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Isolation and characterization of a general amino acid permease from the ectomycorrhizal fungus Amanita muscaria

Published online by Cambridge University Press:  01 November 1999

UWE NEHLS
Affiliation:
Universität Tübingen, Botanisches Institut, Physiologische Ökologie der Pflanzen, Auf der Morgenstelle 1, 72076 Tübingen, Germany
REGINE KLEBER
Affiliation:
Universität Tübingen, Botanisches Institut, Physiologische Ökologie der Pflanzen, Auf der Morgenstelle 1, 72076 Tübingen, Germany
JOACHIM WIESE
Affiliation:
Universität Tübingen, Botanisches Institut, Physiologische Ökologie der Pflanzen, Auf der Morgenstelle 1, 72076 Tübingen, Germany
RÜDIGER HAMPP
Affiliation:
Universität Tübingen, Botanisches Institut, Physiologische Ökologie der Pflanzen, Auf der Morgenstelle 1, 72076 Tübingen, Germany
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Abstract

A cDNA coding for a fungal amino acid transporter (AmAAP1) was identified from Amanita muscaria 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 N source utilized by the fungus. Nitrate was not a suitable N source for A. muscaria and resulted in maximal AmAAP1 expression. The expression of AmAAP1 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 N source.

Type
Research Article
Copyright
© Trustees of the New Phytologist 1999

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