Journal of Biotechnology, 27 (1993) 295- 305 295 © 1993 Elsevier Science Publishers B.V. All rights reserved 0168-1656/93/$06.00 BIOTEC 00812 Phenotypic effects in Saccharomyces cerevisiae after regulated expression of/3-(1,3)-glucanase from Nicotiana plumbaginifolia Jan Dcmolder, Marianne De Backer, Walter Fiers and Roland Contreras Laboratory of Molecular Biology, State Unil'ersity, Gent, Belgium (Accepted 4 April 1992) Summary A recombinant yeast strain was constructed of which the cell wall porosity could be reversibly and conditionally modulated. This strain expresses the Nicotiana plumbaginifolia /3-(l,3)-glucanase under control of the Saccharomyces cereuisiae GALl promoter and the mating factor al prepro-sequence. The following pheno- typic effects were observed after expression of this enzyme: (a) expressed /3-(1,3)- glucanase is toxic to the producing yeast cells, which is reflected by a strong growth inhibition; as/3-(1,3)-glucanase could be detected only inside the ceils, it seems to interfere with cell wall growth from within the cell; (b) after induction of glu- canase, the recombinant strain lost up to 20% of some periplasmic enzymes, as evidenced by the release of normally periplasmic-associated invertase; (c) prelimi- nary growth in a synthetic medium containing galactose significantly increased the transformation efficiency of the recombinant yeast strain. Saccharomyces cerevisiae; Nicotiana plumbaginifolia; fl-(1,3)-Glucanase; Cell wall; Invertase; Transformation Introduction The yeast Saccharomyces cereuisiae offers many advantages as a host for the production of heterologous proteins (Das and Schultz, 1987), but its rigid cell wall Correspondence to: W. Fiers, Laboratory of Molecular Biology,State University, K.L. Ledeganckstraat 35, 9000 Gent, Belgium.