Dr. Alice Cheung
Professor, Biochemistry and Molecular Biology
University of Massachusetts at Amherst
acheung@biochem.umass.edu		 Dr. H-M. Wu
Research Professor, Biochemistry and Molecular Biology
University of Massachusetts at Amherst
hmwu@biochem.umass.edu
Background and Training Background and Training

Ph.D.: Yale University
Postdoctoral training: Harvard University

 Ph.D.: Yale University
Postdoctoral training: Harvard University

Signal transduction in vegetative and reproductive development in plants

Research Summary

The two current major research areas in our laboratory share the common focus of dissecting the signal transduction pathways that mediate plant cell responses to external growth and developmental stimuli. One area of our work is on understanding the signaling of directional pollen tube growth in plant sexual reproduction. Pollen tubes grow in a polar fashion to transport the sperm cells over long distances within the female tissues. The pollen tube growth process is driven by the pollen cytoplasm but is modulated by signals that originate from the female tissues to nourish and guide them to the egg cell. Our efforts are on identifying female signal molecules, their receptors on the pollen surface, and signaling molecules that regulate the pollen cellular machinery for growth.

Among the molecules we are working with are female proteins that stimulate and attract pollen tube growth, pollen surface receptor kinases, pollen cell membrane associated Rac-like G-proteins, their downstream effectors in the form of kinases, the actin regulatory protein cofilin and the actin cytoskeleton (the underlying cellular system that drives the pollen tube growth process), and another family of G-proteins known as Rabs that regulate vesicular transport activities, which is essential for pollen tube elongation. Our ultimate goal is to connect these molecules in a signaling pathway that links the female stimuli to the pollen cellular response.

The second area of our work is on understanding the signaling of plant growth regulators. Our current focus is on the signaling of auxin-mediated gene expression. Despite its importance and extensive understanding on auxin actions, little is known about how this hormone is perceived at the cell surface and transduced to the cytosol to initiate downstream signaling pathways. Our efforts thus far led to the identification of cell surface associated Rac-like G-proteins as mediators of the auxin signal to auxin-responsive genes. Our ultimate goal is to dissect the cross talks and divergence among various signaling pathways that together produce at least a subset of the highly diversed auxin response.

Representative Publications

Nibau, C., Wu, H-M., Cheung, A.  (2006) RAC/ROP GTPases: 'hubs' for signal integration and diversification in plants. Trends Plant Sci.  June, [Epub ahead of print].

Li-zhen Tao, Alice Y. Cheung, Candida Nibau, and Hen-ming Wu . (2005). RAC GTPases in Tobacco and Arabidopsis Mediate Auxin-Induced Formation of Proteolytically Active Nuclear Protein Bodies That Contain AUX/IAA Proteins. Plant Cell 17: 2369-2383.

Barend H.J. de Graaf, Alice Y. Cheung, Tatyana Andreyeva, Kathryn Levasseur, Marcia Kieliszewski, and Hen-ming Wu (2005). Rab11 GTPase-Regulated Membrane Trafficking Is Crucial for Tip-Focused Pollen Tube Growth in Tobacco. Plant Cell 17: 2564-2579.

Cheung, A.Y., and Wu, H-M. (2004). Over-expression of an Arabidopsis Formin Stimulates Supernumerary Actin Cable Formation from Pollen Tube Cell Membrane. Plant Cell 16: 257-269.

Chen, C. Y-h., Cheung, A.Y. and Wu, H-M. (2003). Actin depolymerizing factor mediates Rac/Rop GTPase regulated pollen tube growth. Plant Cell 15: 237-249.

Cheung, A.Y., Chen, C., Tao,L-z., Andreyeva, T., Twell, D. and Wu, H-M. (2003). Regulation of pollen tube growth by Rac-like GTPases. J. Exp. Bot. 54: 73-81.

Tao, L-z., Cheung, A.Y., and Wu, H-M. (2002) Plant Rac-like GTPases are activated by auxin and mediate auxin responsive gene expression. Plant Cell 9: 2745-2760.

Chen, C., Wong, E., Vidali, L., Estavillo, A., Hepler, P.K., Wu, H-M., and Cheung, A.Y. (2002) The regulation of actin organization by actin depolymerizing factor (ADF) in elongating pollen tubes. Plant Cell 9: 2175-2190.

Cheung, A.Y., Chen, C., Glaven, R., Vidali, L., Hepler, P.K., and Wu, H-M. (2002) Rab2 regulate vesicular transport between endoplasmic reticulum and Golgi bodies and is important for pollen tube elongation. Plant Cell, 14: 945-962.

Cheung, A.Y., and Wu, H-M. (2001) Pollen tube guidance--right on target. Science 293: 1441-1442.

Hepler, P.K, Vidali, L, and Cheung, A.Y. (2001) Polarized cell growth in higher plants. Annu. Rev. Cell Dev. Biol. 17: 159-187.

Cheung, A.Y. and Wu, H-M. (2000) Programmed Cell Death in Plant Reproductive Development. Plant Mol. Biol. 44: 267-281.

Wu, H-M. and Cheung, A.Y. (1998) Sexual Reproduction: sex differntiation, pollination and fertilization. Annual Plant Reviews 1: 181-222.

Cheung, A.Y., Wang, H. and Wu, H-M. (1995) A floral transmitting tissue specific glycoprotein atacks pollen tubes and stimulates their growth. Cell 82: 383-393.

Wu, H-M., Wang, H. and Cheung, A.Y. (1995) A pollen tube growth stimulatory glycoprotein is deglycosylated by pollen tubes and displays a glycosylation gradient in the flower. Cell 82: 395-403.