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Abstract Detail

Mycological Section

Mayerhofer, Michael [1], Fraser, Erica [1], Kernaghan, Gavin [2].

Proteolytic activity in fungal root endophytes of woody plants.

The fine roots of woody plants support a wide variety of fungi, including ectomycorrhizal (ECM) species, as well as fungal root endophytes that colonize root tissue internally and asyptomatically. Although the overall function of ECM fungi is well understood, we have very little information on the ways in which fungal root endophytes obtain carbon and nitrogen. In order to assess the saprophytic abilities of some common fungal root endophytes, we determined protein utilization rates, protease levels and protease type among multiple isolates of the root endophytes Phialocephala fortinii s.l., Meliniomyces variabilis and Umbelopsis isabellina over a wide range of pH values. These were compared with data from the ECM fungi Hebeloma incarnatulum and Laccaria bicolor, as well as the saprophyte Irpex lacteus. Protease levels were measured with a fluorescently-labeled casein assay and individual proteases were characterized with specific inhibitors and gelatin zymography. The ECM fungi secreted metallo-proteases with pH optima above 4, while all other species produced aspartic proteases with lower pH optima. The optimal pH for proteolysis was especially low in isolates of M. variabilis. Hierarchical clustering analysis separated the species tested into three groups: strong saprophytes (Irpex and Umbelopsis), weakly proteolytic ECM fungi, and moderately proteolytic ascomycetous endophytes. Our data indicate that fungal endophytes may have the ability to hydrolyze soil protein, which could increase nitrogen availability to the host plant. Saprophytic root endophytes may also play a role in fine root turnover, as they are already present within the tissue upon senescence.

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1 - Mount Saint Vincent University, 166 Bedford Hwy.
2 - Mount Saint Vincent University, Biology, 166 Bedford Highway, Biology, Halifax, NS, B3M 2J6, Canada

dark septate endophyte
ectomycorrhizal fungi
soil nitrogen
fine root turnover.

Presentation Type: Oral Paper:Papers for Sections
Session: 12
Location: Salon 1/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 1:45 PM
Number: 12002
Abstract ID:1161
Candidate for Awards:None

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