Cerato-platanin shows expansin-like activity on cellulosic materials

Abstract

Cerato-platanin (CP) is a non-catalytic protein with a double =β-barrel fold located in the cell wall of the phytopathogenic fungus Ceratocystis platani. CP is released during growth and induces defence-related responses in plants. CP is also the first member of the "cerato-platanin family" (CPF) (Pfam PF07249). In the CPF, the molecular mechanism of action on plants and above all the biological role in fungal life are little-known aspects. However, an expansin-like function has recently been suggested concerning CP. Expansin-like proteins have the ability to act non-hydrolytically on cellulose. In the present work, the expansin-like activity of CP and Pop1, a CP family member, was investigated. Like expansins, CP and Pop1 were able to weaken filter paper in a concentration-dependent manner and without the production of reducing sugars. A metal-dependent polysaccharide monooxygenase-like activity was excluded. The optimum of activity was pH5.0, 38°C. CP was also able to cause fragmentation of the crystalline cellulose Avicel and the breakage and defibration of cotton fibres. However, the interaction did not involve a stable bond with the substrates and CP did not significantly enhance the hydrolytic activity of cellulase. On the other hand, CP and Pop1 bound quickly to chitin. We consider CP as a novel one-domain expansin-like protein. We propose a structural role for CP in the fungal cell wall due to the ability to bind chitin, and hypothesize a functional role in the interaction of the fungus with the plant for the weakening activity shown on cellulose.

Specific Hypersensitive Response–Associated Recognition of New Apoplastic Effectors from Cladosporium fulvum in Wild Tomato

“…Cerato-platanins are predominantly secreted, although several also localize to the cell wall of ascospores, conidia, and hyphae (Boddi et al 2004;Pazzagli et al 1999). Cerato-platanins bind chitin but not cellulose (Baccelli et al 2014;de O. Barsottini et al 2013;Frischmann et al 2013), yet several members have expansin-like loosening activity on cellulosic materials in vitro (Baccelli et al 2014;de O. Barsottini et al 2013). It has thus been hypothesized that cerato-platanins function as expansins required for fungal cellwall remodeling and enlargement, possibly by disrupting noncovalent interactions between b-glucan or chitin molecules (de Oliveira et al 2011).…”

Cerato-platanins: a fungal protein family with intriguing properties and application potential

“…CPPs are structurally rather related to expansins, which are proteins associated with carbohydrate-binding and loosening of the cellulose scaffolds in plant cell walls (de Oliveira et al 2011). However, biochemical analysis of the properties of CPPs showed—somewhat surprisingly—that they have actually both carbohydrate-binding/carbohydrate-loosening properties, similar to expansins (Baccelli et al 2014), but also the ability to self-assemble and change the polarity of surfaces and solutions, which are properties that are reminiscent of hydrophobins (Frischmann et al 2013). …”

Cerato-Platanin Induces Resistance in Arabidopsis Leaves through Stomatal Perception, Overexpression of Salicylic Acid- and Ethylene-Signalling Genes and Camalexin Biosynthesis

“…Concerning the primary role of these proteins, recent results suggest that they are mono-domain expansin-like proteins localised in the cell wall and involved in the hyphal growth and development [8]–[11]. Moreover, a role in the fungus-plant interaction has also been reported [12].…”