Patricia C Zambryski

Professor
Ph.D.  Molecular Biology    University of Colorado, 1974
B.S.   Genetics    McGill University, 1969

281A Koshland
Berkeley, California 94720
zambrysk@nature.berkeley.edu
office: 510-643-9203   lab: 510-643-9204   fax:  510-642-4995

     Recent publications      People

Our laboratory performs research in two distinct areas. In microbial biology we study the molecular mechanisms utilized by Agrobacterium that leads to the genetic transformation of plant cells. In plant biology we study how plant cells communicate with each other via unique plant specific intercellular structures called plasmodesmata.

Agrobacterium mediated DNA transfer to plant cells. A specific DNA segment, T-DNA, is transferred from a large bacterial plasmid across bacterial and plant cell membranes and ultimately integrates stably into the plant nuclear genome. We study Agrobacterium-specific proteins and their respective molecular mechanisms responsible for producing a DNA-protein complex capable of plant cell transformation. Current research is aimed at defining the topology of the bacterial export channel. This channel is the paradigm for type IV secretion systems (T4SS). T4SS are utilized by plant and animal pathogens to transport DNA and as well as protein toxins that manipulate their respective host cells to cause disease.



A model of how the 12 proteins (VirB1-B11, VirD4) essential for T4SS form a membrane-spanning channel is presented in Figure 1. The T-DNA is transferred as a single stranded intermediate called the T-strand. In addition, 4 proteins, VirD2, VirE2, VirE3, and VirF are exported by the T4SS to plant cells. This model was predicted by genetic and bioinformatics approaches. Figure 2 displays one approach to determine the bacterial location of the T4SS. Fusions between green fluorescent protein and T4SS substrate proteins such as VirF locate to the poles of the bacterial cell. Current efforts aim to confirm the topology, location and function of the T4SS.

Plasmodesmata structure and function. Plasmodesmata (PD) are channels that span the plant cell wall, linking the cytoplasm between adjacent cells. These channels are highly dynamic, and impact on all levels of plant growth from general responses to the environment to defense against pathogens. Figure 3 shows that generic PD consist of membranes and spaces. The outer limits of PD are defined by the plasma membrane which is contiguous between two cells. The axial center of PD (called the desmotubule) is defined by endoplasmic reticulum between adjacent cells. The space between the desmotubule and the plasma membrane is called the cytoplasmic sleeve, and represents the contiguous cytoplasm between adjacent cells.

Our laboratory is interested in defining the factors that regulate PD structure and function that are localized at the entrance and along the length of the channel. We have developed a genetic screen using embryo defective lines of Arabidopsis and have several candidate mutants that define genes that affect PD aperture during mid embryogenesis.

We are also studying the innate capacity of plant embryos to traffic proteins cell to cell via PD. Different sized derivatives of green fluorescent protein (GFP) were initially expressed in meristematic regions of the embryo. Subsequent movement of encoded proteins from their site of synthesis then reveals PD aperture. 1X sized GFP moves throughout all regions of the embryo. 2X sized GFP cannot move to the embryonic leaves, and 3X sized GFP cannot move to the tip of the root. Thus, different regions of the embryo contain PD with different apertures that likely regulate the movement of critical regulators of development (see Figure 4).

Recent publications on Agrobacterium mediated DNA transfer to plant cells.

Middleton, R., Sjolander, K., Krishnamurthy, Foley, J., and Zambryski, P. Predicted hexameric structure of the Agrobacterium VirB4 C-terminus suggests VirB4 acts as a docking site during type IV secretion. Proc. Natl. Acad. Sci. USA 102, 1685-1690 (2005)

Zupan, J.R., Ward, D.V., and Zambryski, P. The genome of Agrobacterium tumefaciens: Four parts to decode for interkingdom DNA transfer. Nature Biotech. 20, 129-131 (2002)

Ward, D.V., Draper, O., Zupan, J.R. and Zambryski, P. Protein linkage mapping of the Agrobacterium tumefaciens vir-encoded type IV secretion system reveals protein subassemblies. Proc. Natl. Acad. Sci. USA 99, 11493-11500 (2002)

Ward, D.V., Zupan, J.R., and Zambryski, P. Agrobacterium VirE2 gets the VIP1 treatment in plant nuclear import. Trends Plant Sci, 7, 1-3 (2002)

Ward, D.V., and Zambryski, P.C. The six functions of Agrobacterium VirE2. Proc. Natl. Acad. Sci. 98, 385-386 (2001)

Zupan, J., Muth, T.R., Draper, O., and Zambryski, P. The transfer of DNA from Agrobacterium tumefaciens into plants: a feast of fundamental insights. Plant J. 23, 11-28 (2000)

Llosa, M., Zupan, J., Baron, C., and Zambryski, P. The N- and C- terminal portions of the Agrobacterium VirB1 protein independently enhance tumorigenesis. J. Bacteriol., 182, 3437-3445 (2000)



Recent publications on Plasmodesmata structure and function.

Kim, I., Kobayashi, K, Cho, E., and Zambryski, P. Subdomains for transport via plasmodesmata corresponding to the apical-basal axis are established during Arabidopsis embryogenesis. Proc. Natl. Acad. Sci. USA 102, 11945-11950 (2005)

Kim, I., Cho, E., Crawford, K, Hempel, F.D., and Zambryski, P. Cell-to-cell movement of GFP during Arabidopsis embryogenesis and early seedling development. Proc. Natl. Acad. Sci. USA 102, 2227-2231(2005)

Zambryski, P. Cell-to-cell transport of proteins and fluorescent tracers via plasmodesmata during plant development. J. Cell Biol. 162, 165-168 (2004)

Wu, X., Dinneny, J.R., Crawford, K., Rhee, Y., Citovsky, V., Zambryski, P.C., and Weigel, D. Modes of intercellular transcription factor movement in the Arabidopsis apex. Development, 130, 3735-3745 (2003)

Kim, I., Hempel, F.D., Sha, K., Pfluger, J., and Zambryski, P. Identification of a developmental transition in plasmodesmata function during embryogenesis in Arabidopsis thaliana. Development, 129, 1261-1272 (2002)

Gisel, A., Hempel, F., Barella, S., and Zambryski, P. Leaf to shoot apex movement of symplastic tracer is restricted coincident with flowering in Arabidopsis. Proc. Natl. Acad. Sci. USA, 99, 1713-1717 (2002)

Crawford, K., and Zambryski, P. Non-targeted and targeted protein movement through plasmodesmata in leaves in different developmental and physiological states. Plant Physiol., 125, 1802-1812 (2001)

Zambryski, P., and Crawford, K.M. Plasmodesmata: Gatekeepers for cell-to-cell transport of developmental signals in plants. Annu. Rev. Cell Dev. Biol. 16, 393-421 (2000)

Crawford, K., and Zambryski, P. Subcellular localization determines the availability of non-targeted proteins to plasmodesmatal transport. Curr. Biol. 10, 1032-1040 (2000)