Adhesion of conidia and germlings of the plant pathogenic fungus Bipolaris sorokiniana to solid surfaces

Abstract

Soon after coming in contact with its host, the plant pathogenic fungus Bipolaris sorokiniana produces an extracellular material that appears to be important for adhering conidia and germlings to the host surface. To further understand this step of the infection, the adhesion of B. sorokiniana to artificial solid surfaces was examined. On a hydrophobic (polystyrene) surface adhesion occurred in two stages, the first by conidia and the second by germlings. Conidial adhesion occurred shortly (0-1 h) after hydration. The conidia were easily detached by increasing the shear force and including detergents in the washing buffer. As conidia were hydrophobic, these observations indicate that conidial adhesion to polystyrene is due to weak, hydrophobic interaction. The second stage of adhesion was accompanied by conidial germination and occurred 1-2 h after hydration and contact with the surface. Concomitant with the delayed adhesion, the fungus produced an extracellular matrix (ECM). The adhesion of germlings was firm and surfaceunspecific since they adhered to both hydrophobic and hydrophilic (glass) surfaces. Except for strong bases, hydrochloric acid and broad-specificity proteases (including Pronase E), none of the hydrolytic enzymes, electrolyte solutions, ionic and hydrophobic detergents and organic solvents removed germlings from the solid surfaces. The adhesion of germlings incubated in the presence of the protein glycosylation inhibitor tunicamycin or the lectins Con A (Concanavalin A) and GNA (from Galanthus nivalis) was significantly reduced, which indicates the involvement of surface glycoproteins in this process. The surface proteins of germlings were labelled with "#&I, extracted and analysed by two-dimensional gel electrophoresis. This revealed about 40 surface proteins over a wide pH range (4-10) with molecular masses between 10 and 100 kDa.

Extracellular matrix of Magnaporthe oryzae may have a role in host adhesion during fungal penetration and is digested by matrix metalloproteinases

“…The molecular components of ECM also have remained unclear in spite of reporting many studies on ECM (Apoga and Jansson 2000;Apoga et al 2001;Cole et al 1996;Doss 1999;Hutchison et al 2002;Pain et al 1996). This study provided more information on the ECM components of M. oryzae on both cellulose membranes and host leaves via two immunological techniques with antibodies for four different animal cell adhesion factors (CAFs) and for animal integrin a3.…”

The Role of the Extracellular Matrix (ECM) in Phytopathogenic Fungi: A Potential Target for Disease Control

“…In Bipolaris sorokiniana and Venturia inaequalis, conidium adhesion to the hydrophobic surface is weak, due to the hydrophobic interaction (Apoga et al, 2001;Schumacher et al, 2008). In Nectria haematococca, 90 kDa glycoprotein containing mannose sugar was associated with the development of the adhesiveness of macroconidia (Kwon & Epstein, 1997).…”

“…In this situation, pronase E and all types of collagenase and gelatinase caused a significant detachment of germlings (K. Inoue et al, 2011). Pronase E is known to be a mucoproteindegrading enzyme, and had the ability of moderate removal effect in B. sorokiniana (Apoga et al, 2001). In particular, collagenase type S-1 and gelatinase B seemed to be the most effective ECM target-specific enzymes, and had a minimal effect on appressorium formation, even at the early stages of application.…”

The spore coat of the bean anthracnose fungus Colletotrichum lindemuthianum is required for adhesion, appressorium development and pathogenicity

“…Botrytis cinerea, Discula umbrinella, Phyllosticta ampelicida and Bipolaris sorokiniana, in which there is an initial phase of adhesion mediated by hydrophobic interactions before the secretion of an adhesive ECM [7,9,29,43,44]. This mechanism of adhesion is clearly different to that of some other fungal pathogens in which pre-formed adhesive is secreted ARTICLE IN PRESS on contact with a surface e.g.…”