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Biomedical subjects

G Takeba

Publications and source records attributed to G Takeba.

16 recordsLinked to original sources
PubMed2003

Hypergravity-induced changes in gene expression in Arabidopsis hypocotyls.

Under hypergravity conditions, the cell wall of stem organs becomes mechanically rigid and elongation growth is suppressed, which can be recognized as the mechanism for plants to resist gravitational force. The changes in gene expression by hypergravity treatment were analyzed in Arabidopsis hypocotyls by the differential display method, for identifying genes involved in hypergravity-induced growth suppression. Sixty-two cDNA clones were expressed differentially between the control and 300 g conditions: the expression levels of 39 clones increased, whereas those of 23 clones decreased under hypergravity conditions. Sequence analysis and database searching revealed that 12 clones, 9 up-regulated and 3 down-regulated, have homology to known proteins. The expression of these genes was further analyzed using RT-PCR. Finally, six genes were confirmed to be up-regulated by hypergravity. One of such genes encoded 3-hydroxy-3-methylglutaryl-Coenzyme A reductase (HMGR), which catalyzes a reaction producing mevalonic acid, a key precursor of terpenoids such as membrane sterols and several types of hormones. The expression of HMGR gene increased within several hours after hypergravity treatment. Also, compactin, an inhibitor of HMGR, prevented hypergravity-induced growth suppression, suggesting that HMGR is involved in suppression of Arabidopsis hypocotyl growth by hypergravity. In addition, hypergravity increased the expression levels of genes encoding CCR1 and ERD15, which were shown to take part in the signaling pathway of environmental stimuli such as temperature and water, and those of the alpha-tubulin gene. These genes may be involved in a series of cellular events leading to growth suppression of stem organs under hypergravity conditions.

Arabidopsis↗
PubMed2000

Growth regulation mechanisms in higher plants under microgravity conditions - changes in cell wall metabolism.

During Space Shuttle STS-95 mission, we cultivated seedlings of rice (Oryza sativa L. cv. Koshihikari and cv. Tan-ginbozu) and Arabidopsis (Arabidopsis thaliana L. cv. Columbia and cv. etr1-1) for 68.5, 91.5, and 136 hr on board, and then analyzed changes in the nature of their cell walls, growth, and morphogenesis under microgravity conditions. In space, elongation growth of both rice coleoptiles and Arabidopsis hypocotyls was stimulated. Also, the increase in the cell wall extensibility, especially that in the irreversible extensibility, was observed for such materials. The analyses of the amounts, the structure, and the physicochemical properties of the cell wall constituents indicated that the decreases in levels and molecular masses of cell wall polysaccharides were induced under microgravity conditions, which appeared to contribute to the increase in the wall extensibility. The activity of certain wall enzymes responsible for the metabolic turnover of the wall polysaccharides was increased in space. By the space flight, we also confirmed the occurrence of automorphogenesis of both seedlings under microgravity conditions; rice coleoptiles showed an adaxial bending, whereas Arabidopsis hypocotyls elongated in random directions. Furthermore, it was shown that spontaneous curvatures of rice coleoptiles in space were brought about uneven modifications of cell wall properties between the convex and the concave sides.

Arabidopsis↗
PubMed1997

The nitrate reductase gene isolated from DNA of cultured spinach cells.

The gene encoding nitrate reductase was cloned from the DNA isolated from cultured spinach (Spinacia oleracea cv. Hoyo) cells and sequenced. The clone contains 7612 nucleotides of the gene which consists of four exons interrupted by three introns. The transcription start site was determined by primer extension analysis and located 193 bp upstream of the ATG translation initiation codon. The 5'-flanking region contains a TATA box and CAAT box.

Base Sequence↗
PubMed1996

Noncoding RNA for CR20, a cytokinin-repressed gene of cucumber.

The CR20 gene was identified as a cytokinin-repressed gene in excised cotyledons of cucumber. We determined the sequences of some CR20 cDNAs with different structures and sequenced genomic clones for CR20. This gene consisted of three exons, and there were at least three types of transcript, which seemed to be generated by alternative splicing of the second intron. None of the CR20 transcripts included a long open reading frame (ORF). We isolated a cDNA of Arabidopsis thaliana with cucumber CR20 cDNA as a probe. This cDNA for a gene designated AtCR20-1 also lacked a long ORF. A region of 180 nucleotides was conserved in the CR20 RNA of cucumber and the AtCR20-1 RNA of Arabidopsis, although the homology was relatively low when the entire sequences were compared. Each conserved region consisted of seven elements, and seems to form stable secondary structure. These suggest that CR20 RNA may function as an RNA that is not translated into a protein.

Alternative Splicing↗
PubMed1996

The level of mRNA transcribed from psaL, which encodes a subunit of photosystem I, is increased by cytokinin in darkness in etiolated cotyledons of cucumber.

A cDNA clone for an mRNA whose level increased within 2 h of the start of treatment with N6-benzyladenine in etiolated cotyledons of cucumber was isolated by differential hybridization. The cDNA was homologous to psaL, which encodes subunit XI (PSI-L) of photosystem I. The accumulation of psaL mRNA was specifically induced by cytokinins or light.

Amino Acid Sequence↗
PubMed1995

Cytokinin induces a rapid decrease in the levels of mRNAs for catalase, 3-hydroxy-3-methylglutaryl CoA reductase, lectin and other unidentified proteins in etiolated cotyledons of cucumber.

Large-scale differential hybridization was performed to examine rapid changes in gene expression caused by a phytohormone, cytokinin, in etiolated cotyledons of cucumber (Cucumis sativus L.). We isolated 86 cDNA clones for mRNAs whose levels decreased within 2 h of the start of treatment with N6-benzyladenine (BA). Partial nucleotide sequences showed that some of the cDNAs were homologous to those for catalase, 3-hydroxy-3-methylglutaryl CoA reductase (HMGR) and a lectin. This is the first report that the levels of the mRNAs for those proteins are regulated by a cytokinin in darkness. Together with previous results [Teramoto et al. (1993) Physiol. Plant. 87: 584, (1994) Planta 193: 573, (1995) Planta 196: 387], the present study suggests that the cytokinin act to lower the levels of mRNAs transcribed from various genes in etiolated cotyledons.

Adenine↗
PubMed1994

Isolation of a cDNA clone for a cytokinin-repressed gene in excised cucumber cotyledons.

Rapid changes in gene expression were studied during incubation of cucumber (Cucumis sativus L.) cotyledons with cytokinins in darkness. Complementary-DNA clones for mRNAs whose levels decreased within 4 h of treatment with N6-benzyladenine (BA) were isolated by differential hybridization. One of them (CR9) was sequenced. It is 588 bp long, and would encode a protein consisting of 137 amino-acid residues and having a molecular mass of 15 kDa. The sequence shows a high homology with a light-induced gene from rice. Northern blot analysis of the CR9 transcript showed the level of the mRNA (0.7 kb) to decrease tenfold within 4 h of BA treatment, i.e. well before BA-induced cotyledon expansion was observed. The repression became greater with increasing concentration of BA (10(-8)-10(-5) M). The expression of the CR9 gene was repressed specifically by cytokinins (BA, isopentenyladenine and t-zeatin), but not by adenine or 2,4-dichlorophenoxyacetic acid (auxin). The results are discussed in relation to the primary action of cytokinin.

Adenine↗
PubMed1990

Phytochrome-mediated activation of the gene for cytosolic glutamine-synthetase (GS1) during imbibition of photosensitive lettuce seeds.

A full-length cDNA encoding glutamine synthetase was isolated from a lambda gt11 library constructed from the poly(A)+ RNA isolated from lettuce seeds incubated under red light. The nucleotide sequence of the cDNA and the deduced sequence of amino acids showed a high degree of homology to those of the cytosol-type glutamine synthetase from other plants. Northern and dot-blot analyses of poly(A)+ RNA extracted from the seeds incubated under various light conditions showed that the activation of the gene for cytosolic glutamine-synthetase during imbibition of lettuce seeds is directly or indirectly regulated by phytochrome.

Amino Acid Sequence↗
PubMed1990

Molecular Cloning and Ethylene Induction of mRNA Encoding a Phytoalexin Elicitor-Releasing Factor, beta-1,3-Endoglucanase, in Soybean.

Soybean (Glycine max) beta-1,3-endoglucanase (EC 3.2. 1.39) is involved in one of the earliest plant-pathogen interactions that may lead to active disease resistance by releasing elicitor-active carbohydrates from the cell walls of fungal pathogens. Ethylene induced beta-1,3-endoglucanase activity to 2- to 3-fold higher levels in cotyledons of soybean seedlings. A specific polyclonal antiserum raised against purified soybean beta-1,3-endoglucanase was used to immunoprecipitate in vitro translation products, demonstrating that ethylene induction increased translatable beta-1,3-endoglucanase mRNA. Several cDNA clones for the endoglucanase gene were obtained by antibody screening of a lambda-gt11 expression library prepared from soybean cotyledons. Hybrid-select translation experiments indicated that the cloned cDNA encoded a 36-kilodalton precursor protein product that was specifically immunoprecipitated with beta-1,3-endoglucanase antiserum. Escherichia coli cells expressing the cloned cDNA also synthesized an immunologically positive protein. Nucleotide sequence of three independent clones revealed a single uninterrupted open reading frame of 1041 nucleotides, corresponding to a polypeptide of 347 residue long. The primary amino acid sequence of beta-1,3-endoglucanase as deduced from the nucleotide sequence was confirmed by direct amino acid sequencing of trypsin digests of the glucanase. The soybean beta-1,3-endoglucanase exhibited 53% amino acid homology to a beta-1,3-glucanase cloned from cultured tobacco cells and 48% homology to a beta-(1,3-1,4)-glucanase from barley. Utilizing the largest cloned cDNA (pEG488) as a hybridization probe, it was found that the increase in translatable beta-1,3-endoglucanase mRNA seen upon ethylene treatment of soybean seedlings was due to 50- to 100-fold increase in steady state mRNA levels, indicating that ethylene regulates gene expression of this enzyme important in disease resistance at the level of gene transcription.

Journal Article↗
PubMed1990

A flower-inducing substance of high molecular weight from higher plants.

The flower-inducing activities of aqueous extracts of several plants were fractionated by gel filtration. Three major peaks, corresponding to molecular weights of about 120, 20 to 30, and 5 to 10 kilodaltons, were detected in extracts of Lemna, Pharbitis, and Brassica. The latter two peaks may be degradation products generated during the extraction procedure. In extracts of soybean seeds, only the peak of material of 120 kilodaltons was detected. This is the first published report of a high molecular mass substance with florigenic activity in Lemna plants. The florigenic substance had some properties associated with proteins (or polypeptides), but the activity was unaffected by treatment with proteinase K.

Journal Article↗