Chapter 13 Biochemical Analysis of Polygalacturonases Produced by Ericoid Mycorrhizal Fungi s. PEROTTO" v. (OMETTI" J. D. (OlSSON" I. PERUGINI" and P. BONFANTE*' INTRODUCTION Ericoid mycorrhizal fungi produce a broad set of hydrolytic enzymes capable of degrading various complex substrates (see Leake and Read 1991). Enzymes involved in the degradation of plant wall polysaccharides are part of an arsenal that increases survival of ericoid fungi in the soil matrix, but they are also involved in the localised degradation of the host cell wall during mycorrhizal infection. Only few papers have investigated the production of cell wall hydrolytic enzymes by ecto- and endo- mycorrhizal fungi (Garcia-Romera et al. 1991; Peretto et al. 1993; Cairney and Burke 1994), whereas extensive studies have been performed on both pathogenic bacteria and necrotrophic fungi (see Walton 1994; Sutherland 1995). Among the battery of enzymes involved in the decon- struction of the plant cell wall, pectinolytic enzymes constitute major pathogenicity factors and lead to plant tissue maceration (Alghisi and Favaron 1995). The set of enzymes necessary to degrade pectin, a polymer of galactur- onic acid methylated to a varying degree in the cell wall, includes pectin methylesterases, pectin lyases and polygalacturonases. The last two classes include enzymes that can either randomly cleave the pectin poly- mer, or act exclusively on the terminal sugars. Enzyme forms cleaving randomly (endo fashion) are the most effective in loosening the wall structure and the middle lamella. We have focused here on the identification, purification, and character- ization of two secreted polygalacturonases produced by an ericoid myce- lium. Among endomycorrhizal fungi, ericoid fungi provide a convenient experimental system to approach purification and study of these enzymes, as they are easily grown on mineral media supplemented with complex polysaccharides as the sole carbon source. lUniversita di Torino, Dipartimento di Biologia Vegetale and CSMT-CNR, Viale P.A. Mattioli 25, 10125 Torino, Italy * Corresponding author: P. Bonfante; Phone: 39-11-6502927; Fax: 39-11-6707459; e-mail: bonfante@csmt.to.cnr.it A. Varma (ed.), Mycorrhiza Manual © Springer-Verlag Berlin Heidelberg 1998