Probing for pH-regulated genes in Sinorhizobium medicae using transcriptional analysis.
The low pH sensitivity of Sinorhizobium species is one of the major causes of reduced productivity of Medicago species (such as lucerne) sown in acidic soils. To investigate the pH response of an acid-tolerant Sinorhizobium medicae strain, a pool of random promoter fusions to gusA was created using minitransposon insertional mutagenesis. Acid-activated expression was identified in 11 mutants; rhizobial DNA flanking insertions in 10 mutants could be cloned and the DNA sequences obtained were used to interrogate the genome database of Sinorhizobium meliloti strain 1021. Acid activated expression was detected for fixNO, kdpC, lpiA, and phrR and for genes encoding a putative lipoprotein, two ABC-transporter components, a putative DNA ligase and a MPA1-family protein. These findings implicate cytochrome synthesis, potassium ion cycling, lipid biosynthesis and transport processes as key components of pH response in S. medicae.
Tiwari
Ravi P
RP
Centre for Rhizobium Studies, School of Biological Sciences and Biotechnology, Murdoch University, Murdoch, Western Australia.
Reeve
Wayne G
WG
Fenner
Beau J
BJ
Dilworth
Michael J
MJ
Glenn
Andrew R
AR
Howieson
John G
JG
D004269:DNA, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial; D005819:Genetic Markers; D006863:Hydrogen-Ion Concentration; D029902:Medicago / Q000382:microbiology; D016296:Mutagenesis; D010935:Plant Diseases / Q000382:microbiology; D020579:Sinorhizobium / Q000235:genetics*; D014158:Transcription, Genetic / Q000235:genetics
D004269:DNA, Bacterial; D005819:Genetic Markers