Publications by authors named "Myeong Min Lee"

33 Publications

Overexpression of three related root-cap outermost-cell-specific C2H2-type zinc-finger protein genes suppresses the growth of Arabidopsis in an EAR-motif-dependent manner.

BMB Rep 2020 Mar;53(3):160-165

Department of Systems Biology, Yonsei University, Seoul 03722, Korea.

The root meristem of Arabidopsis thaliana is protected by the root cap, the size of which is tightly regulated by the balance between the formative cell divisions and the dispersal of the outermost cells. We isolated an enhancer-tagged dominant mutant displaying the short and twisted root by the overexpression of ZINC-FINGER OF ARABIDOPSIS THALIANA1 (ZAT1) encoding an EAR motif-containing zinc-finger protein. The growth inhibition by ZAT1 was shared by ZAT4 and ZAT9, the ZAT1 homologues. The ZAT1 promoter was specifically active in the outermost cells of the root cap, in which ZAT1-GFP was localized when expressed by the ZAT1 promoter. The outermost cell-specific expression pattern of ZAT1 was not altered in the sombrero (smb) or smb bearskin1 (brn1) brn2 accumulating additional root-cap layers. In contrast, ZAT4-GFP and ZAT9- GFP fusion proteins were distributed to the inner root-cap cells in addition to the outermost cells where ZAT4 and ZAT9 promoters were active. Overexpression of ZAT1 induced the ectopic expression of PUTATIVE ASPARTIC PROTEASE3 involved in the programmed cell death. The EAR motif was essential for the growth inhibition by ZAT1. These results suggest that the three related ZATs might regulate the maturation of the outermost cells of the root cap. [BMB Reports 2020; 53(3): 160-165].
View Article and Find Full Text PDF

Download full-text PDF

Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7118352PMC
March 2020

POLTERGEIST and POLTERGEIST-LIKE1 are essential for the maintenance of post-embryonic shoot and root apical meristems as revealed by a partial loss-of-function mutant allele of pll1 in Arabidopsis.

Genes Genomics 2020 01 3;42(1):107-116. Epub 2019 Dec 3.

Department of Systems Biology, Yonsei University, 50 Yonsei-ro, Seoul, 03722, Korea.

Background: POLTERGEIST (POL) and POL-LIKE1 (PLL1) encoding related protein phosphatase 2Cs are essential for the establishment of both shoot and root meristems during embryogenesis. As the strong pol pll1 are seedling-lethal due to the lack of hypocotyl vasculature, the roles of POL/PLL1 for the post-embryonic development is difficult to be assessed.

Objective: To prepare a weak pol pll1 double mutant that are able to produce post-embryonic organs.

Methods: Several T-DNA insertion mutants of pll1 were crossed to pol-6 for the preparation of weak pol pll1. To understand the epistatic interactions between POL/PLL1 and CLAVATAs, the phenotypes of clvs pol pll1 were assessed and the expression patterns of stem cell markers were examined in pol pll1. POLpro:PLL1-GFP expression was examined during the embryogenesis with confocal microscopy.

Results: We isolated a pll1-3 (S544N) allele and prepared a weak pol-6 pll1-3. About 5% of pol-6 pll1-3 seedlings continued the post-embryonic development displaying short roots with reduced root meristem, wuschel-like adventitious phyllotaxis, and defective flowers lacking carpel. The clv1, clv2, and clv3 phenotypes led by enlarged shoot meristems were almost completely suppressed in the pol-6 pll1-3. POL/PLL1 were required for the indeterminate floral organ development displayed by agamous. PLL1-GFP asymmetrically localized in the shootward sides of columella cells and increased the size of distal root meristem region by enhancing the WUS-RELATED HOMEOBOX 5 expression suggesting that PLL1 might provide the stem cells and progenies with proper positional information for the asymmetric cell divisions.

Conclusion: Together, POL/PLL1 are required for the maintenance of stem cell pools for the post-embryonic development in Arabidopsis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s13258-019-00894-8DOI Listing
January 2020

QUIRKY regulates root epidermal cell patterning through stabilizing SCRAMBLED to control CAPRICE movement in Arabidopsis.

Nat Commun 2019 04 15;10(1):1744. Epub 2019 Apr 15.

Department of Systems Biology, Yonsei University, 50 Yonsei-ro, Seoul, 03722, Korea.

SCM, a leucine-rich repeat receptor-like kinase, is required for root epidermal cells to appropriately interpret their location and generate the proper cell-type pattern during Arabidopsis root development. Here, via a screen for scm-like mutants we describe a new allele of the QKY gene. We find that QKY is required for the appropriate spatial expression of several epidermal cell fate regulators in a similar manner as SCM in roots, and that QKY and SCM are necessary for the efficient movement of CPC between epidermal cells. We also show that turnover of SCM is mediated by a vacuolar degradation pathway triggered by ubiquitination, and that QKY prevents this SCM ubiquitination through their physical interaction. These results suggest that QKY stabilizes SCM through interaction, and this complex facilitates CPC movement between the epidermal cells to help establish the cell-type pattern in the Arabidopsis root epidermis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-019-09715-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6465271PMC
April 2019

Involvement of Pyridoxine/Pyridoxamine 5'-Phosphate Oxidase (PDX3) in Ethylene-Induced Auxin Biosynthesis in the Arabidopsis Root.

Mol Cells 2018 Dec 14;41(12):1033-1044. Epub 2018 Nov 14.

Department of Systems Biotechnology, Konkuk University, Seoul, Korea.

As sessile organisms, plants have evolved to adjust their growth and development to environmental changes. It has been well documented that the crosstalk between different plant hormones plays important roles in the coordination of growth and development of the plant. Here, we describe a novel recessive mutant, (), which displayed insensitivity to the ethylene precursor, ACC (1-aminocyclopropane-1-carboxylic acid), in the root under the dark-grown conditions. By contrast, roots exhibited a normal growth response to exogenous IAA (indole-3-acetic acid). Thus, it appears that the growth responses of to ACC and IAA resemble those of () mutants. To understand the molecular events underlying the crosstalk between ethylene and auxin in the root, we identified the locus and found that the gene encodes the pyridoxine 5'-phosphate (PNP)/pyridoxamine 5'-phosphate (PMP) oxidase, PDX3. Our results revealed that MINE/PDX3 likely plays a role in the conversion of the auxin precursor tryptophan to indole-3-pyruvic acid in the auxin biosynthesis pathway, in which () and its related genes ( and ; and ) are involved. Considering that TAA1 and TARs belong to a subgroup of PLP (pyridoxal-5'-phosphate)-dependent enzymes, we propose that PLP produced by MINE/PDX3 acts as a cofactor in TAA1/TAR-dependent auxin biosynthesis induced by ethylene, which in turn influences the crosstalk between ethylene and auxin in the Arabidopsis root.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.14348/molcells.2018.0363DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6315319PMC
December 2018

Rhizosphere microbiome structure alters to enable wilt resistance in tomato.

Nat Biotechnol 2018 Oct 8. Epub 2018 Oct 8.

Department of Systems Biology, Division of Life Sciences, and Institute for Life Science and Biotechnology, Yonsei University, Seoul, Republic of Korea.

Tomato variety Hawaii 7996 is resistant to the soil-borne pathogen Ralstonia solanacearum, whereas the Moneymaker variety is susceptible to the pathogen. To evaluate whether plant-associated microorganisms have a role in disease resistance, we analyzed the rhizosphere microbiomes of both varieties in a mesocosm experiment. Microbiome structures differed between the two cultivars. Transplantation of rhizosphere microbiota from resistant plants suppressed disease symptoms in susceptible plants. Comparative analyses of rhizosphere metagenomes from resistant and susceptible plants enabled the identification and assembly of a flavobacterial genome that was far more abundant in the resistant plant rhizosphere microbiome than in that of the susceptible plant. We cultivated this flavobacterium, named TRM1, and found that it could suppress R. solanacearum-disease development in a susceptible plant in pot experiments. Our findings reveal a role for native microbiota in protecting plants from microbial pathogens, and our approach charts a path toward the development of probiotics to ameliorate plant diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/nbt.4232DOI Listing
October 2018

Conservation and Diversification of the SHR-SCR-SCL23 Regulatory Network in the Development of the Functional Endodermis in Arabidopsis Shoots.

Mol Plant 2016 08 25;9(8):1197-1209. Epub 2016 Jun 25.

Department of Systems Biotechnology, Konkuk University, Seoul 05029, Korea. Electronic address:

Development of the functional endodermis of Arabidopsis thaliana roots is controlled, in part, by GRAS transcription factors, namely SHORT-ROOT (SHR), SCARECROW (SCR), and SCARECROW-LIKE 23 (SCL23). Recently, it has been shown that the SHR-SCR-SCL23 regulatory module is also essential for specification of the endodermis (known as the bundle sheath) in leaves. Nevertheless, compared with what is known about the role of the SHR-SCR-SCL23 regulatory network in roots, the molecular interactions of SHR, SCR, and SCL23 are much less understood in shoots. Here, we show that SHR forms protein complexes with SCL23 to regulate transcription of SCL23 in shoots, similar to the regulation mode of SCR expression. Our results indicate that SHR acts as master regulator to directly activate the expression of SCR and SCL23. In the SHR-SCR-SCL23 network, we found a previously uncharacterized negative feedback loop whereby SCL23 modulates SHR levels. Through molecular, genetic, physiological, and morphological analyses, we also reveal that the SHR-SCR-SCL23 module plays a key role in the formation of the endodermis (known as the starch sheath) in hypocotyls. Taken together, our results provide new insights into the regulatory role of the SHR-SCR-SCL23 network in the endodermis development in both roots and shoots.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.molp.2016.06.007DOI Listing
August 2016

BRI1-Associated Receptor Kinase 1 Regulates Guard Cell ABA Signaling Mediated by Open Stomata 1 in Arabidopsis.

Mol Plant 2016 Mar 24;9(3):447-460. Epub 2015 Dec 24.

Department of Biological Sciences, Sookmyung Women's University, Seoul 140-742, Republic of Korea. Electronic address:

Stomatal movements are critical in regulating gas exchange for photosynthesis and water balance between plant tissues and the atmosphere. The plant hormone abscisic acid (ABA) plays key roles in regulating stomatal closure under various abiotic stresses. In this study, we revealed a novel role of BAK1 in guard cell ABA signaling. We found that the brassinosteroid (BR) signaling mutant bak1 lost more water than wild-type plants and showed ABA insensitivity in stomatal closure. ABA-induced OST1 expression and reactive oxygen species (ROS) production were also impaired in bak1. Unlike direct treatment with H2O2, overexpression of OST1 did not completely rescue the insensitivity of bak1 to ABA. We demonstrated that BAK1 forms a complex with OST1 near the plasma membrane and that the BAK1/OST1 complex is increased in response to ABA in planta. Brassinolide, the most active BR, exerted a negative effect on ABA-induced formation of the BAK1/OST1 complex and OST1 expression. Moreover, we found that BAK1 and ABI1 oppositely regulate OST1 phosphorylation in vitro, and that ABI1 interacts with BAK1 and inhibits the interaction of BAK1 and OST1. Taken together, our results suggest that BAK1 regulates ABA-induced stomatal closure in guard cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.molp.2015.12.014DOI Listing
March 2016

TORNADO1 regulates root epidermal patterning through the WEREWOLF pathway in Arabidopsis thaliana.

Plant Signal Behav 2015 ;10(12):e1103407

d Department of Molecular , Cellular and Developmental Biology; University of Michigan ; Ann Arbor , MI USA.

Cell fate in the root epidermis of Arabidopsis thaliana is determined in a position-dependent manner. SCRAMBLED (SCM), an atypical leucine-rich repeat receptor-like kinase, mediates this positional regulation via its effect on WEREWOLF (WER) expression, and subsequently, its downstream transcription factor, GLABRA2 (GL2), which are required for nonhair cell development. Previously, TORNADO1 (TRN1), a plant-specific protein with a leucine-rich repeat ribonuclease inhibitor-like domain, was shown to be required for proper epidermal patterning in Arabidopsis roots. In this work, we analyzed the possible involvement of TRN1 in the known root epidermal gene network. We discovered that the trn1 mutant caused the ectopic expression of WER and the randomized expression of GL2 and EGL3. This suggests that TRN1 regulates the position-dependent cell fate determination by affecting WER expression in Arabidopsis root epidermis. Additionally, the distinct phenotypes of the aerial parts of the trn1-t and scm-2 mutant suggest that TRN1 and SCM might have different functions in the development of aerial parts.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/15592324.2015.1103407DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4854348PMC
October 2016

The Arabidopsis thaliana NGATHA transcription factors negatively regulate cell proliferation of lateral organs.

Plant Mol Biol 2015 Nov 3;89(4-5):529-38. Epub 2015 Oct 3.

Department of Biology, Kyungpook National University, Daegu, 702-701, Korea.

The cell proliferation process of aerial lateral organs, such as leaves and flowers, is coordinated by complex genetic networks that, in general, converge on the cell cycle. The Arabidopsis thaliana NGATHA (AtNGA) family comprises four members that belong to the B3-type transcription factor superfamily, and has been suggested to be involved in growth and development of aerial lateral organs, although its role in the cell proliferation and expansion processes remains to be resolved in more detail. In order to clarify the role of AtNGAs in lateral organ growth, we took a systematic approach using both the loss- and gain-of-functional mutants of all four members. Our results showed that overexpressors of AtNGA1 to AtNGA4 developed small, narrow lateral organs, whereas the nga1 nga2 nga3 nga4 quadruple mutant produced large, wide lateral organs. We found that cell numbers of the lateral organs were significantly affected: a decrease in overexpressors and, inversely, an increase in the quadruple mutant. Kinematic analyses on leaf growth revealed that, compared with the wild type, the overexpressors displayed a lower activity of cell proliferation and yet the mutant a higher activity. Changes in expression of cell cycle-regulating genes were well in accordance with the cell proliferation activities, establishing that the AtNGA transcription factors act as bona fide negative regulators of the cell proliferation of aerial lateral organs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11103-015-0386-yDOI Listing
November 2015

WEREWOLF and ENHANCER of GLABRA3 are interdependent regulators of the spatial expression pattern of GLABRA2 in Arabidopsis.

Biochem Biophys Res Commun 2015 Nov 25;467(1):94-100. Epub 2015 Sep 25.

Department of Systems Biology, Yonsei University, 50 Yonsei-ro, Seoul 03722, Republic of Korea. Electronic address:

In multicellular organisms, cell fates are specified through differential regulation of transcription. Epidermal cell fates in the Arabidopsis thaliana root are precisely specified by several transcription factors, with the GLABRA2 (GL2) homeodomain protein acting at the farthest downstream in this process. To better understand the regulation of GL2 expression, we ectopically expressed WEREWOLF (WER) and ENHANCER OF GLABRA3 (EGL3) in various tissues and examined GL2 expression. Here we show that WER expressed ubiquitously in the root induced GL2 expression only in the root epidermis, whereas co-expression of WER and EGL3 induced GL2 expression in the corresponding tissues. We also found that GL3 accumulated in the nucleus at the early meristematic region and EGL3 accumulated later in the nucleus of epidermal cells. We further found that ectopic expression of WER and EGL3 in ground tissues inhibited GL2 expression in the epidermis. Our results suggest that the co-expression of WER and EGL3 is sufficient for driving GL2 and CPC expression.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bbrc.2015.09.115DOI Listing
November 2015

ANGUSTIFOLIA mediates one of the multiple SCRAMBLED signaling pathways regulating cell growth pattern in Arabidopsis thaliana.

Biochem Biophys Res Commun 2015 Sep 18;465(3):587-93. Epub 2015 Aug 18.

Department of Molecular, Cellular and Developmental Biology, University of Michigan, 830 North University Avenue, Ann Arbor, MI, USA.

In Arabidopsis thaliana, an atypical leucine-rich repeat receptor-like kinase, SCRAMBLED (SCM), is required for multiple developmental processes including root epidermal cell fate determination, silique dehiscence, inflorescence growth, ovule morphogenesis, and tissue morphology. Previous work suggested that SCM regulates these multiple pathways using distinct mechanisms via interactions with specific downstream factors. ANGUSTIFOLIA (AN) is known to regulate cell and tissue morphogenesis by influencing cortical microtubule arrangement, and recently, the AN protein was reported to interact with the SCM protein. Therefore, we examined whether AN might be responsible for mediating some of the SCM-dependent phenotypes. We discovered that both scm and an mutant lines cause an abnormal spiral or twisting growth of roots, but only the scm mutant affected root epidermal patterning. The siliques of the an and scm mutants also exhibited spiral growth, as previously reported, but only the scm mutant altered silique dehiscence. Interestingly, we discovered that the spiral growth of roots and siliques of the scm mutant is rescued by a truncated SCM protein that lacks its kinase domain, and that a juxtamembrane domain of SCM was sufficient for AN binding in the yeast two-hybrid analysis. These results suggest that the AN protein is one of the critical downstream factors of SCM pathways specifically responsible for mediating its effects on cell/tissue morphogenesis through cortical microtubule arrangement.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bbrc.2015.08.067DOI Listing
September 2015

Genetic interaction between GROWTH-REGULATING FACTOR and CUP-SHAPED COTYLEDON in organ separation.

Plant Signal Behav 2015 ;10(2):e988071

a Department of Biology ; Kyungpook National University ; Daegu , Korea.

The Arabidopsis thaliana GROWTH-REGULATING FACTOR (GRF) gene family comprises 9 members and encodes a class of transcription factors. We previously demonstrated that GRF genes played an essential role in formation of the boundary region between cotyledons, since their loss-of-function mutants developed fused cotyledons. Our present study shows that the grf mutants display fused floral organs as well. Such fusion phenotypes of embryonic and post-embryonic floral organs are highly reminiscent of the cup-shaped cotyledon (cuc) mutants. In order to test a genetic interaction between GRFs and CUCs, we constructed cuc1 grf1/2/3, cuc2 grf1/2/3, and cuc3 grf1/2/3 quadruple mutants, and found that the mutants showed dramatic increases in cotyledon fusion as well as floral organ fusion. The results suggest that the signaling pathway of GRFs may be genetically associated with that of CUCs in the organ separation process.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4161/15592324.2014.988071DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4623100PMC
December 2015

Distinct signaling mechanisms in multiple developmental pathways by the SCRAMBLED receptor of Arabidopsis.

Plant Physiol 2014 Oct 18;166(2):976-87. Epub 2014 Aug 18.

Biology Department, Long Island University, Brooklyn, New York 11201 (S.-H.K.);Department of Systems Biology, Yonsei University, Seoul 120-749, Korea (S.W., M.M.L.); andDepartment of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109 (J.S.).

SCRAMBLED (SCM), a leucine-rich repeat receptor-like kinase in Arabidopsis (Arabidopsis thaliana), is required for positional signaling in the root epidermis and for tissue/organ development in the shoot. To further understand SCM action, we generated a series of kinase domain variants and analyzed their ability to complement scm mutant defects. We found that the SCM kinase domain, but not kinase activity, is required for its role in root epidermal patterning, supporting the view that SCM is an atypical receptor kinase. We also describe a previously uncharacterized role for SCM in fruit dehiscence, because mature siliques from scm mutants fail to open properly. Interestingly, the kinase domain of SCM appears to be dispensable for this developmental process. Furthermore, we found that most of the SCM kinase domain mutations dramatically inhibit inflorescence development. Because this process is not affected in scm null mutants, it is likely that SCM acts redundantly to regulate inflorescence size. The importance of distinct kinase residues for these three developmental processes provides an explanation for the maintenance of the conserved kinase domain in the SCM protein, and it may generally explain its conservation in other atypical kinases. Furthermore, these results indicate that individual leucine-rich repeat receptor-like kinases may participate in multiple pathways using distinct signaling mechanisms to mediate diverse cellular communication events.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1104/pp.114.247288DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4213122PMC
October 2014

Nuclear trapping controls the position-dependent localization of CAPRICE in the root epidermis of Arabidopsis.

Plant Physiol 2013 Sep 5;163(1):193-204. Epub 2013 Jul 5.

Department of Systems Biology, Yonsei University, 50 Yonsei-ro, Seoul 120-749, Korea.

Cell fate determination and differentiation are central processes in the development of multicellular organisms, and the Arabidopsis (Arabidopsis thaliana) root epidermis provides a model system to study the molecular basis of these processes. A lateral inhibition mechanism mediated by an R3 single-repeat MYB protein, CAPRICE (CPC), has been proposed to explain the specification of the two types of root epidermal cells (hair cells and nonhair cells). However, it is not clear how CPC acts preferentially in the H-position cells, rather than the N-position cells, where its gene is expressed. To explore this issue, we examined the effect of misexpressed CPC on cell fate specification and CPC localization in the root epidermis. We show that CPC is able to move readily within the root epidermis when its expression level is high and that CPC can induce the hair cell fate in a cell-autonomous manner. We provide evidence that CPC is capable of moving from the stele tissue in the center of the root to the outermost epidermal layer, where it can induce the hair cell fate. In addition, we show that CPC protein accumulates primarily in the nuclei of H-position cells in the early meristematic region, and this localization requires the H-cell-expressed ENHANCER OF GLABRA3 (EGL3) basic helix-loop-helix transcription factor. These results suggest that cell-cell movement of CPC occurs readily within the meristematic region of the root and that EGL3 preferentially traps the CPC protein in the H-position cells of the epidermis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1104/pp.113.221028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3762640PMC
September 2013

A gene regulatory network for root epidermis cell differentiation in Arabidopsis.

PLoS Genet 2012 Jan 12;8(1):e1002446. Epub 2012 Jan 12.

Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.

The root epidermis of Arabidopsis provides an exceptional model for studying the molecular basis of cell fate and differentiation. To obtain a systems-level view of root epidermal cell differentiation, we used a genome-wide transcriptome approach to define and organize a large set of genes into a transcriptional regulatory network. Using cell fate mutants that produce only one of the two epidermal cell types, together with fluorescence-activated cell-sorting to preferentially analyze the root epidermis transcriptome, we identified 1,582 genes differentially expressed in the root-hair or non-hair cell types, including a set of 208 "core" root epidermal genes. The organization of the core genes into a network was accomplished by using 17 distinct root epidermis mutants and 2 hormone treatments to perturb the system and assess the effects on each gene's transcript accumulation. In addition, temporal gene expression information from a developmental time series dataset and predicted gene associations derived from a Bayesian modeling approach were used to aid the positioning of genes within the network. Further, a detailed functional analysis of likely bHLH regulatory genes within the network, including MYC1, bHLH54, bHLH66, and bHLH82, showed that three distinct subfamilies of bHLH proteins participate in root epidermis development in a stage-specific manner. The integration of genetic, genomic, and computational analyses provides a new view of the composition, architecture, and logic of the root epidermal transcriptional network, and it demonstrates the utility of a comprehensive systems approach for dissecting a complex regulatory network.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1371/journal.pgen.1002446DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3257299PMC
January 2012

Cell fate in the Arabidopsis root epidermis is determined by competition between WEREWOLF and CAPRICE.

Plant Physiol 2011 Nov 13;157(3):1196-208. Epub 2011 Sep 13.

Department of Systems Biology, Yonsei University, Seoul 120-749, Korea.

The root hair and nonhair cells in the Arabidopsis (Arabidopsis thaliana) root epidermis are specified by a suite of transcriptional regulators. Two of these are WEREWOLF (WER) and CAPRICE (CPC), which encode MYB transcription factors that are required for promoting the nonhair cell fate and the hair cell fate, respectively. However, the precise function and relationship between these transcriptional regulators have not been fully defined experimentally. Here, we examine these issues by misexpressing the WER gene using the GAL4-upstream activation sequence transactivation system. We find that WER overexpression in the Arabidopsis root tip is sufficient to cause epidermal cells to adopt the nonhair cell fate through direct induction of GLABRA2 (GL2) gene expression. We also show that GLABRA3 (GL3) and ENHANCER OF GLABRA3 (EGL3), two closely related bHLH proteins, are required for the action of the overexpressed WER and that WER interacts with these bHLHs in plant cells. Furthermore, we find that CPC suppresses the WER overexpression phenotype quantitatively. These results show that WER acts together with GL3/EGL3 to induce GL2 expression and that WER and CPC compete with one another to define cell fates in the Arabidopsis root epidermis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1104/pp.111.185785DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3252147PMC
November 2011

WEREWOLF, a regulator of root hair pattern formation, controls flowering time through the regulation of FT mRNA stability.

Plant Physiol 2011 Aug 7;156(4):1867-77. Epub 2011 Jun 7.

National Research Laboratory of Plant Developmental Genetics, School of Biological Sciences, Seoul National University, Seoul 151-742, Korea.

A key floral activator, FT, integrates stimuli from long-day, vernalization, and autonomous pathways and triggers flowering by directly regulating floral meristem identity genes in Arabidopsis (Arabidopsis thaliana). Since a small amount of FT transcript is sufficient for flowering, the FT level is strictly regulated by diverse genes. In this study, we show that WEREWOLF (WER), a MYB transcription factor regulating root hair pattern, is another regulator of FT. The mutant wer flowers late in long days but normal in short days and shows a weak sensitivity to vernalization, which indicates that WER controls flowering time through the photoperiod pathway. The expression and double mutant analyses showed that WER modulates FT transcript level independent of CONSTANS and FLOWERING LOCUS C. The histological analysis of WER shows that it is expressed in the epidermis of leaves, where FT is not expressed. Consistently, WER regulates not the transcription but the stability of FT mRNA. Our results reveal a novel regulatory mechanism of FT that is non cell autonomous.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1104/pp.111.176685DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3149934PMC
August 2011

Funneling of gibberellin signaling by the GRAS transcription regulator scarecrow-like 3 in the Arabidopsis root.

Proc Natl Acad Sci U S A 2011 Feb 18;108(5):2166-71. Epub 2011 Jan 18.

Department of Bioscience and Biotechnology, Konkuk University, Seoul 143-701, Korea.

During plant development, because no cell movement takes place, control of the timing and extent of cell division and coordination of the direction and extent of cell expansion are particularly important for growth and development. The plant hormone gibberellins (GAs) play key roles in the control of these developmental processes. However, little is known about the molecular components that integrate the generic GA signaling into a specific cell/tissue to coordinate cell division and cell expansion. Here we report that scarecrow-like 3 (SCL3), a GRAS protein, acts as a positive regulator to integrate and maintain a functional GA pathway by attenuating the DELLA repressors in the root endodermis. The tissue-specific maintenance of GA signaling in the root endodermis plays distinct roles along the longitudinal root axis. While in the elongation/differentiation zone (EDZ), the endodermis-confined GA pathway by SCL3 controls primarily coordination of root cell elongation; in the meristem zone (MZ) SCL3 in conjunction with the short-root/scarecrow (SHR/SCR) pathway controls GA-modulated ground tissue maturation. Our findings highlight the regulatory network of the GRAS transcription regulators (SCL3, DELLAs, and SHR/SCR) in the root endodermis, shedding light on how GA homeostasis is achieved and how the maintenance of GA signaling controls developmental processes in roots.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.1012215108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3033297PMC
February 2011

Characterization of cp3 reveals a new bri1 allele, bri1-120, and the importance of the LRR domain of BRI1 mediating BR signaling.

BMC Plant Biol 2011 Jan 11;11. Epub 2011 Jan 11.

Division of Biological Science, Sookmyung Women's University, Seoul, Korea.

Background: Since the identification of BRI1 (BRASSINOSTEROID-INSENSITIVE1), a brassinosteroids (BRs) receptor, most of the critical roles of BR in plant development have been assessed using various bri1 mutant alleles. The characterization of individual bri1 mutants has shown that both the extracellular and cytoplasmic domains of BRI1 are important to its proper functioning. Particularly, in the extracellular domain, regions near the 70-amino acid island are known to be critical to BR binding. In comparison, the exact function of the leucine rich-repeats (LRR) region located before the 70-amino acid island domain in the extracellular cellular portion of BRI1 has not yet been described, due to a lack of specific mutant alleles.

Results: Among the mutants showing altered growth patterns compared to wild type, we further characterized cp3, which displayed defective growth and reduced BR sensitivity. We sequenced the genomic DNA spanning BRI1 in the cp3 and found that cp3 has a point mutation in the region encoding the 13th LRR of BRI1, resulting in a change from serine to phenylalanine (S399F). We renamed it bri1-120. We also showed that overexpression of the wild type BRI1 protein rescued the phenotype of bri1-120. Using a GFP-tagged bri1-120 construct, we detected the bri1-120 protein in the plasma membrane, and showed that the phenotypic defects in the rosette leaves of bri1-301, a kinase-inactive weak allele of BRI1, can be restored by the overexpression of the bri1-120 proteins in bri1-301. We also produced bri1-301 mutants that were wild type in appearance by performing a genetic cross between bri1-301 and bri1-120 plants.

Conclusions: We identified a new bri1 allele, bri1-120, whose mutation site has not yet been found or characterized. Our results indicated that the extracellular LRR regions before the 70-amino acid island domain of BRI1 are important for the appropriate cellular functioning of BRI1. Also, we confirmed that a successful interallelic complementation occurs between the extracellular domain mutant allele and the cytoplasmic kinase-inactive mutant allele of BRI1 in vivo.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/1471-2229-11-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3024917PMC
January 2011

BAK7 displays unequal genetic redundancy with BAK1 in brassinosteroid signaling and early senescence in Arabidopsis.

Mol Cells 2010 Mar 21;29(3):259-66. Epub 2010 Jan 21.

Division of Biological Science, Sookmyung Women's University, Seoul, 140-742, Korea.

BRI1-Associated kinase 1 (BAK1), a five leucine-rich-repeat containing receptor-like serine/threonine kinase, has been shown to have dual functions: mediating brassinosteroid (BR) signaling and acting in the BR-independent plant defense response. Sequence analysis has revealed that BAK1 has two homologs, BAK7 and BAK8. Because BAK8 deviates from the canonical RD kinase motif, we focused on the functional analysis of BAK7. The expression pattern and tissues in which BAK7 appeared partially overlapped with those observed for BAK1. Expression levels of BAK7 increased in the bak1 mutant. Overexpression of BAK7 rescued the bri1 mutant phenotype, indicating that BAK7 can compensate for BAK1 in BR-mediated processes, especially in the absence of BAK1. However, root and hypocotyl elongation patterns of transgenic plants overexpressing BAK1 or BAK7 appeared to be different from the patterns observed in a BRI1 overexpressor. Furthermore, the sensitivity of transgenic plants overexpressing BAK7 to brassinazole, a biosynthetic inhibitor of brassinolide (BL), did not change compared to that of wild-type plants. In addition, we generated transgenic plants expressing BAK7 RNA interference constructs and found severe growth retardation and early senescence in these lines. Taken together, these results suggest that BAK7 is a component of the BR signaling pathway, with varying degrees of genetic redundancy with BAK1, and that it affects plant growth via BL-independent pathways in vivo.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10059-010-0024-0DOI Listing
March 2010

The MYB23 gene provides a positive feedback loop for cell fate specification in the Arabidopsis root epidermis.

Plant Cell 2009 Apr 24;21(4):1080-94. Epub 2009 Apr 24.

Department of Biology, Yonsei University, 134 Sinchon-dong, Seoul 120-749, Korea.

The specification of cell fates during development requires precise regulatory mechanisms to ensure robust cell type patterns. Theoretical models of pattern formation suggest that a combination of negative and positive feedback mechanisms are necessary for efficient specification of distinct fates in a field of differentiating cells. Here, we examine the role of the R2R3-MYB transcription factor gene, AtMYB23 (MYB23), in the establishment of the root epidermal cell type pattern in Arabidopsis thaliana. MYB23 is closely related to, and is positively regulated by, the WEREWOLF (WER) MYB gene during root epidermis development. Furthermore, MYB23 is able to substitute for the function of WER and to induce its own expression when controlled by WER regulatory sequences. We also show that the MYB23 protein binds to its own promoter, suggesting a MYB23 positive feedback loop. The localization of MYB23 transcripts and MYB23-green fluorescent protein (GFP) fusion protein, as well as the effect of a chimeric MYB23-SRDX repressor construct, links MYB23 function to the developing non-hair cell type. Using mutational analyses, we find that MYB23 is necessary for precise establishment of the root epidermal pattern, particularly under conditions that compromise the cell specification process. These results suggest that MYB23 participates in a positive feedback loop to reinforce cell fate decisions and ensure robust establishment of the cell type pattern in the Arabidopsis root epidermis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1105/tpc.108.063180DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2685616PMC
April 2009

Key divisions in the early Arabidopsis embryo require POL and PLL1 phosphatases to establish the root stem cell organizer and vascular axis.

Dev Cell 2008 Jul;15(1):98-109

Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA.

Arabidopsis development proceeds from three stem cell populations located at the shoot, flower, and root meristems. The relationship between the highly related shoot and flower stem cells and the very divergent root stem cells has been unclear. We show that the related phosphatases POL and PLL1 are required for all three stem cell populations. pol pll1 mutant embryos lack key asymmetric divisions that give rise to the root stem cell organizer and the central vascular axis. Instead, these cells divide in a superficially symmetric fashion in pol pll1 embryos, leading to a loss of embryonic and postembryonic root stem cells and vascular specification. We present data that show that POL/PLL1 drive root stem cell specification by promoting expression of the WUS homolog WOX5. We propose that POL and PLL1 are required for the proper divisions of shoot, flower, and root stem cell organizers, WUS/WOX5 gene expression, and stem cell maintenance.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.devcel.2008.05.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2581419PMC
July 2008

Large-scale analysis of the GRAS gene family in Arabidopsis thaliana.

Plant Mol Biol 2008 Aug 26;67(6):659-70. Epub 2008 May 26.

Department of Bioscience and Biotechnology, Konkuk University, 1 Hwayang-dong, Gwangjin-gu, Seoul, 143-701, Korea.

GRAS proteins belong to a plant-specific transcription factor family. Currently, 33 GRAS members including a putative expressed pseudogene have been identified in the Arabidopsis genome. With a reverse genetic approach, we have constructed a "phenome-ready unimutant collection" of the GRAS genes in Arabidopsis thaliana. Of this collection, we focused on loss-of-function mutations in 23 novel GRAS members. Under standard conditions, homozygous mutants have no obvious morphological phenotypes compared with those of wild-type plants. Expression analysis of GRAS genes using quantitative real-time RT-PCR (qRT-PCR), microarray data mining, and promoter::GUS reporter fusions revealed their tissue-specific expression patterns. Our analysis of protein-protein interaction and subcellular localization of individual GRAS members indicated their roles as transcription regulators. In our yeast two-hybrid (Y2H) assay, we confirmed the protein-protein interaction between SHORT-ROOT (SHR) and SCARECROW (SCR). Furthermore, we identified a new SHR-interacting protein, SCARECROW-LIKE23 (SCL23), which is the most closely related to SCR. Our large-scale analysis provides a comprehensive evaluation on the Arabidopsis GRAS members, and also our phenome-ready unimutant collection will be a useful resource to better understand individual GRAS proteins that play diverse roles in plant growth and development.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s11103-008-9345-1DOI Listing
August 2008

Distinct and overlapping roles of single-repeat MYB genes in root epidermal patterning.

Dev Biol 2007 Nov 14;311(2):566-78. Epub 2007 Sep 14.

Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA.

Cell specification in the root epidermis of Arabidopsis generates a position-dependent pattern of root-hair cells and non-hair cells. Here we conduct a comprehensive analysis of the five members of a single-repeat R3 MYB gene family, including CAPRICE (CPC), TRIPTYCHON (TRY), ENHANCER of TRY and CPC 1, 2, and 3 (ETC1, ETC2, and ETC3), and study their role and functional relationship in root epidermal cell specification. Based on genetic and expression analyses, CPC, TRY and ETC1, but not ETC2 or ETC3, promote the hair cell fate by inhibiting non-hair specification. Further, we find that single-repeat MYB activity is required for epidermal patterning throughout root development, beginning during embryogenesis. We also identify a novel regulatory interaction whereby GLABRA2 (GL2) promotes TRY (but not CPC or ETC1) expression in the root epidermis, which generates a second lateral inhibition feedback loop. Gene fusion experiments combining CPC regulatory elements with protein-coding regions of each single-repeat MYB gene suggest that all five proteins are functionally similar, although TRY and ETC2 exhibit distinctions from CPC/ETC1/ETC3. These results provide new insight into the function of these single-repeat MYBs and suggest that divergence of their regulatory sequences is largely responsible for their distinct roles in epidermal cell patterning.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ydbio.2007.09.001DOI Listing
November 2007

Single-stranded DNA binding factor AtWHY1 modulates telomere length homeostasis in Arabidopsis.

Plant J 2007 Feb 1;49(3):442-51. Epub 2007 Jan 1.

Department of Biology and Molecular Aging Research Center, Yonsei University, Seoul 120-749, Korea.

Telomere homeostasis, a process that is essential for the maintenance of chromosome integrity, is regulated by telomerase and a collection of associated proteins. By mass spectrometry we have identified a new telomeric protein encoded by the AtWHY1 (Arabidopsis thaliana Whirly 1) gene in Arabidopsis. AtWHY1 specifically binds the single-stranded plant telomeric DNA sequences, but not double-stranded telomeric DNA. To gain insights into the function of AtWHY1 in telomere biogenesis, we have identified two Arabidopsis lines harboring T-DNA insertions in AtWHY1. These lines exhibit neither growth nor developmental defects. However, AtWHY1-deficient plants show a steady increase in the length of telomere tracts over generations. This telomere elongation is correlated with a significant increase in telomerase activity. On the contrary, transgenic plants expressing AtWHY1 show a decreased telomerase activity and shortened telomeres. The evidence presented here indicates that AtWHY1 is a new family of telomere end-binding proteins that plays a role in regulating telomere-length homeostasis in Arabidopsis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1365-313X.2006.02974.xDOI Listing
February 2007

POL and PLL1 phosphatases are CLAVATA1 signaling intermediates required for Arabidopsis shoot and floral stem cells.

Development 2006 Dec 1;133(23):4691-8. Epub 2006 Nov 1.

Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA.

The post-embryonic development of above-ground tissues in plants is dependent upon the maintenance and differentiation of stem cells at the shoot meristem. The Arabidopsis WUSCHEL (WUS) transcription factor establishes an organizing center within the shoot meristem that is essential for specification of stem-cell identity in overlying cells. The CLAVATA (CLV) signaling pathway, including the CLV1 receptor-kinase, promotes the differentiation of stem cells by limiting the WUS expression domain, yet the mechanism of CLV signaling is largely unknown. Previously, we have shown that mutations in two protein phosphatases, POLTERGEIST (POL) and PLL1, partially suppress clv mutant phenotypes. Here, we demonstrate that POL and PLL1 are integral components of the CLV1 signaling pathway. POL and PLL1 are essential for stem-cell specification, and can also block stem-cell differentiation when overexpressed. We provide extensive evidence that POL and PLL1 act downstream of CLV signaling to maintain WUS expression and that they regulate WUS at a transcriptional level. Our findings suggest that POL and PLL1 are central players in regulating the balance between stem-cell maintenance and differentiation, and are the closest known factors to WUS regulation in the shoot meristem.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1242/dev.02652DOI Listing
December 2006

Heterologous expression and molecular and cellular characterization of CaPUB1 encoding a hot pepper U-Box E3 ubiquitin ligase homolog.

Plant Physiol 2006 Dec 13;142(4):1664-82. Epub 2006 Oct 13.

Department of Biology, College of Science, Yonsei University, Seoul 120-749, Korea.

The U-box motif is a conserved domain found in the diverse isoforms of E3 ubiquitin ligase in eukaryotes. From water-stressed hot pepper (Capsicum annuum L. cv Pukang) plants, we isolated C. annuum putative U-box protein 1 (CaPUB1), which encodes a protein containing a single U-box motif in its N-terminal region. In vitro ubiquitination and site-directed mutagenesis assays revealed that CaPUB1 possessed E3 ubiquitin ligase activity and that the U-box motif was indeed essential for its enzyme activity. RNA gel-blot analysis showed that CaPUB1 mRNA was induced rapidly by a broad spectrum of abiotic stresses, including drought, high salinity, cold temperature, and mechanical wounding, but not in response to ethylene, abscisic acid, or a bacterial pathogen, suggesting its role in the early events in the abiotic-related defense response. Because transgenic work was extremely difficult in hot pepper, in this study we overexpressed CaPUB1 in Arabidopsis (Arabidopsis thaliana) to provide cellular information on the function of this gene in the development and plant responses to abiotic stresses. Transgenic Arabidopsis plants that constitutively expressed the CaPUB1 gene under the control of the cauliflower mosaic virus 35S promoter had markedly longer hypocotyls and roots and grew more rapidly than the wild type, leading to an early bolting phenotype. Microscopic analysis showed that 35S::CaPUB1 roots had increased numbers of small-sized cells, resulting in disordered, highly populated cell layers in the cortex, endodermis, and stele. In addition, CaPUB1-overexpressing plants displayed increased sensitivity to water stress and mild salinity. These results indicate that CaPUB1 is functional in Arabidopsis cells, thereby effectively altering cell and tissue growth and also the response to abiotic stresses. Comparative proteomic analysis showed that the level of RPN6 protein, a non-ATPase subunit of the 26S proteasome complex, was significantly reduced in 35SCaPUB1 seedlings as compared to the wild type. Pull-down and ubiquitination assays demonstrated that RPN6 interacted physically with CaPUB1 and was ubiquitinated in a CaPUB1-dependent manner in vitro. Although the physiological function of CaPUB1 is not yet clear, there are several possibilities for its involvement in a subset of physiological responses to counteract dehydration and high-salinity stresses in transgenic Arabidopsis seedlings.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1104/pp.106.087965DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1676043PMC
December 2006

The WEREWOLF MYB protein directly regulates CAPRICE transcription during cell fate specification in the Arabidopsis root epidermis.

Development 2005 Nov 5;132(21):4765-75. Epub 2005 Oct 5.

Department of Biology, Yonsei University, Sinchon 134, Seoul 120-749, Korea.

The Arabidopsis root epidermis is composed of two types of cells, hair cells and non-hair cells, and their fate is determined in a position-dependent manner. WEREWOLF (WER), a R2R3 MYB protein, has been shown genetically to function as a master regulator to control both of the epidermal cell fates. To directly test the proposed role of WER in this system, we examined its subcellular localization and defined its transcriptional activation properties. We show that a WER-GFP fusion protein is functional and accumulates in the nucleus of the N-position cells in the Arabidopsis root epidermis, as expected for a transcriptional regulator. We also find that a modified WER protein with a strong activation domain (WER-VP16) promotes the formation of both epidermal cell types, supporting the view that WER specifies both cell fates. In addition, we used the glucocorticoid receptor (GR) inducible system to show that CPC transcription is regulated directly by WER. Using EMSA, we found two WER-binding sites (WBSs; WBSI and WBSII) in the CPC promoter. WER-WBSI binding was confirmed in vivo using the yeast one-hybrid assay. Binding between the WER protein and both WBSs (WBSI and WBSII), and the importance of the two WBSs in CPC promoter activity were confirmed in Arabidopsis. These results provide experimental support for the proposed role of WER as an activator of gene transcription during the specification of both epidermal cell fates.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1242/dev.02055DOI Listing
November 2005

Functional diversification of MYB23 and GL1 genes in trichome morphogenesis and initiation.

Development 2005 Apr 23;132(7):1477-85. Epub 2005 Feb 23.

Botanical Institute, University of Cologne, Gyrhofstrasse 15, 50931 Cologne, Germany.

The functional diversification of duplicated genes is one of the driving forces in evolution. To understand the molecular mechanisms of gene diversification, we studied the functional relationship of the two Arabidopsis paralogous MYB-related genes GL1 and MYB23. We show that MYB23 controls trichome branching and trichome initiation at leaf edges. The latter is controlled redundantly together with GL1. We show that the two proteins are functionally equivalent during trichome initiation but not during trichome branching. RT-PCR and reporter construct analysis revealed spatial, temporal and genetic differences in transcriptional regulation of the GL1 and MYB23 genes. Presented data indicate that the diversification of GL1 and MYB23 gene functions occurred at the level of cis-regulatory sequences with respect to trichome initiation, and that, in parallel, the diversification with respect to regulation of trichome branching also involved changes in respective proteins.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1242/dev.01708DOI Listing
April 2005