Zhongchi Liu

Professor

Research Interests: Molecular genetics of plant reproductive development in Arabidopsis thaliana.

Lab Web Page

The research in the our lab is focused on understanding the basic mechanisms of higher plant reproductive development. Our approach involves the genetic identification, isolation and analysis of genes that regulate flower organ initiation, differentiation, and development in the model plant Arabidopsis thaliana. Several molecular genetic techniques such as map-based cloning, T-DNA/transposon knockout, yeast two-hybrid screens, and microarray analyses are being used. Ultimately, our study may provide the basis for genetic engineering of plants for agricultural and biomedical applications.

Our current research mainly concerns two aspects of flower development.
First, we are interested in understanding the regulatory mechanism for floral homeotic gene expression. Regulation of homeotic gene expression is critical for proper developmental patterns in both animals and plants. LEUNIG (LUG) and SEUSS (SEU) are two key regulators of the Arabidopsis floral homeotic gene AGAMOUS (AG), which acts to specify stamen and carpel development. Mutations in LEUNIG and SEUSS cause both ectopic and precocious AGAMOUS mRNA expression in flowers, leading to homeotic transformations of floral organ identity as well as loss of floral organs. Mutations in a third gene LARSON (LSN) is a genetic enhancer of lug. Currently, all three genes have been isolated using the map-based approach. LUG and SEU both encode putative transcriptional co-repressors (Conner and Liu, 2000; Franks et al, 2002). LSN encodes a putative DNA-binding transcription factor that might recruit the LUG/SEU co-repressors to the AG cis-regulatory elements. Further molecular analyses of these three genes and the molecular and genetic interactions among the gene products will reveal the molecular mechanism responsible for the domain-specific AG expression.

Second, we are interested in understanding how inflorescence and floral meristems are organized and what genes regulate the cell division activity and cell division orientation in inflorescence and floral meristems. Mutations in TSO1 cause defects in cell division in Arabidopsis floral meristems and cause inflorescence meristem fasciation. We have recently isolated the TSO1 gene using the map-based approach and showed that TSO1 encodes two putative DNA-binding cysteine-rich repeats and is localized to the nucleus (Song et al., 2000). Thus, TSO1 likely encodes a transcriptional regulator that regulates genes involved in cell division and meristem organization. Our lab is further characterizing the TSO1 protein, its localization, and the regulation of its expression. Additional projects involve the identification of genetic enhancers and suppressor, and identifying its target genes.

Recent Publications

C. Wang and Z. Liu (2006). Arabidopsis Ribonucleotide Reductase are Critical for Cell Cycle Progression, DNA Damage Repair, and Plant Development. Plant Cell (In press).

Z. Liu (2005) Regulatory Mechanisms for Floral Organ Identity Specification in Higher Plants. In Gene Expression and Regulation, a Current Scientific Frontiers Book (Ed. J. Ma). Higher Education Press, Beijing and Blackwell Publishing. (In press)

Bao, X., Franks, R.G., Levin, J.Z., and Liu, Z. (2004) Repression of AGAMOUS by BELLRINGR, in Floral and Inflorescence Meristems.  Plant Cell 16, 1478-1489.

Sridhar, V.V., Surendrarao, A., Gonzalez, D., Conlan, R.S., and Liu, Z. (2004) Transcriptional repression of target genes by LEUNIG and SEUSS, two interacting regulatory proteins for Arabidopsis flower development.  PNAS (in press).

Franks, R. Wang, C., Levin, J. Z., and Liu, Z. (2002) SEUSS, a member of a novel family of plant regulatory proteins, represses floral homeotic gene expression with LEUNIG. DEVELOPMENT 129: 253-263.

Franks, R.G. and Liu Z. (2001) Floral Homeotic Gene Regulation. HORTICULTURAL REVIEWS 27, 41-77.

Song J, Leung T, Ehler LK, Wang C, Liu Z. (2000) Regulation of meristem organization and cell division by TSO1, an Arabidopsis gene with cysteine-rich repeats. DEVELOPMENT 127,2207-2217.

Liu, Z., Franks, R.G. and Klink, V. P. (2000) Regulation of marginal tissue formation by LEUNIG and AINTEGUMENTA. PLANT CELL 12, 1893-1902.

Conner, J. and Liu Z. (2000) LEUNIG, a putative transcriptional co-repressor that regulates AGAMOUS expression during flower development. PNAS 97, 12902-12907.

Scovel, G., Altshuler, T., Liu, Z., and Vainstein, A. (2000) The EVERGREEN gene is essential for flower initiation in carnation. J. of Heredity 91, 487-491.

Liu, Z., Running, M. R., and Meyerowitz, E. M. (1997) TSO1 function in cell division during Arabidopsis flower development, DEVELOPMENT 124, 665-672.

Liu, Z., and Meyerowitz E. M. (1995). LEUNIG regulates AGAMOUS expression in Arabidopsis flowers. DEVELOPMENT 121, 975-991.