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Shigeo Yoshida

Publications and source records attributed to Shigeo Yoshida.

At least 55 records · Page 3Linked to original sources
PubMed2005

A novel glucosyltransferase involved in steroid saponin biosynthesis in Solanum aculeatissimum.

Steroidal saponins are widely distributed in many plant species. Their diverse structures have resulted in a wide range of applications, including drug and medicine production. It has been suggested that the nature of the non-saccharide and oligosaccharide portions of the saponin molecule both contribute to the properties of individual saponins. Despite numerous studies on the occurrence, chemical structure, and varying pharmaceutical activities of steroidal saponins, their biosynthesis pathway is poorly understood. Glycosylation is thought to be the final step in steroidal saponin biosynthesis and it is thought to be involved in regulating the biological activities of saponins. Isolation of the glycosyltransferases that catalyze the transfer of sugar molecules to steroidal compounds will help to clarify the mechanisms that produce diverse saponins and control their activities in plants. In this study, we obtained three cDNAs encoding putative glycosyltransferases from Solanum aculeatissimum. One of the three, SaGT4A showed UDP-glucosyltransferase activity. This is the first cloned glucosyltransferase involved in steroidal saponin biosynthesis. SaGT4A catalyzes the 3-O-glucosylation of steroidal sapogenins, such as diosgenin, nuatigenin, and tigogenin. This enzyme also glucosylates steroidal alkaloids, such as solanidine, solasodine, and tomatidine. Gene expression analysis revealed that the accumulation of SaGT4A transcripts showed a unique response to wounding stress indicating the involvement of SaGT4A in plant defense system.

Amino Acid Sequence↗
PubMed2005

Hairy root-activation tagging: a high-throughput system for activation tagging in transformed hairy roots.

Activation tagging is a powerful technique for generating gain-of-function mutants in plants. We developed a new vector system for activation tagging of genes in "transformed hairy roots". The binary vector pHR-AT (Hairy Root-Activation Tagging) and its derivative pHR-AT-GFP contain a cluster of rol (rooting locus) genes together with the right border facing four tandem repeats of the cauliflower mosaic virus (CaMV) 35S enhancer element on the same T-DNA. Transformation experiments using Arabidopsis, potato, and tobacco as model plants revealed that upon inoculating plants with Agrobacterium tumefaciens harboring these vectors, a large number of independently transformed roots could be induced from explants within a short period of time, and root culture lines were subsequently established. Molecular analyses of the pHR-AT-GFP-transformed Arabidopsis lines showed that expression of the genes adjacent to the T-DNA insertion site was significantly increased. This system may facilitate application of the activation-tagging approach to plant species that are recalcitrant to the regeneration of transgenic plants. High-throughput metabolic profiling of activation-tagged root culture lines will offer opportunities for identifying regulatory or biosynthetic genes for the production of valuable secondary metabolites of interest.

Arabidopsis↗
PubMed2005

Serous retinal detachment in an elderly patient with Philadelphia-chromosome-positive acute lymphoblastic leukemia.

PURPOSE: To describe an elderly woman who presented with a serous retinal detachment (SRD) as the first sign of Philadelphia-chromosome-positive acute lymphoblastic leukemia (Ph(+) ALL). DESIGN: Observational case report. METHODS: A complete ophthalmic and systemic evaluation was performed on a 62-year-old woman because of decreased vision of 20/60 OD and 20/25 OS. RESULTS: Fundus examination revealed a SRD involving the fovea, OU. Fluorescein angiography disclosed multifocal spots of hyperfluorescence in the early phase, and diffuse subretinal accumulation of fluorescein in the late phase. She was diagnosed with Ph(+) ALL because of systemic findings. She underwent systemic chemotherapy and went into complete remission. Visual acuity improved to 20/20 in both eyes with resolution of the bilateral SRD. CONCLUSIONS: Our observations indicate that a sudden appearance of SRD, even in an elderly patient, warrants a thorough systemic screening for underlying leukemia. This is especially important, because prompt systemic chemotherapy can improve the visual acuity and the prognosis.

Antineoplastic Agents↗
PubMed2005

De novo insG619 mutation in PAX2 gene in a Japanese patient with papillorenal syndrome.

PURPOSE: To describe a Japanese patient with papillorenal syndrome (PRS) and to identify the genetic defect responsible for the disease. DESIGN: Interventional case report. METHODS: Complete ophthalmologic and systemic examinations were performed, and direct genomic sequencing of the PAX2 gene. RESULTS: Fundus examination of a 3-year-old Japanese girl showed atypical coloboma bilaterally. At 6 years of age, she presented with proteinuria, and renal ultrasonography showed hypoplastic kidneys bilaterally. Molecular genetic analysis of the PAX2 gene revealed a de novo heterozygous insertion of a G at position 619. CONCLUSIONS: Our findings suggest that an abnormal development of the optic stalk led to the optic disk dysplasia in PAX2-associated PRS. This indicates that we should consider renal abnormalities when an atypical round coloboma is present. Molecular genetic analysis of the PAX2 gene in combination with renal ultrasonography can help in making an earlier diagnosis of the disease.

Abnormalities, Multiple↗
PubMed2005

Autoregulation and homodimerization are involved in the activation of the plant steroid receptor BRI1.

The leucine-rich-repeat receptor serine/threonine kinase, BRI1, is a cell-surface receptor for brassinosteroids (BRs), the steroid hormones of plants, yet its activation mechanism is unknown. Here, we report a unique autoregulatory mechanism of BRI1 activation. Removal of BRI1's C terminus leads to a hypersensitive receptor, indicated by suppression of dwarfism of BR-deficient and BR-perception mutants and by enhanced BR signaling as a result of elevated phosphorylation of BRI1. Several sites in the C-terminal region can be phosphorylated in vitro, and transgenic Arabidopsis expressing BRI1 mutated at these sites demonstrates an essential role of phosphorylation in BRI1 activation. BRI1 is a ligand-independent homo-oligomer, as evidenced by the transphosphorylation of BRI1 kinase in vitro, the dominant-negative effect of a kinase-inactive BRI1 in transgenic Arabidopsis, and coimmunoprecipitation experiments. Our results support a BRI1-activation model that involves inhibition of kinase activity by its C-terminal domain, which is relieved upon ligand binding to the extracellular domain.

Amino Acid Sequence↗
PubMed2005

CYP90C1 and CYP90D1 are involved in different steps in the brassinosteroid biosynthesis pathway in Arabidopsis thaliana.

Brassinosteroids (BRs) are plant hormones that are essential for a wide range of developmental processes in plants. Many of the genes responsible for the early reactions in the biosynthesis of BRs have recently been identified. However, several genes for enzymes that catalyze late steps in the biosynthesis pathways of BRs remain to be identified, and only a few genes responsible for the reactions that produce bioactive BRs have been identified. We found that the ROTUNDIFOLIA3 (ROT3) gene, encoding the enzyme CYP90C1, which was specifically involved in the regulation of leaf length in Arabidopsis thaliana, was required for the late steps in the BR biosynthesis pathway. ROT3 appears to be required for the conversion of typhasterol to castasterone, an activation step in the BR pathway. We also analyzed the gene most closely related to ROT3, CYP90D1, and found that double mutants for ROT3 and CYP90D1 had a severe dwarf phenotype, whereas cyp90d1 single knockout mutants did not. BR profiling in these mutants revealed that CYP90D1 was also involved in BR biosynthesis pathways. ROT3 and CYP90D1 were expressed differentially in leaves of A. thaliana, and the mutants for these two genes differed in their defects in elongation of hypocotyls under light conditions. The expression of CYP90D1 was strongly induced in leaf petioles in the dark. The results of the present study provide evidence that the two cytochrome P450s, CYP90C1 and CYP90D1, play distinct roles in organ-specific environmental regulation of the biosynthesis of BRs.

Amino Acid Sequence↗
PubMed2005

BAS1 and SOB7 act redundantly to modulate Arabidopsis photomorphogenesis via unique brassinosteroid inactivation mechanisms.

Active brassinosteroids (BRs), such as brassinolide (BL) and castasterone (CS), are growth-promoting plant hormones. An Arabidopsis cytochrome P450 monooxygenase (CYP734A1, formerly CYP72B1), encoded by the BAS1 gene, inactivates BRs and modulates photomorphogenesis. BAS1 was identified as the overexpressed gene responsible for a dominant, BR-deficient mutant, bas1-D. This mutant was isolated in an activation-tagged screen designed to identify redundant genes that might not be identified in classic loss-of-function screens. Here we report the isolation of a second activation-tagged mutant with a BR-deficient phenotype. The mutant phenotype is caused by the overexpression of SOB7 (CYP72C1), a homolog of BAS1. We generated single and double null-mutants of BAS1 and SOB7 to test the hypothesis that these two genes act redundantly to modulate photomorphogenesis. BAS1 and SOB7 act redundantly with respect to light promotion of cotyledon expansion, repression of hypocotyl elongation and flowering time in addition to other phenotypes not regulated by light. We also provide biochemical evidence to suggest that BAS1 and SOB7 act redundantly to reduce the level of active BRs, but have unique mechanisms. Overexpression of SOB7 results in a dramatic reduction in endogenous CS levels, and although single null-mutants of BAS1 and SOB7 have the same level of CS as the wild type, the double null-mutant has twice the amount. Application of BL to overexpression lines of BAS1 or SOB7 results in enhanced metabolism of BL, though only BAS1 overexpression lines confer enhanced conversion to 26-OHBL, suggesting that SOB7 and BAS1 convert BL and CS into unique products.

Amino Acid Sequence↗
PubMed2005

A single amino acid insertion in the WRKY domain of the Arabidopsis TIR-NBS-LRR-WRKY-type disease resistance protein SLH1 (sensitive to low humidity 1) causes activation of defense responses and hypersensitive cell death.

In this study we characterized the sensitive to low humidity 1 (slh1) mutant of Arabidopsis ecotype No-0 which exhibits normal growth on agar plate medium but which on transfer to soil shows growth arrest and development of necrotic lesions. cDNA microarray hybridization and RNA gel blot analysis revealed that genes associated with activation of disease resistance were upregulated in the slh1 mutants in response to conditions of low humidity. Furthermore, the slh1 mutants accumulate callose, autofluorescent compounds and salicylic acid (SA). We demonstrate that SA is required for the slh1 phenotype but not PAD4 or NPR1. SLH1 was isolated by map-based cloning and it encodes a resistance (R)-like protein consisting of a domain with Toll and interleukin-1 receptor homology (TIR), a nucleotide-binding domain (NB), leucine-rich repeats (LRR) and a carboxy-terminal WRKY domain. SLH1 is identical to the R gene RRS1-R of the Arabidopsis ecotype Nd-1, a gene which confers resistance to the bacterial pathogen Ralstonia solanacearum GMI1000 and also functions as an R gene to this pathogen in No-0. We identified a 3 bp insertion mutation in slh1 that results in the addition of a single amino acid in the WRKY domain; thereby impairing its DNA-binding activity. Our data suggest that SLH1 disease resistance signaling may be negatively regulated by its WRKY domain in the R protein and that the constitutive defense activation conferred by the slh1 mutation is inhibited by conditions of high humidity.

Amino Acid Sequence↗
PubMed2005

RAPD markers encoding retrotransposable elements are linked to the male sex in Cannabis sativa L.

Male-associated DNA sequences were analyzed in Cannabis sativa L. (hemp), a dioecious plant with heteromorphic sex chromosomes. DNA was isolated from male and female plants and subjected to random amplified polymorphic DNA analysis. Of 120 primers, 17 yielded 400 to 1500-bp fragments detectable in male, but not female, plants. These fragments were cloned and used as probes in gel-blot analysis of genomic DNA. When male and female DNA was hybridized with 2 of these male-specific fragments, MADC(male-associated DNA sequences in C. sativa)3 and MADC4, particularly intense bands specific to male plants were detected in addition to bands common to both sexes. The MADC3 and MADC4 sequences were shown to encode gag/pol polyproteins of copia-like retrotransposons. Fluorescence in situ hybridization with MADC3 and MADC4 as probes revealed a number of intense signals on the Y chromosome as well as dispersed signals on all chromosomes. The gel-blot analysis and fluorescence in situ hybridization results presented here support the hypothesis that accumulation of retrotransposable elements on the Y chromosome might be 1 cause of heteromorphism of sex chromosomes.

Cannabis↗
PubMed2004

Preference of DNA methyltransferases for CpG islands in mouse embryonic stem cells.

Many CpG islands have tissue-dependent and differentially methylated regions (T-DMRs) in normal cells and tissues. To elucidate how DNA methyltransferases (Dnmts) participate in methylation of the genomic components, we investigated the genome-wide DNA methylation pattern of the T-DMRs with Dnmt1-, Dnmt3a-, and/or Dnmt3b-deficient ES cells by restriction landmark genomic scanning (RLGS). Approximately 1300 spots were detected in wild-type ES cells. In Dnmt1(-/-) ES cells, additional 236 spots emerged, indicating that the corresponding loci are methylated by Dnmt1 in wild-type ES cells. Intriguingly, in Dnmt3a(-/-)Dnmt3b(-/-) ES cells, the same 236 spots also emerged, and no additional spots appeared differentially. Therefore, Dnmt1 and Dnmt3a/3b share targets in CpG islands. Cloning and virtual image RLGS revealed that 81% of the RLGS spots were associated with genes, and 62% of the loci were in CpG islands. By contrast to the previous reports that demethylation at repeated sequences was severe in Dnmt1(-/-) cells compared with Dnmt3a(-/-)Dnmt3b(-/-) cells, a complete loss of methylation was observed at RLGS loci in Dnmt3a(-/-)Dnmt3b(-/-) cells, whereas methylation levels only decreased to 16% to 48% in the Dnmt1(-/-) cells. We concluded that there are CpG islands with T-DMR as targets shared by Dnmt1 and Dnmt3a/3b and that each Dnmt has target preferences depending on the genomic components.

Animals↗
PubMed2004

A novel inhibitor of 9-cis-epoxycarotenoid dioxygenase in abscisic acid biosynthesis in higher plants.

Abscisic acid (ABA) is a major regulator in the adaptation of plants to environmental stresses, plant growth, and development. In higher plants, the ABA biosynthesis pathway involves the oxidative cleavage of 9-cis-epoxycarotenoids, which may be the key regulatory step in the pathway catalyzed by 9-cis-epoxycarotenoid dioxygenase (NCED). We developed a new inhibitor of ABA biosynthesis targeting NCED and named it abamine (ABA biosynthesis inhibitor with an amine moiety). Abamine is a competitive inhibitor of NCED, with a Ki of 38.8 microm. In 0.4 m mannitol solution, which mimics the effects of osmotic stress, abamine both inhibited stomatal closure in spinach (Spinacia oleracea) leaves, which was restored by coapplication of ABA, and increased luminescence intensity in transgenic Arabidopsis containing the RD29B promoter-luciferase fusion. The ABA content of plants in 0.4 m mannitol was increased approximately 16-fold as compared with that of controls, whereas 50 to 100 microm abamine inhibited about 50% of this ABA accumulation in both spinach leaves and Arabidopsis. Abamine-treated Arabidopsis was more sensitive to drought stress and showed a significant decrease in drought tolerance than untreated Arabidopsis. These results suggest that abamine is a novel ABA biosynthesis inhibitor that targets the enzyme catalyzing oxidative cleavage of 9-cis-epoxycarotenoids. To test the effect of abamine on plants other than Arabidopsis, it was applied to cress (Lepidium sativum) plants. Abamine enhanced radicle elongation in cress seeds, which could be due to a decrease in the ABA content of abamine-treated plants. Thus, it is possible to think that abamine should enable us to elucidate the functions of ABA in cells or plants and to find new mutants involved in ABA signaling.

Abscisic Acid↗
PubMed2004

A new lead compound for abscisic acid biosynthesis inhibitors targeting 9-cis-epoxycarotenoid dioxygenase.

9-cis-Epoxycarotenoid dioxygenase (NCED), a key enzyme in abscisic acid (ABA) biosynthesis, cleaves the olefinic double bond of 9-cis-epoxycarotenoid. Several analogues of nordihydroguaiaretic acid (NDGA) were designed and synthesized, and their efficacy as inhibitors of NCED was examined. One of the synthesized compounds (20) was found to be an inhibitor of this enzyme, and inhibited ABA accumulation and stomatal closing, suggesting that 20 should be ABA biosynthesis inhibitor.

Abscisic Acid↗
PubMed2004

Expression profiling of the developing and mature Nrl-/- mouse retina: identification of retinal disease candidates and transcriptional regulatory targets of Nrl.

The rod photoreceptor-specific neural retina leucine zipper protein Nrl is essential for rod differentiation and plays a critical role in regulating gene expression. In the mouse retina, rods account for 97% of the photoreceptors; however, in the absence of Nrl (Nrl-/-), no rods are present and a concomitant increase in cones is observed. A functional all-cone mouse retina represents a unique opportunity to investigate, at the molecular level, differences between the two photoreceptor subtypes. Using mouse GeneChips (Affymetrix), we have generated expression profiles of the wild-type and Nrl-/- retina at three time-points representing distinct stages of photoreceptor differentiation. Comparative data analysis revealed 161 differentially expressed genes; of which, 78 exhibited significantly lower and 83 higher expression in the Nrl-/- retina. Hierarchical clustering was utilized to predict the function of these genes in a temporal context. The differentially expressed genes primarily encode proteins associated with signal transduction, transcriptional regulation, intracellular transport and other processes, which likely correspond to differences between rods and cones and/or retinal remodeling in the absence of rods. A significant number of these genes may serve as candidates for diseases involving rod or cone dysfunction. Chromatin immunoprecipitation assay showed that in addition to the rod phototransduction genes, Nrl might modulate the promoters of many functionally diverse genes in vivo. Our studies provide molecular insights into differences between rod and cone function, yield interesting candidates for retinal diseases and assist in identifying transcriptional regulatory targets of Nrl.

Animals↗
PubMed2004

GIANT CHLOROPLAST 1 is essential for correct plastid division in Arabidopsis.

Plastids are vital plant organelles involved in many essential biological processes. Plastids are not created de novo but divide by binary fission mediated by nuclear-encoded proteins of both prokaryotic and eukaryotic origin. Although several plastid division proteins have been identified in plants, limited information exists regarding possible division control mechanisms. Here, we describe the identification of GIANT CHLOROPLAST 1 (GC1), a new nuclear-encoded protein essential for correct plastid division in Arabidopsis. GC1 is plastid-localized and is anchored to the stromal surface of the chloroplast inner envelope by a C-terminal amphipathic helix. In Arabidopsis, GC1 deficiency results in mesophyll cells harbouring one to two giant chloroplasts, whilst GC1 overexpression has no effect on division. GC1 can form homodimers but does not show any interaction with the Arabidopsis plastid division proteins AtFtsZ1-1, AtFtsZ2-1, AtMinD1, or AtMinE1. Analysis reveals that GC1-deficient giant chloroplasts contain densely packed wild-type-like thylakoid membranes and that GC1-deficient leaves exhibit lower rates of CO(2) assimilation compared to wild-type. Although GC1 shows similarity to a putative cyanobacterial SulA cell division inhibitor, our findings suggest that GC1 does not act as a plastid division inhibitor but, rather, as a positive factor at an early stage of the division process.

Amino Acid Sequence↗
PubMed2004

Chloroplast division site placement requires dimerization of the ARC11/AtMinD1 protein in Arabidopsis.

Chloroplast division is mediated by the coordinated action of a prokaryote-derived division system(s) and a host eukaryote-derived membrane fission system(s). The evolutionary conserved prokaryote-derived system comprises several nucleus-encoded proteins, two of which are thought to control division site placement at the midpoint of the organelle: a stromal ATPase MinD and a topological specificity factor MinE. Here, we show that arc11, one of 12 recessive accumulation and replication of chloroplasts (arc) mutants in Arabidopsis, contains highly elongated and multiple-arrayed chloroplasts in developing green tissues. Genomic sequence analysis revealed that arc11 contains a missense mutation in alpha-helix 11 of the chloroplast-targeted AtMinD1 changing an Ala at position 296 to Gly (A296G). Introduction of wild-type AtMinD1 restores the chloroplast division defects of arc11 and quantitative RT-PCR analysis showed that the degree of complementation was highly dependent on transgene expression levels. Overexpression of the mutant ARC11/AtMinD1 in transgenic plants results in the inhibition of chloroplast division, showing that the mutant protein has retained its division inhibition activity. However, in contrast to the defined and punctate intraplastidic localization patterns of an AtMinD1-YFP fusion protein, the single A296G point mutation in ARC11/AtMinD1 results in aberrant localization patterns inside chloroplasts. We further show that AtMinD1 is capable of forming homodimers and that this dimerization capacity is abolished by the A296G mutation in ARC11/AtMinD1. Our data show that arc11 is a loss-of-function mutant of AtMinD1 and suggest that the formation of functional AtMinD1 homodimers is paramount for appropriate AtMinD1 localization, ultimately ensuring correct division machinery placement and chloroplast division in plants.

Amino Acid Sequence↗
PubMed2004

Comprehensive comparison of auxin-regulated and brassinosteroid-regulated genes in Arabidopsis.

Although numerous physiological studies have addressed the interactions between brassinosteroids and auxins, little is known about the underlying molecular mechanisms. Using an Affymetrix GeneChip representing approximately 8,300 Arabidopsis genes, we studied comprehensive transcript profiles over 24 h in response to indole-3-acetic acid (IAA) and brassinolide (BL). We identified 409 genes as BL inducible, 276 genes as IAA inducible, and 637 genes in total. These two hormones regulated only 48 genes in common, suggesting that most of the actions of each hormone are mediated by gene expression that is unique to each. IAA-up-regulated genes were enriched in genes regulated in common. They were induced quickly by IAA and more slowly by BL, suggesting divergent physiological roles. Many were early auxin-inducible genes and their homologs, namely SAUR, GH3, and IAA. The comprehensive comparison also identified IAA- and BL-specific genes, which should help to elucidate the specific actions of each hormone. The identified genes were classified using hierarchical clustering based on the similarity of their responses to the two hormones. Gene classification also allowed us to analyze the frequency of cis-elements. The TGTCTC element, a core element of the previously reported auxin response element, was not enriched in genes specifically regulated by IAA but was enriched in the 5'-flanking region of genes up-regulated by both IAA and BL. Such gene classification should be useful for predicting the functions of unknown genes, to understand the roles of these two hormones, and the promoter analysis should provide insight into the interaction of transcriptional regulation by the two hormones.

Arabidopsis↗
PubMed2004

Induction of IL-8, MCP-1, and bFGF by TNF-alpha in retinal glial cells: implications for retinal neovascularization during post-ischemic inflammation.

BACKGROUND: We have demonstrated that macrophages/microglia were activated during post-ischemic inflammation in a mouse model of ischemic retinal neovascularization, and that the angiogenesis induced by tumor necrosis factor-alpha (TNF-alpha) appeared to be modulated through such angiogenic factors as interleukin-8 (IL-8), vascular endothelial growth factor (VEGF), and basic fibroblast growth factor (bFGF) in microvascular endothelial cells. We have extended these studies, and investigated whether TNF-alpha is localized in macrophages/microglia in the mouse model of retinal neovascularization, and whether TNF-alpha can induce angiogenic factors in retinal glial cells. METHODS: C57BL/6 J pups were placed in a 75% oxygen environment on postnatal day 7 (P7) for 5 days and then returned to room air. The co-localization of TNF-alpha with macrophages/microglia in the ischemic retina was examined by fluorescent immunohistochemistry. Bovine retinal glial cells were isolated for Northern blot analysis to quantify the expression levels of monocyte chemotactic protein-1 (MCP-1), IL-8, bFGF, and VEGF. RESULTS: Double staining of retinas revealed that the TNF-alpha expression level was enhanced in macrophages/microglia 4 days after the hypoxia. Cellular mRNA levels of MCP-1, IL-8, and bFGF, but not VEGF, were increased after treating retinal glial cells with TNF-alpha (100 U/ml). CONCLUSIONS: The results indicate that TNF-alpha is produced by activated macrophages/microglia and may participate in retinal neovascularization during post-ischemic inflammation through the induction of potent angiogenic factors in an autocrine or paracrine manner.

Animals↗