Poster: Cell Walls

Abs # 1272: The functions of b-galactosidases in the plant cell wall

Presenter:	Pérez-Almeida, Iris B, ibperez@purdue.edu
Authors	Pérez-Almeida, Iris B (A)   Carpita, Nicholas C (A)
Affiliations:	(A): Purdue University, Dept. of Botany and Plant Pathology

The Arabidopsis genome contains 18 sequences that putatively encode for b-galactosidase proteins (At-bgal). All At-bgal peptide sequences include the putative active-site consensus motif G-G-P-[LIVM]2-X2-Q-X-E-N-E-[FY]. Of these, 12 are predicted to be secreted to the cell wall, where they are presumably involved in modification of cell-wall polymers. Knowledge about the function of the b-galactosidases against specific polysaccharides is sparse. The major targets for action by b-galactosidases are fucogalacto-xyloglucans, pectic (1-4)-b-galactans, type I arabinogalactans, and the type II (1-3) (1-6)-b-galactosyl residues of AGPs. We are using a novel in planta protein homologous expression system to produce specific members of the Arabidopsis cell-wall b-galactosidase gene family and establish their enzyme activity against artificial a- and b-glycosides, such as p-nitrophenyl-b-D-galactoside as well as characterize their activities against several native polysaccharide substrates. Through the use of promoter-marker fusions, we are documenting the temporal and spatial expression pattern of these genes. In a complementary approach, the identification of homozygous mutants from the collection of T-DNA insertional mutants generated by the Salk Institute Genomic Analysis Laboratory (http://signal.salk.edu/cgi-bin/tdnaexpress) will enable the examination of the function of these enzymes in a broader biological context. Supported by the NSF Plant Genome Research Program