Carbohydrate Polymers 86 (2011) 1646–1650 Contents lists available at ScienceDirect Carbohydrate Polymers j ourna l ho me pag e: www.elsevier.com/locate/carbpol A novel polysaccharide secreted by pal/rim mutants of the phytopathogen fungus Ustilago maydis Citlali Fonseca-García a , Mercedes G. López b , Elva T. Aréchiga-Carvajal c , José Ruiz-Herrera a,∗ a Departamento de Ingeniería Genética, Unidad Irapuato Gto, Centro de Investigación y de Estudios Avanzados del IPN, CP 36821 Irapuato Guanajuato, Mexico b Departamento de Biotecnología y Bioquímica, Unidad Irapuato Gto, Centro de Investigación y de Estudios Avanzados del IPN, CP 36821 Irapuato Guanajuato, Mexico c Facultad de Ciencias Biológicas, Universidad de Nuevo León, Monterrey, NL, Mexico a r t i c l e i n f o Article history: Received 28 February 2011 Received in revised form 29 June 2011 Accepted 30 June 2011 Available online 7 July 2011 Keywords: Polysaccharide (1 →3)--d-Glucan Ustilago maydis Pal/Rim pathway a b s t r a c t Linear (1 → 3)--d-glucans and side-chain-branched -d-glucans are major constituents of capsular materials, with roles in bacterial aggregation, virulence and carbohydrate storage; whereas branched (1 → 3),(1 → 6)--d-glucans constitute the most abundant components in the cell walls of fungi. In the present manuscript we describe the chemical characterization of a linear -d-glucan secreted by mutants of the Basidiomycota biotrophic fungus Ustilago maydis affected in the Pal/Rim pathway involved in pH responses, that in contrast is not made by the wild type strain, at least in measurable amounts. The polysaccharide was obtained from the culture medium of a rim13::Cbx mutant of the fungus by ethanol precipitation, and analyzed using FT-IR spectroscopy, NMR spectroscopy in solid and liquid states, HPAEC- PAD chromatography, thin layer chromatography, enzymatic digestion and immunodetection. Our data revealed that, according to its characteristics, the polysaccharide is a (1 → 3)--d-glucan, and that the mutants used represent a relevant resource of this polysaccharide with wide applications. © 2011 Elsevier Ltd. All rights reserved. 1. Introduction -d-glucans made of glucose units bound by different link- ages, with variable physical properties, and widely distinct roles, constitute an important source of polysaccharides in fungi. Accord- ingly, they may constitute intracellular reserve material, important structural component of the cell wall, or mucilaginous material secreted to the medium; but as a rule they are made of branched (1 → 3),(1 → 6)--d-glucans (for a review see Ruiz-Herrera, 1991), although the extent of the side chain substitutions can vary considerably (Schmid et al., 2001). For example, many of these polysaccharides including schizophyllan (also named sizofiran) from Schizophyllum commune, and scleroglucan from Sclerotium glucanicum both have a (1 → 3)--D-linked backbone, with an average of one (1 → 6)--D-glucose substitution every three back- bone residues (Johnson et al., 1963; Kikumoto & Kimura, 1971); whereas on the other hand the cell wall of fungi and yeasts contains highly branched (1 → 3),(1 → 6)--d-glucans (Fleet & Manners, 1976; Manners, Mason, & Patterson, 1973). Many other fungal -d-glucans have been described, but their detailed struc- ture and branching frequencies are still mostly unclear (Seviour, Stasinopoulos, & Auer, 1992). Interestingly the only unbranched (1 → 3)--d-glucan was described to be synthesized under artifi- ∗ Corresponding author. Tel.: +52 462 62 39652; fax: +52 462 6245849. E-mail address: jruiz@ira.cinvestav.mx (J. Ruiz-Herrera). cial conditions by Saccharomyces cerevisiae protoplasts (Kopecka & Kreger, 1986), or cell-free extracts (Larriba, Morales, & Ruiz- Herrera, 1981). As occurs with other polysaccharides, (1 → 3)--d-glucans present a wide range of potential applications in various industries and notably in agronomy, cosmetics, therapeutic aspects, foods and others. In the food industry, beside classical applications of polysaccharides as thickening agents, (1 → 3)--d-glucans have an increasing interest in the areas of edible films, thus numer- ous patented applications have been directed to obtain capsules or “tablet-like” ingredients which can deliver their content further on after ingestion or during cooking, as food for domestic animals, and as low calorie supplement (Laroche & Michaud, 2007). From a biological point of view, it has been recognized for a long time that (1 → 3)--d-glucans belong to the group of biological response modifiers (BRM), that do not have direct cytotoxic activities, but are able to boost the natural defense mechanisms of the host (Williams et al., 1991). Their benefits to health include markedly stimulating the immune system from attack by pathogenic microbes and from harmful effects of environmental toxins and carcinogens (Brown & Gordon, 2005; Vetvicka & Yvin, 2004). In animal experiments, -d-glucans have shown different activities against sarcomas, mammary cancer, some chemically induced cancers, adenocarci- noma, colon cancer and some leukemias (Chihara, Hamuro, Maeda, Arai, & Fukuoka, 1987; Jeannin et al., 1988). It has also been reported that they may reduce blood glucose concentrations after eating, possibly by delaying stomach emptying so that dietary glucose is 0144-8617/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbpol.2011.06.077