Universität Tübingen Botanisches Institut
Lehrstuhl Physiologische Ökologie der Pflanzen
Nehls U, Kleber R, Wiese J, Hampp R (1999) Isolation and characterization of an general amino acid permease from the ectomycorrhizal fungus Amanita muscaria. New Phytologist 144: 343-349. A cDNA coding for a fungal amino acid transporter (AmAAP1) was identified from A. muscaria/Populus hybr. ectomycorrhizas. The transporter gene was expressed at a basal level under all conditions investigated, but its expression was enhanced 10-fold in the absence of a nitrogen source utilized by the fungus. Nitrate was not a suitable nitrogen source for A. muscaria and resulted in maximal AmAAP1 expression. The expression of Amaap in a yeast mutant revealed its function as a high affinity amino acid transporter with a broad substrate spectrum. AmAAP1 takes up all investigated amino acids with KM values between 22 µM for histidine and up to 100 µM for proline. Gene expression and amino acid uptake data together indicate two main functions for AmAAP1, uptake of amino acids from soil for fungal nutrition, and prevention of an amino acid loss by hyphal leakage in the absence of a suitable nitrogen source.
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