than are wild-type strains.…”

“…campestris (33) are more susceptible to photooxidative damage than are wild-type strains. In vitro, xanthomonadin protects membrane lipids in egg-phosphatidylcholine liposomes against peroxidation (37). A transposon-induced xanthomonadin-deficient mutant of X. campestris pv.…”