Biotin-Binding Proteins in the Defense of Mushrooms against Predators and Parasites

Abstract

Tamavidins are fungal biotin-binding proteins (BBPs) displaying antifungal activity against phytopathogens. Here we show high toxicity of tamavidins toward nematodes, insects, and amoebae. As these organisms represent important phyla of fungal predators and parasites, we propose that BBPs are part of the chemical defense system of fungi.

Toxicity of Potential Fungal Defense Proteins towards the Fungivorous Nematodes Aphelenchus avenae and Bursaphelenchus okinawaensis

“…The sequestration of an essential vitamin by a proteolysis-resistant, high-affinity binding protein seems to be a powerful way to prevent predation. Our results confirm those of previous studies, in which biotin-binding proteins have been implicated in fungal resistance and employed as effective repellents in plants for several different predators and parasites ( 33 , 47 ). The lack of toxicity of tamavidin 1 expression for the producing organisms E. coli ( 33 ) and A. gossypii (this study) suggests that there is no freely available biotin in the cytoplasm of these organisms.…”

“…2B and C ). Toxicity of this protein is thought to depend on the sequestration of free biotin, thus reducing the bioavailability for the predator of this essential nutrient ( 29 , 33 , 47 ). The sequestration of an essential vitamin by a proteolysis-resistant, high-affinity binding protein seems to be a powerful way to prevent predation.…”

“…They are characterized by a very strong noncovalent binding to biotin and have been implicated as antimicrobial host defense factors that create a “biotin-free zone” ( 29 – 32 ). The cytoplasmic biotin-binding proteins of the basidiomycete Pleurotus cornucopiae , tamavidin 1 (Tam1) and 2 (Tam2), were shown to be toxic to C. elegans , an Acanthamoeba sp., and Drosophila melanogaster ( 33 ).…”

“…The contribution of individual proteins to fungal resistance toward ecologically relevant fungivores has hardly been investigated in the past. To date, most studies determined the toxicity of individual heterologously expressed proteins to model organisms ( 18 , 28 , 33 – 35 ). In contrast, for this study, we assessed the potentials of different protein classes as resistance molecules against two fungivorous nematode species.…”

Induced Fungal Resistance to Insect Grazing: Reciprocal Fitness Consequences and Fungal Gene Expression in the Drosophila-Aspergillus Model System

“…they harm or repel fungivores [1–5]. Despite increasing evidence of such sophisticated defences against fungivores, it is still unclear whether fungi primarily invest energy and resources in defensive traits regardless of the presences of fungivores ( constitutive resistance ) or whether they have evolved, in analogy to herbivore-plant interactions [6], the ability to show phenotypic variation in response to attack ( inducible resistance ).…”