Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Royal Society  

All plant cells are encased in primary cell walls that determine plant morphology, but also protect the cells against the environment. Certain cells also produce a secondary wall that supports mechanically demanding processes, such as maintaining plant body stature and water transport inside plants. Both these walls are primarily composed of polysaccharides that are arranged in certain patterns to support cell functions. A key requisite for patterned cell walls is the arrangement of cortical microtubules that may direct the delivery of wall polymers and/or cell wall producing enzymes to certain plasma membrane locations. Microtubules also steer the synthesis of cellulose—the load-bearing structure in cell walls—at the plasma membrane. The organization and behaviour of the microtubule array are thus of fundamental importance to cell wall patterns. These aspects are controlled by the coordinated effort of small GTPases that probably coordinate a Turing's reaction–diffusion mechanism to drive microtubule patterns. Here, we give an overview on how wall patterns form in the water-transporting xylem vessels of plants. We discuss systems that have been used to dissect mechanisms that underpin the xylem wall patterns, emphasizing the VND6 and VND7 inducible systems, and outline challenges that lay ahead in this field.

DOI： 10.1098/rsob.210208

PubMed

Other Link： https://royalsocietypublishing.org/doi/full-xml/10.1098/rsob.210208

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Association for the Advancement of Science (AAAS)  

[Figure: see text].

DOI： 10.1126/science.aba5531

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Authorship：Last author   Language：English   Publishing type：Part of collection (book)   Publisher：Springer US  

DOI： 10.1007/978-1-0716-1744-1_13

PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：FRONTIERS MEDIA SA  

In Arabidopsis thaliana, the vacuolar proton-pumping pyrophosphatase (H+-PPase) is highly expressed in young tissues, which consume large amounts of energy in the form of nucleoside triphosphates and produce pyrophosphate (PPi) as a byproduct. We reported that excess PPi in the H+-PPase loss-of-function fugu5 mutant severely compromised gluconeogenesis from seed storage lipids, arrested cell division in cotyledonary palisade tissue, and triggered compensated cell enlargement; this phenotype was recovered upon sucrose supply. Thus, we provided evidence that the hydrolysis of inhibitory PPi, rather than vacuolar acidification, is the major contribution of H+-PPase during seedling establishment. Here, examination of the epidermis revealed that fugu5 pavement cells exhibited defective puzzle-cell formation. Importantly, removal of PPi from fugu5 background by the yeast cytosolic PPase IPP1, in fugu5-1 AVP1(pro)::IPP1 transgenic lines, restored the phenotypic aberrations of fugu5 pavement cells. Surprisingly, pavement cells in mutants with defects in gluconeogenesis (pck1-2) or the glyoxylate cycle (icl-2; mls-2) showed no phenotypic alteration, indicating that reduced sucrose production from seed storage lipids is not the cause of fugu5 epidermal phenotype. fugu5 had oblong cotyledons similar to those of angustifolia-1 (an-1), whose leaf pavement cells display an abnormal arrangement of cortical microtubules (MTs). To gain insight into the genetic interaction between ANGUSTIFOLIA and H+-PPase in pavement cell differentiation, an-1 fugu5-1 was analyzed. Surprisingly, epidermis developmental defects were synergistically enhanced in the double mutant. In fact, an-1 fugu5-1 pavement cells showed a striking three-dimensional growth phenotype on both abaxial and adaxial sides of cotyledons, which was recovered by hydrolysis of PPi in an-1 fugu5-1 AVP1(pro)::IPP1. Live imaging revealed that cortical MTs exhibited a reduced velocity, were slightly fragmented and sparse in the above lines compared to the WT. Consistently, addition of PPi in vitro led to a dose-dependent delay of tubulin polymerization, thus supporting a link between PPi and MT dynamics. Moreover, mathematical simulation of three-dimensional growth based on cotyledon proximo-distal and medio-lateral phenotypic quantification implicated restricted cotyledon expansion along the medio-lateral axis in the crinkled surface of an-1 fugu5-1. Together, our data suggest that PPi homeostasis is a prerequisite for proper pavement cell morphogenesis, epidermal growth and development, and organ flattening.

DOI： 10.3389/fpls.2020.00031

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.cub.2019.09.049

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PubMed

Authorship：Corresponding author   Language：English  

DOI： 10.1007/978-1-4939-9469-4_23

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Patterned cell wall deposition is crucial for cell shapes and functions. In Arabidopsis xylem vessels, ROP11 GTPase locally inhibits cell wall deposition through microtubule disassembly, inducing pits in cell walls. Here, we show that an additional ROP signaling pathway promotes cell wall growth at pit boundaries. Two proteins, Boundary of ROP domain1 (BDR1) and Wallin (WAL), localize to pit boundaries and regulate cell wall growth. WAL interacts with F-actin and promotes actin assembly at pit boundaries while BDR1 is a ROP effector. BDR1 interacts with WAL, suggesting that WAL could be recruited to the plasma membrane by a ROP-dependent mechanism. These results demonstrate that BDR1 and WAL mediate a ROP-actin pathway that shapes pit boundaries. The study reveals a distinct machinery in which two closely associated ROP pathways oppositely regulate cell wall deposition patterns for the establishment of tiny but highly specialized cell wall domains.

DOI： 10.1038/s41467-019-08396-7

PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.24480/bsj-review.9c5.00144

Language：English   Publishing type：Research paper (scientific journal)  

Pith parenchyma cells store water in various plant organs. These cells are especially important for producing sugar and ethanol from the sugar juice of grass stems. In many plants, the death of pith parenchyma cells reduces their stem water content. Previous studies proposed that a hypothetical D gene might be responsible for the death of stem pith parenchyma cells in Sorghum bicolor, a promising energy grass, although its identity and molecular function are unknown. Here, we identify the D gene and note that it is located on chromosome 6 in agreement with previous predictions. Sorghum varieties with a functional D allele had stems enriched with dry, dead pith parenchyma cells, whereas those with each of six independent nonfunctional D alleles had stems enriched with juicy, living pith parenchyma cells. D expression was spatiotemporally coupled with the appearance of dead, air-filled pith parenchyma cells in sorghum stems. Among D homologs that are present in flowering plants, Arabidopsis ANAC074 also is required for the death of stem pith parenchyma cells. D and ANAC074 encode previously uncharacterized NAC transcription factors and are sufficient to ectopically induce programmed death of Arabidopsis culture cells via the activation of autolytic enzymes. Taken together, these results indicate that D and its Arabidopsis ortholog, ANAC074, are master transcriptional switches that induce programmed death of stem pith parenchyma cells. Thus, targeting the D gene will provide an approach to breeding crops for sugar and ethanol production.

DOI： 10.1073/pnas.1807501115

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PubMed

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Rho GTPases play crucial roles in cell polarity and pattern formation. ROPs, Rho of plant GTPases, are widely involved in cell wall patterning in plants, yet the molecular mechanism underlying their action remains unknown. Arabidopsis ROP11 is locally activated to form plasma membrane domains, which direct formation of cell wall pits in metaxylem vessel cells through interaction with cortical microtubules. Here, we show that the pattern formation of cell wall pits is governed by ROP activation via a reaction-diffusion mechanism. Genetic analysis and reconstructive assays revealed that ROPGEF4/7 and ROPGAP3/4, which encode ROP activators and inactivators, respectively, regulated the formation of ROP-activated domains; these in turn determined the pattern of cell wall pits. Mathematical modelling showed that ROP-activation cycle generated ROP domains by reaction-diffusion mechanism. The model predicted that a positive feedback and slow diffusion of ROP11-ROPGEF4 complex were required to generate ROP-activated domains. ROPGEF4 formed a dimer that interacted with activated ROP11 in vivo, which could provide positive feedback for ROP activation. ROPGEF4 was highly stable on the plasma membrane and inhibited ROP11 diffusion. Our study indicated that ROP-based reaction-diffusion system self-organizes ROP-activated domains, thereby determines the pit pattern of metaxylem vessels.

DOI： 10.1038/s41598-018-29543-y

PubMed

Authorship：Corresponding author   Language：English   Publishing type：Thesis (other)  

DOI： 10.1007/978-1-4939-8612-5_26

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Tokyo  

Plant cortical microtubules have crucial roles in cell wall development. Cortical microtubules are tightly anchored to the plasma membrane in a highly ordered array, which directs the deposition of cellulose microfibrils by guiding the movement of the cellulose synthase complex. Cortical microtubules also interact with several endomembrane systems to regulate cell wall development and other cellular events. Recent studies have identified new factors that mediate interactions between cortical microtubules and endomembrane systems including the plasma membrane, endosome, exocytic vesicles, and endoplasmic reticulum. These studies revealed that cortical microtubule-membrane interactions are highly dynamic, with specialized roles in developmental and environmental signaling pathways. A recent reconstructive study identified a novel function of the cortical microtubule-plasma membrane interaction, which acts as a lateral fence that defines plasma membrane domains. This review summarizes recent advances in our understanding of the mechanisms and functions of cortical microtubule-membrane interactions.

DOI： 10.1007/s10265-017-0995-4

Scopus

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Society of Plant Biologists  

Proper patterning of the cell wall is essential for plant cell development. Cortical microtubule arrays direct the deposition patterns of cell walls at the plasma membrane. However, the precise mechanism underlying cortical microtubule organization is not well understood. Here, we show that a microtubule-associated protein, CORD1 (CORTICAL MICROTUBULE DISORDERING1), is required for the pitted secondary cell wall pattern of metaxylem vessels in Arabidopsis thaliana. Loss of CORD1 and its paralog, CORD2, led to the formation of irregular secondary cell walls with small pits in metaxylem vessels, while overexpressing CORD1 led to the formation of abnormally enlarged secondary cell wall pits. Ectopic expression of CORD1 disturbed the parallel cortical microtubule array by promoting the detachment of microtubules from the plasma membrane. A reconstructive approach revealed that CORD1-induced disorganization of cortical microtubules impairs the boundaries of plasma membrane domains of active ROP11 GTPase, which govern pit formation. Our data suggest that CORD1 promotes cortical microtubule disorganization to regulate secondary cell wall pit formation. The Arabidopsis genome has six CORD1 paralogs that are expressed in various tissues during plant development, suggesting they are important for regulating cortical microtubules during plant development.

DOI： 10.1105/tpc.17.00663

Scopus

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：CELL PRESS  

Spatial control of cell-wall deposition is essential for determining plant cell shape [1]. Rho-type GTPases, together with the cortical cytoskeleton, play central roles in regulating cell-wall patterning [2]. In meta-xylem vessel cells, which are the major components of xylem tissues, active ROP11 Rho GTPases form oval plasma membrane domains that locally disrupt cortical microtubules, thereby directing the formation of oval pits in secondary cell walls [3-5]. However, the regulatory mechanism that determines the planar shape of active Rho of Plants (ROP) domains is still unknown. Here we show that IQD13 associates with cortical microtubules and the plasma membrane to laterally restrict the localization of ROP GTPase domains, thereby directing the formation of oval secondary cell-wall pits. Loss and overexpression of IQD13 led to the formation of abnormally round and narrow secondary cell-wall pits, respectively. Ectopically expressed IQD13 increased the presence of parallel cortical microtubules by promoting microtubule rescue. A reconstructive approach revealed that IQD13 confines the area of active ROP domains within the lattice of the cortical microtubules, causing narrow ROP domains to form. This activity required the interaction of IQD13 with the plasma membrane. These findings suggest that IQD13 positively regulates microtubule dynamics as well as their linkage to the plasma membrane, which synergistically confines the area of active ROP domains, leading to the formation of oval secondary cell-wall pits. This finding sheds light on the role of microtubule-plasma membrane linkage as a lateral fence that determines the planar shape of Rho GTPase domains.

DOI： 10.1016/j.cub.2017.06.059

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Cortical microtubules (MTs) play a major role in the patterning of secondary cell wall (SCW) thickenings in tracheary elements (TEs) by determining the sites of SCW deposition. The EXO70A1 subunit of the exocyst secretory vesicle tethering complex was implicated to be important for TE development via the MT interaction. We investigated the subcellular localization of several exocyst subunits in the xylem of Arabidopsis thaliana and analyzed the functional significance of exocyst-mediated trafficking in TE development. Live cell imaging of fluorescently tagged exocyst subunits in TE using confocal microscopy and protein-protein interaction assays were performed to describe the role of the exocyst and its partners in TE development. In TEs, exocyst subunits were localized to the sites of SCW deposition in an MT-dependent manner. We propose that the mechanism of exocyst targeting to MTs involves the direct interaction of exocyst subunits with the COG2 protein. We demonstrated the importance of a functional exocyst subunit EXO84b for normal TE development and showed that the deposition of SCW constituents is partially compromised, possibly as a result of the mislocalization of secondary cellulose synthase in exocyst mutants. We conclude that the exocyst complex is an important factor bridging the pattern defined by cortical MTs with localized secretion of the SCW in developing TEs.

DOI： 10.1111/nph.14267

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Authorship：Corresponding author   Language：English   Publishing type：Part of collection (book)   Publisher：Humana Press Inc.  

In vitro xylem differentiation is a powerful technique that can be used to elucidate the process of xylem development that occurs deep inside plant tissues in nature. The experimental procedure described here is designed to induce metaxylem vessel differentiation at exceptionally high frequency and synchronicity using genetically engineered Arabidopsis cell suspensions. By triggering a transcriptional switch, over 80% of the cells synchronously differentiate into xylem cells within 32 h of treatment with estradiol. Exogenous marker genes can be transiently introduced into the cells by coculturing them with transformed Agrobacterium before inducing xylem differentiation. This system is fast, easy to handle, and highly compatible with molecular and cell biology techniques used to explore xylem cell differentiation.

DOI： 10.1007/978-1-4939-6722-3_6

Scopus

PubMed

Language：Japanese  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：FRONTIERS RESEARCH FOUNDATION  

Plant cortical microtubules, which form a highly ordered array beneath the plasma membrane, play essential roles in determining cell shape and function by directing the arrangement of cellulosic and non-cellulosic compounds on the cell surface. Interphase transverse arrays of cortical microtubules self-organize through their dynamic instability and inter-microtubule interactions, and by branch-form microtubule nucleation and severing. Recent studies revealed that distinct spatial signals including ROP GTPase, cellular geometry, and mechanical stress regulate the behavior of cortical microtubules at the subcellular and supercellular levels, giving rise to dramatic rearrangements in the cortical microtubule array in response to internal and external cues. Increasing evidence indicates that negative regulators of microtubules also contribute to the rearrangement of the cortical microtubule array. In this review, I summarize recent insights into how the rearrangement of the cortical microtubule array leads to proper, flexible cell wall patterning.

DOI： 10.3389/fpls.2015.00236

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

Xylem vessel cells develop secondary cell walls in distinct patterns. Cortical microtubules are rearranged into distinct patterns and regulate secondary cell wall deposition; however, it is unclear how exocytotic membrane trafficking is linked to cortical microtubules. Here, we show that the novel coiled-coil proteins vesicle tethering 1 (VETH1) and VETH2 recruit EXO70A1, an exocyst subunit essential for correct patterning of secondary cell wall deposition, to cortical microtubules via the conserved oligomeric Golgi complex (COG) 2 protein. VETH1 and VETH2 encode an uncharacterized domain of an unknown function designated DUF869, and were preferentially up-regulated in xylem cells. VETH1-green fluorescent protein (GFP) and VETH2-GFP co-localized at novel vesicle-like small compartments, which exhibited microtubule plus-end-directed and end-tracking dynamics. VETH1 and VETH2 interacted with COG2, and this interaction promoted the association between cortical microtubules and EXO70A1 These results suggest that the VETH-COG2 complex ensures the correct secondary cell wall deposition pattern by recruiting exocyst components to cortical microtubules.

DOI： 10.1093/pcp/pcu197

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PubMed

Language：English   Publishing type：Part of collection (book)   Publisher：Wiley Blackwell  

This chapter introduces cortical microtubule associations with secondary wall development. It discusses the recently established experimental systems contributing to cellular analysis in living xylem cells. The chapter summarizes recent insights into the molecular mechanisms underlying the regulation of secondary cell wall patterns in xylem fibers and protoxylem and metaxylem vessels. It focuses on the emerging interaction between microtubules and ROP GTPases. The development of a number of Arabidopsis xylem cell differentiation systems contributed to the discovery of master xylem differentiation transcription factors. The chapter discusses the current understanding of the molecular mechanisms underlying secondary wall patterning in xylem fibers and protoxylem and metaxylem vessels. In addition to various microtubule-associated proteins (MAPs) and ROP GTPases, proper delivery and synthesis of secondary cell wall components appears to be required for secondary wall patterns.

DOI： 10.1002/9781118647363.ch7

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：CELL PRESS  

Higher organisms possess mechanisms to maintain stem cells' proliferative and pluripotent states in stem cell niches [1]. Plants possess two types of stem cell niches in the root and shoot apical meristems, where regulatory interactions exist between stem cells and organizing cells. Recent studies provided new insights into the molecular mechanism of stem cell maintenance [2-4]. However, earlier and more essential developmental events such as the acquisition of stem cell proliferative activity are still unknown. In vascular tissues, procambial cells function as stem cells and differentiate into xylem, phloem, and procambium. Procambial cell proliferation starts at root apical meristem (RAM) postembryonically; therefore, procambial cell development in RAM is a good model for investigating the regulation of stem cell proliferation. LONESOME HIGHWAY (LHW) and TARGET OF MONOPTEROS5 (TMO5), as well as its homolog, TMO5-LIKE1 (T5L1), encode bHLH proteins that function as heterodimers (LHW-TMO5 and LHW-T5L1) in vascular tissue organization [5-7]. LHW-T5L1 promotes vascular-cell-specific proliferation in RAM [7]. Here, we demonstrate that LHW-T5L1 promotes expression of key cytokinin production genes, including LONELY GUY3 (LOG3) and LOG4, in xylem precursor cells, resulting in elevated cytokinin levels in the surrounding cells. LHW-T5L1 can also promote expression of AHP6, which suppresses cytokinin signaling and then maintains xylem precursor cells at a nondividing state. Our results indicate that LHW-T5L1 establishes xylem precursor cells as a signal center that promotes procambial-cell-specific proliferation through cytokinin response.

DOI： 10.1016/j.cub.2014.07.050

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PubMed

Language：English   Publisher：FRONTIERS RESEARCH FOUNDATION  

Regulation of plant cell wall deposition and patterning is essential for the normal growth and development of plants. Small GTPases play pivotal roles in the modulation of primary cell wall formation by controlling cytoskeletal organization and membrane trafficking. However, the functions of small GTPases in secondary cell wall development are poorly understood. Recent studies on xylem cells revealed that the Rho of plants (ROP) group of small GTPases critically participates in the spatial patterning of secondary cell walls. In differentiating xylem cells, a specific GTPase-activating protein (GAP)/guanine nucleotide exchange factor (GEE) pair facilitates local activation of ROP11 to establish de novo plasma membrane domains. The activated ROP11 then recruits a microtubule-associated protein, MIDD1, to mediate the mutual inhibition between cortical microtubules and active ROP. Furthermore, recent works suggest that certain small GTPases, including ROP and Rab GTPases, regulate membrane trafficking to establish secondary cell wall deposition and patterning. Accordingly, this mini-review assesses and summarizes the current literature regarding the emerging functions of small GTPases in the development of secondary cell walls.

DOI： 10.3389/fpls.2014.00428

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PubMed

Language：English   Publisher：CURRENT BIOLOGY LTD  

Proper patterning of cellulosic cell walls is critical for cell shaping and differentiation of plant cells. Cortical microtubule arrays regulate the deposition patterns of cellulose microfibrils by controlling the targeting and trajectory of cellulose synthase complexes. Although some microtubule-associated proteins (MAPs) regulate the arrangement of cortical microtubules, knowledge about the overall mechanism governing the spacing of cortical microtubules is still limited. Recent studies reveal that ROP GTPases and MAPs spatially regulate the assembly and disassembly of cortical microtubules in developing xylem cells, in which localized secondary cell walls are deposited. Here, we review recent insights into the regulation of xylem cell wall patterning by cortical microtubules, ROP GTPases, and MAPs.

DOI： 10.1016/j.pbi.2013.10.010

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PubMed

Language：Japanese   Publisher：Japan Society for Bioscience, Biotechnology, and Agrochemistry  

DOI： 10.1271/kagakutoseibutsu.51.795

J-GLOBAL

Language：English   Publisher：FRONTIERS RESEARCH FOUNDATION  

Patterning of the cellulosic cell wall underlies the shape and function of plant cells. The cortical microtubule array plays a central role in the regulation of cell wall patterns. However, the regulatory mechanisms by which secondary cell wall patterns are established through cortical microtubules remain to be fully determined. Our recent study in xylem vessel cells revealed that a mutual inhibitory interaction between cortical microtubules and distinct plasma membrane domains leads to distinctive patterning in secondary cell walls. Our research revealed that the recycling of active and inactive ROP proteins by a specific GAP and GEE pair establishes distinct de novo plasma membrane domains. Active ROP recruits a plant-specific microtubule-associated protein, MIDD1, which mediates the mutual interaction between cortical microtubules and plasma membrane domains. In this mini review, we summarize recent research regarding secondary wall patterning, with a focus on the emerging interplay between plasma membrane domains and cortical microtubules through MIDD1 and ROP.

DOI： 10.3389/fpls.2013.00511

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SOC PLANT BIOLOGISTS  

Plant cortical microtubule arrays determine the cell wall deposition pattern and proper cell shape and function. Although various microtubule-associated proteins regulate the cortical microtubule array, the mechanisms underlying marked rearrangement of cortical microtubules during xylem differentiation are not fully understood. Here, we show that local Rho of Plant (ROP) GTPase signaling targets an Arabidopsis thaliana kinesin-13 protein, Kinesin-13A, to cortical microtubules to establish distinct patterns of secondary cell wall formation in xylem cells. Kinesin-13A was preferentially localized with cortical microtubules in secondary cell wall pits, areas where cortical microtubules are depolymerized to prevent cell wall deposition. This localization of Kinesin-13A required the presence of the activated ROP GTPase, MICROTUBULE DEPLETION DOMAIN1 (MIDD1) protein, and cortical microtubules. Knockdown of Kinesin-13A resulted in the formation of smaller secondary wall pits, while overexpression of Kinesin-13A enlarged their surface area. Kinesin-13A alone could depolymerize microtubules in vitro; however, both MIDD1 and Kinesin-13A were required for the depolymerization of cortical microtubules in vivo. These results indicate that Kinesin-13A regulates the formation of secondary wall pits by promoting cortical microtubule depolymerization via the ROP-MIDD1 pathway.

DOI： 10.1105/tpc.113.117853

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PubMed

Language：Japanese  

CiNii Books

J-GLOBAL

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Xylem development is a process of xylem cell terminal differentiation that includes initial cell division, cell expansion, secondary cell wall formation and programmed cell death (PCD). PCD in plants and apoptosis in animals share many common characteristics. Caspase-3, which displays Asp-Glu-Val-Asp (DEVD) specificity, is a crucial executioner during animal cells apoptosis. Although a gene orthologous to caspase-3 is absent in plants, caspase-3-like activity is involved in many cases of PCD and developmental processes. However, there is no direct evidence that caspase-3-like activity exists in xylem cell death. In this study, we showed that caspase-3-like activity is present and is associated with secondary xylem development in Populus tomentosa. The protease responsible for the caspase-3-like activity was purified from poplar secondary xylem using hydrophobic interaction chromatography (HIC), Q anion exchange chromatography and gel filtration chromatography. After identification by liquid chromatography-tandem mass spectrometry (LC-MS/MS), it was revealed that the 20S proteasome (20SP) was responsible for the caspase-3-like activity in secondary xylem development. In poplar 20SP, there are seven a subunits encoded by 12 genes and seven beta subunits encoded by 12 genes. Pharmacological assays showed that Ac-DEVD-CHO, a caspase-3 inhibitor, suppressed xylem differentiation in the veins of Arabidopsis cotyledons. Furthermore, clasto-lactacystin beta-lactone, a proteasome inhibitor, inhibited PCD of tracheary element in a VND6-induced Arabidopsis xylogenic culture. In conclusion, the 20S proteasome is responsible for caspase-3-like activity and is involved in xylem development.

DOI： 10.1111/j.1365-313X.2012.05070.x

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER ASSOC ADVANCEMENT SCIENCE  

A specifically patterned cell wall is a determinant of plant cell shape. Yet, the precise mechanisms that underlie initiation of cell wall patterning remain elusive. By using a reconstitution assay, we revealed that ROPGEF4 (Rho of plant guanine nucleotide exchange factor 4) and ROPGAP3 [ROP guanosine triphosphatase (GTPase)-activating protein 3] mediate local activation of the plant Rho GTPase ROP11 to initiate distinct pattern of secondary cell walls in xylem cells. The activated ROP11 recruits MIDD1 to induce local disassembly of cortical microtubules. Conversely, cortical microtubules eliminate active ROP11 from the plasma membrane through MIDD1. Such a mutual inhibitory interaction between active ROP domains and cortical microtubules establishes the distinct pattern of secondary cell walls. This Rho-based regulatory mechanism shows how plant cells initiate and control cell wall patterns to form various cell shapes.

DOI： 10.1126/science.1222597

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PubMed

Language：English   Publisher：CURRENT BIOLOGY LTD  

Xylem cell differentiation involves temporal and spatial regulation of secondary cell wall deposition. The cortical microtubules are known to regulate the spatial pattern of the secondary cell wall by orientating cellulose deposition. However, it is largely unknown how the microtubule arrangement is regulated during secondary wall formation. Recent findings of novel plant microtubule-associated proteins in developing xylem vessels shed new light on the regulation mechanism of the microtubule arrangement leading to secondary wall patterning. In addition, in vitro culture systems allow the dynamics of microtubules and microtubule-associated proteins during secondary cell wall formation to be followed. Therefore, this review focuses on novel aspects of microtubule dynamics leading to secondary cell wall patterning with a focus on microtubule-associated proteins.

DOI： 10.1016/j.pbi.2011.10.005

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

P>The nuclear envelope (NE) is a highly active structure with a specific set of nuclear envelope proteins acting in diverse cellular events. SUN proteins are conserved NE proteins among eukaryotes. Although they form nucleocytoplasmic linkage complexes in metazoan cells, their functions in the plant kingdom are unknown. To understand the function of plant SUN proteins, in this study we first investigated the dynamics of Arabidopsis SUN proteins during mitosis in Arabidopsis roots and cultured cells. For this purpose, we performed dual and triple visualization of these proteins, microtubules, chromosomes, and endoplasmic reticulum (ER) in cultured cells, and observed their dynamics during mitosis using a high-speed spinning disk confocal microscope. The localizations of SUN proteins changed dynamically during mitosis, tightly coupled with NE dynamics. Moreover, NE re-formation marked with SUN proteins is temporally and spatially coordinated with plant-specific microtubule structures such as phragmoplasts. Finally, the analysis with gene knockdowns of AtSUN1 and AtSUN2 indicated that they are necessary for the maintenance and/or formation of polarized nuclear shape in root hairs. These results suggest that Arabidopsis SUN proteins function in the maintenance or formation of nuclear shape as components of the nucleocytoskeletal complex.

DOI： 10.1111/j.1365-313X.2011.04523.x

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SOC PLANT BIOLOGISTS  

Xylem consists of three types of cells: tracheary elements (TEs), parenchyma cells, and fiber cells. TE differentiation includes two essential processes, programmed cell death (PCD) and secondary cell wall formation. These two processes are tightly coupled. However, little is known about the molecular mechanisms underlying these processes. Here, we show that VASCULAR-RELATED NAC-DOMAIN6 (VND6), a master regulator of TEs, regulates some of the downstream genes involved in these processes in a coordinated manner. We first identified genes that are expressed downstream of VND6 but not downstream of SECONDARY WALL-ASSOCIATED NAC DOMAIN PROTEIN1 (SND1), a master regulator of xylem fiber cells, using transformed suspension culture cells in microarray experiments. We found that VND6 and SND1 governed distinct aspects of xylem formation, whereas they regulated a number of genes in common, specifically those related to secondary cell wall formation. Genes involved in TE-specific PCD were upregulated only by VND6. Moreover, we revealed that VND6 directly regulated genes that harbor a TE-specific cis-element, TERE, in their promoters. Thus, we found that VND6 is a direct regulator of genes related to PCD as well as to secondary wall formation.

DOI： 10.1105/tpc.110.075036

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：CELL PRESS  

Plant cells have evolved cortical microtubules, in a two-dimensional space beneath the plasma membrane [1, 2], that regulate patterning of cellulose deposition [3]. Although recent studies have revealed that several microtubule-associated proteins [4-8] facilitate self-organization of transverse cortical microtubules [9-11], it is still unknown how diverse patterns of cortical microtubules are organized in different xylem cells [12-17], which are the major components of wood. Using our newly established in vitro xylem cell differentiation system, we found that a novel microtubule end-tracking protein, microtubule depletion domain 1 (MIDD1), was anchored to distinct plasma membrane domains and promoted local microtubule disassembly, resulting in pits on xylem cell walls. The introduction of RNA interference for MIDD1 resulted in the failure of local microtubule depletion and the formation of secondary walls without pits. Conversely, the overexpression of MIDD1 reduced microtubule density. MIDD1 has two coiled-coil domains for the binding to microtubules and for the anchorage to plasma membrane domains, respectively. Combination of the two coils caused end tracking of microtubules during shrinkage and suppressed their rescue events. Our results indicate that MIDD1 integrates spatial information in the plasma membrane with cortical microtubule dynamics for determining xylem cell wall pattern.

DOI： 10.1016/j.cub.2010.05.038

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

The intracellular membrane dynamics of Arabidopsis cells under high salt treatment were investigated. When Arabidopsis was treated with high levels of NaCl in hydroponic culture, root tip cells showed rapid changes in the vacuolar volume, a decrease in the number of small acid compartments, active movement of vesicles and accumulation of Na(+) both in the central vacuole and in the vesicles around the main vacuole observed with the Na(+)-dependent fluorescence of Sodium Green. Detailed observation of Arabidopsis suspension-cultured cells under high salt treatment showed a similar pattern of response to that observed in root tip cells. Immunostaining of suspension-cultured cells with antibodies against AtNHX1 clearly showed the occurrence of dotted fluorescence in the cytoplasm only under salt treatment. We also confirmed the existence of AtNHX1 in the vacuolar membrane isolated from suspension-cultured cells with immunofluorescence. Knockout of the vacuolar Q(a)-SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) protein VAM3/SYP22 caused an increase in salt tolerance. In mutant plants, the distribution of Na(+) between roots and shoots differed from that of wild-type plants, with Na(+) accumulating more in roots and less in the shoots of the mutant plants. The role of vesicle traffic under salt stress is discussed.

DOI： 10.1093/pcp/pcp143

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

Eukaryotic cells have developed several essential membrane components. In flowering plants, appropriate structures and distributions of the major membrane components are predominantly regulated by actin microfilaments. In this study, we have focused on the regulatory mechanism of vacuolar structures in the moss, Physcomitrella patens. The high ability of P. patens to undergo homologous recombination enabled us stably to express green fluorescent protein (GFP) or red fluorescent protein (RFP) fusion proteins, and the simple body structure of P. patens enabled us to perform detailed visualization of the intracellular vacuolar and cytoskeletal structures. Three-dimensional analysis and high-speed time-lapse observations revealed surprisingly complex structures and dynamics of the vacuole, with inner sheets and tubular protrusions, and frequent rearrangements by separation and fusion of the membranes. Depolymerization of microtubules dramatically affected these structures and movements. Dual observation of microtubules and vacuolar membranes revealed that microtubules induced tubular protrusions and cytoplasmic strands of the vacuoles, indicative of interactions between microtubules and vacuolar membranes. These results demonstrate a novel function of microtubules in maintaining the distribution of the vacuole and suggest a functional divergence of cytoskeletal functions in land plant evolution.

DOI： 10.1093/pcp/pcp031

Web of Science

PubMed

Language：English   Publishing type：Part of collection (book)   Publisher：ELSEVIER ACADEMIC PRESS INC  

The plant vacuole is a multifunctional organelle and is essential for plant development and growth. The most distinctive feature of the plant vacuole is its size, which usually occupies over 80-90% of the cell volume in well-developed somatic cells, and is therefore highly involved in cell growth and plant body size. Recent progress in the visualization of the vacuole, together with developments in image analysis, has revealed the highly organized and complex morphology of the vacuole, as well as its dynamics. The plant vacuolar membrane (VM) forms not only a typically large vacuole but also other structures, such as tubular structures, transvacuolar strands, bulbs, and sheets. In higher plant cells, actin microfilaments are mainly located near the VM and are involved in vacuolar shape changes with the actin-myosin systems. Most recently, microtubule-dependent regulation of vacuolar structures in moss plant cells was reported, suggesting a diversity of mechanisms regulating vacuolar morphogenesis.

DOI： 10.1016/S1937-6448(09)77003-0

Web of Science

PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Cyclobutane pyrimidine dimers (CPDs) constitute a majority of DNA lesions caused by ultraviolet-B (UVB). CPD photolyase, which rapidly repairs CPDs, is essential for plant survival under sunlight containing UVB. Our earlier results that the transcription of the cucumber CPD photolyase gene (CsPHR) was activated by light have prompted us to propose that this light-driven transcriptional activation would allow plants to meet the need of the photolyase activity upon challenges of UVB from sunlight. However, molecular mechanisms underlying the light-dependent transcriptional activation of CsPHR were unknown. In order to understand spectroscopic aspects of the plant response, we investigated the wavelength-dependence (action spectra) of the light-dependent transcriptional activation of CsPHR. In both cucumber seedlings and transgenic Arabidopsis seedlings expressing reporter genes under the control of the CsPHR promoter, the action spectra exhibited the most predominant peak in the long-wavelength UVB waveband (around 310 nm). In addition, a 95-bp cis-acting region in the CsPHR promoter was identified to be essential for the UVB-driven transcriptional activation of CsPHR. Thus, we concluded that the photoperception of long-wavelength UVB by UVB photoreceptor(s) led to the induction of the CsPHR transcription via a conserved cis-acting element.

DOI： 10.1007/s00425-008-0803-4

Web of Science

PubMed

Language：English  

DOI： 10.1101/gad.1644008

Web of Science

PubMed

Language：English   Publisher：SPRINGER TOKYO  

The water and mineral conductive tube, the xylem vessel and tracheid, is a highly conspicuous tissue due to its elaborately patterned secondary-wall deposition. One constituent of the xylem vessel and tracheid, the tracheary element, is an empty dead cell that develops secondary walls in the elaborate patterns. The wall pattern is appropriately regulated according to the developmental stage of the plant. The cytoskeleton is an essential component of this regulation. In fact, the cortical microtubule is well known to participate in patterned secondary cell wall formation. The dynamic rearrangement of the microtubules and actin filaments have also been recognized in the cultured cells differentiating into tracheary elements in vitro. There has recently been considerable progress in our understanding of the dynamics and regulation of cortical microtubules, and several plant microtubule associated proteins have been identified and characterized. The microtubules have been observed during tracheary element differentiation in living Arabidopsis thaliana cells. Based on this recently acquired information on the plant cytoskeleton and tracheary element differentiation, this review discusses the role of the cytoskeleton in secondary cell wall formation.

DOI： 10.1007/s10265-006-0260-8

Web of Science

PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：BLACKWELL PUBLISHING  

The actin cytoskeleton of higher plants plays an essential role in plant morphogenesis and in maintaining various cellular activities. In this study we established a tobacco BY-2 cell line, stably transformed with a GFP-fimbrin actin-binding domain (ABD) 2 construct, that allows visualization of actin microfilaments (MFs) in living cells. Using this cell line, designated BY-GF11, we performed time-sequential observations of MF dynamics during cell-cycle progression. Detailed analyses revealed the appearance of a broad MF band in the late G(2) phase that separated to form a structure corresponding to the so-called actin-depleted zone (ADZ) in mitosis. In BY-GF11, the MF structure at the cell cortex in mitosis appeared to form two bands rather than the ADZ. Measurements of fluorescent intensities of the cell cortex indicated an MF distribution that resembled two peaks, and we therefore named the structure MF 'twin peaks' (MFTP). The cell plate formed exactly within the valley between the MFTP at cytokinesis, and this cell-plate guidance was distorted by disruption of the MFTP by an inhibitor of actin polymerization. These results suggest that the MFTP originates from the broad MF band in the G(2) phase and functions as a marker of cytokinesis.

DOI： 10.1111/j.1365-313X.2005.02558.x

Web of Science

PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SOC PLANT BIOLOGISTS  

Cortical microtubules participate in the deposition of patterned secondary walls in tracheary element differentiation. In this study, we established a system to induce the differentiation of tracheary elements using a transgenic Arabidopsis (Arabidopsis thaliana) cell suspension stably expressing a green fluorescent protein-tubulin fusion protein. Approximately 30% of the cells differentiated into tracheary elements 96 h after culture in auxin-free media containing 1 mu m brassinolide. With this differentiation system, we have been able to time-sequentially elucidate microtubule arrangement during secondary wall thickening. The development of secondary walls could be followed in living cells by staining with fluorescein-conjugated wheat germ agglutinin, and the three-dimensional structures of the secondary walls could be simultaneously analyzed. A single microtubule bundle first appeared beneath the narrow secondary wall and then developed into two separate bundles locating along both sides of the developing secondary wall. Microtubule inhibitors affected secondary wall thickening, suggesting that the pair of microtubule bundles adjacent to the secondary wall played a crucial role in the regulation of secondary wall development.

DOI： 10.1104/pp.104.052613

Web of Science

PubMed

Event date： 2023.12

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Event date： 2023.12

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Event date： 2023.11

Language：English   Presentation type：Oral presentation (invited, special)  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2023.9

Language：Japanese   Presentation type：Oral presentation (general)  

Event date： 2023.7

Language：English   Presentation type：Poster presentation  

Event date： 2023.7

Language：English   Presentation type：Oral presentation (invited, special)  

Event date： 2023.3

Presentation type：Oral presentation (general)  

Event date： 2022.9

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Event date： 2022.7

Language：English   Presentation type：Poster presentation  

Event date： 2021.11

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：オンライン  

Event date： 2021.3

Language：Japanese   Presentation type：Poster presentation  

Event date： 2020.12

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：鹿児島大学, 鹿児島市  

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Mishima, Shizuoka, Japan  

Language：English   Presentation type：Poster presentation  

Venue：Gateaux kingdom SAPPORO, Sapporo, Hokkaido  

Language：English   Presentation type：Poster presentation  

Venue：Kyoto University, Kyoto, Japan  

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Polonia Castle (Dom Polonii), Pułtusk, Poland  

Language：English   Presentation type：Oral presentation (invited, special)  

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Palais Des Congres, Paris, France  

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Academia Sinica, Taipei, Taiwan  

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Shanghai Center for Plant Stress Biology, Shanghai  

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Korea  

Presentation type：Oral presentation (invited, special)  

Venue：大阪大学吹田キャンパス、吹田市、大阪  

Language：Japanese   Presentation type：Poster presentation  

Venue：東京理科大学野田キャンパス  

Language：Japanese   Presentation type：Poster presentation  

Venue：東京理科大学野田キャンパス  

Language：Japanese   Presentation type：Poster presentation  

Venue：鹿児島大学、鹿児島市  

Language：Japanese   Presentation type：Poster presentation  

Venue：東京理科大学野田キャンパス  

Language：Japanese   Presentation type：Poster presentation  

Language：Japanese   Presentation type：Poster presentation  

Language：Japanese   Presentation type：Poster presentation  

Venue：那覇、沖縄  

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Lyon, France  

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Kyoto University, Kyoto, Japan  

Language：English   Presentation type：Oral presentation (invited, special)  

Language：English   Presentation type：Oral presentation (invited, special)  

Language：English   Presentation type：Oral presentation (invited, special)  

Venue：Port Island, Kobe, Japan  

Language：English   Presentation type：Poster presentation  

Venue：Kumamoto University, Kumamoto  

Language：English   Presentation type：Poster presentation  

Venue：Proctor Academy, Andover, NH, USA  

Language：English   Presentation type：Poster presentation  

Venue：Andover, NH, USA  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：札幌コンベンションセンター  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：札幌コンベンションセンター  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：English   Presentation type：Oral presentation (invited, special)  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学、名古屋  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：名古屋大学・名古屋  

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：東北大学川内キャンパス・仙台  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島国際会議場、広島市  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島国際会議場、広島市  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：広島国際会議場、広島市  

Language：Japanese   Presentation type：Oral presentation (general)  

Presentation type：Oral presentation (invited, special)  

Venue：京都、京都市  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：札幌コンベンションセンター  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東北大学川内キャンパス・仙台  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京理科大学野田キャンパス  

Venue：鹿児島大学、鹿児島市  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：岩手大学、盛岡、岩手  

Language：English   Presentation type：Poster presentation  

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：東京大学、文京区、東京  

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：大阪府豊中市  

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：神戸大学、神戸  

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Language：Japanese   Presentation type：Poster presentation  

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：福井大学文京キャンパス・福井  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京農業大学世田谷キャンパス、世田谷区  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：朱鷺メッセ、新潟市  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：朱鷺メッセ、新潟市  

Presentation type：Oral presentation (invited, special)  

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：大阪大学吹田キャンパス  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Public lecture, seminar, tutorial, course, or other speech  

Venue：神奈川, 川崎市, 明治大学生田キャンパス  

Language：English   Presentation type：Oral presentation (invited, special)  

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：東京大学本郷キャンパス、文京区、東京  

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：明治大学中野キャンパス  

Language：Japanese   Presentation type：Oral presentation (invited, special)  

Venue：朱鷺メッセ、新潟市  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：東京農業大学世田谷キャンパス、世田谷区  

Language：Japanese   Presentation type：Oral presentation (general)  

Language：Japanese  

Language：English   Presentation type：Oral presentation (invited, special)  

日本植物学会第８６回大会シンポジウム

Type：Competition, symposium, etc. 

日本植物学会第７９会大会シンポジウム

Type：Competition, symposium, etc. 

日本植物学会第７５回大会シンポジウム