Digitale Medien
Oxford, UK
:
Blackwell Science, Ltd
Plant, cell & environment
24 (2001), S. 0
ISSN:
1365-3040
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Biologie
Notizen:
In the soils of mature forests, nitrogen availability is mainly the result of litter decomposition. Thus protein degradation is of major interest for nutrition. Two aspartic proteases were excreted in a pH-dependent manner by the ectomycorrhizal fungus Amanita muscaria grown in liquid culture. AmProt1 with a molecular mass of approximately 45 kDa was mainly present at pH values up to 5·4, whereas the excretion of AmProt2 with a molecular mass of about 90 kDa was only detectable at pH values between pH 5·4 and 6·3. In addition, the pH optima of both enzymes differed significantly. AmProt1 had a narrow pH optimum around 3, whereas AmProt2 had a broad pH optimum between 3 and 5·5 and a higher affinity to the substrate methylcasein. One cDNA-clone (AmProt1*) that presumably encodes AmProt1 was identified. Like AmProt1, this cDNA was expressed in a pH-dependent manner. In addition, carbohydrate and to a lesser extent nitrogen depletion significantly enhanced AmProt1* expression. In fully developed Populus hyb./A. muscaria ectomycorrhizas the expression of AmProt1* was significantly higher in hyphae of the Hartig net compared with those of the fungal sheath. The role of AmProt1 and AmProt2 for fungal physiology and competitiveness is discussed.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1046/j.1365-3040.2001.00717.x
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