Poster: Cell walls

Abs # 621: Molecular characterization of a predicted glycosyltransferase from Lycopersicon esculentum

Presenter:	Link, Bruce M, Bruce.Link@uconn.edu
Authors	Link, Bruce M (A)   Li, Xuemei  (A)   Verma, Rajeev  (A)   Reiter, Wolf-Dieter  (A)
Affiliations:	(A): University of Connecticut

The cell wall is a critical component of all higher plants and is composed of pectins, hemicelluloses, and cellulose. For most dicot and non-graminaceous monocot plants, the principal hemicellulose is xyloglucan (XyG), which has a β-(1->4)-D-glucan backbone similar to cellulose. In most XyGs, three consecutive glucose residues are substituted by D-xylose in an α-(1->6)-linkage leaving a fourth glucosyl residue unbranched. This structure is called XXXG in standard nomenclature. Recently we demonstrated that the MUR3 gene product of Arabidopsis thaliana attaches D-galactose to the last xylose residue within the XXXG repeat unit leading to the formation of XXLG building blocks. Solanaceous plants have a XyG structure that is different from other dicots primarily because of the absence of the third xylose residue, and the substitution of L-arabinose for D-galactose during modification of the XyG core structure. In an effort to identify a XyG-specific arabinosyltransferase we transformed mur3 Arabidopsis plants with the MUR3 homologue from tomato (LeGT1), and are currently analyzing XyGs from the cell walls of the transgenic plants to determine the function of this gene. In a complementary approach we are using protein expression systems to produce full length and truncated versions of LeGT1 for in vitro glycosyltransferase assays with mur3 xyloglucan as the substrate.