tailieunhanh - Báo cáo lâm nghiệp: "Production and characterization of exocellular in ectomycorrhizal fungi proteases"

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: Production and characterization of exocellular in ectomycorrhizal fungi proteases. | 728s Ann. Sci. For. 1989 46 suppl. 728s-730s Forest Tree Physiology E. Dreyer et al. eds. Elsevier INRA Production and characterization of exocellular proteases in ectomycorrhizal fungi K. El-Badaoui and B. Botton Université de Nancy I Faculte des Sciences Laboratoire de Physiologie Végétale et Forestiere BP 239 54506 Vandoeuvre-lès-Nancy Cedex France Introduction Mycorrhizas grow very often in soil layers in which organic nitrogen compounds are present in large quantities. The ability of several ectomycorrhizal fungi to assimilate proteins and to transfer their nitrogen to plants has already been demonstrated Abuzinadah and Read 1986 Abuzinadah et al. 1986 . These results suggest that proteases are excreted by the fungi and protease activities detected in mycorrhizaforming fungi were reported by Lyr 1963 and Ramstedt and Soderhall 1983 . In this study the process of production of exocellular proteases has been investigated in free living fungi as well as in mycorrhizas. Experiments were carried out with Amanita rubescens and Lacta-rius subdulcis which live in organic horizons and with Cenococcum geophilum and Hebeloma crustuliniforme which live predominantly in mineral soil layers. Materials and Methods The fungi were collected from mycorrhizas. They were grown in shaken cultures at 25 c in Pachlewski s medium containing nitrogen as either diammonium tartrate or proteins bovine serum albumin BSA gelatin casein or proteins extracted from the litter Botton et al. 1986 . Enzyme activities were determined in culture filtrates either by spectrophotometry or by spectrofluorometry using fluorescein isothiocyanate-labeled BSA FITC-BSA as described by Twining 1984 . Proteins purified from the litter by ammonium sulfate fractionation and DEAE-cellulose chromatography were also labeled with FITC and used as a substrate and as inducers. Results Protease activity remained at a very low level when the fungus was cultivated in the presence of ammonium but increased strongly .

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