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

Abstract

The spores (conidia) of the bean anthracnose fungal pathogen, Colletotrichum lindemuthianum, adhere to the aerial parts of plants to initiate the infection process. In previous studies we have shown that the Colletotrichum spores are surrounded by a fibrillar spore coat, comprising several major glycoproteins. Previous evidence showed that a monoclonal antibody (UB20) that recognised these glycoproteins was able to inhibit adhesion of spores to a hydrophobic surface. In this paper we have further studied the role of the spore coat in adhesion, germination and fungal development by studying the effects of UB20 and protease treatment of spores. The latter treatment has previously been shown to remove the spore coat. Spores germinate on glass, polystyrene and water agar, however, appressoria only develop on glass or polystyrene, showing a requirement for a hard surface. Removal of the spore coat with protease inhibits adhesion at 30 min, before the secretion of ECM glycoproteins. Protease treatment also inhibits the development of appressoria and reduces pathogenicity on leaves. Incubation of spores with the MAb UB20 inhibits adhesion at 30 min, but does not affect appressorium formation or pathogenicity. The results suggest that an intact spore coat has two functions; it is required for adhesion to a hydrophobic surface and for the detection of a hard surface necessary for appressorium formation. We suggest that contact with a hard surface, rather than adhesion, is the key event leading to appressorium formation. r

H2O2 plays an important role in the lifestyle of Colletotrichum gloeosporioides during interaction with cowpea [Vigna unguiculata (L.) Walp.]

“…These structures can vary greatly in morphology and the complete cycle varies in duration from less than 24 h to over 3 d (Perfect et al 2001). The spherical vesicles shown in this study are also found in P. vulgaris against Colletotrichum lindemuthianum (Rawlings et al 2007) and in cucumber against C. orbiculare (Asakura et al 2012). However, this structure differs morphologically from that of Colletotrichum destructivum, which does not develop spherically, but rather as swollen multilobed vesicles during infection (Shen et al 2001).…”

“…In contrast to SA treatment, although there was long germ-tube formation in GO/G-treated leaves, appressorial formation was accompanied by melanization ( Fig 4D). As previously described (Perfect et al1999;Wharton & Di eguez-Uribeondo 2004;Rawlings et al 2007) during this process, the conidium adheres to the cuticle and germinates, producing a germ-tube that differentiates into melanized appressoria. After melanization, a narrow penetration hypha emerges at the base of the appressorium and subsequently penetrates directly into the cuticle, forming biotrophic vesicles and primary hyphae (M€ unch et al 2008).…”

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

“…However, UB20 treatment did not affect appressorium formation and pathogenicity. The conidium adhesion deficiency was compensated after germination, suggesting that germ tube adhesion was involved in appressorium formation and pathogenicity (Rawlings et al, 2007).…”

Transmission of anthracnose (Colletotrichum lindemuthianum) in dry bean (Phaseolus vulgaris L.) with artificial and natural inoculum in a wet and dry canopy

“…Canopy moisture also played an important role in disease transmission, which agrees with previous work (Schwartz et al 2005). Canopy moisture increased the disease severity, particularly with the natural inoculum source, which may be due to an interaction with the mucilaginous sheath surrounding the spores (Rawlings et al 2007). The results of the current study indicate that a natural source of inoculum tended to fall between the two concentrations of artificial inoculum in relation to disease severity, although no attempt was made to determine the spore concentration of the natural inoculum source.…”

“…Each spore and germ tube is surrounded by a mucilaginous sheath, thought to aid in the attachment of the appressoria to the plants surface (Young and Kauss 1984;Nicholson et al 1992;Perfect et al 1999). Removal of the sheath inhibits adhesion of the spores to plants (Rawlings et al 2007). This sheath is composed of proline-rich glycoproteins that contain germination inhibitors (Young and Kauss 1984;Nicholson et al 1992).…”