Poster: Cell Walls

Abs # 1245: Localization of fucosylated and non-fucosylated xyloglucans during biosynthesis and mobilization of storage cell walls in seeds of Hymenaea courbaril

Presenter:	Braga, Marcia Regina , bragamr@canalvip.com.br
Authors	Braga, Marcia Regina  (A)   Tiné, Marco Aurélio S (A)   Freshour, Glenn  (B)   Amaral, Lourdes V (A)   Buckeridge, Marcos S (A)   Hahn, Michael G (B)
Affiliations:	(A): Instituto de Botanica , Sao Paulo, SP, Brazil (B): The University of Georgia, Athens, GA, USA

Many plants accumulate storage xyloglucans(XGs) in their seeds during maturation and then mobilize these storage polysaccharide reserves during germination. The structures of such storage XGs usually differ from those of primary cell walls. During structural studies of the storage XG synthesized by the tropical legume, Hymenaea courbaril, we detected the presence of small amounts of fucosylated primary wall XG. We have now used the monoclonal antibody, CCRC-M1, which specifically recognizes a fucose-containing epitope found in many XGs, to localize fucosylated XG in H. courbaril seeds during maturation and germination. In mature seeds, fucosylated XG is present in two narrow wall domains, one inner layer near the plasma membrane, and one outer layer near the middle lammela. The larger wall domain located between these two domains appears to contain the non-fucosylated storage XG. During seed maturation, the domains are laid down sequencially; first a layer of fucosylated XG, followed by the layer containing storage XGs, and finally a second layer of fucosylated XG. During seed germination, only the central wall domain containing the storage XGs is degraded. These results suggest that fucosylation of XG is carefully regulated during storage wall biosynthesis and that storage mobilization must be finely controlled to selectively mobilize only the appropriate polysaccharide(s) within storage tissues. [Supported by US Dept of Energy and FAPESP-Brazil]