Member Institutions:

• Bowling Green State U.
• Cleveland State U.
• Kent State U.
• Medical College of Ohio
• Miami U.
• The Ohio State U.
• Ohio U.
• University of Cincinnati
• University of Toledo
• Wright State U.
• Youngstown State U.

Iris Meier Assistant Professor Department of Plant Biology The Ohio State University Room 210 Rightmire Hall 1060 Carmack Roadd Columbus, Ohio 43210 Phone (614) 292-8323 email meier.56@osu.edu	Back to Scientists

Research Interests

Organ-Specific Gene Expression in Plants

This project focuses on the question of how organ-specific and developmental patterns of transcriptional activity are established in plants. As a model system, we are studying the differential activity between leaves and fruit of the tomato RBCS gene family promoters. (RBCS genes code for the small subunit of ribulose-1, 5-bisphosphate carboxylase, the key enzyme of photosynthetic carbon dioxide fixation.) We have identified the two cis-acting elements necessary for high-level promoter activity in leaves and have shown that only one of them is necessary for high-level activity in fruit. We have isolated a transcription factor that binds to the leaf-specific element and have shown that it is a member of a novel class of myb-like DNA-binding proteins. In addition, we have characterized the developmental inactivation of RBCS promoters during fruit development, and have shown that it is caused by a loss of DNA-binding activity of the transcription factor family that binds to the cis-acting element utilized in fruit.

Structure and Function of the Plant Nuclear Matrix

Recently, it has been suggested that nuclear processes, such as replication, transcription, and splicing, are spatially organized and associated with a nuclear framework called the nuclear matrix, a structure of unknown molecular composition. It has been shown that chromatin is attached to the nuclear matrix via specific DNA fragments called matrix attachment regions (MARs). We have begun to dissect the plant nuclear matrix by isolating a DNA binding protein with specific affinity for MARs. We have shown that MAR binding filament-like protein 1 (MFP1) is associated with speckle-like structures at the nuclear periphery that are part of isolated nuclei and the nuclear matrix. A predicted N-terminal transmembrane domain is necessary for the specific targeting of MFP1 to the speckles, indicating an association with the nuclear envelope-endoplasmatic reticulum continuum. We have identified a novel protein that specifically interacts with MFP1 in yeast two-hybrid and in vitro binding assays. MFP1 associated factor 1 (MAF1) is a small, soluble, serine/threonine-rich protein that is ubiquitously expressed and has no similarity to know proteins. MAF1, like MFP1, is located at the nuclear periphery and is a component of the nuclear matrix. These data indicate that MFP1 and MAF1 are components of a nuclear substructure, previously undescribed in plants, that connects the nuclear envelope and the internal nuclear matrix, and suggest a function for MFP1 in attaching chromatin to specific sites at the nuclear periphery.

We have identified the Arabidopsis genes coding for MFP1 and MAF1 and are now initiating a reverse genetic approach to identify T-DNA tagged knock-out mutations in the two genes. These mutants will be valuable tools to understand the in vivo function of the novel proteins. We will search for phenotypic alterations on a morphological, cell-biological and molecular level. In order to follow the localization pattern of MFP1 and MAF1 during cell cycle, we are creating stably transformed cell suspension lines that will express MFP1-GFP and MAF1-GFP fusion proteins. The study of the localization of similar proteins from animals has provided some of the first molecular insights into the complex process of disintegration and re-establishment of the interphase nucleus during cell division. Any information about similar molecular events in the even less characterized plant nucleus would be extremely valuable.

Improvement of Transgene Expression in Plants

We will utilize some of the information gained from the studies of the plant nuclear matrix to develop novel approaches to improve the expression of foreign genes in transgenic plants. Experiments with animal and plant MARs have shown that these elements can increase and stabilize the expression of transgenes. MARs and their interaction with the nuclear matrix have therefore attracted much attention as potential novel tools for the genetic engineering of crop plants, where the achievement of high and consistent levels of gene expression over several generations is still a major challenge.

Selected References

RBSC Gene Regulation

• Rose, A., Meier, I., and Wienand, U. (1999). The tomato I-box binding factor LeMYBI is a member of a novel class of Myb-like proteins. Plant J. 20, 641-652.
• Baum, K., Wienand, U., and Meier, I. (1999). Reduction of G-box binding factor DNA binding activity, but not G-box binding factor abundance, causes the down regulation of RBCS2 expression during early tomato fruit development. FEBS L. 454, 95-99.
• Baum, K., Groning, B., and Meier, I. (1997). Improved ballistic transient transformation conditions for tomato fruit allow identification of organ-specific contributions of I-box and G-box to the RBCS2 promoter activity. Plant J. 12, 463-469.
• Meier, I., Groning, B., Michalowski, S. and Spiker, S. (1997). The tomato RBCS3A promoter requires integration into the chromatin for correct organ-specific regulation. FEBS L. 415, 91-95.
• Meier, I., Callan, K.L., Fleming, A.J., and Gruissem, W. (1995). Organ-specific differential regulation of a promoter subfamily for the ribulose-1,5-biphosphate carboxylase/oxygenase small subunit genes in tomato. Plant Phys. 107, 1105-1118.

Plant Nuclear Matrix

• Harder, P. A., Silverstein, R. A., and Meier, I. (2000). Conservation of matrix attachment region-binding filament-like protein 1 among higher plants. Plant Phys. 122, 225-242.
• Samaniego, R., Yu, W. , Meier, I., and Moreno Diaz de la Espina, S., Characterization and high resolution subcellular distribution of the MAR-binding protein MFP1 in A. cepa cells. Plant Journal, submitted.
• Gindullis, F., Peffer, N.J., and Meier, I. (1999) MAF1, a novel plant protein interacting with MAR-binding protein MFP1, is located at the nuclear envelope. Plant Cell 11,1755-1767.
• Gindullis, F., and Meier, I. (1999) Matrix Attachment Region Binding Protein MFP1 is Localized in Discrete Domains at the Nuclear Envelope. Plant Cell 11, 1117-1128.

(comments)

• Meier, I., Phelan, T., Gruissem, W., Spiker, S., and Schneider, D. (1996) MFP1, a novel plant filament-like protein with affinity for matrix attachment region DNA. Plant Cell 8, 2105-2115.

Ohio State Department of Biochemistry
Ohio State University homepage
Back to Scientists