Stress responses in alfalfa (Medicago sativa L.) XIX. Transcriptional activation of oxidative pentose phosphate pathway genes at the onset of the isoflavonoid phytoalexin response

Article on stress responses in alfalfa (Medicago sativa L.) XIX and transcriptional activation of oxidative pentose phosphate pathway genes at the onset of the isoflavonoid phytoalexin response

Comparative nucleotide sequence analysis of growth-rate-regulated gnd alleles from natural isolates of Escherichia coli and from Salmonella typhimurium LT-2.

A comparative study of gnd genes from Escherichia coli strains isolated from natural populations and laboratory strains and from Salmonella typhimurium was undertaken. In the accompanying paper (G. J. Barcak and R. E. Wolf, Jr., J. Bacteriol. 170:365-371, 1988), we showed that the growth-rate-dependent regulation of gnd expression was conserved among four natural E. coli isolates and E. coli B/r in a manner qualitatively similar to that of the gene from E. coli K-12. Here, we report the DNA sequence of the 5' regulatory region and the first 125 codons of the structural gene for the five E. coli gnd genes and the gnd gene from S. typhimurium LT-2. The sequences differed from one another by 5% on the average. All sequences defined putative secondary structures of the mRNA leader, which were previously proposed to be important in the regulation of the K-12 gene. In addition, a sequence between codons 69 and 74, which is highly complementary to the ribosome-binding site of the mRNA, was conserved in all the genes. The sequence data are discussed with respect to potential regulatory consequences

Growth-rate-dependent expression and cloning of gnd alleles from natural isolates of Escherichia coli.

6-Phosphogluconate dehydrogenase (6PGD), encoded by gnd, is highly polymorphic among isolates of Escherichia coli form natural populations. As a means of characterizing the growth-rate-dependent regulation of the level of 6PGD, five gnd alleles, including the E. coli B/r allele, were crossed into E. coli K-12 with bacteriophage P1. In each of the isogenic strains, the level of 6PGD was two- to threefold higher in cells grown on glucose than in cells grown on acetate. The level of enzyme activity in the acetate-grown cells varied about sixfold within the set of isogenic strains. The physiological importance of these differences in enzyme level is discussed. The gnd gene was cloned from five E. coli strains and Salmonella typhimurium LT-2 and mapped with twelve restriction endonucleases. gnd was located and oriented on the chromosomal DNAs. The restriction maps of the genes were aligned at conserved restriction sites, and the relative divergence of the genes was estimated from restriction site polymorphisms. The E. coli gnd genes differed from the S. typhimurium gene by about 11%. Most of the E. coli genes differed from one another by less than 5%, but one allele differed from the others by about 10%. Only the gnd gene from E. coli K-12 had an IS5 element located nearby