Poster: Cell Walls

Abs # 1267: Efforts to identify xyloglucan glucan synthase

Presenter:	Konishi, Teruko , konishit@msu.edu
Authors	Konishi, Teruko  (A)   Wilkerson, Curtis  (A)   Keegstra, Kenneth  (A)
Affiliations:	(A): MSU-DOE Plant Research Laboratory

Xyloglucan is composed of a b(1,4)glucan backbone that is substituted by xylosyl, galactosyl, and fucosyl residues. Xyloglucan synthesis occurs in the Golgi membrane before the polysaccharide is delivered to cell walls via secretary vesicles. As part of our efforts to identify and characterize the xyloglucan glucan synthase that catalyzes the transfer of glucose from UDP-glucose to xyloglucan backbone, we prepared a Golgi-rich fraction from etiolated pea seedlings using flotation centrifugation. The Golgi enriched fraction was compared with other fractions enriched in tonoplast, ER, mitochondria, and plasma membrane. Xyloglucan fucosyltransferase and xylosyltransferase activity was the highest in the Golgi fraction, on the other hand GS-II activity was the highest in the plasma membrane fraction. Western blotting using plasma membrane, mitochondorial and chloroplast marker antibodies showed that this Golgi fraction did not contain a significant level of plasma membrane, mitochondria, or chloroplasts. Analysis of the polypeptides present in the Golgi-rich fraction using mass spectroscopy is underway. Results of these and other efforts to identify the polypeptides responsible for xyloglucan glucan synthase activity will be presented.