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B L Berg

Publications and source records attributed to B L Berg.

9 recordsLinked to original sources
PubMed1999

Genetic regulation of vascular tissue patterning in Arabidopsis.

Plants transport water and nutrients through a complex vascular network comprised of interconnected, specialized cell types organized in discrete bundles. To identify genetic determinants of vascular tissue patterning, we conducted a screen for mutants with altered vascular bundle organization in Arabidopsis cotyledons. Mutations in two genes, CVP1 and CVP2 (for cotyledon vascular pattern), specifically disrupt the normal pattern of vascular bundles in cotyledons, mature leaves, and inflorescence stems. The spatial distribution of the procambium, the precursor to mature vascular tissue, is altered in cvp1 and cvp2 embryos, suggesting that CVP1 and CVP2 act at a very early step in vascular patterning. Similarly, in developing stems of cvp1 and leaves of cvp2, the pattern of vascular differentiation is defective, but the maturation of individual vascular cells appears to be normal. There are no discernible alterations in cell morphology in cvp2 mutants. In contrast, cvp1 mutants are defective in directional orientation of the provascular strand, resulting in a failure to establish uniformly aligned vascular cells, and they also show a reduction in vascular cell elongation. Neither cvp1 nor cvp2 mutants displayed altered auxin perception, biosynthesis, or transport, suggesting that auxin metabolism is not generally affected in these mutants.

Arabidopsis↗
PubMed1998

Chromosome dynamics: yeast pulls it apart.

Sister chromatid cohesion and chromosome condensation are both essential to the successful completion of mitosis. The recent identification and characterization of the yeast Mcd1p/Scc1p protein reveals a previously unsuspected mechanistic link between these processes.

Anaphase↗
PubMed1991

Nitrate-inducible formate dehydrogenase in Escherichia coli K-12. I. Nucleotide sequence of the fdnGHI operon and evidence that opal (UGA) encodes selenocysteine.

The fdnGHI operon of Escherichia coli encodes nitrate-inducible formate dehydrogenase. We report here the entire nucleotide sequence of fdnGHI. The sequence contains three open reading frames of sizes appropriate to encode the three subunits of formate dehydrogenase-N. fdnG contains an in-frame UGA codon that specifies selenocysteine incorporation, and the predicted amino acid sequence of FdnG shows similarity to two other bacterial formate dehydrogenase enzymes. FdnH contains 4 cysteine clusters typical of those found in iron-sulfur proteins. FdnG also contains a cysteine cluster. Evidence from sequence and spectral analyses suggest that FdnI encodes cytochrome bFdn556. Implications for the membrane topology of formate dehydrogenase-N and its mechanism of proton translocation are discussed.

Amino Acid Sequence↗
PubMed1991

Nitrate-inducible formate dehydrogenase in Escherichia coli K-12. II. Evidence that a mRNA stem-loop structure is essential for decoding opal (UGA) as selenocysteine.

fdnG, encoding the selenopeptide of Escherichia coli formate dehydrogenase-N, contains an in-frame opal (UGA) codon at amino acid position 196 that directs selenocysteine incorporation. We have identified sequences that contribute to the mRNA context required for decoding this UGA as selenocysteine. We identified a potential stem-loop structure immediately downstream of UGA196 that is comparable in size and structure to a stem-loop predicted to form in fdhF, which encodes the selenopeptide of E. coli formate dehydrogenase-H. Mutational analysis of the fdnG stem-loop structure suggests that it is critical for decoding UGA196 as selenocysteine. Our data indicate that both stability and specific nucleotide sequences of the stem-loop likely contribute to the appropriate mRNA context for selenocysteine incorporation into the fdnG gene product.

Base Composition↗
PubMed1991

Genetic evidence that genes fdhD and fdhE do not control synthesis of formate dehydrogenase-N in Escherichia coli K-12.

Enterobacteria synthesize two formate dehydrogenases, formate dehydrogenase-N (encoded by fdnGHI) and formate dehydrogenase H (encoded by fdhF). Previous work has identified two rha-linked Salmonella typhimurium genes, fdnB and fdnC, which are required primarily for formate dehydrogenase-N activity. Analogous mutants, termed fdhD and fdhE, have been isolated in Escherichia coli. We used gene fusions between fdnG, the structural gene for the large subunit of formate dehydrogenase-N, and lacZ, the structural gene for beta-galactosidase, to examine E. coli fdnGHI operon expression in fdhD and fdhE insertion mutants. Expression of the phi (fdnG-lacZ) gene fusions was little affected by these insertions, suggesting that fdhD and fdhE do not control transcription or UGA decoding of the formate dehydrogenase-N structural genes. Our complementation tests, with cloned E. coli fdhD and fdhE genes, indicate that the S. typhimurium fdnC and fdnB genes are functionally homologous to the E. coli fdhD and fdhE genes, respectively.

Cloning, Molecular↗
PubMed1990

Structural genes for nitrate-inducible formate dehydrogenase in Escherichia coli K-12.

Formate oxidation coupled to nitrate reduction constitutes a major anaerobic respiratory pathway in Escherichia coli. This respiratory chain consists of formate dehydrogenase-N, quinone, and nitrate reductase. We have isolated a recombinant DNA clone that likely contains the structural genes, fdnGHI, for the three subunits of formate dehydrogenase-N. The fdnGHI clone produced proteins of 110, 32 and 20 kDa which correspond to the subunit sizes of purified formate dehydrogenase-N. Our analysis indicates that fdnGHI is organized as an operon. We mapped the fdn operon to 32 min on the E. coli genetic map, close to the genes for cryptic nitrate reductase (encoded by the narZ operon). Expression of phi(fdnG-lacZ) operon fusions was induced by anaerobiosis and nitrate. This induction required fnr+ and narL+, two regulatory genes whose products are also required for the anaerobic, nitrate-inducible activation of the nitrate reductase structural gene operon, narGHJI. We conclude that regulation of fdnGHI and narGHJI expression is mediated through common pathways.

Aldehyde Oxidoreductases↗
PubMed1988

Influence of nar (nitrate reductase) genes on nitrate inhibition of formate-hydrogen lyase and fumarate reductase gene expression in Escherichia coli K-12.

In Escherichia coli, aerobiosis inhibits the synthesis of enzymes for anaerobic respiration (e.g., nitrate reductase and fumarate reductase) and for fermentation (e.g., formate-hydrogen lyase). Anaerobically, nitrate induces nitrate reductase synthesis and inhibits the formation of both fumarate reductase and formate-hydrogen lyase. Previous work has shown that narL+ is required for the effects of nitrate on synthesis of both nitrate reductase and fumarate reductase. Another gene, narK (whose function is unknown), has no observable effect on formation of these enzymes. We report here our studies on the role of nar genes in fumarate reductase and formate-hydrogen lyase gene expression. We observed that insertions in narX (also of unknown function) significantly relieved nitrate inhibition of fumarate reductase gene expression. This phenotype was distinct from that of narL insertions, which abolished this nitrate effect under certain growth conditions. In contrast, insertion mutations in narK and narGHJI (the structural genes for the nitrate reductase enzyme complex) significantly relieved nitrate inhibition of formate-hydrogen lyase gene expression. Insertions in narL had a lesser effect, and insertions in narX had no effect. We conclude that nitrate affects formate-hydrogen lyase synthesis by a pathway distinct from that for nitrate reductase and fumarate reductase.

Aldehyde Oxidoreductases↗
PubMedDate not supplied

Compliance, diet and cultural factors among black Americans with end-stage renal disease.

This article examines dietary compliance among a sample consisting predominantly of Black End-Stage Renal Disease (ESRD) patients. Previous research on ESRD patients has concentrated on dietary compliance as engendered by a White middle-class medical value system. The current research suggests that this approach may deter compliance rather than encourage it in an ESRD patient population which tends to be composed disproportionately of Blacks. Findings from a structured interview schedule administered to 23 ESRD patients, and their blood analyses, indicate that while patients claim to be compliant, their subjective laboratory results suggest the contrary. As a possible explanation of this result, this article argues that renal dietary restrictions are both too rigid and alien in the context of a Black cultural world view and the eating patterns related to this cultural ethos.

Adolescent↗