The life cycle of an organism is dictated by an internal clock. In plants, the developmental clock can be manipulated by environmental factors. Thus plants undergo various phases of growth from juvenile to adult, and from vegetative to reproductive, that are manifested by distinct morphological features. To study the mechanism of the developmental clock, we characterized a set of Arabidopsis mutants called embryonic flower that flowered upon germination, bypassing the vegetative development. The phenotypes of the mutants support the hypothesis that maturation/aging in plants is controlled by the gradual loss of a function, whose rate of decrease can be influenced by the environmental factors acting via the late-flowering and the early-flowering genes. The EMBRYONIC FLOWER genes play a central role in this function that controls plant maturation.
The primary shoot and root organs are initiated during embryogenesis. To study embryogenesis, we use somatic embryos developed from tissue culture cells of carrots. Seed-specific genes have been cloned to study developmental and hormonal regulation of gene expression during seed development.
After germination, plants produce new organs from shoot and root apices. Spatial differentiation of the proliferative cells from the differentiating cells within an organ may be accomplished by the regulation of the cell division cycle. To investigate the mechanism of organ initiation and differentiation, we are characterizing a set of Arabidopsis root mutants impaired in root pattern formation, in root meristematic activity, and in the maintenance of differentiated state in mature root cells. For example, the monopteros root mutants are impaired in cell division pattern in the embryonic, not lateral root ontogeny; the root meristemless mutants are impaired in activating cell division at the root tip after, but not during embryonic and lateral root ontogeny; and the short tap and starchy root mutants are impaired in suppressing cell proliferation in the primary, but not lateral roots. The characterization of these mutants will elucidate the mechanism underlying spatial differentiation of cell division and cell differentiation during root organogenesis.
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Mutations in EMBRYONIC FLOWER genes cause Arabidopsis embryos to flower right after germination, producing miniature flowering plants, shown here on a penny for scale. (Linda Castle, artist)
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Recent publications
Cheng JC, Lertpiriyapong K, Wang S, and Z. R. Sung. 2000. The role of the Arabidopsis ELD1 gene in cell development and photomorphogenesis in darkness. Plant Physiol. 123:509-520.
Vernous T, Wilson RC, Seeley KA, Reichheld J, Muroy S, Brown S, Maughan S, Cobbett C, Van Montagu M, Inze D, May M, Z. R. Sung. The Rootmeristeless1/Cadmium sensitive2 gene defines a gltathione-dependent pathway involved in initiation and maintenance of cell division during postembryonic root development. The Plant Cell 12:97-109.
Yoshida N, Yanai Y, Chen L, Kato Y, Hiratsuka J, Miwa T, Sung ZR, Takahashi S.Embryonic flower2, a novel polycomb group protein homolog, mediates shoot development and flowering in Arabidopsis. Plant Cell. 13: 2471-2481.
Aubert D, Chen L, Moon Y, Martin D, Castle LA, Tang C, and Sung ZR. 2001. EMF1, a novel protein involved in the control of shoot architecture and flowering in Arabidopsis. The Plant Cell 13: 1865-1875.
Avsian-Kretchmer O, Cheng J, Chen L, Motezuma E, and Sung ZR. 2002. Indole acetic acid distribution coincides with vascular differentiation pattern during Arabidopsis leaf ontogeny. Plant Physiol. 2002. 130: 199-209.
Sung ZR, Chen L, Moon YH, Lertpiriyapong K, 2003. Mechanism of floral repression in Arabidopsis. Current Opinions in Plant Biology. in press.
Moon YH, Chen L, Pan R, Chang HS, Zhu T, Maffeo DM, and Sung ZR. 2003. EMF genes maintain vegetative development by repressing the flower program in Arabidopsis. The Plant Cell. 15: 681-693.
Lertpiriyapong K. and Z. R. Sung. 2003. The elongation defective1 mutant of
Arabidopsis is impaired in the gene encoding a serine-rich secreted protein. Plant
Molecular Biology. 53:581-595.
Chanvivattana, Y. A. Bishop, D. Schubert, C. Stock, Y.-H. Moon, Z. R. Sung
and J. Goodrich. 2004. Interaction of Polycomb-group proteins controlling
flowering in Arabidopsis. Development 131:5263-5276.
Calonje M., and Z. R. Sung. 2006. Complexity beneath the silence. Current Opinion in Plant Biology. 9: 530-537.
Calonje, M., R. Sanchez, L. Chen, Z. R. Sung. 2008. EMBRYONIC FLOWER1 participates in Polycomb Group-mediated AGAMOUS gene Silencing in Arabidopsis. Plant Cell 20:277-291.
Sanchez-Pulido, L., Devos, D., Sung, Z. R. and M. Calonje. 2008. RAWUL: A New Ubiquitin-like Domain in PRC1 Ring finger proteins that unveils the existence of putative plant PRC1 orthologs. BMC Genomics. 9:308-319.
Sanchez R., M. Calonje, Y. Kim, and Z. R. Sung. Stage-specific effect of emf1 on Arabidopsis development. Molecular Plant (in press). |
