Peptide uptake in the ectomycorrhizal fungus Hebeloma cylindrosporum: characterization of two di- and tripeptide transporters (HcPTR2A and B).

• Constraints on plant growth imposed by low availability of nitrogen are a characteristic feature of ecosystems dominated by ectomycorrhizal plants. Ectomycorrhizal fungi play a key role in the N nutrition of plants, allowing their host plants to access decomposition products of dead plant and animal materials. Ectomycorrhizal plants are thus able to compensate for the low availability of inorganic N in forest ecosystems. • The capacity to take up peptides, as well as the transport mechanisms involved, were analysed in the ectomycorrhizal fungus Hebeloma cylindrosporum. • The present study demonstrated that H. cylindrosporum mycelium was able to take up di- and tripeptides and use them as sole N source. Two peptide transporters (HcPTR2A and B) were isolated by yeast functional complementation using an H. cylindrosporum cDNA library, and were shown to mediate dipeptide uptake. • Uptake capacities and expression regulation of both genes were analysed, indicating that HcPTR2A was involved in the high-efficiency peptide uptake under conditions of limited N availability, whereas HcPTR2B was expressed constitutively. [ABSTRACT FROM AUTHOR]