Hen-Ming Wu

Signal transduction pathways in the regulation of plant hormone responses and reproduction

PhD: Yale University

Postdoctoral training: Harvard University

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 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 to identify 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 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.

• Wu, H-M., Hazak, O., Cheung, AY., Yalovsky, S. RAC/ROP GTPases and Auxin Signaling. 2011. The Plant Cell.[PubMed]
• Lu, Y., Chanroj, S., Zulkifli, L., Johnson, M., Uozumi, N., Cheung, A.Y., Sze, H. Pollen Tubes Lacking a Pair of K+ Transporters Fail to Target Ovules in Arabidopsis. 2011. The Plant Cell, 23: 81-93. [PubMed]
• Nibau C., Di Stilio V.S., Wu, H-M., Cheung A.Y. Arabidopsis and Tobacco superman regulate hormone signaling and mediate cell proliferation and differentiation. 2010. J. Exp. Bot. 62, 949-961. [PubMed]
• Duan Q., Kita D., Li C., Cheung A.Y. and Wu H-M. FERONIA receptor-like kinase regulates RHO GTPase signaling of root hair development. Proc. Nat'l Acad. Sci. USA 2010, 107: 17821-17826. [PubMed]
• Cheung, A.Y, Boavida,L., Aggarwal, M., Wu, H-M, Feijo J. The Pollen Tube Journey in the Pistil and Imaging the In Vivo process by two-Photon Microscopy. J. Exp. Bot. 2010, 61:1907-1915. [PubMed]
• Cheung AY, Q Duan, S Santos Costad, BHJ de Graaf, VS Di Stilio, J Feijod, and H-M Wu. The Dynamic Pollen Tube Cytoskeleton: Live Ce l Studies Using Actin-Binding and Microtubule-Binding Reporter Proteins. 2008. Molecular Plant. [PubMed]
• Nibau, C., Wu, H-M., Cheung, A. (2006) RAC/ROP GTPases: 'hubs' for signal integration and diversification in plants. Trends Plant Sci. June. [PubMed]