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K Iba

Publications and source records attributed to K Iba.

At least 37 records · Page 2Linked to original sources
PubMed1998

Two maize genes encoding omega-3 fatty acid desaturase and their differential expression to temperature.

We have isolated two maize cDNAs and the corresponding genes encoding fatty acid desaturase with Arabidopsis thaliana FAD7 gene as a probe. They shared almost 90% identity at DNA sequence level. Northern analysis revealed that both genes are expressed in leaves, but not in roots at normal temperature- and low temperature-growth condition. The overall level of these transcripts are elevated upon exposure to low temperature. The tissue-specific expression and DNA sequence data indicate that both genes encode plastidic omega-3 fatty acid desaturases. One of them is expressed exclusively at normal temperature but not at 5 degrees C, whereas the other is expressed inversely. We, therefore, termed them ZmFAD7 and ZmFAD8, respectively. Among other stresses, high-salt treatment induced the accumulation of the ZmFAD7 and ZmFAD8 transcripts in roots but drought had no effect on their expression. Cycloheximide induced the accumulation of the ZmFAD7 transcript in roots. The genomic clones of ZmFAD7 and ZmFAD8 consist of 8 exons and 7 introns as same as in the cases of A. thaliana FAD7 and FAD8 genes and the sizes of the 6 internal exons were identical among them. A phylogenetic analysis of ZmFAD7, ZmFAD8 amino acid sequences and those originated from other plant species is also presented.

Amino Acid Sequence↗
PubMed1998

Characterization of transgenic tobacco with an increased alpha-linolenic acid level

Microsomal omega-3 fatty acid desaturase catalyzes the conversion of 18:2 (linoleic acid) to 18:3 (alpha-linolenic acid) in phospholipids, which are the main constituents of extrachloroplast membranes. Transgenic tobacco (Nicotiana tabacum) plants with increased 18:3 contents (designated SIIn plants) were produced through the introduction of a construct with the tobacco microsomal omega-3 fatty acid desaturase gene under the control of the highly efficient promoter containing the E12Omega sequence. 18:3 contents in the SIIn plants were increased by about 40% in roots and by about 10% in leaves compared with the control plants. With regard to growth at 15 degreesC and 25 degreesC and the ability to tolerate chilling at 1 degreesC and 5 degreesC, there were no discernible differences between the SIIn and the control plants. Freezing tolerance in leaves and roots, which was assessed by electrolyte leakage, was almost the same between the SIIn and the control plants. The fluidity of plasma membrane from the SIIn plants was almost the same as that of the control plants. These results indicate that an increase in the 18:3 level in phospholipids is not directly involved in compensation for the diminishment in growth or membrane properties observed under low temperatures.

Journal Article↗
PubMed1998

Co-integration, co-expression and co-segregation of an unlinked selectable marker gene and NtFAD3 gene in transgenic rice plants produced by particle bombardment.

Using the scutellar tissue of rice mature embryos as a target tissue, a selectable marker gene, bar, and an unselectable gene, fatty acid desaturase gene from tobacco (NtFAD3), on separate plasmids, were introduced by particle bombardment. Co-integration, co-expression and inheritance of these genes were analyzed as well as seed fertility of the transgenic plants. Twenty-three out of 32 bialaphos-resistant plants integrated the NtFAD3 gene, which was confirmed by Southern-blot analysis of R0 plants, and showed one to more than 20 hybridizing bands of exogenous DNA, indicating a 72% (23/32) co-integration frequency. However, the frequency of the transgenic plants containing the 1.4-kb fragment of NtFAD3 gene was 34% (11/32). Northern-blot analysis revealed that seven out of ten fertile transgenic rice plants which had a 1.4-kb fragment of NtFAD3 cDNA expressed NtFAD3 mRNA. The NtFAD3 gene under the control of CaMV35S promoter stably expressed in the transgenic rice plants and modified the proportions of linoleic acid (18:2) and linolenic acid (18:3) in fatty acids; the content of 18:2 decreased and that of 18:3 increased. Fourteen out of 32 (44%) transgenic plants set seeds and 18 (56%) showed low fertility or sterility. Molecular analysis of the selfed progeny indicated that all copies in almost all R0 plants were inherited as a single dominant hemizygous locus.

Fatty Acid Desaturases↗
PubMed1997

Structure, chromosomal location and expression of a rice gene encoding the microsome omega-3 fatty acid desaturase.

The omega-3 fatty acid desaturases are membrane-bound enzymes catalyzing the conversion of linoleic acid to linolenic acid in lipids, and are located both in the microsome and plastid envelopes as two different isoforms. A cDNA encoding the microsome omega-3 fatty acid desaturase (OsFAD3) and the corresponding genomic clone were isolated from rice (Oryza sativa L.). The OsFAD3 gene was composed of 8 exons and 7 introns. A microsatellite was present in the second exon of the OsFAD3 gene, showing polymorphism between Indica and Japonica rice varieties. The mapping of this microsatellite showed that the OsFAD3 gene was located on chromosome 11. Expression of the OsFAD3 cDNA in tobacco hairy root tissues and subsequent analysis of fatty acid compositions demonstrated the activity of the microsome omega-3 fatty acid desaturase. The OsFAD3 mRNA was abundant in root tissues, but was hardly detectable in leaves. In root tissues, a high level of the OsFAD3 mRNA was observed at 15 degrees C and 20 degrees C, with its level decreasing markedly at temperatures below 10 degrees C. The accumulation of the OsFAD3 mRNA in leaf tissues remained at quite low levels, both at normal growth temperatures and at chilling temperatures. Similar temperature responses of the OsFAD3 gene were observed both in chilling- tolerant and in chilling-intolerant rice cultivars.

Chromosome Mapping↗
PubMed1997

Existence of three regulatory regions each containing a highly conserved motif in the promoter of plastid-encoded RNA polymerase gene (rpoB).

The plastid gene rpoB encodes a plastid-specific, DNA-dependent RNA polymerase. A study of a barley mutant, albostrians, indicated that rpoB itself is transcribed by a nuclear-encoded RNA polymerase. However, the molecular nature of the nuclear-encoded RNA polymerase and mechanisms of the transcriptional regulation of rpoB expression have not been elucidated. Using an in vivo transient assay system for gene expression in plastids, the 5'-flanking region of rpoB from Arabidopsis thaliana in plastids of cultured BY-2 tobacco cells was analyzed. A series of deletion analyses of the 5'-flanking region indicated that there were two positive and one negative regulatory regions for rpoB expression. Comparison of the 5'-flanking sequences of rpoB among several plant species revealed the existence of three conserved motifs in these regions.

Arabidopsis↗
PubMed1997

Wounding changes the spatial expression pattern of the arabidopsis plastid omega-3 fatty acid desaturase gene (FAD7) through different signal transduction pathways.

The Arabidopsis FAD7 gene encodes a plastid omega-3 fatty acid desaturase that catalyzes the desaturation of dienoic fatty acids in membrane lipids. The mRNA levels of the Arabidopsis FAD7 gene in rosette leaves rose rapidly after local wounding treatments. Wounding also induced the expression of the FAD7 gene in roots. To study wound-responsive expression of the FAD7 gene in further detail, we analyzed transgenic tobacco plants carrying the -825 Arabidopsis FAD7 promoter-beta-glucuronidase fusion gene. In unwounded transformants, FAD7 promoter activity was restricted to the tissues whose cells contained chloroplasts. Activation of the FAD7 promoter by local wounding treatments was more substantial in stems (29-fold) and roots (10-fold) of transgenic plants than it was in leaves (approximately two-fold). Significant induction by wounding was observed in the overall tissues of stems and included trichomes, the epidermis, cortex, vascular system, and the pith of the parenchyma. Strong promoter activity was found preferentially in the vascular tissues of wounded roots. These results indicate that wounding changes the spatial expression pattern of the FAD7 gene. Inhibitors of the octadecanoid pathway, salicylic acid and n-propyl gallate, strongly suppressed the wound activation of the FAD7 promoter in roots but not in leaves or stems. In unwounded plants, exogenously applied methyl jasmonate activated the FAD7 promoter in roots, whereas it repressed FAD7 promoter activity in leaves. Taken together, wound-responsive expression of the FAD7 gene in roots is thought to be mediated via the octadecanoid pathway, whereas in leaves, jasmonate-independent wound signals may induce the activation of the FAD7 gene. These observations indicate that wound-responsive expression of the FAD7 gene in aerial and subterranean parts of plants is brought about by way of different signal transduction pathways.

Acetates↗
PubMed1997

All-trans retinoic acid inhibits dexamethasone-induced ALP activity and mineralization in human osteoblastic cell line SV HFO.

We have recently established a human osteoblastic cell line (SV-HFO) in a culture system, in which the cells are mineralized by treatment with dexamethasone (Dex). Using this system, we examined the effects of all trans-retinoic acid (RA) on the mineralization of the cells. RA inhibited the mineralization, coincident with the inhibition of alkaline phosphatase (ALP). On the other hand, RA induced osteocalcin secretion and had no effect on the expression of the other osteoblastic markers such as type I collagen and osteonectin. To further clarify the mechanism of inhibition of mineralization by RA, we used the retinoic acid receptor (RAR) alpha-selective (Am80), beta-selective (CD2019) and gamma-selective (CD437) agonists instead of RA. RAR alpha- and RAR beta-selective agonists inhibited the mineralization and ALP activity of the cells, while the RAR gamma-selective agonist had no such effects. On the other hand, the RAR gamma-selective agonist induced osteocalcin secretion, but RAR alpha- and RAR beta-selective agonists had no effect on osteocalcin secretion. These results suggested that the inhibitory effect of RA on the mineralization of human osteoblasts is mediated by the activation of RAR alpha and/or RAR beta and that RAR gamma preferentially regulates the expression of osteocalcin without influence on mineralization.

Alkaline Phosphatase↗
PubMed1997

[Effects of long-term administration of alfacalcidol on bone mass and bone metabolism in patients with primary osteoporosis--comparison with calcium preparations].

Long-term administration of active vitamin D3 can reduce the loss of bone mass and the incidence of fractures in Japanese whose intake of calcium (Ca) is low. In a crossover study, we examined the safety and efficacy of 1 alpha (OH)D3 and combination therapy with a Ca preparation. We measured bone mass, the incidence of fractures and bone metabolism in 33 elderly patients with a high risk of fracture (mean age: 77.5 %/- 7.8 (SD) years). Subjects were randomly assigned to receive calcium lactate alone for 12 months after 12 months of combination therapy with 1 alpha (OH)D3 (1 microgram/day) (A-C group, 17 patients) or to take calcium lactate alone for 12 months and then undergo 12 months of combination therapy with 1 alpha(OH)D3 (C-A group, 16 patients). These subjects were followed for 24 months. In the A-C group, the bone mineral density (BMD) of the lumbar spine (L2-4 BMD) measured 6 months after the start of 1 alpha (OH)D3 administration was 3% higher than the baseline value. In the C-A group, L2-4 BMD measured 6 months after the start of calcium lactate administration had decreased by approximately 2%. The rate of decrease was the same 12 months after the start of administration. The differences in L2-4 BMD between the two groups 6 and 12 months after the start of administration were significant (p = 0.023 and p = 0.005, respectively). In the A-C group, the mean BMD of the distal one-third radius measured 6 months after the start of administration had increased by 5%, but the increase was 1% when measured 12 months after the start of administration. In the C-A group, there were no such changes. The incidence of vertebral fracture during combination therapy with 1 alpha(OH) D3 and Ca preparations in the A-C group was significantly lower than that in the C-A group (chi square test, p < 0.05). The serum Ca level in the C-A group gradually increased, as measured 6 and 12 months after the start of combination therapy with 1 alpha(OH) D3 and Ca preparations, although these changes were within the reference range. There was no hypercalciuria. Serum intact parathyroid hormone levels had decreased from 26.5 +/- 11.3 pg/ml and 30.7 +/- 10.3 pg/ml to 19.8 +/- 9.7 pg/ml and 25.5 +/- 9.6 pg/ml in the A-C group and the C-A group, respectively, by 6 months after the start of administration. The rate of decrease was significantly higher in the A-C group (p = 0.004). These findings suggest that long-term administration of 1 alpha(OH)D3 is safe even when combined with administration of Ca preparations, and that this agent inhibits parathyroid function, and thus prevents loss of bone mass and reduces the incidence of vertebral fracture.

Aged↗
PubMed1996

Quantitative determination of amlodipine in serum by liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry.

A sensitive and specific liquid chromatographic method coupled with tandem mass spectrometry was developed for the quantification of amlodipine in human and rat serum, which is a dihydropyridine derivative with calcium antagonist activity. An atmospheric pressure chemical ionization interface was used as the ion source and the analysis was performed in the selected reactive monitoring (SRM) mode. Deuterated amlodipine was used as the internal standard, and serum samples were treated with diethyl ether extraction prior to analysis. Serum levels in the range 0.014-7.2 ng ml-1 were measured accurately by this method, and the lower limit of quantitation (LOQ) was 0.014 ng ml-1 using 1 ml of human serum. The accuracy was within 7% of the expected values. The intra-assay precision was less than 3% and the inter-assay precision was less than 6%. The method was applied to a pharmacokinetic study of amlodipine in rats, in which the measurable range was 0.14-72 ng ml-1 using 0.1 ml of serum because of a limitation on the sample volume.

Amlodipine↗
PubMed1996

Modification of fatty acid composition by over- and antisense-expression of a microsomal omega-3 fatty acid desaturase gene in transgenic tobacco.

omega-3 fatty acid desaturases, which catalyse the conversion of linoleic acid (18:2) to linolenic acid (18:3) in lipids, are located in the microsomes and plastid membranes. Transgenic tobacco plants were produced that express the transcripts of a tobacco microsomal omega-3 fatty acid desaturase gene (NtFad3) in antisense and sense orientations under the control of the cauliflower mosaic virus 35S promoter. The antisense construct has the 0.5-kb fragment of the NtFad3 cDNA containing a 3'-flanking region and a part of the coding region in antisense orientation. The antisense-transformant lines showed decreases of the steady-state NtFad3 mRNA level to 30% of the control plants. In these lines, the 18:3 content decreased to about 80% in root tissues and to about 70-80% in leaf tissues when compared with the control plants. The sense construct has the 1.4-kb full-length cDNA of NtFad3. In one of the sense-transformant lines, the NtFad3 mRNA level increased 8 times when compared with that of the control plants. In this line, the 18:3 content increased by about 1.5-fold in root tissues and by about 1.1-fold in leaf tissues. These results indicate that the up- and down-regulation of the transcript level in the microsomal omega-3 fatty acid desaturase gene is useful to modify the 18:3 content in the vegetative tissues of higher plants.

Antisense Elements (Genetics)↗
PubMed1996

Phase-Dependent effects of transforming growth factor beta 1 on osteoblastic markers of human osteoblastic cell line sV-HFO during mineralization.

A human osteoblastic cell line (SV-HFO) established in our laboratory expresses osteoblastic markers, including mineralization in vitro, in response to differentiation-inducing agents such as dexamethasone. In this study, we examined the effects of transforming growth factor beta 1 (TGF-beta 1) on the mineralization of SV-HFO cells and show that TGF-beta 1 inhibited the mineralization of the cells via down regulation of tetranectin and alkaline phosphatase without influencing other osteoblastic markers. To examine precisely the effects of TGF-beta 1 on the process of mineralization, we tentatively divided the whole process of mineralization into four phases: induced ALP activity (days 0-5), maximal ALP activity (days 5-10), early mineralization (days 10-15), and progressive mineralization (days 15-20). These inhibitory effects of TGF-beta 1 on the expression of tetranectin and alkaline phosphatase, like that on mineralization, were observed only when TGF-beta 1 was applied in the early phase of the process of mineralization. On the other hand, the other osteoblastic markers were not influenced by treatment with TGF-beta 1. These results suggest that TGF-beta 1 may inhibit mineralization of osteoblasts by the downregulation of tetranectin and alkaline phosphatase expression in the early phase. Thus, TGF-beta 1 has phase-dependent effects on a human osteoblastic cell line during the process of mineralization.

Alkaline Phosphatase↗
PubMed1996

Specific expression of the chloroplast gene for RNA polymerase (rpoB) at an early stage of leaf development in rice.

The rpoB gene for the beta subunit of rice chloroplast RNA polymerase was found to be highly expressed in unexpanded immature leaves that contained proplastids, indicating the specific expression of rpoB at an early stage of chloroplast development. A putative transcription start site (tss) was identified, but the 5' upstream region of the tss had no sequences resembling typical --35 and --10 elements. A palindromic sequence and high AT-content were recognized.

Base Sequence↗
PubMed1996

cDNA cloning of a wounding-inducible gene encoding a plastid omega-3 fatty acid desaturase from tobacco.

A cDNA encoding the plastid omega-3 fatty acid desaturase was isolated from a tobacco (Nicotiana tabacum cv. SR1) leaf cDNA library. The amino terminal extension of the deduced amino acid sequence of this clone had a characteristic feature of the transit peptides of plastid-destined proteins. Northern analysis indicated that the mRNA corresponding to this cDNA was present in leaves, but was not detected in roots. Responses to wounding of the plastid and microsome omega-3 desaturase genes were investigated in tobacco leaves. The mRNA level of the plastid omega-3 desaturase gene increased to about 2-fold that of unwounded controls at 12 h after a wounding treatment. On the other hand, the mRNA level of the microsome omega-3 desaturase gene remained constant in the wounded leaves. Linolenic acid contents of major leaf polar lipids increased by wounding. These results indicate that wounding enhances the accumulation of the plastid omega-3 desaturase mRNA, and increases the conversion of linoleic acid to linolenic acid in leaf polar lipids.

Amino Acid Sequence↗
PubMed1995

Transforming growth factor-beta 1 downregulates dexamethasone-induced tetranectin gene expression during the in vitro mineralization of the human osteoblastic cell line SV-HFO.

In the present study, we examined the regulation of tetranectin gene expression using a human osteoblastic cell line, SV-HFO, that undergoes mineralization upon treatment with dexamethasone. We found that the expression of tetranectin and alkaline phosphatase mRNA was induced by dexamethasone treatment as evidenced by Northern blotting. When transforming growth factor-beta 1 (TGF-beta 1) was added together with dexamethasone to the SV-HFO cell cultures, the mineralization process was markedly suppressed and the expression of tetra nectin and alkaline phosphatase was downregulated in a dose-dependent manner. These results demonstrate that the expression of tetranectin in these osteoblastic cells is regulated by dexamethasone and TGF-beta 1 and that tetranectin expression is tightly linked to the process of mineralization.

Biomarkers, Tumor↗
PubMed1995

Tissue-specific and light-responsive regulation of the promoter region of the Arabidopsis thaliana chloroplast omega-3 fatty acid desaturase gene (FAD7).

The Arabidopsis FAD7 gene encodes a chloroplast omega-3 fatty acid desaturase that catalyzes the desaturation of lipid-linked dienoic fatty acids (18:2 and 16:2). An 825 bp FAD7 promoter fragment upstream from the transcriptional start point contained several short sequences which were homologous to the cis-elements (box II, G-box, etc.) conserved in many light-responsive genes. We introduced the FAD7 promoter fused to the beta-glucuronidase (GUS) or the luciferase (LUC) reporter gene into tobacco plants. The -825 promoter sequence conferred tissue-specific and light-responsive expression to both these reporter genes in transgenic tobacco, indicating that these expressions of the FAD7 gene were regulated mainly at the transcriptional level. Histochemical GUS staining showed that the activity of the FAD7 promoter is restricted to the tissues with chloroplast-containing cells although the staining was noticeably absent in the chloroplast-containing cells associated with vascular systems. The 5' deletion experiments of the promoter revealed that the -362/-166 region, containing two putative box II sequences, was responsible for the tissue-specific and light-responsive expression of the FAD7 gene.

Arabidopsis↗
PubMed1995

A novel Ti-plasmid-convertible lambda phage vector system suitable for gene isolation by genetic complementation of Arabidopsis thaliana mutants.

A new lambda phage vector system, lambda TI, has been constructed to facilitate genetic complementation of higher plant mutations. The lambda TI vectors are stable, and by using the Cre-lox site-specific recombination, are automatically convertible into Ti-plasmid binary vectors which are capable of expressing genes in higher plants. Two lambda TI vectors were constructed: (i) lambda TI1, which can generate a Ti-plasmid that contains the cauliflower mosaic virus (CaMV) 35S promoter and is suitable for the expression of cDNA in transformed plants and (ii) lambda TI2, which can generate a Ti-plasmid with the multicloning site (MCS). cDNA and genomic libraries, which were constructed from the cruciferous plant Arabidopsis thaliana in these lambda TI vectors, can be probed by large DNA fragments of more than 100 kb, such as yeast artificial chromosomes (YACs), enabling the direct screening of the clones in the chromosome region containing a specified genetic locus. These libraries will certainly become powerful tools for the genetic complementation of Arabidopsis mutant phenotypes by quickly providing transformation-competent clones.

Agrobacterium tumefaciens↗