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Iris Meier

Greg ArmstrongDr. Iris Meier
Professor
Ph.D., University of Duesseldorf, Germany, 1987.
M.S. Technical University, Darmstadt, Germany, 1984.

Contact:
The Ohio State University
Plant Cellular and Molecular Biology
244 Rightmire Hall
1060 Carmack Road
Columbus, OH 43210

Office: 614.292.8323
Laboratory: 614.292.5623
Fax: 614.292.5379
e-Mail: Meier.56@osu.edu

Download CV

Meier Lab Web Site

Focus:

Positioning and function of the plant Ran cycle; Arabidopsis nuclear pore and nuclear envelope proteins; Structure and function of long coiled-coil proteins.

Research Interests:

Anchoring of Ran signal transduction in plants:

An emerging theme in signal transduction research is how the different pathways of signaling events are both separated and coordinated in a temporal and spatial manner in the living cell. It is becoming increasingly evident that discrete spatial positioning within the cell is a major aspect of this coordination. However, how this positioning is achieved for individual signaling molecules remains a fundamental question of molecular cell biology.

The small GTPase Ran is involved in nucleocytoplasmic transport, spindle formation, nuclear envelope (NE) formation, and cell-cycle control. In vertebrates, these functions are controlled by a three-dimensional gradient of Ran-GTP to Ran-GDP, established by the spatial separation of Ran GTPase-activating protein (RanGAP) and the Ran guanine nucleotide exchange factor RCC1. While this spatial separation is established by the NE during interphase, it is orchestrated during mitosis by association of RCC1 with the chromosomes and RanGAP with the spindle and kinetochores. SUMOylation of vertebrate RanGAP1 is required for NE, spindle, and centromere association.
Figure 1
Figure 1.
Model of the Ran cycle at the animal nuclear pore.

Arabidopsis RanGAP1 (AtRanGAP1) lacks the SUMOylated C-terminal domain of vertebrate RanGAP, but contains a plant-specific N-terminal domain (WPP domain), which is necessary and sufficient for its targeting to the NE in interphase. Human and plant RanGAP-targeting domains are kingdom specific. AtRanGAP1 has a mitotic trafficking pattern uniquely different from that of vertebrate RanGAP, which includes targeting to the outward-growing rim of the cell plate. The WPP domain is necessary and sufficient for this targeting. Point mutations in conserved residues of the WPP domain also abolish targeting to the nuclear rim and the cell plate, suggesting that the same mechanism is involved in both targeting events. These results indicate that plant and animal RanGAPs undergo different migration patterns during cell division, which require their kingdom-specific targeting domains.

Recently, we have identified a novel family of plant-specific, nuclear pore-associated proteins in Arabidopsis, which are necessary and sufficient to anchor RanGAP to the Arabidopsis nuclear envelope at the root meristem. Interestingly, they are not required for RanGAP anchoring in differentiated cells and during cytokinesis, implying additional anchors in plants. These findings suggest a separate evolution of RanGAP targeting mechanisms in different kingdom.

Figure 2
Figure 2.
GFP localization of Arabidopsis RanGAP (left) and MAF1 (right) in tobacco BY-2 cells.

Key reading:

  • Zhao, Q*, Brkljacic, J*, and Meier, I (2008) Two distinct, interacting classes of nuclear envelope-associated coiled-coil proteins are required for the tissue-specific nuclear envelope targeting of Arabidopsis RanGAP. Plant Cell 20, 1639-1651 (* joint first authors).

  • Xu X, Meulia T and Meier I. (2007). Anchorage of Plant RanGAP to the Nuclear Envelope Involves Novel Nuclear-Pore-Associated Proteins. Curr Biol. 17: 1157-1163.

  • Jeong SY, Rose A, Joseph J, Dasso M, Meier, I. (2005). Plant-specific mitotic targeting of RanGAP requires a functional WPP domain. Plant J. 42:270-82.

  • Rose, A. and Meier, I. (2001). A domain unique to plant RanGAP is responsible for its targeting to the plant nuclear rim. Proc. Natl. Acad. Sci. U.S.A. 98, 15377-15382.

 

Nuclear Pore and Nuclear Envelope Protein Function:

Currently, we are specifically investigating a multifunctional inner nuclear pore protein known under different names in different organisms. Vertebrate Tpr, Drosophila Megator (Mtor) and yeast Mlp1/Mlp2 are long coiled-coil proteins associated with the inner basket filaments of the nuclear pore. They are involved in mRNA export, telomere organization, spindle pole assembly, and unspliced RNA retention. We have identified a single gene in Arabidopsis thaliana, NUCLEAR PORE ANCHOR (NUA), which encodes a protein of 237 kD with similarity to Tpr, Mtor and Mlp1/Mlp2. Immunolocalization in Arabidopsis root cells demonstrates that NUA is located at the inner surface of the nuclear envelope in interphase and in the vicinity of the spindle in prometaphase. Four T-DNA insertion lines were characterized in detail. They comprise an allelic series of increasing severity for several correlating phenotypes, such as early flowering under short days and long days, increased abundance of SUMO conjugates, altered expression of several flowering regulators, and nuclear accumulation of poly(A)+ RNA. Nua mutants phenocopy mutants of EARLY IN SHORT DAYS 4 (ESD4), an Arabidopsis SUMO protease concentrated at the nuclear periphery. Nua esd4 double mutants resemble nua and esd4 single mutants, suggesting that the two proteins act in the same pathway or complex, supported by yeast two-hybrid interaction. Together, our data indicate that NUA is a component of nuclear pore-associated steps of sumoylation and mRNA export in plants, and that defects in these processes affect the signaling events of flowering time regulation and additional developmental processes. 

In contrast with vertebrates, the protein composition of the NE and the function of NE proteins are barely understood in plants. MFP1 attachment factor 1 (MAF1) is a plant-specific NE-associated protein first identified in tomato (Lycopersicon esculentum). We have shown that two Arabidopsis thaliana MAF1 homologs, WPP1 and WPP2, are associated with the NE specifically in undifferentiated cells of the root tip. Reentry into cell cycle after callus induction from differentiated root segments reprograms their NE association. Based on green fluorescent protein fusions and immunogold labeling data, the proteins are associated with the outer NE and the nuclear pores in interphase cells and with the immature cell plate during cytokinesis. RNA interference-based suppression of the Arabidopsis WPP family causes shorter primary roots, a reduced number of lateral roots, and reduced mitotic activity of the root meristem. Together, these data suggest the existence of regulated NE targeting in plants and identify a class of plant-specific NE proteins involved in mitotic activity.

Key reading: 

  • Xu X, Rose A, Muthuswamy S, Jeong S-Y, Venkatakrishnan S,  Zhao Q, and Meier I. (2007). NUCLEAR PORE ANCHOR, the Arabidopsis Homolog of Tpr/Mlp1/Mlp2/Megator, Is Involved in mRNA Export and SUMO Homeostasis and Affects Diverse Aspects of Plant Development. Plant Cell 19: 1537-1548. 

  • Patel S, Rose A, Meulia T, Dixit R, Cyr RJ, Meier, I. (2004). Arabidopsis WPP-Domain Proteins Are Developmentally Associated with the Nuclear Envelope and Promote Cell Division. Plant Cell 16:3260-3273.

Genomic analysis of long coiled-coil proteins:

We have begun a comprehensive study of coiled-coil proteins present in organisms with fully sequenced genomes. Coiled-coil domains are characterized by a heptad repeat pattern in which residues in the first and fourth position are hydrophobic, and residues in the fifth and seventh position are predominantly charged or polar. In animals and yeast, the motif has been identified in a variety of proteins associated with the cytoskeleton, the Golgi, centromers, centrosomes, the nuclear matrix, and chromatin. Despite the different cellular functions of proteins containing long coiled-coil domains, the general theme is the association of functional proteins (e.g signal transduction components) with the solid-state components of the cell.

In contrast to animals and yeast, few long coiled-coil proteins have been functionally investigated in plants. The heptad repeat pattern can be used by computational methods to predict coiled-coil domains in amino acid sequences. In collaboration with the Ohio Supercomputer Center (OSC), we have established the algorithm Multicoil on a 146-processor Silicon Graphics cluster, have analyzed the 25,828 annotated Arabidopsis open reading frames and have established a database of structural, functional, and localization information for Arabidospis coiled-coil proteins (www.coiled-coil.org).
Figure 3
Figure 3.
Molecular modeling of an Arabidopsis coiled-coil protein onto the coiled-coil domain of Tropomyosin.

Following up on this work, we have performed a large-scale computational analysis comparing and grouping all long coiled-coil proteins from 22 genomes, to determine kingdom-specificity of coiled-coil protein families. Proteins with extended coiled-coil domains (more than 250 amino acids) are largely absent from bacterial genomes, but present in archaea and eukaryotes. The structural maintenance of chromosomes proteins and their relatives are the only long coiled-coil protein family clearly conserved throughout all kingdoms, indicating their ancient nature. Motor proteins, membrane tethering and vesicle transport proteins are the dominant eukaryote-specific long coiled-coil proteins, suggesting that coiled-coil proteins have gained functions in the increasingly complex processes of subcellular infrastructure maintenance and trafficking control of the eukaryotic cell.

Key reading:

  • Rose A, Schraegle SJ, Stahlberg EA and Meier, I (2005). Coiled-coil protein composition of 22 proteomes - differences and common themes in subcellular infrastructure and traffic control. BMC Evol. Biol 5:66.

  • Rose, A., Manikantan, S., Schraegle, S., Maloy, M., Stahlberg, E. and Meier, I. (2004). Genome-wide Identification of Arabidopsis Coiled-coil Proteins and Establishment of the ARABI-COIL Database. Plant Physiol. 134:927-939.

Teaching:

Lab Members:

Graduate Students

Postdoctoral Fellows

Lab Alumni:

Publications (past 5 years):

Research

  1. Zhao, Q*, Brkljacic, J*, and Meier, I (2008) Two distinct, interacting classes of nuclear envelope-associated coiled-coil proteins are required for the tissue-specific nuclear envelope targeting of Arabidopsis RanGAP. Plant Cell 20, 1639-1651. (* joint first authors).

  2. Meier I, Xu X, Brkljacic J, Zhao Q, and Wang HJ  (2008) Going Green: Plants’ Alternative Way to Position the Ran Gradient. J. Microscopy 231, 225-233.

  3. Merchant S.S. et al. (Meier, I. - author 48 out of 117 authors). (2007) The Chlamydomonas genome reveals the evolution of key animal and plant functions. Science 318, 245-250.

  4. Xu X, Meulia T and Meier I. (2007). Anchorage of Plant RanGAP to the Nuclear Envelope Involves Novel Nuclear-Pore-Associated Proteins. Curr Biol. 17: 1157-1163.

  5. Xu X, Rose A, Muthuswamy S, Jeong S-Y, Venkatakrishnan S,  Zhao Q, and Meier I. (2007). NUCLEAR PORE ANCHOR, the Arabidopsis Homolog of Tpr/Mlp1/Mlp2/Megator, Is Involved in mRNA Export and SUMO Homeostasis and Affects Diverse Aspects of Plant Development. Plant Cell 19: 1537-1548.

  6. Zhao Q, Leung S, Corbett AH, Meier, I. (2006) Identification and characterization of the Arabidopsis orthologs of nuclear transport factor 2, the nuclear import factor of ran. Plant Physiol. 140:869-78.

  7. Samaniego R, Jeong SY, Meier, I, de la Espina SM. (2006) Dual location of MAR-binding, filament-like protein 1 in Arabidopsis, tobacco, and tomato. Planta 223:1201-6.

  8. Samaniego R, Jeong SY, de la Torre C, Meier, I, Moreno Diaz de la Espina S. (2006). CK2 phosphorylation weakens 90 kDa MFP1 association to the nuclear matrix in Allium cepa. J Exp Bot. 57:113-24.

  9. Rose A, Schraegle SJ, Stahlberg EA and Meier, I (2005). Coiled-coil protein composition of 22 proteomes - differences and common themes in subcellular infrastructure and traffic control. BMC Evol. Biol 5:66; doi:10.1186/1471-2148-5-66

  10. Patel, S., Brkljacic, J., Gindullis, F., Rose, A. and Meier, I. (2005) The plant nuclear envelope protein MAF1 has an additional location at the Golgi and binds to a novel Golgi-associated coiled-coil protein. Planta 222:1028-40.

  11. Jeong SY, Rose A, Joseph J, Dasso M, Meier, I. (2005). Plant-specific mitotic targeting of RanGAP requires a functional WPP domain. Plant J. 42:270-82.

  12. Patel S, Rose A, Meulia T, Dixit R, Cyr RJ, Meier, I. (2004). Arabidopsis WPP-Domain Proteins Are Developmentally Associated with the Nuclear Envelope and Promote Cell Division. Plant Cell 16:3260-3273. [PDF]

  13. Jeong, S.Y., Peffer, N, and Meier, I. (2004). Phosphorylation by Protein Kinase CK II Modulates the DNA-Binding Activity of a Chloroplast Nucleoid-Associated Protein. Planta 219:298-302. [PDF]

  14. Rose, A., Manikantan, S., Schraegle, S., Maloy, M., Stahlberg, E. and Meier, I. (2004). Genome-wide Identification of Arabidopsis Coiled-coil Proteins and Establishment of the ARABI-COIL Database. Plant Physiol. 134:927-939. [PDF]

Reviews and book chapters:

  1. Xu XM and Meier I. (2008). The Nuclear Pore Comes to the Fore. Trends in Plant Sci. 13, 1-50.

  2. Meier, I. (2007). Composition of the Plant Nuclear Envelope: Theme and variations. J Exp Bot. 58, 27-34.

  3. Calikowski TT, Meier, I. (2006). Isolation of nuclear proteins. In: Arabidopsis Protocols. Eds: Julio Salinas and Jose J. Sanchez-Serrano. Methods Mol Biol. 323:393-402. Humana press, Totowa, New Jersey.

  4. Meier, I. (2005). Subnuclear Trafficking and the Nuclear Matrix. In: Nuclear Import and Export in Plants and Animals. Eds. Tzfira, T., and Citovsky, V., Landes Bioscience, Austin, Texas.

  5. Meier, I. (2005). Global plant biotechnology and the need for an educated public. Minerva Biotecnologica 17, 21-31

  6. Meier, I. (2005) Nucleocytoplasmic trafficking in plant cells. Int. Rev. Cytol. 244, 95-135

  7. Rose A, Patel S, Meier, I. (2004). Plant nuclear envelope proteins. Symp Soc Exp Biol. 56:69-88.

  8. Rose, A., and Meier, I. (2004). Scaffolds, levers, rods, and springs: diverse cellular functions of long coiled-coil proteins. Cell. Mol. Life Sci. 61:1996-2009.

  9. Rose A, Patel S, Meier I. (2004). The plant nuclear envelope. Planta 218:327-36

Edited Books:

  1. Functional Organization of the Plant Nucleus. Plant Cell Monographs. Meier, Iris (Ed.); Springer, Heidelberg, 2009.

 

 

 

Current Research Funding:

Revised: 6-oct-08

PCMB NEWS

A MDA (Muscular Dystrophy Association) sponsored post-doctoral position is available in the Department of Plant Cellular and Molecular Biology/Molecular and Cellular Biochemistry at Ohio State University in Columbus, Ohio, starting on August 1st 2008.

The researcher will work in the field of mitochondria biogenesis and study the assembly process of c-type cytochromes, a class of hemoproteins with covalent attachment of the heme co-factor to a CXXCH motif on the apocytochrome. Cytochromes c are versatile molecules that function in electron transfer reactions but also in signaling the death pathways. Their assembly process is not understood and in humans mutations in the only known cytochrome c assembly factor cause a neurodevelopmental disease with cardiomyopathic manifestations.

The future hire will use yeast as an experimental system and focus on 1) elucidating the biochemical activity of Cyc2p a novel mitochondrial flavoprotein that controls a yet-to-be-defined redox step in the heme attachment reaction to apocytochrome and 2) identifying additional mammalian cytochrome-c assembly factors. Because we suspect a role of Cyc2p in thiol-based chemistry, the researcher will also take part in on-going genetic experiments to 3) further dissect the pathway(s) that operate in intermembrane thiol-based redox chemistry. Thiol-based chemistry in the mitochondrial intermembrane space is a recent and novel development in the field since the discovery of catalysts that promote disulfide bond formation. Molecular genetics and biochemical approaches will be used to answer the scientific questions we are interested in. Interested candidates should send a cover letter, resume, and a list of three referees to Dr. Patrice Hamel at hamel.16@osu.edu. Use Post-doctoral Position in the subject line. For additional information, see also Dr. Hamel's Web Site.

Erich Grotewold Receives Grant from US-Israeli Binational Agricultural Research and Development Fund

We are pleased to announce that Erich Grotewold has been awarded another new grant. This is a 3-year award from the US-Israeli Binational Agricultural Research and Development Fund. It is in the amount of $137,000 and is entitled "Regulation of tomato fruit development by interacting MYB proteins."

Erich Grotewold Receives DOE And NSF Grants

Erich Grotewold has been awarded 3-year grant in the amount o $449,390 from the DOE, entitled "Engineering phenolic metabolism in the grasses using transcription factors."

Erich has also been awarded a second, major grant from NSF (Plant Genome). It is a 3-year award in the amount of $2,479,632 entitled "The Grass Regulome Initiative: Integrating control of gene expression and agronomic traits across the grasses.

David Somers' Lab Published In Nature

David Somers’ group has published an article in Nature (Sept. 20) entitled, “ZEITLUPE is a circadian photoreceptor stabilized by GIGANTEA in blue light.” Woe-Yeon Kim and Sumire Fujiwara are co-first authors.

Erich Grotewold Awarded USDA Grant

Erich Grotewold has been awarded a grant from the USDA in the amount of $201,025 for a two-year study entitled, “Transposons as gene control elements.”

Rebecca Lamb Receives OPBC Award

Rebecca Lamb has received an award of $57,567 over two years from the OPBC for a study entitled, ”Two Arabidopsis WWE-PARP proteins involved in abiotic stress response and development.”

Plant Biotechnology In-Floor Seminar Series Schedule

Follow the link below for a schedule of informal 30-40 min seminars that will take place at noon on Fridays in room 189 of Rightmire Hall.
Schedule [pdf]

News Archive

Read past information and news articles.