Timonen Sari, Sen Robin
Department of Biosciences, Division of General Microbiology, Biocenter, P.O. Box 56, 00014 University of Helsinki, Finland.
To whom correspondence should be addressed. E-mail:
New Phytol. 1998 Feb;138(2):355-366. doi: 10.1046/j.1469-8137.1998.00103.x.
Isozyme expression of nutrient-mobilizing and defence-related enzymes were examined in different functional components of intact Scots pine (Pinus sylvestris L.) ectomycorrhizal root systems developed in natural unsterilized forest humus. Scots pine seedlings colonized by Suillus bovinus (L. ex Fr.) O. Kuntze or Paxillus involutus (Batsch ex Fr.) strains were grown on humus in two-dimensional Perspex⌖ microcosms to allow development of complete ectomycorrhizal root systems. Soluble proteins from uncolonized short roots, whole mycorrhizal root tips or dissected mantle and core fractions, fungal strands and the outermost soil colonizing fine hyphae were subjected to native polyacrylamide gel electrophoresis and stained to detect esterase, acid phosphatase, peroxidase and different polyphenoloxidase isozyme activities. Tissue-specific esterase isozymes were detected in all components and most, including unique Hartig net isozymes, were of fungal origin. High fungal acid phosphatase activities were detected in mycorrhiza and fine hyphae of S. bovinus, supporting earlier findings of active phosphatase activity at the fungal interface in the Hartig net region and in the fine hyphal margins of extramatrical mycelium actively colonizing the humus. All compartments in the P. involutus mycorrhizosphere had weaker acid-phosphatase activities. Peroxidases formed a large part of the soluble-protein content in non-mycorrhizal short roots. The amount of peroxidases, on a tissue f. wt basis, was similar in mycorrhizal and non-mycorrhizal roots, but differential isozyme expression was detected, indicating a change in root peroxidase activities following mycorrhiza formation. The expression of DL-3,4-dihydroxyphenylalanine metabolizing polyphenol oxidase enzymes was reduced in mycorrhizas compared with non-mycorrhizal short roots. In the extramatrical mycelial components, fine hyphae expressed the highest polyphenoloxidase activity. P. involutus displayed some polyphenol-oxidizing isoenzymes not detected in S. bovinus systems. Laccase activity was not detected in the plant and fungal components examined. It is concluded that enzyme activities and isozyme expression are differentially regulated in the different functional components of Scots pine mycorrhizospheres.
在天然未灭菌森林腐殖质中发育的完整欧洲赤松（Pinus sylvestris L.）外生菌根根系的不同功能组分中，检测了与养分调动和防御相关酶的同工酶表达。用褐环乳牛肝菌（Suillus bovinus (L. ex Fr.) O. Kuntze）或卷缘桩菇（Paxillus involutus (Batsch ex Fr.)）菌株侵染的欧洲赤松幼苗，在二维有机玻璃微宇宙中的腐殖质上生长，以使完整的外生菌根根系得以发育。对未侵染的短根、整个菌根根尖或解剖后的菌套和髓芯部分、真菌菌丝以及最外层土壤定殖的细菌丝中的可溶性蛋白质进行非变性聚丙烯酰胺凝胶电泳，并进行染色，以检测酯酶、酸性磷酸酶、过氧化物酶和不同多酚氧化酶的同工酶活性。在所有组分中均检测到组织特异性酯酶同工酶，其中大多数，包括独特的哈蒂氏网同工酶，都源自真菌。在褐环乳牛肝菌的菌根和细菌丝中检测到较高的真菌酸性磷酸酶活性，这支持了早期在哈蒂氏网区域的真菌界面以及积极定殖腐殖质的根外菌丝细菌丝边缘存在活跃磷酸酶活性的发现。卷缘桩菇菌根际的所有区室酸性磷酸酶活性较弱。过氧化物酶在非菌根短根的可溶性蛋白质中占很大一部分。以组织鲜重计，菌根和非菌根根中的过氧化物酶量相似，但检测到同工酶表达存在差异，表明菌根形成后根过氧化物酶活性发生了变化。与非菌根短根相比，菌根中DL - 3,4 - 二羟基苯丙氨酸代谢多酚氧化酶的表达降低。在根外菌丝组分中，细菌丝表现出最高的多酚氧化酶活性。卷缘桩菇显示出一些在褐环乳牛肝菌系统中未检测到的多酚氧化同工酶。在所检测的植物和真菌组分中未检测到漆酶活性。得出的结论是，欧洲赤松菌根际不同功能组分中的酶活性和同工酶表达受到不同的调控。
