Ph.D.:	Hebrew University of Jerusalem, 1992
Phone:	(Office) + 972 -3 - 640 7641/2 (Telefax) + 972 -3 - 640 9380
E-mail:	niro@tauex.tau.ac.il
Room#:	406 Britannia Bldg.

Research Interests

Regulation of Development by Polycomb Proteins.

The Development of multicellular organisms is controlled largely by transcription regulatory genes which are temporally and spatially regulated to ensure proper differentiation of cells, tissues and organs. Polycomb group proteins (PcG) operate as part of complexes, maintaining the repressed transcriptional state of genes. These complexes affect the degree of localized chromatin condensation, and suppress homeotic gene transcription. In Arabidopsis, the PcG complex contains three main protein families: WD, single zinc finger and SET domain proteins. Mutation in each of the Arabidopsis PcG proteins triggered improper developmental programs of the gametophyte and/or the sporophyte. For example, when the function of the WD40 FIE protein, homolog of ESC form Drosophila, is compromised mutant plants develops endosperm without fertilization (Ohad et al. 1996; Ohad et al. 1999). Mutations in polycomb genes de-repress the expression of homeobox transcription factor genes resulting in subsequent homeotic transformations (Katz et al. 2004). Our working hypothesis is that in Arabidopsis at list three different PcG complexes may assemble, each at a particular developmental stage to control proper development.

Specific topics:

Elucidating the structure and function of the different PcG complexes, using genetic molecular and biochemical tools. This project is in collaboration with Prof. R. Fischer (http://plantbio.berkeley.edu/faculty_pages/fischer.html)
Study the imprinting of the endosperm specific Polycomb group gene MEDEA (MEA) by an auto regulatory mechanism of Polycomb group complexes. This project is performed in collaboration with Dr. F. Berger (http://www.tll.org.sg ).
Examine PcG functional evolution; using Physcomitrella patens as a model system representing early terrestrial plants. This project is part of collaboration with Prof. R. Reski (http://www.cosmoss.org), and in conjunction with the European Physcomitrella Net (www.physcomitrella.eu).
Elucidating root response to mechanical stimulation, in collaboration with Prof. A. Eshel (http://www.tau.ac.il/lifesci/plant_aciences/usr/amram/)

Selected Publications

• Mosquna, A. Katz, E. L. Decker, S. A Rensing, R. Reski and N. Ohad .Regulation of stem cell maintenance by the Polycomb protein FIE has been conserved during land plant evolution. Development Vol. 136(14) 2009 (pp. 2433-2444).

• P. Jullien, A. Mosquna, M. Ingouff, T. Sakata, N. Ohad and F. Berger. Retinoblastoma and its binding partner MSI1 Control imprinting in Arabidopsis . PLoS Biol. Vol. 8(6), 2008 (pp. 1693-1705).

• N. Ohad , K. Shichrur and S. Yalovsky. The analysis of protein-protein interactions in plants by Bimolecular Fluorescence Complementation (BiFC). Plant Physiol , Vol. 145, 2007 (pp. 1090–1099) .

• N. Ohad. Parental conflict overcome. Nature Vol. 447, 2007 (pp. 275-276).

• K. Aviezer-Hagai, J. Skovorodnikova, M. Galigniana, O. Farchi-Pisanty, E. Maayan, S. Bocovza, Y. Efrat, P. Doring, N. Ohad and A. Breiman. Arabidopsis immunophilins ROF1 (AtFKBP62) and ROF2 (AtFKBP65) exhibit tissue specificity, are heat-stress induced, and bind HSP9. Plant Mol. Biol Vol. 63(2), 2007 (pp. 237-55).

• A. Yano, Y. Kodama, A. Koike, T. Shinya, H. Kim, M. Matsumoto, S. Ogita, Y. Wada, N. Ohad and H. Sano. Interaction between Methyl CpG-Binding protein and Ran GTPase during Cell Division in Tobacco Cultured Cells. Annals of Botany Vol. 98, 2006 (pp. 1179- 1187).

• P. Jullien, T. Kinoshita, N. Ohad , and F. Berger. Maintenance of DNA methylation during the Arabidopsis life cycle is essential for parental imprinting. Plant Cell . Vol. 18, 2006 (pp. 1360-1372).

• P. Jullien, A. Katz, M. Oliva, N. Ohad and F. Berger. Polycomb group complexes self-regulate imprinting of the Polycomb group gene MEDEA in Arabidopsis. Current Biology Vol. 16, 2006, (pp. 486–492).

• A. Zemach, Y. Li, M. Oliva, A. Mosquna, H. Ben-Meir, Y. Avivi, N. Ohad , and G. Grafi. Different Domains Control the Localization and Mobility of LIKE HETEROCHROMATIN PROTEIN1 in Arabidopsis Nuclei. Plant Cell . Vol. 18, 2006, (pp. 133-145).

• A. Eshel, A. Katz, Y. Waisel, N. Ohad . Roots of tomato respond to mechanical stimulation by induction of touch genes. Plant Biosystems Vol. 139/2, 2005, (pp. 209-213) .

• K. Bracha-Drori, K. Shichrur, A. Katz, M. Oliva, R. Angelovici, S. Yalovsky and N. Ohad . Detection of protein-protein interactions in plants by YFP fluorescence complementation. The Plant Journal Vol. 40, 2004 (pp. 419- 4 27 ).

• A. Mosquna, A. Katz, S. Shochat, G. Grafi and N. Ohad. Interaction of FIE a polycomb protein with pRb: possible mechanism regulating endosperm development. Mol. Genet Genomics . Vol. 271, 2004 (pp. 651-657).

• A. Katz, M. Oliva, A. Mosquna, O. Hakim, and. N. Ohad . FIE and CURLY LEAF polycomb proteins interact in the regulation of homeobox gene expression during sporophyte development. The Plant Journal Vol. 37, 2004 (pp. 707-719).

• T-F. Hsieh, O. Hakim, N. Ohad and R. Fischer. From flour to flower: how polycomb group proteins influence multiple aspects of plant development. Trends Plant Sci. Vol. 9, 2003 (pp. 439-445).

• Yadegari, R., Kinoshita, K., Lotan, O., Cohen, G., Katz, A., Choi, Y., Katz, A., Nakashima, K, Harada,J.J., Goldberg, R.B., Fischer, R.L., and Ohad, N. (2000) Mutations in the FIE and MEA Genes That Encode Interacting Polycomb Proteins Cause Parent-of-Origin Effects on Seed Development by Distinct Mechanisms . The Plant Cell 12: 2367-2382.

• Ohad, N ., Yadegari, R., Kinoshita, T., Margossian, L., Hannon, M., Michaeli, D., Harada, J.J., Goldberg, R.B., Fischer, R.L. (1999) Mutations in FIE, a WD Polycomb Group Gene, Allow Endosperm Development Without Fertilization. The Plant Cell 11:407-415.

• Kiyosue, T., Ohad, N ., Yadegari, R., Hannon, M., Dinneny, J., Wells, D., Katz, A., Margossian, L., Harada, J.J., Goldberg, R.B., Fischer, R.L. (1999) Control of fertilization-independent endosperm development by the MEDEA polycomb gene in Arabidopsis. Proc. Natl. Acad. Sci. USA 96:4186-4191.

• Ohad, N. , Margossian, L., Hsu, Y.-C., Williams, C., Repetti, P., Fischer, R.L. (1996) A Mutation that Allows Endosperm Development Without Fertilization. Proc. Natl. Acad. Sci. USA 93:5319-5324.

Courses

1. First year mandatory course for 300 Students, "Introduction to Plant Biology"
2. Third year students laboratory class "Advanced laboratory in Plant Molecular Biology"
3. Advanced class for M.Sc. students. :"Molecular mechanisms controlling plant Development"

Education and professional career

1982-1985 Hebrew University of Jerusalem, B. Sc. Biology & Earth Sciences
1985-1987 Hebrew University of Jerusalem, M. Sc. Molecular Biology & Genetics
1987-1992 Hebrew University of Jerusalem, Ph. D. Molecular Biology & Genetics
1992-1997 University of California at Berkeley, Department of Plant Biology, Postdoctoral fellow.
1998-Present Member of the Department of Plant Sciences, Tel-Aviv University