Bialaphos sodium

A 64-year-old man with ethanol intoxication, ingested a bottle of Herbiace (100 ml, 32 w/v% of bialaphos, CAS #35597-43-4, Meiji Seika Kaisha, Tokyo, Japan). He had severe metabolic acidosis and was treated with infusions of sodium bicarbonate and furosemide, plus gastric lavage and enema. The metabolic acidosis improved 15 hours after treatment but nystagmus, apnea and convulsions were progressive. Although his sensorium was clear, spontaneous respirations were not observed for 64 hours. The electroencephalographic findings of atypical triphasic waves and slow waves suggest a unique response to bialaphos poisoning. His clinical course indicates that the management of apnea is critically important to recovery from bialaphos poisoning.

To identify the genetic loci that control salt tolerance in higher plants, a large-scale screen was conducted with a bialaphos marker-based T-DNA insertional collection of Arabidopsis ecotype C24 mutants. One line, osm1 (for osmotic stress-sensitive mutant), exhibited increased sensitivity to both ionic (NaCl) and nonionic (mannitol) osmotic stress in a root-bending assay. The osm1 mutant displayed a more branched root pattern with or without stress and was hypersensitive to inhibition by Na(+), K(+), and Li(+) but not Cs(+). Plants of the osm1 mutant also were more prone to wilting when grown with limited soil moisture compared with wild-type plants. The stomata of osm1 plants were insensitive to both ABA-induced closing and inhibition of opening compared with wild-type plants. The T-DNA insertion appeared in the first exon of an open reading frame on chromosome 1 (F3M18.7, which is the same as AtSYP61). This insertion mutation cosegregated closely with the osm1 phenotype and was the only functional T-DNA in the mutant genome. Expression of the OSM1 gene was disrupted in mutant plants, and abnormal transcripts accumulated. Gene complementation with the native gene from the wild-type genome completely restored the mutant phenotype to the wild type. Analysis of the deduced amino acid sequence of the affected gene revealed that OSM1 is related most closely to mammalian syntaxins 6 and 10, which are members of the SNARE superfamily of proteins required for vesicular/target membrane fusions. Expression of the OSM1 promoter::beta-glucuronidase gene in transformants indicated that OSM1 is expressed in all tissues except hypocotyls and young leaves and is hyperexpressed in epidermal guard cells. Together, our results demonstrate important roles of OSM1/SYP61 in osmotic stress tolerance and in the ABA regulation of stomatal responses.

Streptomyces hygroscopicus, which produces the glutamine synthetase inhibitor phosphinothricin, possesses at least two genes (glnA and glnB) encoding distinct glutamine synthetase isoforms (GSI and GSII). The glnB gene was cloned from S. hygroscopicus DNA by complementation in an Escherichia coli glutamine auxotrophic mutant (glnA). glnB was subcloned in Streptomyces plasmids by insertion into pIJ486 (pMSG3) and pIJ702 (pMSG5). Both constructions conferred resistance to the tripeptide form of phosphinothricin (bialaphos) and were able to complement a glutamine auxotrophic marker in S. coelicolor. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of S. lividans(pMSG5) revealed a highly overexpressed 40-kilodalton protein. When GS was purified from this strain, it was indistinguishable in apparent molecular mass from the 40-kilodalton protein. The nucleic acid sequence of the cloned region contained an open reading frame which encoded a protein whose size, amino acid composition, and N-terminal sequence corresponded to those of the purified GS. glnB had a high G + C content and codon usage typical of streptomycete genes. A comparison of its predicted amino acid sequence with the protein data bases revealed that it encoded a GSII-type enzyme which had previously been found only in various eucaryotes (47 to 50% identity) and nodulating bacteria such as Bradyrhizobium spp. (42% identity). glnB had only 13 to 18% identity with eubacterial GSI enzymes. Southern blot hybridization experiments showed that sequences similar to glnB were present in all of the five other Streptomyces species tested, as well as Frankia species. These results do not support the previous suggestion that GSII-type enzymes found in members of the family Rhizobiaceae represent a unique example of interkingdom gene transfer associated with symbiosis in the nodule. Instead they imply that the presence of more than one gene encoding GS may be more common among soil microorganisms than previously appreciated.