title: A thioredoxin of Sinorhizobium meliloti CE52G is required for melanin production and symbiotic nitrogen fixation.
abstract: A miniTn5-induced mutant of a melanin-producing strain of Sinorhizobium meliloti (CE52G) that does not produce melanin was mapped to a gene identified as a probable thioredoxin gene. It was proved that the thiol-reducing activity of the mutant was affected. Addition to the growth medium of substrates that induce the production of melanin (L-tyrosine, guaiacol, orcinol) increased the thioredoxin-like (trxL) mRNA level in the wild-type strain. The mutant strain was affected in the response to paraquat-induced oxidative stress, symbiotic nitrogen fixation, and both laccase and tyrosinase activities. The importance of thioredoxin in melanin production in bacteria, through the regulation of laccase or tyrosinase activities, or both, by the redox state of structural or catalytic SH groups, is discussed.
authors.affiliation: Department of Plant Pathology and Microbiology, The Otto Warburg Minerva Center for Agricultural Biotechnology, The Hebrew University of Jerusalem, Faculty of Agricultural, Food and Environmental Quality Sciences, Rehovot, Israel. scs@iibce.edu.uy
authors.forename: Susana
authors.initials: S
authors.lastname: Castro-Sowinski
authors.forename: Ofra
authors.initials: O
authors.lastname: Matan
authors.forename: Paula
authors.initials: P
authors.lastname: Bonafede
authors.forename: Yaacov
authors.initials: Y
authors.lastname: Okon
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001483:Base Sequence; D002874:Chromosome Mapping; D042845:Laccase / Q000378:metabolism; D000455:Medicago sativa / Q000382:microbiology; D008543:Melanins / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D014442:Monophenol Monooxygenase / Q000378:metabolism; D009154:Mutation; D009586:Nitrogen Fixation; D018384:Oxidative Stress; D010269:Paraquat / Q000494:pharmacology; D010802:Phylogeny; D012333:RNA, Messenger / Q000378:metabolism; D016962:Sinorhizobium meliloti / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D013559:Symbiosis / Q000502:physiology; D013879:Thioredoxins / Q000145:classification / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D008543:Melanins; D012333:RNA, Messenger; D013879:Thioredoxins; D042845:Laccase; D014442:Monophenol Monooxygenase; D010269:Paraquat