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Appl. Environ. Microbiol. doi:10.1128/AEM.02765-07
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Imaging Long Distance -Aminoisobutyric Acid Translocation Dynamics During Resource Capture by Serpula lacrymans

Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK

^* To whom correspondence should be addressed. Email: sarah.watkinson{at}plants.ox.ac.uk.

	Abstract

AIB (-aminoisobutyric acid) is a nonmetabolised amino acid analogue of alanine, which at low (µM) concentrations acts as a tracer for amino acid movements. At high concentrations (mM) it competitively inhibits membrane transport and metabolism of protein amino acids, and acts as a systemic translocated inhibitor of mycelial extension in fungi. AIB can control mycelial spread of the basidiomycete Serpula lacrymans, the cause of brown rot of wood in buildings. However, it is not known how effectively the inhibitor is distributed throughout the mycelium. Realistically heterogeneous microcosms, in which the fungus grew across nutritionally-inert sand to colonise discrete wood resources, were used to investigate patterns of inhibition and translocation following local application of AIB. At 0.1M concentration, locally-applied AIB caused immediate arrest of extension throughout the whole mycelium, maintained for a six-week experimental period.

The dynamics of translocation of sub-toxic amounts of [1-¹⁴C--aminoisobutyric acid] (¹⁴C-AIB), were mapped by Photon Counting Scintillation Imaging (PCSI) in conjunction with destructive harvest, to establish the velocity, direction and rate of translocation, and the extent of ¹⁴C-AIB reallocation accompanying the invasion of fresh wood. Locally-applied ¹⁴C-AIB was distributed throughout complex mycelial networks within 2h of application, becoming localized in growing margins by 12h. Encounter with a fresh wood resource triggered a widespread response, causing withdrawal of ¹⁴C-AIB from throughout the network accompanied by accumulation in the newly-colonised wood and associated mycelium. The results are discussed in the context of nutrient dynamics in wood decomposer fungi, and the mechanism of the amino acid reallocation response.