Open AccessRhizobium meliloti mutants unable to synthesize anthranilate display a novel symbiotic phenotype
Author(s) -
Gary Barsomian,
Ana Urzainqui,
Karin N. Lohman,
Graham C. Walker
Publication year - 1992
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.174.13.4416-4426.1992
Subject(s) - biology , mutant , rhizobium , biochemistry , tryptophan , biosynthesis , rhizobiaceae , sinorhizobium meliloti , auxotrophy , symbiosis , amino acid , gene , genetics , bacteria
Analyses of Rhizobium meliloti trp auxotrophs suggest that anthranilate biosynthesis by the R. meliloti trpE(G) gene product is necessary during nodule development for establishment of an effective symbiosis. trpE(G) mutants, as well as mutants blocked earlier along this pathway in aromatic amino acid biosynthesis, form nodules on alfalfa that have novel defects. In contrast, R. meliloti trp mutants blocked later in the tryptophan-biosynthetic pathway form normal, pink, nitrogen-fixing nodules. trpE(G) mutants form two types of elongated, defective nodules containing unusually extended invasion zones on alfalfa. One type contains bacteroids in its base and is capable of nitrogen fixation, while the other lacks bacteroids and cannot fix nitrogen. The trpE(G) gene is expressed in normal nodules. Models are discussed to account for these observations, including one in which anthranilate is postulated to act as an in planta siderophore.