Poster: Cell Walls

Abs # 1262: Seed gums: b-mannan synthase from guar seed is a member of the cellulose synthase super gene family

Presenter:	Dhugga, Kanwarpal S, Kanwarpal.Dhugga@pioneer.com
Authors	Dhugga, Kanwarpal S (A)   Barreiro, Roberto  (A)   Whitten, Brad  (A)   Stecca, Kevin  (A)   Dolan, Maureen  (A)   Kinney, Tony  (A)   Tomes, Dwight  (A)   Nichols, Scott  (A)   Anderson, Paul  (A)
Affiliations:	(A): Pioneer Hi-Bred International, Inc., A DuPont Company

Galactomannans, referred to as gums because of their ability to form viscous solutions at low concentrations, are cell wall storage polysaccharides in the seeds of endospermic legumes. Gums have wide-ranging applications in food, cosmetics, textile, construction, and mining industries. The polysaccharide galactomannan is formed by the combined actions of Golgi-resident enzymes b-mannan synthase and a-galactosyltransferase and then exported to the cell wall by exocytosis. From an EST database constructed from developing guar seeds, we have isolated a cDNA the derived protein product of which contains the conserved motifs found in the derived protein sequences of the cellulose synthase (CesA) and CesA-like (Csl) genes from plants and related genes from other organisms. Based on the correlation of its expression with the mannan synthase activity and its occurrence only in the endosperm, where galactomannan is accumulated, we have named this gene b-mannan synthase. The particulate fractions derived from the soybean somatic embryos transformed with the guar b-mannan synthase gene contain as high levels of mannan synthase activity as the ones from guar seeds. The product formed by the enzyme derived from the transgenic soybean somatic embryos is degraded by endo-b-mannanse but not by cellulase or lichenase. Our results provide the biochemical proof for the involvement of Csl genes in b-polysaccharide formation in plants.