title: Environmental modulation of the pssTNOP gene expression in Rhizobium leguminosarum bv. trifolii.
abstract: Exopolysaccharide production by Rhizobium leguminosarum bv. trifolii is required for successful establishment of nitrogen-fixing symbiosis with clover (Trifolium pratense L.). Using plasmid-borne transcriptional fusions of promoters of pss genes with promoterless lacZ the effect of root exudate, phosphate, and ammonia on expression of pssT, pssN, pssO, and pssP genes in wild-type strain RtTA1 background was determined. A stimulating effect of these environmental factors on pssO and pssP gene expression was observed. The putative pssO gene promoter was determined to be a strong promoter within which the divergent nod-box element was identified. The pssO promoter was slightly inducible in a flavonoid-dependent manner in wild-type R. leguminosarum bv. trifolii strains RtTA1 and ANU843 and very weakly active in a mutant of strain ANU843 that lacks the regulatory nodD gene. The expression of pssO and pssP genes in planta was investigated using plasmid-borne pssO-gusA and pssP-gusA fusions under different phosphate availability to clover. The level of pssO-gusA fusion expression was shown to be dependent on phosphate concentration in the plant growth medium.
authors.affiliation: Department of General Microbiology, Maria Curie-Skłodowska University, Lublin, Poland.
authors.forename: Jerzy
authors.initials: J
authors.lastname: Wielbo
authors.forename: Andrzej
authors.initials: A
authors.lastname: Mazur
authors.forename: Jarosław E
authors.initials: JE
authors.lastname: Król
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Marczak
authors.forename: Anna
authors.initials: A
authors.lastname: Skorupska
mesh_terms: D019677:Artificial Gene Fusion; D001483:Base Sequence; D005419:Flavonoids / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D023061:Gene Order; D005798:Genes, Bacterial; D017930:Genes, Reporter; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D029902:Medicago / Q000382:microbiology; D008969:Molecular Sequence Data; D010710:Phosphates / Q000378:metabolism; D010936:Plant Extracts / Q000378:metabolism; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D016961:Rhizobium leguminosarum / Q000235:genetics*; D013559:Symbiosis; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D005419:Flavonoids; D010710:Phosphates; D010936:Plant Extracts; D011135:Polysaccharides, Bacterial; D000644:Quaternary Ammonium Compounds; D001616:beta-Galactosidase; D005966:Glucuronidase