Akiko Yoshida

The University of Tokyo, Tōkyō, Japan

Are you Akiko Yoshida?

Claim your profile

Publications (9)75.02 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The DWARF14 (D14) gene of rice functions within the signaling pathway of strigolactones, a group of plant hormones that inhibits shoot branching. We isolated a recessive mutant named super apical dormant (sad1-1) from a suppressor screen of d14-1. The growth of tillers (vegetative shoot branches) is suppressed in both the d14-1 sad1-1 double mutant and the sad1-1 single mutant. In addition, the sad1-1 mutant shows pleiotropic defects throughout development. SAD1 encodes an ortholog of RPA34.5, a subunit of RNA polymerase I (Pol I). Consequently, the level of ribosomal RNA (rRNA) is severely reduced in the sad1-1 mutant. These results indicate that proper ribosome function is a prerequisite for normal development in plants. The Arabidopsis ortholog of SAD1 was previously isolated as a Mediator-interacting protein. Here we show that SAD1 interacts physically with the Mediator complex through a direct binding with OsMED4, a component of the middle module of the Mediator complex in rice. It is known that Mediator interacts with Pol II, which transcribes mRNAs and functions as a central regulator of transcription. This study indicates a novel aspect of Mediator function in Pol I-controlled rRNA transcription. TFIIF2 and RPC53 are counterparts of RPA34.5 in Pol II and Pol III, respectively. We demonstrate that the rice orthologs of these proteins also interact with OsMED4. Our results suggest that interaction with MED4 in the Mediator complex is a common feature of the three types of RNA polymerases.This article is protected by copyright. All rights reserved.
    No preview · Article · Nov 2014 · The Plant Journal
  • Junko Kyozuka · Hiroki Tokunaga · Akiko Yoshida
    [Show abstract] [Hide abstract]
    ABSTRACT: The grass inflorescence is interesting from the points of view of development and evolution. In the grass family, flowers are produced on small branches called spikelets. The recent isolation of regulators of spikelet meristem (SM) identity has shed new light on development and the evolution of the gene networks involved. The timing of SM specification is mediated by the combinatorial functions of these regulators, and determines the grass inflorescence form. Furthermore, tight links between meristem cell proliferation, maintenance of meristem indeterminacy, and suppression of the spikelet identity are being uncovered.
    No preview · Article · Feb 2014 · Current opinion in plant biology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Inflorescence structures result from the activities of meristems, which coordinate both the renewal of stem cells in the center and organ formation at the periphery. The fate of a meristem is specified at its initiation and changes as the plant develops. During rice inflorescence development, newly formed meristems acquire a branch meristem (BM) identity, and can generate further meristems or terminate as spikelets. Thus, the form of rice inflorescence is determined by a reiterative pattern of decisions made at the meristems. In the dominant gain-of-function mutant tawawa1-D, the activity of the inflorescence meristem (IM) is extended and spikelet specification is delayed, resulting in prolonged branch formation and increased numbers of spikelets. In contrast, reductions in TAWAWA1 (TAW1) activity cause precocious IM abortion and spikelet formation, resulting in the generation of small inflorescences. TAW1 encodes a nuclear protein of unknown function and shows high levels of expression in the shoot apical meristem, the IM, and the BMs. TAW1 expression disappears from incipient spikelet meristems (SMs). We also demonstrate that members of the SHORT VEGETATIVE PHASE subfamily of MADS-box genes function downstream of TAW1. We thus propose that TAW1 is a unique regulator of meristem activity in rice and regulates inflorescence development through the promotion of IM activity and suppression of the phase change to SM identity.
    Preview · Article · Dec 2012 · Proceedings of the National Academy of Sciences
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The meristem initiates lateral organs in a regular manner, and proper communication between the meristem and the lateral organs ensures the normal development of plants. Here, we show that mutation of the rice (Oryza sativa) gene TONGARI-BOUSHI1 (TOB1) results in pleiotropic phenotypes in spikelets, such as the formation of a cone-shaped organ instead of the lemma or palea, the development of two florets in a spikelet, or premature termination of the floret meristem, in addition to reduced growth of the lemma or palea and elongation of the awn. These phenotypes seem to result from not only failure in growth of the lateral organs, but also defects in maintenance and organization of the meristem. For example, the cone-shaped organ develops as a ring-like primordium from an initial stage, suggesting that regulation of organ initiation in the meristem may be compromised. TOB1 encodes a YABBY protein, which is closely related to FILAMENTOUS FLOWER in Arabidopsis thaliana, and is expressed in the lateral organ primordia without any patterns of polarization. No TOB1 expression is detected in the meristem, so TOB1 may act non-cell autonomously to maintain proper meristem organization and is therefore likely to play an important role in rice spikelet development.
    Full-text · Article · Feb 2012 · The Plant Cell
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Accumulation of cadmium (Cd) in rice (Oryza sativa L.) grains poses a potential health problem, especially in Asia. Most Cd in rice grains accumulates through phloem transport, but the molecular mechanism of this transport has not been revealed. In this study, we identified a rice Cd transporter, OsLCT1, involved in Cd transport to the grains. OsLCT1-GFP was localized at the plasma membrane in plant cells, and OsLCT1 showed Cd efflux activity in yeast. In rice plants, strong OsLCT1 expression was observed in leaf blades and nodes during the reproductive stage. In the uppermost node, OsLCT1 transcripts were detected around large vascular bundles and in diffuse vascular bundles. RNAi-mediated knockdown of OsLCT1 did not affect xylem-mediated Cd transport but reduced phloem-mediated Cd transport. The knockdown plants of OsLCT1 accumulated approximately half as much Cd in the grains as did the control plants. The content of other metals in rice grains and plant growth were not negatively affected by OsLCT1 suppression. These results suggest that OsLCT1 functions at the nodes in Cd transport into grains and that in a standard japonica cultivar, the regulation of OsLCT1 enables the generation of "low-Cd rice" without negative effects on agronomical traits. These findings identify a transporter gene for phloem Cd transport in plants.
    Full-text · Article · Dec 2011 · Proceedings of the National Academy of Sciences
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Post-embryonic development depends on the activity of meristems in plants, and thus control of cell fate in the meristem is crucial to plant development and its architecture. In grasses such as rice and maize, the fate of reproductive meristems changes from indeterminate meristems, such as inflorescence and branch meristems, to determinate meristems, such as the spikelet meristem. Here we analyzed a recessive mutant of rice, aberrant spikelet and panicle1 (asp1), that showed pleiotropic phenotypes such as a disorganized branching pattern, aberrant spikelet morphology, and disarrangement of phyllotaxy. Close examination revealed that regulation of meristem fate was compromised in asp1: degeneration of the inflorescence meristem was delayed, transition from the branch meristem to the spikelet meristem was accelerated, and stem cell maintenance in both the branch meristem and the spikelet meristem was compromised. The genetic program was also disturbed in terms of spikelet development. Gene isolation revealed that ASP1 encodes a transcriptional co-repressor that is related to TOPLESS (TPL) in Arabidopsis and RAMOSA ENHANCER LOCUS2 (REL2) in maize. It is likely that the pleiotropic defects are associated with de-repression of multiple genes related to meristem function in the asp1 mutant. The asp1 mutant also showed de-repression of axillary bud growth and disturbed phyllotaxy in the vegetative phase, suggesting that the function of this gene is closely associated with auxin action. Consistent with these observations and the molecular function of Arabidopsis TPL, auxin signaling was also compromised in the rice asp1 mutant. Taken together, these results indicate that ASP1 regulates various aspects of developmental processes and physiological responses as a transcriptional co-repressor in rice.
    Full-text · Article · Dec 2011 · The Plant Journal
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The mechanism of floral organ specification is principally conserved in angiosperms, as demonstrated by the ABC model. By contrast, mechanisms that regulate the development of organs or structures specific to a group of species remain unclear. Grasses have unique inflorescence units, comprising spikelets and florets. In the genus Oryza (rice), the single spikelet consists of a fertile floret subtended by a lemma and a palea, two sterile lemmas, and rudimentary glumes. Each sterile lemma is a tiny glume-like organ with a smooth surface. Here, we have examined a long sterile lemma1 (g1) mutant, in which the sterile lemma is enlarged like the lemma. Detailed phenotypic analysis reveals that the large sterile lemma in the g1 mutant appears to be caused by homeotic transformation of the sterile lemma into a lemma, suggesting that G1 is involved in the repression of lemma identity to specify the sterile lemma. Gene isolation reveals that G1 is a member of a plant-specific gene family that encodes proteins with a previously uncharacterized domain, named here ALOG (Arabidopsis LSH1 and Oryza G1). G1 mRNA is expressed in sterile lemma primordia throughout their development, and G1 protein is localized in the nucleus. A trans-activation assay using the yeast GAL4 system suggests that G1 is involved in transcriptional regulation. Repression of lemma identity by G1 is consistent with a hypothesis proposed to explain the morphological evolution of rice spikelets. We also show that a wild rice species, Oryza grandiglumis, that forms large sterile lemmas has serious mutations in the G1 gene.
    Full-text · Article · Nov 2009 · Proceedings of the National Academy of Sciences
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: CLAVATA signaling restricts stem cell identity in the shoot apical meristem (SAM) in Arabidopsis thaliana. In rice (Oryza sativa), FLORAL ORGAN NUMBER2 (FON2), closely related to CLV3, is involved as a signaling molecule in a similar pathway to negatively regulate stem cell proliferation in the floral meristem (FM). Here we show that the FON2 SPARE1 (FOS1) gene encoding a CLE protein functions along with FON2 in maintenance of the FM. In addition, FOS1 appears to be involved in maintenance of the SAM in the vegetative phase, because constitutive expression of FOS1 caused termination of the vegetative SAM. Genetic analysis revealed that FOS1 does not need FON1, the putative receptor of FON2, for its action, suggesting that FOS1 and FON2 may function in meristem maintenance as signaling molecules in independent pathways. Initially, we identified FOS1 as a suppressor that originates from O. sativa indica and suppresses the fon2 mutation in O. sativa japonica. FOS1 function in japonica appears to be compromised by a functional nucleotide polymorphism (FNP) at the putative processing site of the signal peptide. Sequence comparison of FOS1 in about 150 domesticated rice and wild rice species indicates that this FNP is present only in japonica, suggesting that redundant regulation by FOS1 and FON2 is commonplace in species in the Oryza genus. Distribution of the FNP also suggests that this mutation may have occurred during the divergence of japonica from its wild ancestor. Stem cell maintenance may be regulated by at least three negative pathways in rice, and each pathway may contribute differently to this regulation depending on the type of the meristem. This situation contrasts with that in Arabidopsis, where CLV signaling is the major single pathway in all meristems.
    Full-text · Article · Oct 2009 · PLoS Genetics
  • Source
    Takuya Suzaki · Akiko Yoshida · Hiro-Yuki Hirano
    [Show abstract] [Hide abstract]
    ABSTRACT: Postembryonic development in plants depends on the activity of the shoot apical meristem (SAM) and root apical meristem (RAM). In Arabidopsis thaliana, CLAVATA signaling negatively regulates the size of the stem cell population in the SAM by repressing WUSCHEL. In other plants, however, studies of factors involved in stem cell maintenance are insufficient. Here, we report that two proteins closely related to CLAVATA3, FLORAL ORGAN NUMBER2 (FON2) and FON2-LIKE CLE PROTEIN1 (FCP1/Os CLE402), have functionally diversified to regulate the different types of meristem in rice (Oryza sativa). Unlike FON2, which regulates the maintenance of flower and inflorescence meristems, FCP1 appears to regulate the maintenance of the vegetative SAM and RAM. Constitutive expression of FCP1 results in consumption of the SAM in the vegetative phase, and application of an FCP1 CLE peptide in vitro disturbs root development by misspecification of cell fates in the RAM. FON1, a putative receptor of FON2, is likely to be unnecessary for these FCP1 functions. Furthermore, we identify a key amino acid residue that discriminates between the actions of FCP1 and FON2. Our results suggest that, although the basic framework of meristem maintenance is conserved in the angiosperms, the functions of the individual factors have diversified during evolution.
    Full-text · Article · Sep 2008 · The Plant Cell