Taku Takahashi

The University of Tokyo, Tokyo, Tokyo-to, Japan

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Publications (30)134.58 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The class IV Homeodomain-leucine zipper (HD-ZIP IV) gene family includes several genes that are functionally significant in epidermal development. Our recent study revealed that double mutants of the epidermis-expressed HD-ZIP IV members, PROTODERMAL FACTOR2 (PDF2) in combination with some HOMEODOMAIN GLABROUS (HDG, pronounced "hedge") genes, affect stamen development and specification of petal and stamen identity, possibly in a non cell-autonomous manner. However, the effect of the pdf2 mutations on the floral development was largely different depending on T-DNA insertion loci: pdf2-1 hdg flowers exhibited homeotic conversion of petals and stamens, while pdf2-2 hdg flowers had only a reduced number of stamens. Here, we used two additional pdf2 alleles to make double mutants and found that their floral phenotypes were rather similar to those of pdf2-2 hdg. The allele-specific effect caused by pdf2-1, which carries a T-DNA in a steroidogenic acute regulatory protein-related lipid transfer (START) domain-encoding region, suggests the importance of the START domain in proper function of HD-ZIP IV proteins.
    Plant signaling & behavior 01/2014; 8(12).
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    ABSTRACT: Thermospermine, a structural isomer of spermine, is widely distributed in the plant kingdom and has been shown to play a role in repressing xylem differentiation by studies of its deficient mutant, acaulis5 (acl5), in Arabidopsis. Our results of microarray and real-time PCR analyses revealed that, in addition to a number of genes involved in xylem differentiation, genes related to auxin signaling were up-regulated in acl5 seedlings. These genes include MONOPTEROS, an auxin response factor gene, which acts as a master switch for auxin-dependent procambium formation, and its target genes. Their expression was reduced by exogenous treatment with thermospermine or by transgenic induction of the ACL5 gene. We examined the effect of synthetic polyamines on the expression of these auxin-related genes and on the vascular phenotype of acl5, and found that tetramines containing the NC3NC3N chain could mimic the effect of thermospermine but longer polyamines containing the same chain had little or no such effect. We also found that thermospermine had an inhibitory effect on lateral root formation in wild-type seedlings and it was mimicked by synthetic tetramines with the NC3NC3N chain. These results suggest the importance of the NC3NC3N chain of thermospermine in its action in modulating auxin signaling.
    Frontiers in Plant Science 01/2014; 5:94. · 3.60 Impact Factor
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    ABSTRACT: Herein, we report a novel method for the determination of polyamines in a sample extracted from Arabidopsis thaliana by capillary electrophoresis (CE) using salicylaldehyde-5-sulfonate (SAS) as a derivatizing reagent. An aldehyde group of SAS forms a Schiff base with amino groups of aliphatic polyamines, resulting in an anionic species with an absorption band in the ultraviolet region. The derivatization method was straightforward since the derivatives were formed by mixing a sample with the derivatizing reagent at a neutral pH. In addition, the negative charges induced by SAS led to a high resolution with a short analysis time. This method permitted the separation of five polyamines, which play important roles in plants. However, further improvement in sensitivity was needed for the determination of the polyamines in plant samples. Therefore, the CE method was coupled with solid-phase extraction (SPE) using an ion-pairing formation with sodium dodecyl benzene sulfonate. The SPE method improved the concentration limits of detection to sub-μM levels, which corresponded with a 10-fold enhancement. The calibration curves for cadaverine, putrescine, and spermidine were linear with concentrations that ranged from 1 to 20 μM and correlation coefficients (R2) were greater than 0.998. The proposed method was applied to the determination of spermidine in a plant sample, Arabidopsis thaliana.
    Analytical methods 05/2013; 5(11):2854-2859. · 1.86 Impact Factor
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    ABSTRACT: Development of the epidermis involves members of the class IV homeodomain-leucine zipper (HD-ZIP IV) transcription factors. The Arabidopsis HD-ZIP IV family consists of 16 members, among which PROTODERMAL FACTOR2 (PDF2) and ARABIDOPSIS THALIANA MERISTEM LAYER1 (ATML1) play an indispensable role in the differentiation of shoot epidermal cells. However, the functions of other HD-ZIP IV genes that are also expressed specifically in the shoot epidermis remain not fully elucidated. We constructed double mutant combinations of these HD-ZIP IV mutant alleles and found that the double mutants of pdf2-1 with homeodomain glabrous1-1 (hdg1-1), hdg2-3, hdg5-1 and hdg12-2, produced abnormal flowers with sepaloid petals and carpelloid stamens in association with reduced expression of the petal and stamen identity gene APETALA3 (AP3). Expression of another petal and stamen identity gene PISTILATA (PI) was less affected in these mutants. We confirmed that the AP3 expression in pdf2-1 hdg2-3 was normally induced at initial stages of flower development but attenuated both in the epidermis and internal cell layers of developing flowers. Since the expression of PDF2 and these HD-ZIP IV genes during floral organ formation is exclusively limited to the epidermal cell layer, these double mutations may have non-cell-autonomous effects on the AP3 expression in the internal cell layers. Our results suggest that cooperative functions of PDF2 and other members of the HD-ZIP IV family in the epidermis are crucial for normal development of floral organs in Arabidopsis. This article is protected by copyright. All rights reserved.
    The Plant Journal 04/2013; · 6.58 Impact Factor
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    ABSTRACT: NIMA-related kinase 6 (NEK6) regulates cellular expansion and morphogenesis through microtubule organizaiton in Arabidopsis thaliana. Loss-of-function mutations in NEK6 (nek6/ibo1) cause ectopic outgrowth and microtubule disorganization in epidermal cells. We recently found that NEK6 forms homodimers and heterodimers with NEK4 and NEK5 to destabilize cortical microtubules possibly by direct binding to microtubules and the β-tubulin phosphorylation. Here, we identified a new allele of NEK6 and further analyzed the morphological phenotypes of nek6/ibo1 mutants, along with alleles of nek4 and nek5 mutants. Phenotypic analysis demonstrated that NEK6 is required for the directional growth of roots and hypocotyls, petiole elongation, cell file formation, and trichome morphogenesis. In addition, nek4, nek5, and nek6/ibo1 mutants were hypersensitive to microtubule inhibitors such as propyzamide and taxol. These results suggest that plant NEKs function in directional cell growth and organ development through the regulation of microtubule organization.
    Plant signaling & behavior 10/2012; 7(12).
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    ABSTRACT: Thermospermine, a structural isomer of spermine, is synthesized by a thermospermine synthase designated ACAULIS5 (ACL5). Thermospermine-deficient acl5 mutant of Arabidopsis thaliana shows severe dwarfism and excessive xylem differentiation. By screening for compounds that affect xylem differentiation in the acl5 mutant, we identified auxin analogs that remarkably enhanced xylem vessel differentiation in the acl5 mutant but not in the wild type. The xylem-inducing effect of auxin analogs was clearly suppressed by thermospermine, indicating that auxin-inducible xylem differentiation is normally limited by thermospermine. Here, we further characterized xylem-inducing effect of auxin analogs in various organs. Auxin analogs promoted protoxylem differentiation in roots and cotyledons in the acl5 mutant. Our results indicate that the opposite action between thermospermine and auxin in xylem differentiation is common in different organs and also suggest that thermospermine might be required for the suppression of protoxylem differentiation.
    Plant signaling & behavior 08/2012; 7(8):937-9.
  • Ayaka Takano, Jun-Ichi Kakehi, Taku Takahashi
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    ABSTRACT: Thermospermine is a structural isomer of spermine, which is one of the polyamines studied extensively in the past, and is produced from spermidine by the action of thermospermine synthase encoded by a gene named ACAULIS5 (ACL5) in plants. According to recent genome sequencing analyses, ACL5-like genes are widely distributed throughout the plant kingdom. In Arabidopsis, ACL5 is expressed specifically during xylem formation from procambial cells to differentiating xylem vessels. Loss-of-function mutants of ACL5 display overproliferation of xylem vessels along with severe dwarfism, suggesting that thermospermine plays a role in the repression of xylem differentiation. Studies of suppressor mutants of acl5 that recover the wild-type phenotype in the absence of thermospermine suggest that thermospermine acts on the translation of specific mRNAs containing upstream open reading frames (uORFs). Thermospermine is a novel type of plant growth regulator and may also serve in the control of wood biomass production.
    Plant and Cell Physiology 02/2012; 53(4):606-16. · 4.98 Impact Factor
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    ABSTRACT: Thermospermine, a structural isomer of spermine, is produced through the action of ACAULIS5 (ACL5) and suppresses xylem differentiation in Arabidopsis thaliana. To elucidate the molecular basis of the function of thermospermine, we screened chemical libraries for compounds that can modulate xylem differentiation in the acl5 mutant, which is deficient in thermospermine and shows a severe dwarf phenotype associated with excessive proliferation of xylem vessels. We found that the isooctyl ester of a synthetic auxin, 2,4-D, remarkably enhanced xylem vessel differentiation in acl5 seedlings. 2,4-D, 2,4-D analogs and IAA analogs, including 4-chloro IAA (4-Cl-IAA) and IAA ethyl ester, also enhanced xylem vessel formation, while IAA alone had little or no obvious effect on xylem differentiation. These effects of auxin analogs were observed only in the acl5 mutant but not in the wild type, and were suppressed by the anti-auxin, p-chlorophenoxyisobutyric acid (PCIB) and α-(phenyl ethyl-2-one)-IAA (PEO-IAA), and also by thermospermine. Furthermore, the suppressor of acaulis51-d (sac51-d) mutation, which causes SAC51 overexpression in the absence of thermospermine and suppresses the dwarf phenotype of acl5, also suppressed the effect of auxin analogs in acl5. These results suggest that the auxin signaling that promotes xylem differentiation is normally limited by SAC51-mediated thermospermine signaling but can be continually stimulated by exogenous auxin analogs in the absence of thermospermine. The opposite action between thermospermine and auxin may fine-tune the timing and spatial pattern of xylem differentiation.
    Plant and Cell Physiology 02/2012; 53(4):635-45. · 4.98 Impact Factor
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    ABSTRACT: NimA-related kinase 6 (NEK6) has been implicated in microtubule regulation to suppress the ectopic outgrowth of epidermal cells; however, its molecular functions remain to be elucidated. Here, we analyze the function of NEK6 and other members of the NEK family with regard to epidermal cell expansion and cortical microtubule organization. The functional NEK6-green fluorescent protein fusion localizes to cortical microtubules, predominantly in particles that exhibit dynamic movement along microtubules. The kinase-dead mutant of NEK6 (ibo1-1) exhibits a disturbance of the cortical microtubule array at the site of ectopic protrusions in epidermal cells. Pharmacological studies with microtubule inhibitors and quantitative analysis of microtubule dynamics indicate excessive stabilization of cortical microtubules in ibo1/nek6 mutants. In addition, NEK6 directly binds to microtubules in vitro and phosphorylates β-tubulin. NEK6 interacts and co-localizes with NEK4 and NEK5 in a transient expression assay. The ibo1-3 mutation markedly reduces the interaction between NEK6 and NEK4 and increases the interaction between NEK6 and NEK5. NEK4 and NEK5 are required for the ibo1/nek6 ectopic outgrowth phenotype in epidermal cells. These results demonstrate that NEK6 homodimerizes and forms heterodimers with NEK4 and NEK5 to regulate cortical microtubule organization possibly through the phosphorylation of β-tubulins.
    The Plant Journal 05/2011; 67(6):993-1005. · 6.58 Impact Factor
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    Taku Takahashi, Satoshi Naito, Yoshibumi Komeda
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    ABSTRACT: A detailed study of the expression of the promoter of the HSP18.2 gene from Arabidopsis fused to the bacterial gene for β-glucuronidase (GUS) in transgenic Arabidopsis plants is described. High levels of GUS activity were induced in all organs of transformants except for seeds during heat shock. The optimum temperature for expression of GUS in Arabidopsis was 35°C regardless of the plant growth temperature. Heat shock of 40°C did not induce any detectable levels of GUS activity. Pre-incubation at 35°C was found to have a protective effect on the induction of GUS activity at 40°C. GUS activity was also increased in response to a gradual increase in temperature. Histochemical analysis revealed that basal levels of GUS activity were induced in the vascular tissue of leaves and sepals, as well as at the tips of carpels, at the normal growth temperature. Heat treatment of a limited part of the plant tissue did not appear to cause systemic induction of GUS activity. To extend the analysis of the plant heat-shock response, we attempted to screen mutations in genes involved in the regulation of the induction of heat-shock protein (HSP) genes, using the GUS gene as a selection marker in transgenic Arabidopsis plants, and the results of this analysis are described.
    The Plant Journal 02/2011; 2(5):751 - 761. · 6.58 Impact Factor
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    ABSTRACT: SYP2 proteins are a sub-family of Qa-SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) that may be responsible for protein trafficking between pre-vacuolar compartments (PVC) and vacuoles. Arabidopsis thaliana SYP22/VAM3/SGR3 and SYP21/PEP12 proteins function independently, but are both reported to be essential for male gametophytic viability. Here, we systematically examined the redundancy of three SYP2 paralogs (i.e. SYP21, 22 and 23) using a Col-0 ecotype harboring a SYP2 paralog (SYP23/PLP) that lacked a transmembrane domain. Surprisingly, no visible phenotypes were observed, even in the double knockout syp21/pep12 syp23/plp. Deficiency of either SYP21/PEP12 or SYP23/PLP in the syp22 background resulted in a defect in vacuolar protein sorting, characterized by abnormal accumulation of protein precursors in seeds. SYP21/PEP12 knockdown enhanced the syp22 phenotype (i.e. semi-dwarfism, poor leaf vein development and abnormal development of myrosin cells), and additional knockout of SYP23/PLP further aggravated the phenotype. A GFP-SYP23/PLP fusion localized to the cytosol, but not to the PVC or vacuolar membrane, where SYP21/PEP12 or SYP22/VAM3, respectively, were localized. Immunoprecipitation analysis showed that SYP23/PLP interacted with the vacuolar Qb- and Qc-SNAREs, VTI11 and SYP5, respectively, suggesting that SYP23/PLP is able to form a SNARE complex anchoring the membrane. Unexpectedly, we found that expression of multiple copies of a genomic fragment of SYP23/PLP suppressed the abnormal syp22-3 phenotype. Thus, SYP2 proteins, including cytosolic SYP23/PLP, appear to function redundantly in vacuolar trafficking and plant development.
    The Plant Journal 12/2010; 64(6):924-35. · 6.58 Impact Factor
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    ABSTRACT: Thermospermine is a structural isomer of spermine and is required for stem elongation in Arabidopsis thaliana. We noted the C3C3 arrangement of carbon chains in thermospermine (C3C3C4), which is not present in spermine (C3C4C3), and examined if it is functionally replaced with norspermine (C3C3C3) or not. Exogenous application of norspermine to acl5, a mutant defective in the synthesis of thermospermine, partially suppressed its dwarf phenotype, and down-regulated the level of the acl5 transcript which is much higher than that of the ACL5 transcript in the wild type. Furthermore, in the Zinnia culture, differentiation of mesophyll cells into tracheary elements was blocked by thermospermine and norspermine but not by spermine. Our results indicate that norspermine can functionally substitute for thermospermine.
    FEBS letters 07/2010; 584(14):3042-6. · 3.54 Impact Factor
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    Taku Takahashi, Jun-Ichi Kakehi
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    ABSTRACT: BACKGROUND: Polyamines are small polycationic molecules found ubiquitously in all organisms and function in a wide variety of biological processes. In the past decade, molecular and genetic studies using mutants and transgenic plants with an altered activity of enzymes involved in polyamine biosynthesis have contributed much to a better understanding of the biological functions of polyamines in plants. POSSIBLE ROLES: Spermidine is essential for survival of Arabidopsis embryos. One of the reasons may lie in the fact that spermidine serves as a substrate for the lysine hypusine post-translational modification of the eukaryotic translation initiation factor 5A, which is essential in all eukaryotic cells. Spermine is not essential but plays a role in stress responses, probably through the modulation of cation channel activities, and as a source of hydrogen peroxide during pathogen infection. Thermospermine, an isomer of spermine, is involved in stem elongation, possibly by acting on the regulation of upstream open reading frame-mediated translation. CONCLUSIONS: The mechanisms of action of polyamines differ greatly from those of plant hormones. There remain numerous unanswered questions regarding polyamines in plants, such as transport systems and polyamine-responsive genes. Further studies on the action of polyamines will undoubtedly provide a new understanding of plant growth regulation and stress responses.
    Annals of Botany 10/2009; 105(1):1-6. · 3.45 Impact Factor
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    ABSTRACT: Disruption of the Arabidopsis thaliana ACAULIS5 (ACL5) gene, which has recently been shown to encode thermospermine synthase, results in a severe dwarf phenotype. A previous study showed that sac51-d, a dominant suppressor mutant of acl5-1, has a premature termination codon in an upstream open reading frame (ORF) of SAC51, which encodes a putative transcription factor, and suggested the involvement of upstream ORF-mediated translational control in ACL5-dependent stem elongation. Here we report the identification of a gene responsible for sac52-d, another semi-dominant suppressor mutant of acl5-1. SAC52 encodes ribosomal protein L10 (RPL10A), which is highly conserved among eukaryotes and implicated in translational regulation. Transformation of acl5-1 mutants with a genomic fragment containing the sac52-d allele rescued the dwarf phenotype of acl5-1. GUS reporter activity under the control of a SAC51 promoter with its upstream ORF was higher in acl5-1 sac52-d than in acl5-1, suggesting that suppression of the acl5-1 phenotype by sac52-d is attributable, in part, to enhanced translation of certain transcripts including SAC51. We also found that a T-DNA insertion allele of SAC52/RPL10A causes lethality in the female gametophyte.
    The Plant Journal 09/2008; 56(6):881-90. · 6.58 Impact Factor
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    ABSTRACT: Loss-of-function mutants of the ACAULIS5 (ACL5) gene in Arabidopsis thaliana have severe defects in stem elongation. ACL5 was previously reported as encoding a spermine synthase. A more recent study, however, showed that the bacterial expressed recombinant ACL5 protein catalyzes the conversion of spermidine to thermospermine, a structural isomer of spermine, rather than to spermine. In the present study, we found that thermospermine was detected in wild-type seedlings but was not detectable in the acl5-1 mutant. We further examined the effect of exogenous application of these isomers on the growth of acl5-1. Daily application of 0.1 mM thermospermine onto the shoot apex partially rescued the dwarf phenotype of acl5-1, while that of spermine had no effects on the morphology of the mutant. The acl5-1 transcript level in acl5-1 seedlings, which is much higher than the ACL5 transcript level in wild-type seedlings, was reduced by exogenous thermospermine. Thus we conclude that thermospermine is indeed produced through the action of ACL5 and required for stem elongation in Arabidopsis.
    Plant and Cell Physiology 08/2008; 49(9):1342-9. · 4.98 Impact Factor
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    ABSTRACT: Loss-of-function mutants of the Arabidopsis thaliana ACAULIS 5 (ACL5) gene, which encodes spermine synthase, exhibit a severe dwarf phenotype. To elucidate the ACL5-mediated regulatory pathways of stem internode elongation, we isolated four suppressor of acaulis (sac) mutants that reverse the acl5 dwarf phenotype. Because these mutants do not rescue the dwarfism of known phytohormone-related mutants, the SAC genes appear to act specifically on the ACL5 pathways. We identify the gene responsible for the dominant sac51-d mutant, which almost completely suppresses the acl5 phenotype. sac51-d disrupts a short upstream open reading frame (uORF) of SAC51, which encodes a bHLH-type transcription factor. Our results indicate that premature termination of the uORF in sac51-d results in an increase in its own transcript level, probably as a result of an increased translation of the main ORF. We suggest a model in which ACL5 plays a role in the translational activation of SAC51, which may lead to the expression of a subset of genes required for stem elongation.
    Development 10/2006; 133(18):3575-85. · 6.21 Impact Factor
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    ABSTRACT: The Arabidopsis (Arabidopsis thaliana) genome contains 16 genes belonging to the class IV homeodomain-Leucine zipper gene family. These include GLABRA2, ANTHOCYANINLESS2, FWA, ARABIDOPSIS THALIANA MERISTEM LAYER1 (ATML1), and PROTODERMAL FACTOR2 (PDF2). Our previous study revealed that atml1 pdf2 double mutants have severe defects in the shoot epidermal cell differentiation. Here, we have characterized additional members of this gene family, which we designated HOMEODOMAIN GLABROUS1 (HDG1) through HDG12. Analyses of transgenic Arabidopsis plants carrying the gene-specific promoter fused to the bacterial beta-glucuronidase reporter gene revealed that some of the promoters have high activities in the epidermal layer of the shoot apical meristem and developing shoot organs, while others are temporarily active during reproductive organ development. Expression profiles of highly conserved paralogous gene pairs within the family were found to be not necessarily overlapping. Analyses of T-DNA insertion mutants of these HDG genes revealed that all mutants except hdg11 alleles exhibit no abnormal phenotypes. hdg11 mutants show excess branching of the trichome. This phenotype is enhanced in hdg11 hdg12 double mutants. Double mutants were constructed for other paralogous gene pairs and genes within the same subfamily. However, novel phenotypes were observed only for hdg3 atml1 and hdg3 pdf2 mutants that both exhibited defects in cotyledon development. These observations suggest that some of the class IV homeodomain-Leucine zipper members act redundantly with other members of the family during various aspects of cell differentiation. DNA-binding sites were determined for two of the family members using polymerase chain reaction-assisted DNA selection from random oligonucleotides with their recombinant proteins. The binding sites were found to be similar to those previously identified for ATML1 and PDF2, which correspond to the pseudopalindromic sequence 5'-GCATTAAATGC-3' as the preferential binding site.
    Plant physiology 09/2006; 141(4):1363-75. · 6.56 Impact Factor
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    ABSTRACT: Myrosin cells in Capparales plants are idioblasts that accumulate thioglucoside glucohydrolase (TGG, also called myrosinase), which hydrolyzes glucosinolates to produce toxic compounds for repelling pests. Here, we show that AtVAM3 is involved in development of myrosin cells. It has been shown that yeast VAM3 is a Q(a)-SNARE that is involved in vesicle transport of vacuolar proteins and vacuolar assembly. We found that two Arabidopsis atvam3 alleles, atvam3-3 and atvam3-4/ssm, accumulate large amounts of TGG1 and TGG2 that are enzymatically active. An immunogold analysis revealed that TGGs were specifically localized in the vacuole of myrosin cells in atvam3 mutants. This result indicates that TGGs are normally transported to vacuoles in these mutants and that AtVAM3 is not essential for vacuolar transport of the proteins. We developed a staining method with Coomassie brilliant blue that detects myrosin cells in whole leaves by their high TGG content. This method showed that atvam3 leaves have a larger number of myrosin cells than do wild-type leaves. Myrosin cells were scattered along leaf veins in wild-type leaves, while they were abnormally distributed in atvam3 leaves. The mutants developed a network of myrosin cells throughout the leaves: myrosin cells were not only distributed continuously along leaf veins, but were also observed independent of leaf veins. The excess of myrosin cells in atvam3 mutants might be responsible for the abnormal abundance of TGGs and the reduction of elongation of inflorescence stems and leaves in these mutants. Our results suggest that AtVAM3 has a plant-specific function in development of myrosin cells.
    Plant and Cell Physiology 02/2006; 47(1):164-75. · 4.98 Impact Factor
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    ABSTRACT: The short stem and midrib (ssm) mutants of Arabidopsis thaliana show both semi-dwarf and wavy leaf phenotypes due to defects in the elongation of the stem internodes and leaves. Moreover, these abnormalities cannot be recovered by exogenous phytohormones. ssm was originally identified as a single recessive mutant of the ecotype Columbia (Col-0), but genetic crossing experiments have revealed that this mutant phenotype is restored by another gene that is functional in the ecotype Landsberg erecta (Ler) and not in Col-0. Map-based cloning of the gene that is defective in ssm mutants has uncovered a small deletion in the sixth intron of a gene encoding a syntaxin, VAM3/SYP22, which has been implicated in vesicle transport to the vacuole. This mutation appears to cause a peptide insertion in the deduced VAM3/SYP22 polypeptide sequence due to defective splicing of the shortened sixth intron. Significantly, when compared with the wild-type Ler genome, the wild-type Col-0 genome has a single base pair deletion causing a frameshift mutation in SYP23, a gene with the highest known homology to VAM3/SYP22. These findings suggest that VAM3/SYP22 and SYP23 have overlapping functions and that the vesicle transport mediated by these syntaxins is important for shoot morphogenesis.
    Plant and Cell Physiology 09/2005; 46(8):1358-65. · 4.98 Impact Factor
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    ABSTRACT: Xyloglucan endotransglucosylases/hydrolases (XTHs) are a class of enzymes capable of catalyzing the molecular grafting between xyloglucans and/or the endotype hydrolysis of a xyloglucan molecule. They are encoded by 33 genes in Arabidopsis. Whereas recent studies have revealed temporally and spatially specific expression profiles for individual members of this family in plants, their biological roles are still to be clarified. To identify the role of each member of this gene family, we examined phenotypes of mutants in which each of the Arabidopsis XTH genes was disrupted. This was undertaken using a reverse genetic approach, and disclosed two loss-of-function mutants for the AtXTH27 gene, xth27-1 and xth27-2. These exhibited short-shaped tracheary elements in tertiary veins, and reduced the number of tertiary veins in the first leaf. In mature rosette leaves of the mutant, yellow lesion-mimic spots were also observed. Upon genetic complementation by introducing the wild-type XTH27 gene into xth27-1 mutant plants, the number of tertiary veins was restored, and the lesions disappeared completely. Extensive expression of the pXTH27::GUS fusion gene was observed in immature tracheary elements in the rosette leaves. The highest level of AtXTH27 mRNA expression in the rosette leaves was observed during leaf expansion, when the tracheary elements were elongating. These findings indicate that AtXTH27 plays an essential role during the generation of tracheary elements in the rosette leaves of Arabidopsis.
    The Plant Journal 06/2005; 42(4):525-34. · 6.58 Impact Factor

Publication Stats

881 Citations
134.58 Total Impact Points

Institutions

  • 2011–2013
    • The University of Tokyo
      • • Department of Biological Sciences
      • • Laboratory of Molecular Genetics
      Tokyo, Tokyo-to, Japan
  • 2005–2013
    • Okayama University
      • • Division of Earth, Life, and Molecular Sciences
      • • Department of Biology
      Okayama, Okayama, Japan
  • 2002–2006
    • Hokkaido University
      • Division of Biological Sciences
      Sapporo-shi, Hokkaido, Japan