Trehalose Phosphorylase Activity and Carbohydrate Levels During Axenic Fruiting in Three Agaricus bisporus Strains |
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Authors: | Wim JB Wannet Emile MJ Aben Chris van der Drift Leo JLD Van Griensven Godfried D Vogels Huub JM Op den Camp |
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Institution: | (1) Department of Microbiology, Faculty of Science, University of Nijmegen, Toernooiveld 1, NL-6525 ED Nijmegen, The Netherlands , NL;(2) Mushroom Experimental Station, Postbus 6042, NL-5960 AA, Horst, The Netherlands , NL |
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Abstract: | Three strains of Agaricus bisporus (B430, 116, and 155.8), which share the ability to form hyphal aggregates on solid media under axenic conditions, were investigated
with respect to carbohydrate levels and activities of enzymes involved in their carbon metabolism. The size and macroscopic
appearance of the aggregates, when grown on diluted medium, suggest that substrate limitation plays a role in the process
of fruiting body development in A. bisporus. The enzymes trehalose phosphorylase (TP), mannitol dehydrogenase (MD), and glucose-6-phosphate dehydrogenase (G6PD) seem
to be developmentally regulated, in contrast to hexokinase (HK). Activities of TP (measured in the direction of trehalose
degradation), MD, and G6PD were higher in the hyphal aggregates compared with the mycelium, whereas HK activity varied little.
In the period preceding the axenic formation of hyphal aggregates, synthesis of trehalose by TP approximately doubled in the
mycelium. The carbohydrate levels, which were measured by HPLC, varied in a way similar to their corresponding enzymes. The
results indicate synthesis of trehalose in the mycelium of A. bisporus before the hyphal aggregates arise. Subsequently, translocation of the trehalose takes place from the mycelium to the emerging
aggregates. In these small aggregates the trehalose is rapidly broken down to yield glucose and glucose-1-phosphate, serving
as carbon and energy sources for further growth of the aggregates and for the synthesis of the osmolyte mannitol.
Received: 4 March 1999 / Accepted: 4 June 1999 |
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