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A Komamine

Publications and source records attributed to A Komamine.

At least 19 recordsLinked to original sources
PubMed2001

Isolation and purification of tyrosine hydroxylase from callus cultures of Portulaca grandiflora.

Tyrosine hydroxylase was separated from polyphenol oxidase activity and was highly purified from betacyanin producing callus cultures of Portulaca grandiflora. The purified enzyme catalyzed the formation of DOPA (L-3,4-dihydroxyphenylalanine) from tyrosine and required the pterin compounds (6-methyl-5,6,7,8-tetrahydropterin; 5,6,7,8-tetrahydrobiopterin; 6,7-dimethyl-5,6,7,8-tetrahydropterin) as coenzyme. The K(m) values for tyrosine and 6-methyl-5,6,7,8-tetrahydropterin were 0.5 mM and 0.15 mM, respectively. This enzyme was activated by Fe(2+) and Mn(2+), and inhibited by metal chelating agents.

Catalysis↗
PubMed1999

Synchronization of somatic embryogenesis at high frequency using carrot suspension cultures: model systems and application in plant development.

Materials and methods for the high frequency induction and synchronous somatic embryogenesis from cultured cells of higher plants are described, using carrot suspension cultures as a model system of higher plants. The following four synchronous systems of somatic embryogenesis, which were established in our laboratories, are reported: (1) Somatic embryogenesis from single cells. a) Small spherical single cells, obtained from suspension cultures in the presence of 2,4-D, zeatin and mannitol by sieving, density gradient centrifugation in Percoll solutions and manual picking up, form embryogenic cell clusters, which differentiate to embryos at high frequency, when embryogenic cell clusters are transferred to a medium lacking 2,4-D. b) Explants of hypocotyls of regenerated plantlets from somatic embryos were cultured after treatment with 2,4-D for 12-24 h, and then transferred into a fresh medium lacking 2,4-D. Single cells are released from hypocotyl explants and differentiated into embryos at high frequency. In this system, a large number of single cells and embryogenic cells can be collected. (2) Somatic embryogenesis from embryogenic cell clusters, which are obtained from suspension cultures by sieving, density gradient centrifugation in Ficoll solutions, and subsequent centrifugation at a low speed, differentiate synchronously to globular embryos at high frequency. Plantlets are formed from globular embryos. (3) Embryogenic cell clusters obtained according to the procedure described in (2) are cultured at cell densities of 2x10(3) cell clusters ml(-1). Globular embryos differentiate to torpedo-shaped embryos and subsequently to plantlets at high frequency when they are cultured at densities below 150 globular embryos ml(-1).

Daucus carota↗
PubMed1998

Expression of extensin genes is dependent on the stage of the cell cycle and cell proliferation in suspension-cultured Catharanthus roseus cells.

To isolate cDNAs expressed at a specific phase of the cell cycle in a higher plant, we performed differential screening of a cDNA library prepared from the S-phase cells of synchronized cultures of Catharanthus roseus. Sequence analysis shows that two of the identified cDNAs, cyc15 and cyc17, encode extensins that represent a family of cell wall hydroxyproline-rich glycoproteins. Protein sequences deduced from the two cDNAs contain the characteristic pentapeptide repeat sequence, Ser-Pro-Pro-Pro-Pro, which is commonly observed in extensins. The protein sequences also share several other extensin characteristics such as the presence of a N-terminal signal peptide and a high content of Tyr and Lys residues. When C. roseus cell suspension cultures were synchronized by phosphate starvation, the mRNAs of both cyc15 and cyc17 were transiently expressed during the S and G2 phases of the cell cycle. However, significant amounts of the mRNAs also accumulated in phosphate-starved cells arrested in the G1 phase. In asynchronous cultures, both genes were expressed during the stationary phase, when cell proliferation ceased. The observed patterns of expression suggest that the extensin genes, cyc15 and cyc17, are under two types of regulation: one that depends on the stage of the cell cycle and another that is induced during the growth arrest. Thus, the products of these genes may function both during the progression through the cell cycle and in the strengthening of the cell wall after cell division.

Amino Acid Sequence↗
PubMed1998

A novel cis-acting element in promoters of plant B-type cyclin genes activates M phase-specific transcription.

Plant B-type cyclin genes are expressed late in the G2 and M phases of the cell cycle. Previously, we showed that the promoter of a Catharanthus roseus B-type cyclin, CYM, could direct M phase-specific transcription of a beta-glucuronidase reporter gene in synchronously dividing BY2 tobacco cells. In this study, we determined the regulatory elements contained within the CYM promoter by using a luciferase reporter gene. Mutational analysis showed that a 9-bp element is essential for M phase-specific promoter activity in synchronized BY2 cells. The CYM promoter contains three other sequences similar to this element. A gain-of-function assay demonstrated that when fused to a heterologous promoter, these elements are sufficient for M phase-specific expression; therefore, we named these elements M-specific activators (MSAs). We found MSA-like sequences in B-type cyclin promoters from tobacco, soybean, and Arabidopsis as well as in the promoters of two M phase-specific genes, NACK1 and NACK2, which encode tobacco kinesin-like proteins. Thus, MSA may be a common cis-acting promoter element that controls M phase-specific expression of cell cycle-related genes in plants.

Base Sequence↗
PubMed1998

Organogenic responses in tissue culture of srd mutants of Arabidopsis thaliana.

In Arabidopsis thaliana, shoot redifferentiation and root redifferentiation can be induced at high frequency from hypocotyl and root explants by a two-step culture method. Tissues are precultured on callus-inducing medium and then transferred onto shoot-inducing medium for shoot redifferentiation or onto root-inducing medium for root redifferentiation. In an attempt to dissect these organogenic processes genetically, we characterized the responses in tissue culture of srd1, srd2 and srd3 mutants that were originally isolated as temperature-sensitive strains with defects in shoot redifferentiation (Yasutani, I., Ozawa, S., Nishida, T., Sugiyama, M. and Komamine, A. (1994) Plant Physiol. 105, 815-822). These mutants exhibited temperature sensitivity at different steps of organogenesis, which allowed the identification of three states associated with organogenic competence: IC (incompetent); CR (competent with respect to root redifferentiation); and CSR (competent with respect to shoot and root redifferentiation). Hypocotyl explants were shown to be in the IC state at the initiation of culture and to enter the CSR state, via the CR state, during preculture on callus-inducing medium, whereas root explants seemed to be in the CR state at the initiation of culture. The transition from IC to CR and that from CR to CSR appeared to require the functions of SRD2 and SRD3, respectively. It appears that explants in the CSR state redifferentiate shoots with the aid of the products of SRD1 and SRD2 when transplanted onto shoot-inducing medium. Histological examination of the srd mutants revealed that the function of SRD2 is required not only for organogenesis but also for the reinitiation of cell proliferation in hypocotyl explants during culture on callus-inducing medium. Linkage analysis using RFLP markers indicated that SRD1, SRD2, and SRD3 are located at the lower region, the central region, and the upper region of chromosome 1, respectively.

Arabidopsis↗
PubMed1997

Cell-cycle-regulated transcription of A- and B-type plant cyclin genes in synchronous cultures.

Synchronously dividing cell cultures of Catharanthus roseus were used to isolate cDNAs for two mitotic cyclins, named CYS and CYM. The deduced protein sequence of CYS is similar to that of A-type cyclins, and CYM belongs to the group of B-type cyclins. In a fashion similar to the pattern of expression seen for A-type and B-type cyclins in mammalian cells, CYS is expressed before CYM in C. roseus cells during the cell cycle. CYS mRNA accumulated at the onset of S phase and disappeared early in the G2 phase, whereas CYM mRNA was detected in the G2 and M phases of the cell cycle. Tobacco homologs of the two genes showed similar cell-cycle dependent expression patterns in synchronous cultures of tobacco BY2 cells. In both systems, CYS was expressed much earlier in the cell cycle than most other plant A-type cyclins, and hence CYS along with the soybean cyc1GM can be classified into a distinct subclass. The activities of CYM and CYS promoters during the cell cycle were analyzed in stably transformed tobacco BY2 cells. Cyclin promoter sequences of 0.5 kb could confer the typical cell-cycle-dependent expression to the beta-glucuronidase (GUS) reporter gene: the CYS promoter directed S-phase-specific expression, whereas the CYM promoter drove M-phase-specific expression. These results indicate the important role of transcriptional regulation in the oscillations of cyclin mRNA levels during the cell cycle.

Cell Cycle↗
PubMed1997

Plant 21D7 protein, a nuclear antigen associated with cell division, is a component of the 26S proteasome.

Previously, we cloned a carrot (Daucus carota L.) cDNA encoding a 45-kD protein, 21D7, located in the nuclei of proliferating cells. The 21D7 protein is similar to the partial sequence of a regulatory subunit of the bovine 26S proteasome, p58 (G. DeMartino, C.R. Moomaw, O.P. Zagnitko, R.J. Proske, M. Chu-Ping, S.J. Afendis, J.C. Swaffield, C.A. Slaughter [1994] J Biol Chem 269: 20878-20884) and to the deduced sequence encoded by the Saccharomyces cerevisiae gene SUN2 (M. Kawamura, K. Kominami, J. Takeuchi, A. Toh-e [1996] Mol Gen Genet 251: [146-152]). In our work, the expression of plant 21D7 cDNA rescued the yeast sun2 mutant. Fractionation of carrot and spinach (Spinacia oleracea L.) crude extracts showed that the 21D7 protein sedimented with the active 26S proteasomes. The cessation of cell proliferation in carrot suspensions at the stationary phase caused 26S proteasome dissociation and, correspondingly, the 21D7 protein sedimented together with the free regulatory complexes of the 26s proteasomes. Large-scale purification of carrot 26s proteasomes resulted in co-isolation of the 21D7 protein. Polyacrylamide gel electrophoresis under nondenaturing conditions showed that the 21D7 protein had the same mobility as the 26S proteasome and that proteasome dissociation changed the mobility of the 21D7 protein accordingly. We conclude that the 21D7 protein is a subunit of the plant 26S proteasome and that it probably belongs to the proteasome regulatory complex.

Animals↗
PubMed1997

Changes in the activity and mRNA of cinnamyl alcohol dehydrogenase during tracheary element differentiation in zinnia.

Changes in the enzymatic activity of cinnamyl alcohol dehydrogenase (CAD) and in the expression of a gene for CAD during tracheary element (TE) differentiation were investigated in cultures of single cells isolated from the mesophyll of zinnia (Zinnia elegans). In cultures in which TE differentiation was induced (TE-inductive cultures), CAD activity increased from h 36 after the start of culture (12 h before the start of thickening of the secondary cell wall) and peaked at h 72, when lignin was actively being deposited. In control cultures in which TE differentiation was not induced, CAD activity remained at a very low level for 5 d. Some isoforms of CAD were detected only in the TE-inductive cultures by native gel electrophoresis and subsequent staining for CAD activity. A cDNA clone for CAD, ZCAD1, was isolated from Z. elegans using a cDNA clone for CAD from Aralia cordata as the probe. RNA gel-blot analysis revealed that in the TE-inductive cultures the level of ZCAD1 mRNA increased from h 36 and peaked at h 48 to 60. No such increases were observed in control cultures. These results indicated that both the gene expression and the activity of CAD are strictly regulated, in association with lignification, during TE differentiation in Z. elegans.

Alcohol Oxidoreductases↗
PubMed1996

Betacyanins from plants and cell cultures of Phytolacca americana.

Betacyanins from cell cultures of Phytolacca americana were characterized and compared with those of the stems and ripening fruits of the plant. Whereas in fruits prebetanin (betanin 6'-O-sulphate) and its isoform predominate, in the stem and cell cultures feruloylated derivatives occur as the major components. These were rigorously identified by various spectroscopic techniques (DAD-HPLC, NMR, LC-MS and electrospray MS-MS) and carbohydrate analyses as betanidin 5-O-[(5"-O-E-feruloyl)-2'-O-beta-D-apiofuranosyl] -beta-D-glucopyranoside, a new betacyanin of higher plants, and betanidin 5-O-(6'-O-E-feruloyl)-beta-D-glucopyranoside (lampranthin II), together with their isoforms.

Betacyanins↗
PubMed1995

Isolation and characterization of homeobox-containing genes of carrot.

Homeodomains (HDs) are DNA-binding domains that have been well characterized in animals, and HD proteins are thought to be regulators of transcription. To investigate the regulation of gene expression during somatic embryogenesis in carrot, an attempt was made to isolate cDNA clones that encode HD proteins. A cDNA library from carrot somatic embryos was screened with a degenerate oligonucleotide probe that corresponded to a conserved amino acid sequence of HDs, and one cDNA clone (CHB1) encoding an HD protein was isolated. The amino acid sequence deduced from the nucleotide sequence of this clone contained a putative leucine zipper motif adjacent to the anticipated HD. The homeodomain/leucine zipper (HD-Zip) sequence of this cDNA was used for further screening, and five additional independent clones (CHB2 through CHB6) were isolated. Although the HD-Zip sequences encoded by these clones were similar to each other, the sequences beyond the HD-Zip regions varied greatly. Transcripts corresponding to CHB1 through CHB6 were expressed at different times during somatic embryogenesis. In particular, transcripts corresponding to CHB2 were expressed in close association with the early development of embryos.

Amino Acid Sequence↗
PubMed1995

Isolation of a carrot gene expressed specifically during early-stage somatic embryogenesis.

We report the first successful isolation by subtractive hybridization of a gene expressed specifically during somatic embryogenesis. Embryogenic cell clusters, 32-50 microns in diameter, were isolated by sieving and density-gradient centrifugation. The cDNA library was constructed from proglobulars which were formed from embryogenic cell clusters 3 days after transfer to auxin-free modified Lin and Staba's medium. For use as probe in screening, the same cDNA used for library construction was enriched for specific sequences using subtractive hybridization. The cDNA used for subtraction was prepared from suspension cultures 5 days after subculturing in auxin-containing medium. Nine independent differentially expressed cDNA clones were obtained from a screen of 150,000 recombinant phages. Northern analysis indicated one of these, CEM6, to be expressed specifically during somatic embryogenesis. In addition, one hybridizing transcript was detected in plantlet cotyledons, and two transcripts were detected in hypocotyls. Two separate and distinct hybridizing transcripts are expressed specifically in hypocotyl tissue. The amino acid sequence deduced from the nucleotide sequence of the CEM6 cDNA indicates that it encodes a glycine-rich protein containing a hydrophobic signal-sequence like domain. Its early embryo-specific expression and sequence characteristics suggest an important role as a cell wall protein in embryogenesis.

Amino Acid Sequence↗
PubMed1995

Cloning and characterization of polyphenol oxidase cDNAs of Phytolacca americana.

Two cDNA clones encoding polyphenol oxidases were isolated from a cDNA library constructed from a log-phase suspension culture of Phytolacca americana (pokeweed) producing betalains. The clones exhibit 93 and 86% sequence identity at the nucleotide and deduced amino acid levels, respectively. Both clones contain two copper-binding domains characterized by histidine-rich regions, which are found ubiquitously in all polyphenol oxidases/tyrosinases, and a putative third histidine-rich, copper-binding region, which is common to all plant polyphenol oxidases. One of the Phytolacca cDNA deduced amino acid sequences contains the ubiquitous transit peptide for all proteins targeted to the internal lumen of thylakoid membranes of plastids and is considered to be 98 residues in length based on a proposed sequence cleavage site motif. This would produce a processed peptide of approximately 54 kD. In addition to common features of transit peptides, it was found that an additional conserved region for polyphenol oxidases was located between the hydroxy amino acid-rich region and the thylakoid transfer domain. Spatial and temporal expression was investigated by northern blot analysis of total RNA from various organs of Phytolacca plants. Transcripts of the two clones were found to be 2.1 and 2.3 kb, respectively. Both transcripts were present only at substantial levels in ripening, betalain-containing fruit.

Amino Acid Sequence↗
PubMed1994

Meristem-specific gene expression directed by the promoter of the S-phase-specific gene, cyc07, in transgenic Arabidopsis.

A genomic clone for the cyc07 gene, which is expressed specifically at the S phase during the cell cycle in synchronous cultures of periwinkle (Catharanthus roseus) cells, was isolated. Determination of the nucleotide sequence of the clone revealed that the cyc07 gene consists of seven exons separated by six introns. Genomic Southern analysis indicated that the cyc07 gene is present as a single copy per haploid genome in periwinkle. Expression of related genes was detected in a wide range of other plants. Transgenic Arabidopsis plants were generated that expressed the gene for beta-glucuronidase (GUS) under the control of the promoter of the cyc07 gene. The tissue-specific pattern of expression directed by the promoter was investigated by analysis of GUS activity. Histochemical tests demonstrated that 589 bp of the 5'-upstream sequence of the cyc07 gene could direct specifical expression of the GUS reporter gene in meristematic tissues in transgenic plants. The spatial pattern of expression directed by the promoter was closely correlated with meristematic activity and cell proliferation, suggesting an association between the function of the cyc07 gene and cell proliferation.

Amino Acid Sequence↗
PubMed1994

Mechanisms of the proliferation and differentiation of plant cells in cell culture systems.

Plant cell functions have been investigated in various cell culture systems. In this review, we summarize results obtained from investigations of gene expression during the cell cycle in synchronized cultures of Catharanthus roseus during somatic embryogenesis in suspension cultures of Daucus carota, during organogenesis in tissue cultures of Arabidopsis thaliana and during the transdifferentiation of isolated mesophyll cells to tracheary elements in single-cell cultures of Zinnia elegans.

Cell Cycle↗
PubMed1993

Precise mapping and molecular characterization of the MFT1 gene involved in import of a fusion protein into mitochondria in Saccharomyces cerevisiae.

Garrett et al. [Mol. Gen. Genet. 225 (1991) 483-491] recently reported that an Atp2-lacZ fusion protein was transported into mitochondria in yeast, thus identifying the MFT1 (mitochondrial fusion targeting) gene as a genomic fragment which complements a mutation (mft1) that failed in targeting a fusion protein into mitochondria. They mapped this gene to the ORF, which we have independently identified as a gene homologous to the cyc07 gene, which is expressed specifically in the S phase during the plant cell cycle. We have mapped the MFT1 gene precisely and found that this gene should correspond to the neighboring ORF, rather than the ORF they identified.

Amino Acid Sequence↗
PubMed1993

Isolation and characterization of a cDNA clone for plant nuclear antigen 21D7 associated with cell division.

A cDNA clone was isolated from a carrot (Daucus carota L.) cDNA expression library using monoclonal antibody 21D7, which recognizes a nuclear antigen associated with cell division in plant cells. To show that the isolated cDNA encodes the 21D7 antigen, a polyclonal antiserum was raised against a recombinant fusion protein specified by the cDNA. Both the polyclonal antiserum and the monoclonal antibody 21D7 recognized the same plant protein on immunoblots, in immunoprecipitation experiments, and in peptide mapping. Analysis of the cDNA revealed that the deduced amino acid sequence has 45% identity to the predicted sequence of the mouse transplantation antigen P91A from mutant tumor cells that is responsible for the immune rejection of the corresponding cell clone in a syngeneic mouse. The expression of the plant cDNA at the mRNA level was highly correlated with cell proliferation. In suspension cultures of Catharanthus roseus (L.) G Don. cells, the highest level of expression was observed during the midlogarithmic phase of growth. When auxin was added to stimulate cell division of auxin-starved cells arrested in the G1 phase, transcription was immediately enhanced, and the level of expression remained high throughout the G1 and S phases and dropped dramatically at the end of DNA replication.

Amino Acid Sequence↗
PubMed1992

A gene expressed preferentially in the globular stage of somatic embryogenesis encodes elongation-factor 1 alpha in carrot.

We have isolated cDNA of genes that are preferentially expressed during somatic embryogenesis of carrot (Daucus carota L.) by differential screening of globular embryos and cells that are dividing in an unorganized manner. As a result of Northern-blot analysis, one of the genes identified in this way, which we refer to as CEM1, was found to be expressed at high levels in somatic embryos at the globular and heart-shaped stages. In-situ hybridization using globular embryos revealed that the mRNA transcribed from CEM1 was located preferentially in the spherical region of the globular embryo. A homology search using the amino acid sequence deduced from the nucleotide sequence of the CEM1 cDNA revealed that CEM1 encodes the eukaryotic translational elongation-factor 1 alpha.

Amino Acid Sequence↗