Remy Bitoun | International Rice Research Institute (original) (raw)

Papers by Remy Bitoun

Research paper thumbnail of A pleiotropic mutation results in cross-resistance to auxin, abscisic acid and paclobutrazol

MGG Molecular & General Genetics, 1990

Mutant lines of Nicotiana plumbaginifolia resistant to the synthetic auxins 1-naphthaleneacetic a... more Mutant lines of Nicotiana plumbaginifolia resistant to the synthetic auxins 1-naphthaleneacetic acid (NAA) and indole-3-butyric acid (IBA) were isolated as germinating seedlings on selective medium. In each case, resistance was conferred by a single recessive nuclear mutation at one of 3 loci designated ibal, iba2 and iba3. Labelling studies with 14C NAA suggest that resistance was not due to changes in the uptake or metabolism of NAA. Plants homozygous for the ibal mutation exhibit a syndrome of atypical germination and growth suggestive of a defect in the biosynthesis, metabolism or localization of abscisic acid. Wildtype seeds treated with gibberellin exhibit the same syndrome, including resistance to NAA and IBA. On the basis of these observations, we propose that auxin toxicity in seeds may be mediated by a block in gibberellin biosynthesis.

Research paper thumbnail of The phosphoenolpyruvate dependent carbohydrate phosphotransferase system of Escherichia coli

FEMS Microbiology Letters, 1983

Research paper thumbnail of Transcriptional analysis of promoter mutations in the Klebsiella pneumoniae nifHDKY operon

Journal of Bacteriology, 1986

Previously isolated promoter mutations that allow expression of the Klebsiella pneumoniae nifHDKY... more Previously isolated promoter mutations that allow expression of the Klebsiella pneumoniae nifHDKY operon in the absence of nifA (R. Bitoun, J. Berman, A. Zilberstein, D. Holland, J.B. Cohen, D. Givol, and A. Zamir, Proc. Natl. Acad. Sci. USA, 80:5812-5816, 1983) were further characterized. pRB1 and pRB5, containing, respectively, point and duplication mutations in the nifHDKY regulatory region, were transformed into Escherichia coli and K. pneumoniae hosts with different nifA and ntrA backgrounds. nif transcription start sites were determined by nuclease S1 mapping. The results indicated that nifA-independent expression from both mutants did not require ntrA. Transcription from pBR5 started 3 base pairs (bp) upstream of the start site of nif-regulated transcription and could stem from a canonical promoter sequence generated at the junction between the two copies of the duplicated sequence. In the presence of nifA-ntrA, transcription from pRB5 started predominantly at the site charac...

Research paper thumbnail of Promoter mutations that allow nifA-independent expression of the nitrogen fixation nifHDKY operon

Proceedings of the National Academy of Sciences, 1983

The nifHDKY operon of Klebsiella pneumoniae encodes for structural polypeptides of nitrogenase an... more The nifHDKY operon of Klebsiella pneumoniae encodes for structural polypeptides of nitrogenase and requires the nifA gene product for transcription. Mutations that allow transcription of the nifHDKY operon in absence of the nifA gene product were characterized in plasmids containing the regulatory region of nifHDKY and nifH fused in phase to lacZ. beta-Galactosidase activity served as a measure for nifH expression. Most mutations were located in the nif regulatory region and included insertion sequence 2 (IS2) insertions, a sequence duplication, and a base substitution. In Escherichia coli, beta-galactosidase activity expressed from the mutant plasmids in the absence of nifA was 6-30% of the nifA-activated, parental level. Expression from most mutant plasmids was further increased by nifA. In K. pneumoniae, IS2-containing plasmids expressed low levels of beta-galactosidase and responded poorly, if at all, to activation by nifA, whereas expression from other mutant types was similar ...

Research paper thumbnail of Ethanol-resistant mutants ofotiana plumbaginifolia are deficient in the expression of pollen and seed alcohol dehydrogenase activity

MGG Molecular & General Genetics, 1990

Six independent mutant lines of Nicotiana plumbaginifolia resistant to ethanol, designated E3, E8... more Six independent mutant lines of Nicotiana plumbaginifolia resistant to ethanol, designated E3, E8, El01, Ell2, E144 and E251, were isolated as germinating seedlings on selective medium. In all cases, resistance to ethanol was conferred by a single recessive nuclear mutation at the same locus. Mutant seeds and pollen lacked detectable ADH activity, with the exception of E251 where a residual activity was detected. An antiserum directed against Arab# dopsis thaliana ADH detected an ADH-related polypeptide of 44 kDa present in wild-type seeds and, to a lesser extent, in the seeds of the leaky mutant E251. No ADH-related polypeptide could be detected in seeds of the other mutants. However, all of them had a nearly normal level of ADH mRNA except one which did not synthesize any mRNA. These results suggest that these ethanol-resistant mutants are impaired in one of the structural genes coding for alcohol dehydrogenase. The corresponding locus has been designated Adhl.

Research paper thumbnail of Outreading promoters are located at both ends of the Gamma-delta transposon

MGG Molecular & General Genetics, 1989

Two plasmids were isolated containing oppositely oriented gamma-delta insertions between the wild... more Two plasmids were isolated containing oppositely oriented gamma-delta insertions between the wild-type transcription initiation site of the nifHDKY operon and the nifH coding sequence. The nifHDKY promoter of Klebsiella pneumoniae, similar to other nitrogen fixation (nif) promoters, normally requires the products of ntrA and nifA for activity. Mutations that allowed constitutive expression of the nifHDKY operon were searched for by transforming a plasmid, containing the regulatory region of this operon followed by an in-frame nifH'-'lacZ fusion, into a Lac- Escherichia coli strain (which contains no nifA) and screening for Lac+ derivatives. The plasmids described here were isolated from such derivatives and directed the constitutive expression of beta-galactosidase. Deletion analysis indicated that gamma-delta promoters other than those transcribing tnpA and tnpR were involved in this expression. Nuclease S1 mapping revealed outward-reading transcription initiation sites in both the gamma end and the delta end of the transposon. Most interestingly, one initiation site on each end was located in corresponding positions within the terminal inverted repeats. The sites were in the center of the longest sequence, of 12 bp, contiguously conserved between the terminal inverted repeats of gamma-delta and the related transposon Tn3. In gamma-delta and Tn3, this sequence has been recently implicated in transposase binding. These results suggest a possible interrelationship between transcription from the "end" promoters and transposition.

Research paper thumbnail of Spontaneous amplification of yeast CEN ARS plasmids

MGG Molecular & General Genetics, 1986

Transformation of Saccharomyces cerevisiae with several yeast CEN4 ARS1 plasmids containing the h... more Transformation of Saccharomyces cerevisiae with several yeast CEN4 ARS1 plasmids containing the his3-A4 allele (as well as the URA3 and TRP1 markers) yielded His + transformants at 0.1%-50% the frequency of Ura + Trp + transformants. Additional His + derivatives arose on continuous growth of transformants originally scored as His-Ura + Trp +. In all cases, the His + phenotype was not due to plasmid or host mutations but invariably correlated with an up to ]2-fold increase in plasmid copy number. On removal of selective pressure, the His + phenotype was lost more readily than the Ura + Trp + markers, with a corresponding decrease in plasmid copy number. Also, the amplification did not decrease the mitotic loss rate of the Ura + Trp + markers. These results indicate that CEN ARS plasmids can be spontaneously amplified to higher levels than previously observed. However, when amplified, apparently not all copies exhibit the characteristic stability of CEN ARS plasmids.

Research paper thumbnail of A yeast strain producing lys2 deletions at a high frequency after sporulation

Research paper thumbnail of Selection of in vivo deletions in Sacharomyces cerevisiae

Journal of Bacteriology, 1988

Research paper thumbnail of Selection of in vivo deletions in Saccharomyces cerevisiae

Journal of bacteriology, 1988

A general screening procedure has been devised for the selection of in vivo-generated deletions i... more A general screening procedure has been devised for the selection of in vivo-generated deletions in haploid Saccharomyces cerevisiae cells. It is based on the introduction into a cyh2 host (resistant to the drug cycloheximide) of a tandemly duplicated CYH2 gene (a dominant allele, conferring sensitivity to cycloheximide), and subsequent selection for Cyhr derivatives. The duplicated CYH2 gene has been introduced on CEN ARS plasmids or integrated into chromosome II. A variable but significant proportion of the Cyhr derivatives of such transformants were deletion mutants in which both CYH2 copies had suffered deletions. Some of the deletions extended into sequences outside the tandemly duplicated CYH2 gene. A total of 61 independently selected deletions ranged in length from 3.1 to over 20 kilobases and had no obvious preferred endpoints. Restriction analysis showed that other frequently isolated Cyhr derivatives appeared to retain one of the two CYH2 copies. Such single-copy derivativ...

Research paper thumbnail of A pleiotropic mutation results in cross-resistance to auxin, abscisic acid and paclobutrazol

MGG Molecular & General Genetics, 1990

Mutant lines of Nicotiana plumbaginifolia resistant to the synthetic auxins 1-naphthaleneacetic a... more Mutant lines of Nicotiana plumbaginifolia resistant to the synthetic auxins 1-naphthaleneacetic acid (NAA) and indole-3-butyric acid (IBA) were isolated as germinating seedlings on selective medium. In each case, resistance was conferred by a single recessive nuclear mutation at one of 3 loci designated ibal, iba2 and iba3. Labelling studies with 14C NAA suggest that resistance was not due to changes in the uptake or metabolism of NAA. Plants homozygous for the ibal mutation exhibit a syndrome of atypical germination and growth suggestive of a defect in the biosynthesis, metabolism or localization of abscisic acid. Wildtype seeds treated with gibberellin exhibit the same syndrome, including resistance to NAA and IBA. On the basis of these observations, we propose that auxin toxicity in seeds may be mediated by a block in gibberellin biosynthesis.

Research paper thumbnail of The phosphoenolpyruvate dependent carbohydrate phosphotransferase system of Escherichia coli

FEMS Microbiology Letters, 1983

Research paper thumbnail of Transcriptional analysis of promoter mutations in the Klebsiella pneumoniae nifHDKY operon

Journal of Bacteriology, 1986

Previously isolated promoter mutations that allow expression of the Klebsiella pneumoniae nifHDKY... more Previously isolated promoter mutations that allow expression of the Klebsiella pneumoniae nifHDKY operon in the absence of nifA (R. Bitoun, J. Berman, A. Zilberstein, D. Holland, J.B. Cohen, D. Givol, and A. Zamir, Proc. Natl. Acad. Sci. USA, 80:5812-5816, 1983) were further characterized. pRB1 and pRB5, containing, respectively, point and duplication mutations in the nifHDKY regulatory region, were transformed into Escherichia coli and K. pneumoniae hosts with different nifA and ntrA backgrounds. nif transcription start sites were determined by nuclease S1 mapping. The results indicated that nifA-independent expression from both mutants did not require ntrA. Transcription from pBR5 started 3 base pairs (bp) upstream of the start site of nif-regulated transcription and could stem from a canonical promoter sequence generated at the junction between the two copies of the duplicated sequence. In the presence of nifA-ntrA, transcription from pRB5 started predominantly at the site charac...

Research paper thumbnail of Promoter mutations that allow nifA-independent expression of the nitrogen fixation nifHDKY operon

Proceedings of the National Academy of Sciences, 1983

The nifHDKY operon of Klebsiella pneumoniae encodes for structural polypeptides of nitrogenase an... more The nifHDKY operon of Klebsiella pneumoniae encodes for structural polypeptides of nitrogenase and requires the nifA gene product for transcription. Mutations that allow transcription of the nifHDKY operon in absence of the nifA gene product were characterized in plasmids containing the regulatory region of nifHDKY and nifH fused in phase to lacZ. beta-Galactosidase activity served as a measure for nifH expression. Most mutations were located in the nif regulatory region and included insertion sequence 2 (IS2) insertions, a sequence duplication, and a base substitution. In Escherichia coli, beta-galactosidase activity expressed from the mutant plasmids in the absence of nifA was 6-30% of the nifA-activated, parental level. Expression from most mutant plasmids was further increased by nifA. In K. pneumoniae, IS2-containing plasmids expressed low levels of beta-galactosidase and responded poorly, if at all, to activation by nifA, whereas expression from other mutant types was similar ...

Research paper thumbnail of Ethanol-resistant mutants ofotiana plumbaginifolia are deficient in the expression of pollen and seed alcohol dehydrogenase activity

MGG Molecular & General Genetics, 1990

Six independent mutant lines of Nicotiana plumbaginifolia resistant to ethanol, designated E3, E8... more Six independent mutant lines of Nicotiana plumbaginifolia resistant to ethanol, designated E3, E8, El01, Ell2, E144 and E251, were isolated as germinating seedlings on selective medium. In all cases, resistance to ethanol was conferred by a single recessive nuclear mutation at the same locus. Mutant seeds and pollen lacked detectable ADH activity, with the exception of E251 where a residual activity was detected. An antiserum directed against Arab# dopsis thaliana ADH detected an ADH-related polypeptide of 44 kDa present in wild-type seeds and, to a lesser extent, in the seeds of the leaky mutant E251. No ADH-related polypeptide could be detected in seeds of the other mutants. However, all of them had a nearly normal level of ADH mRNA except one which did not synthesize any mRNA. These results suggest that these ethanol-resistant mutants are impaired in one of the structural genes coding for alcohol dehydrogenase. The corresponding locus has been designated Adhl.

Research paper thumbnail of Outreading promoters are located at both ends of the Gamma-delta transposon

MGG Molecular & General Genetics, 1989

Two plasmids were isolated containing oppositely oriented gamma-delta insertions between the wild... more Two plasmids were isolated containing oppositely oriented gamma-delta insertions between the wild-type transcription initiation site of the nifHDKY operon and the nifH coding sequence. The nifHDKY promoter of Klebsiella pneumoniae, similar to other nitrogen fixation (nif) promoters, normally requires the products of ntrA and nifA for activity. Mutations that allowed constitutive expression of the nifHDKY operon were searched for by transforming a plasmid, containing the regulatory region of this operon followed by an in-frame nifH'-'lacZ fusion, into a Lac- Escherichia coli strain (which contains no nifA) and screening for Lac+ derivatives. The plasmids described here were isolated from such derivatives and directed the constitutive expression of beta-galactosidase. Deletion analysis indicated that gamma-delta promoters other than those transcribing tnpA and tnpR were involved in this expression. Nuclease S1 mapping revealed outward-reading transcription initiation sites in both the gamma end and the delta end of the transposon. Most interestingly, one initiation site on each end was located in corresponding positions within the terminal inverted repeats. The sites were in the center of the longest sequence, of 12 bp, contiguously conserved between the terminal inverted repeats of gamma-delta and the related transposon Tn3. In gamma-delta and Tn3, this sequence has been recently implicated in transposase binding. These results suggest a possible interrelationship between transcription from the "end" promoters and transposition.

Research paper thumbnail of Spontaneous amplification of yeast CEN ARS plasmids

MGG Molecular & General Genetics, 1986

Transformation of Saccharomyces cerevisiae with several yeast CEN4 ARS1 plasmids containing the h... more Transformation of Saccharomyces cerevisiae with several yeast CEN4 ARS1 plasmids containing the his3-A4 allele (as well as the URA3 and TRP1 markers) yielded His + transformants at 0.1%-50% the frequency of Ura + Trp + transformants. Additional His + derivatives arose on continuous growth of transformants originally scored as His-Ura + Trp +. In all cases, the His + phenotype was not due to plasmid or host mutations but invariably correlated with an up to ]2-fold increase in plasmid copy number. On removal of selective pressure, the His + phenotype was lost more readily than the Ura + Trp + markers, with a corresponding decrease in plasmid copy number. Also, the amplification did not decrease the mitotic loss rate of the Ura + Trp + markers. These results indicate that CEN ARS plasmids can be spontaneously amplified to higher levels than previously observed. However, when amplified, apparently not all copies exhibit the characteristic stability of CEN ARS plasmids.

Research paper thumbnail of A yeast strain producing lys2 deletions at a high frequency after sporulation

Research paper thumbnail of Selection of in vivo deletions in Sacharomyces cerevisiae

Journal of Bacteriology, 1988

Research paper thumbnail of Selection of in vivo deletions in Saccharomyces cerevisiae

Journal of bacteriology, 1988

A general screening procedure has been devised for the selection of in vivo-generated deletions i... more A general screening procedure has been devised for the selection of in vivo-generated deletions in haploid Saccharomyces cerevisiae cells. It is based on the introduction into a cyh2 host (resistant to the drug cycloheximide) of a tandemly duplicated CYH2 gene (a dominant allele, conferring sensitivity to cycloheximide), and subsequent selection for Cyhr derivatives. The duplicated CYH2 gene has been introduced on CEN ARS plasmids or integrated into chromosome II. A variable but significant proportion of the Cyhr derivatives of such transformants were deletion mutants in which both CYH2 copies had suffered deletions. Some of the deletions extended into sequences outside the tandemly duplicated CYH2 gene. A total of 61 independently selected deletions ranged in length from 3.1 to over 20 kilobases and had no obvious preferred endpoints. Restriction analysis showed that other frequently isolated Cyhr derivatives appeared to retain one of the two CYH2 copies. Such single-copy derivativ...