Whole genome
screen for ldb mutants in Saccharomyces cerevisiae.
Isaac Corbacho,
Isabel Olivero, Luis M. Hernández
Department of Microbiology, University of Extremadura, Avda. Elvas s/n,
Badajoz, 06071, Spain (icorbacho@unex.es)
The low dye
binding phenotype (ldb) of S. cerevisiae was described as a reduction in the
affinity of the cells for the dye alcian blue as a consequence of the decrease
in the negative charge of the cell surface (1). In the conditions of the assay,
only the phosphate groups linked to the mannan oligosaccharides are responsible
for this charge (2). Thus, the ldb phenotype reflects defects in
phosphorylation of these residues. In the previous work we isolated several ldb
mutants by random mutagenesis followed by a specific selection method using
QAE-Sephadex beads (1). In the present work we checked the collection of S.
cerevisiae
deletion strains to look for mutants with an ldb phenotype and to identify the
non-essential genes whose deletion results in such a phenotype. Each of the
4894 strains in the Mat 'a' set was assayed for the alcian-blue-binding
capacity using a modification of the assay method (3). We found over two
hundreds strains that showed a detectable ldb phenotype. The selected mutants
were classified into three groups: severe, moderate, or weak reduction in the
blue colour as compared to the wild type. The results of this study will help
to identify genes involved in the phosphorylation process and will also
contribute to the functional characterization of the S. cerevisiae genome. (1) Mañas P, et
al (1997) Glycobiology 7, 487-497. (2) Ballou CE (1990) Methods Enzymol. 185, 440-470. (3) Corbacho
I, et al (2002) Abstract no. 149. Glycobiology 12, 691.