Báo cáo lâm nghiệp: Changing electrophoretic patterns of glutamate dehydrogenases and aspartate aminotransferases in a few tree species under the influence of ectomycorrhization

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Báo cáo lâm nghiệp: "Changing electrophoretic patterns of glutamate dehydrogenases and aspartate aminotransferases in a few tree species under the influence of ectomycorrhization"Changing electrophoretic patterns of glutamate dehydro-genases and aspartate aminotransferases in a few treespecies under the influence of ectomycorrhization B. Dell 2 M. Chalot 1B. Botton1 Universit6 de Nancy I, Facult6 des Sciences, Laboratoire de Physiologie V6g6tale et Forestiere,BP 239, 54506 Vandceuvre-les-Nancy Cedex, France, and2 Murdoch University, School of Biological and Environmental Sciences, Murdoch, Western Austra-lia, 6150 AustraliaIntroduction tate aminotransferase (AAT), an enzyme which converts glutamate into aspartate.Numerous studies have demonstrated thewidespread existence oftwo systems for Materials and Methodsnitrogen assimilation in plants andmicroorganisms: the glutamate dehydro-genase (GDH) pathway and the glutamine Norway spruce (Picea excelsa) roots and Hebeloma sp. ectomycorrhizas were obtainedsynthetase (GS)/glutamate synthase from 4 yr old plants grown under nursery condi-(GOGAT) cycle. While the GS/GOGAT tions. Douglas fir (Pseudotsuga douglasii ) rootspathway is operative in higher plants (Lea either non-mycorrhizal or ectomycorrhizal withand Miflin, 1974), ammonia assimilation Laccaria laccata (strain S 238) were collected from 1 yr old seedlings grown under nurseryin fungi generally occurs via the GDH conditions. Beech (Fagus sylvatica) roots andpathway (Pateman and Kinghorn, 1975), Paxillus involutus (Naudet strain) ectomycorrhi-although some non-mycorrhizal fungi well Hebeloma crustuliniforme ecto- zas as asseem capable of utilizing the alternative mycorrhizas were collected from 4-6 mo oldglutamine synthetase/glutamate synthase seedlings grown in a pasteurized peat mix under nursery conditions. The fungi were culti-route (Kusnan et al., 1987). In mycorrhizal vated in pure culture in Pachlewski’s medium.associations, preliminary data have shown Enzyme activities and protein concentrationthat the fungal pathways of nitrogen as- were determined according to methods de-similation in beech-mycorrhizas are modi- scribed elsewhere (Khalid et al., 1988; Dell etfied by the establishment of the symbiosis al., 1989). Electrophoresis was carried out on 6% polyacrylamide slab gels. The bands ofand that glutamate dehydrogenase plays NADP-GDH and NAD-GDH activities were lo-a minor role in this process (Martin et al., cated by using a tetrazolium assay system (Blu-1986). Taking these observations into menthal and Smith, 1973) and AAT activity wasaccount, we studied a few ectomycorrhizal revealed with Fast violet blue (Khalid et aL,associations, focusing on GDH and aspar- 1988).Results level of NADP-GDH activity in the fungus (one major band and one minor band). Both GDHs were detected in spruce ecto-In the free-living fungus Hebeloma sp. a mycorrhizas (Fig. 1 A). In the Beech-H.high level of NADP-GDH activity was crustuliniforme association, the singlefound, whereas only NAD-GDH activity band of NADP-GDH activity found in thewas detected in non-mycorrhizal roots. In fungus was represented as traces in thethe association spruce-Hebefoma, both mycorrhiza, which exhibited a high level ofactivities were present (Table I). A similar NAD-GDH activity as did the non-mycor-distribution of enzyme activities was rhizal roots (Fig. 1 B).observed in the Douglas fir-L. laccata As for aspartate aminotransferase, theassociation (not shown). distinct isoforms found in mycorrhizas, These results contrast with those ob- always corresponded to the host root iso-tained with Beech ectomycorrhizas where forms, whereas the fungal form found inNADP-specific activity was very low (Table the fungus cultivated in pure culture wasI). Identical data were also obtained with not detected. Dissection of the mycorrhizalthe associations beech-P. involutus and tissues in spruce confirmed these results:Beech-H. crustuliniforme (not shown). the vascular cylinder free of fungus and In the the cortical region including host cells and Spruce-Hebeloma sp. associa- fungal hyphae revealed identical isoforms,tion, gel electrophoresis confirmed the ...