TY - JOUR
T1 - Expression and regulation of phosphate stress inducible genes in Sinorhizobium meliloti
AU - Summers, Michael L.
AU - Elkins, James G.
AU - Elliott, Brian A.
AU - McDermott, Timothy R.
PY - 1998/11
Y1 - 1998/11
N2 - Sinorhizobium meliloti 104A14 was mutated with transposon Tn5B22, which creates lacZ transcriptional fusions when inserted in the correct orientation relative to the promoter. This promoter reporter allowed us to identify six phosphate stress inducible (psi) genes in S. meliloti that are up-regulated in response to inorganic phosphate (P(i)) starvation. The transposon and flanking DNA were cloned from each psi::Tn5B22 reporter mutant and the junction DNA sequenced. High identity/similarity of the inferred peptides with those in major data bases allowed identification of the following genes: dnaK, expC, pssB, ackA, vipC, and prkA. The prkA homolog was also found to be upregulated in response to carbon starvation and when nitrate replaced ammonium as the nitrogen source. Through allele replacement techniques, PhoB- mutants were generated for the expC, ackA, vipC, and pssB reporter strains. Loss of a functional PhoB resulted in the absence of P(i)sensitive induction in all four genes. These experiments suggest the Pho regulon in S. meliloti includes genes that presumably are not directly linked to P(i) acquisition or assimilation. The psi strains were tested for their symbiotic properties under growth conditions that were P(i)-limiting or P(i)-nonlimiting for the host plant. All were Nod+ and Fix+ except the reporter strain of dnaK transcription, which was less effective than the wild-type strain under both P treatments, indicating DnaK is required for optimum symbiotic function.
AB - Sinorhizobium meliloti 104A14 was mutated with transposon Tn5B22, which creates lacZ transcriptional fusions when inserted in the correct orientation relative to the promoter. This promoter reporter allowed us to identify six phosphate stress inducible (psi) genes in S. meliloti that are up-regulated in response to inorganic phosphate (P(i)) starvation. The transposon and flanking DNA were cloned from each psi::Tn5B22 reporter mutant and the junction DNA sequenced. High identity/similarity of the inferred peptides with those in major data bases allowed identification of the following genes: dnaK, expC, pssB, ackA, vipC, and prkA. The prkA homolog was also found to be upregulated in response to carbon starvation and when nitrate replaced ammonium as the nitrogen source. Through allele replacement techniques, PhoB- mutants were generated for the expC, ackA, vipC, and pssB reporter strains. Loss of a functional PhoB resulted in the absence of P(i)sensitive induction in all four genes. These experiments suggest the Pho regulon in S. meliloti includes genes that presumably are not directly linked to P(i) acquisition or assimilation. The psi strains were tested for their symbiotic properties under growth conditions that were P(i)-limiting or P(i)-nonlimiting for the host plant. All were Nod+ and Fix+ except the reporter strain of dnaK transcription, which was less effective than the wild-type strain under both P treatments, indicating DnaK is required for optimum symbiotic function.
KW - Acetyl-phosphate
KW - Heal shock protein
KW - Polysaccharide
UR - http://www.scopus.com/inward/record.url?scp=0032213669&partnerID=8YFLogxK
U2 - 10.1094/MPMI.1998.11.11.1094
DO - 10.1094/MPMI.1998.11.11.1094
M3 - Article
C2 - 9805396
AN - SCOPUS:0032213669
SN - 0894-0282
VL - 11
SP - 1094
EP - 1101
JO - Molecular Plant-Microbe Interactions
JF - Molecular Plant-Microbe Interactions
IS - 11
ER -