Poster: Cell Walls

Abs # 1258: Visualization of polarized accumulation and disappearance of (1->4)-b-D-galactan in immature tracheary elements.

Presenter:	Naoki, Shinohara , shino@biol.s.u-tokyo.ac.jp
Authors	Naoki, Shinohara  (A)   Koichi, Kakegawa  (B)   Hiroo, Fukuda  (A)
Affiliations:	(A): Graduate School of Science, University of Tokyo (B): Forestry and Forest Products Research Institute

Recently it has been revealed that the changes in the molecules composing cell walls are not only results but also causes of plant cell differentiation. On this viewpoint, to understand xylem cell differentiation, we tried to isolate monoclonal antibodies recognizing a variety of cell wall molecules up-regulated during xylogenesis by phage display subtraction using the walls of cultured Zinnia cells undergoing xylogenesis. As a result, we succeeded in the isolation of several monoclonal antibodies recognizing tracheary elements preferentially. Of the monoclonal antibodies, one (designated as XD3) against the most dominant epitope was shown to recognize (1->4)-b-D-galactan in CDTA-soluble pectic fraction. Further studies revealed that this antibody combining site was internal five consecutive (1->4)-linked b-D-galactosyl residues. Immunolabeling of cultured Zinnia cells and seedlings with XD3 demonstrated that XD3 epitope appears predominantly on the primary wall of immature tracheary elements with a polarity, and then disappeared in mature tracheary elements. This fact indicates that the accumulation of (1->4)-b-D-galactan is precisely regulated in the cellular and subcellular localization in relation to the processes of tracheary element differentiation, and suggests that (1->4)-b-D-galactan may play an important role in xylogenesis. We would like to discuss the functions of (1->4)-b-D-galactan during xylogenesis along with some recent knowledge.