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R B Meagher

Publications and source records attributed to R B Meagher.

At least 73 records · Page 4Linked to original sources
PubMed1987

Expression of a gene encoding a glycine-rich protein in petunia.

We have investigated the expression of a gene that codes for a glycine-rich structural protein (GRP1) in petunia. This gene is expressed as a single polyadenylated RNA of approximately 1,600 bases which was found to be present in leaves, stems, and flowers of petunia but not in roots. In the organs in which GRP1-specific mRNA was expressed, its steady-state levels were highest in stems and leaves and lowest in flowers. This analysis also revealed that the pattern of organ-specific expression for several of the GRP1-related genes was distinctly different. In addition, it was found that the levels of GRP1 RNA were significantly higher in young leaves and stems than in old, implying developmental regulation of the gene. GRP1-specific RNA in both old and young tissue that had been wounded was found to be increased at least 25-fold over that in young unwounded tissue. Increased levels of GRP1 mRNA were seen within 5 min after wounding, with substantial increases apparent by 30 min. Maximal levels of accumulation of GRP1 transcripts occurred 90 min after wounding. The enhancement of GRP1 mRNA levels by wounding appears to be one of the earliest events of the plant wound response and is distinct from that which we observed for the PAL gene in petunia. Using S1 analysis and RNA primer extension, we demonstrated that the same transcriptional start site was used by the GRP1 gene in all organs and in wounded and unwounded tissue. The potential significance of these data with regard to wound signal transduction is discussed.

DNA Restriction Enzymes↗
PubMed1986

The molecular evolution of actin.

We have investigated the molecular evolution of plant and nonplant actin genes comparing nucleotide and amino acid sequences of 20 actin genes. Nucleotide changes resulting in amino acid substitutions (replacement substitutions) ranged from 3-7% for all pairwise comparisons of animal actin genes with the following exceptions. Comparisons between higher animal muscle actin gene sequences and comparisons between higher animal cytoplasmic actin gene sequences indicated less than 3% divergence. Comparisons between plant and nonplant actin genes revealed, with two exceptions, 11-15% replacement substitution. In the analysis of plant actins, replacement substitution between soybean actin genes SAc1, SAc3, SAc4 and maize actin gene MAc1 ranged from 8-10%, whereas these members within the soybean actin gene family ranged from 6-9% replacement substitution. The rate of sequence divergence of plant actin sequences appears to be similar to that observed for animal actins. Furthermore, these and other data suggest that the plant actin gene family is ancient and that the families of soybean and maize actin genes have diverged from a single common ancestral plant actin gene that originated long before the divergence of monocots and dicots. The soybean actin multigene family encodes at least three classes of actin. These classes each contain a pair of actin genes that have been designated kappa (SAc1, SAc6), lambda (SAc2, SAc4) and mu (SAc3, SAc7). The three classes of soybean actin are more divergent in nucleotide sequence from one another than higher animal cytoplasmic actin is divergent from muscle actin. The location and distribution of amino acid changes were compared between actin proteins from all sources. A comparison of the hydropathy of all actin sequences, except from Oxytricha, indicated a strong similarity in hydropathic character between all plant and nonplant actins despite the greater number of replacement substitutions in plant actins. These protein sequence comparisons are discussed with respect to the demonstrated and implicated roles of actin in plants and animals, as well as the tissue-specific expression of actin.

Actins↗
PubMed1985

Divergence and differential expression of soybean actin genes.

DNA sequence analysis as well as genomic blotting experiments using cloned soybean actin DNA sequences as probes show that large sequence heterogeneity exists among members of the soybean actin multigene family. This heterogeneity suggested that the members of this family might be diverged in function and/or regulation. Five of the six soybean actin gene family members examined are shown to be significantly more diverged from one another than members of other known actin gene families. This high level of divergence was utilized in the preparation of actin gene-specific probes in the analysis of the complexity and expression of these members of the soybean actin gene family. Hybridization studies indicate that the six soybean actin genes fall into three classes with a pair of genes in each class. These six genes account for all but two actin gene fragments detected in the soybean genome. We have compared the relative steady state mRNA levels of these classes of soybean actin genes in three organs of soybean. We find that actin genes SAc6 and SAc7 are most highly expressed accounting for 80% of all actin mRNA with respect to the six soybean actin genes examined. Actin genes SAc3 and SAc1 are expressed at intermediate and low levels respectively; and SAc2 and SAc4 are expressed at barely detectable levels. Four of the six soybean actin genes appear to be expressed at the same level in root, shoot and hypocotyl. SAc3 and SAc7 genes appear to be more highly expressed in shoot and 2,4-dichlorophenoxyacetic acid-induced hypocotyl than in root and hypocotyl.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗
PubMed1985

Transcriptional regulation of a gene encoding the small subunit of ribulose-1,5-bisphosphate carboxylase in soybean tissue is linked to the phytochrome response.

The effects of white light, far-red light, and darkness on the transcription of a soybean ribulose-1,5-biphosphate carboxylase small subunit gene, SRS1, were investigated. RNA was labeled with [alpha-32P]UTP in nuclei isolated from plants grown under different conditions of light and darkness and used to probe Southern blots and dot blots. The levels of small subunit mRNA synthesis were normalized to ribosomal RNA synthesis. We demonstrate that the SRS1 gene is transcribed at a rate 16- to 32-fold higher in plants grown in the light than in those grown in darkness. Transcription of the small subunit increased dramatically when plants grown in darkness were given 30 min to 6 h of light and then leveled off after 24 to 48 h of exposure. When light-grown seedlings were exposed to greater than 2 h of darkness, a gradual decrease in transcription was detected. This decrease in transcription reached basal dark-grown levels after 48 h of exposure to darkness. The increase in transcription in etiolated seedlings treated with white light for 15 min could be reduced to basal levels if the treatment was followed by treatment with far-red light for 15 min. In addition, transcription in ligh-grown seedlings was reduced to basal levels when plants were exposed to far-red light for 15 min. The transcription of this ribulose-1,5-biphosphate carboxylase small subunit gene is strongly positively regulated by white light, is negatively regulated by far-red light, and exhibits a classic phytochrome-linked response.

Darkness↗
PubMed1983

Characterization and preliminary mapping of cauliflower mosaic virus transcripts.

Using Northern blot analysis we have studied the transcription of the CM4-184 Ga. strain of cauliflower mosaic virus (CaMV) DNA. This analysis reveals that this CaMV strain, like the Cabb-BS and the Cabb B-JI strains, produces both a genomic length transcript and a 1900-nucleotide (nt) transcript during infection. In addition, we detect an 1800-nt PA+ transcript mapping primarily to the EcoRI-c region of the virus, and three apparent minor viral-specific PA + RNAs of 4900, 4500, and 4300 nt. We also report the presence of two small viral single-stranded DNAs produced during infection, and show that both DNAs are derived from the EcoRI-b region of the virus.

Chromosome Mapping↗
PubMed1983

The MBHI: its utilization in assessment and management of the coronary bypass surgery patient.

Coronary heart disease is the leading cause of death in the United States today. Coronary bypass surgery is increasingly employed as a procedure to prolong the life of these patients. A major problem is optimizing the management of this vast patient population which is composed of individuals who may have experienced sudden entry into the patient role. Central to this is the task of characterizing certain critical features of the psychological makeup of these patients so as to modify or eliminate negative behavioral influences. The MBHI, developed for medical patients, serves in both diagnosis and treatment planning, facilitating and, when needed, psychotherapeutic intervention.

Adaptation, Psychological↗
PubMed1983

Multiple, discrete 35S transcripts of cauliflower mosaic virus.

We have devised a modification of the Berk and Sharp procedure that allows us to detect the presence of a diverse population of 35S full-length, genomic viral transcripts of cauliflower mosaic virus (CaMV). Using this procedure we have been able to identify and characterize four such 35S transcripts. The first 35S RNA that we have mapped, 35S-1, is a slightly longer than full-length transcript, beginning approximately at nucleotide 7500 and ending at nucleotide 7650 and corresponds to a previously characterized 35S transcript of the CabbB-JI strain of CaMV. The second transcript, 35S-2, begins and ends near nucleotide 8000 on the genome map. The third and fourth 35S RNAs, 35S-3, and 35S-4, have their 5' ends lying, respectively, at approximately nucleotides 1200 and 2100, while their 3' ends lie near nucleotides 1300 and 1900. In addition to the four characterized 35S RNAs, we present evidence for a fifth 35S RNA which may begin and end near nucleotide 5700.

Base Sequence↗
PubMed1983

Genes encoding actin in higher plants: intron positions are highly conserved but the coding sequences are not.

We have isolated actin genes from genomic libraries of two highly diverged plants, maize and soybean. The complete nucleotide sequences of a maize actin gene, MAc1, and a soybean actin gene, SAc1, were determined. The nucleotide sequences of these two actin genes and of a previously sequenced soybean actin gene were compared with the actin gene sequences from a wide spectrum of evolutionarily diverged eukaryotes. Some striking features pertinent to the evolution and function of the plant actin gene families have emerged. The deduced amino acid sequence of the plant actins resembles both cytoplasmic- and muscle-specific actins. DNA sequence analysis as well as genomic blotting experiments using cloned actin sequences as probes show that large sequence heterogeneity exists among members of the plant actin multigene families and between genes from two highly diverged plant species. The sequences of the first nine amino acids at the amino terminal end of the plant actins are far more conserved between distant plant actins than the corresponding sequences in distantly related animal actin genes, suggesting a unique and conserved function for the NH2 terminal sequence in higher plants. The soybean and maize actin genes examined each contain three introns in precisely the same positions, quite contrary to the divergent placement of introns observed in animal, protozoan, and fungal actins. The position of the first intron in soybean and maize actin genes corresponds precisely to the position of an intron found in a nematode actin gene. The position of the second intron coincides with one found in rat and chicken skeletal actin genes. These data suggest that the numerous introns found in all actins are of ancient origin. The degree of silent substitution and replacement substitution was compared among plant actin genes and to those of animal, protozoan, and yeast actin genes. It is clear that the silent substitution sites are saturated among all the genes compared, whereas the replacement sites have diverged in only 5-17% of their possible positions. By these criteria the most distant animal actins are only 6% diverged. The three plant actin genes examined are 8-10% diverged in replacement sites from each other and approximately 14% diverged in replacement sites from any of the animal actins examined. The data in this manuscript suggest that the families of soybean and maize actin genes may have diverged from a single common ancestral actin gene long before the divergence of monocots and dicots.

Actins↗
PubMed1982

Complete nucleotide sequence of a soybean actin gene.

Soybean contains a small multigene family of actin-related sequences. We have determined the complete nucleotide sequence of a soybean actin gene carried on the recombinant plasmid pSAc3. As deduced from the nucleotide sequence, this soybean actin is composed of 376 amino acids. Compared to other eukaryotic actins, pSAc3 actin has a deletion of one amino acid between residues 118 and 122. The initiator methionine is followed by alanine, which is not found at this position in other eukaryotic actins. pSAc3 actin differs, in primary sequence, more from fungal and animal actins than any of the known nonplant actins differ from each other. pSAc3 actin appears to be related to both cytoplasmic and muscle specific actins in the location of specific NH(2)-terminal amino acids. The coding sequence is interrupted by three small introns, each less than 90 base pairs long. The splice junctions are similar to those found in other eukaryotic genes, suggesting the presence of a similar splicing apparatus in higher plants. Introns 1 and 3 interrupt the reading frame after codons 20 and 355, respectively. Intron 2 splits a glycine codon at position 151. None of these intron positions is conserved relative to the positions of introns in other actin genes examined.

Journal Article↗
PubMed1982

The nucleotide sequence, expression, and evolution of one member of a multigene family encoding the small subunit of ribulose-1,5-bisphosphate carboxylase in soybean.

We have examined the nuclear genes encoding the small subunit of ribulose-1,5-bisphosphate (RuBP) carboxylase from soybean. One member of this gene family, designated SRS1, has been isolated from a soybean DNA library constructed in the lambda vector Charon 4A. The complete nucleotide sequence and structure of this gene including its two introns and portions of the 5' and 3' flanking sequences were determined. The first exon encodes the entire transit peptide (55 amino acids) and the first 2 amino acids of the mature sequence. Based on analysis of the nucleotide sequence, we concluded that the precursor of the soybean small subunit consists of 178 amino acids. A gene-specific probe for SRS1 was used to show that this gene is transcribed and that steady-state levels of its transcript are strongly light regulated. S1 nuclease mapping was used to locate the potential start of transcription in the sequence and showed that the small subunit gene contains a cap site, TATA box, and -80 sequence, which match the consensus animal sequences. The mature SRS1 small subunit polypeptide of 123 amino acids contains 30 and 34 amino acid replacements relative to the previously determined amino acid sequences from pea and spinach, respectively. Southern blotting of restriction digests of soybean nuclear DNA and data on the complete structure of SRS1 suggest that a multigene family of at least 10 members encodes the RuBP carboxylase small subunit in soybean. Quantitative evolutionary comparison of the soybean small subunit sequence for SRS1 and the pea small subunit sequence suggests that these two genes diverged long before the divergence of pea and soybean.

Amino Acid Sequence↗
PubMed1981

Cloning a promoter that puts the expression of tetracycline resistance under the control of the regulatory elements of the mer operon.

We have sub-cloned from the Eco RI-H fragments of the IncFII plasmid R100 a 260-bp EcoRI fragment, using the promoter-cloning vehicle, pBRH4, (The Inc FII plasmid codes for the mer operon, and pBRH4 expresses tetracycline resistance only when the deleted tet promoter has been replaced by another sequence that can serve as a promotor). With the 260-bp fragment inserted, the derivative plasmid, pFB4, directs the expression of tetracycline resistance only if there is a second plasmid in the strain that carries the merR-positive regulatory element. Under these conditions, the level of tetracycline resistance is directly proportional to the concentration of Hg2+ present in the medium. The 260-bp fragment also allows low-level constitutive expression of tet resistance when transactivated with merR mutants that have a "micro-constitutive" phenotype. The 260-bp mer promoter fragment contains a single HincII site; there is also but one HincII site in the EcoRI-H fragment of R100 from which the promoter fragment was derived. Restriction analysis of purified Eco RI-H DNA shows that the single HincII site is at 550 bp from the "right"terminus of the IS1b element, which is also present in the EcoRI-H fragment. Because of its biological activity and its location within the "H" fragment, this promoter is very likely a promoter for the structural genes of the operon.

Chromosome Mapping↗
PubMed1981

Multigene family of actin-related sequences isolated from a soybean genomic library.

We have investigated the actin-related sequences in soybean using heterologous actin DNA probes from Dictyostelium, Drosophila, and yeast. Southern blot analysis of restriction digests of soybean DNA indicates that actin is encoded in a small multigene family. In order to isolate individual members of this gene family, we have constructed a soybean genomic library in the lambda vehicle Charon 4A. A partial characterization of this library shows it to be nearly complete. We have isolated from this library a number of recombinant clones that hybridize to actin-coding sequences from all three heterologous probes. We have identified the fragments containing the actin-related sequences on the physical maps of two of these clones lambda SAc1 and lambda SAc3. These fragments were subcloned in the plasmid vehicle pBR322. Using electron microscope heteroduplex mapping we show that the subclones, pSAc1 and pSAc3, share homology with the entire actin-coding sequence (1.1 kb) of Drosophila and Dictyostelium. Furthermore, pSAc1 and pSAc3 have additional homology of approximately 0.22 kb at the 5' ends of their coding sequences. No homology is detected in the 3' flanking regions of these clones. The actin sequence in pSAc1 contains an interruption of approximately 0.30 kb located 0.39 kb from the 5' end of the actin polypeptide coding region.

Actins↗
PubMed1981

Isolation and Mapping of Small Cauliflower Mosaic Virus DNA Fragments Active as Promoters in Escherichia coli.

Small EcoRI(*) fragments of cauliflower mosiac virus DNA (strain CM4-184), which act as promoters for the tetracycline resistance gene on the promoter probe plasmid pBRH4 in Escherichia coli, have been isolated and mapped on the viral genome. Two regions of the viral genome contain DNA sequences with promoter activity in E. coli. Two independent cloned fragments from one region direct a high level of tetracycline resistance (up to 38 mug of tetracycline per ml). Two independent fragments from the second region of the viral genome also direct tetracycline resistance, but at lower levels. The activity of the two fragments with the strongest promoter activity in E. coli may direct transcription of the viral genome in a clockwise direction. This is consistent with the direction of transcription predicted from sequence analysis of the viral DNA (Franck et al., Cell 21: 285-294, 1980). One of these fragments maps at the start of a large open translational reading frame which is predicted to contain the coding sequence for the viral coat protein. Each promoter-active fragment is located in the 5'-terminal portion of one of the six open reading frames predicted from the DNA sequence.

Journal Article↗
PubMed1977

Purification and partial amino acid sequence of the cyanogen bromide fragments of muconolactone isomerase from Pseudomonas putida.

Muconolactone isomerase is shown to be resistant to proteolytic cleavage by trypsin. Cyanogen bromide cleavage at the methionine residues of the polypeptide is at least 95% complete. Six cyanogen bromide fragments are separated on DEAE-cellulose. One fragment is shown by amino acid analysis and carboxyl-terminal analysis to be an incomplete cleavage product. The five remaining fragments represent the entire polypeptide and have been ordered with respect to the entire muconolactone isomerase sequence. Approximately 50% of the polypeptide sequence could be determined from these fragments by the dansyl-Edman technique. The possible evolutionarily homologous origins of muconolactone isomerase and two analogous isomerases, carboxymuconolactone decarboxylase and sigma5-3-ketosteroid isomerase, are discussed.

Amino Acid Sequence↗